Point Source Emission Inventories on Native American Reservations and Tribal Lands

Transcription

1 Point Source Emission Inventories on Native American Reservations and Tribal Lands Draft Report Prepared for The Western Regional Air Partnership Prepared by Eastern Research Group, Inc Perimeter Park Drive Morrisville, NC ENVIRON Golden Gate Plaza 101 Rowland Way Novata, CA ERG Contract Number August 8, 2005

2 TABLE OF CONTENTS Section Page LIST OF TABLES...xiii LIST OF FIGURES...xv 1.0 INTRODUCTION Background Objectives and General Methodology ARAPAHOE AND SHOSHONE TRIBES OF THE WIND RIVER RESERVATION Emissions Point Sources Oil and Gas Sources Emissions Colville Reservation Emissions Point Sources Emissions CONFEDERATE TRIBES OF THE WARM SPRINGS RESERVATION Emissions Point Sources Emissions NAVAJO NATION Emissions Point Sources Oil and Gas Sources Emissions xi

3 TABLE OF CONTENTS Section Page 6.0 TOHONO O ODHAM NATION Emissions Point Sources Emissions TOHONO O ODHAM NATION Emissions Oil and Gas Sources Emissions TOHONO O ODHAM NATION Emissions Point Sources Emissions REFERENCES xii

4 LIST OF APPENDICES Appendix A Wyoming Emission Factor Documentation Appendix B Sample Calculation for the VOC and Minor NO x Processes Appendix C Navajo Nation Area Sources Appendix D Yakama Nation Minor Source Candidate List LIST OF TABLES Table Page 2-1 Point Sources Emissions for the Wind River Reservation (tpy) Oil and Gas Fields on the Wind River Reservation The Average Depth and Duration of Drilling on the Wind River Reservation by Formation Emissions From Point Sources on the Wind River Reservation Reported in a Previous Inventory Wyoming DEQ Emission Factors for Minor NO x and VOC Wellhead Processes Well-Specific Data Obtained From the Oil and Gas Commission Comparison of Total Oil and Gas Production From the WYOGCC and From the SOGC Summary of 2002 NO x Emissions on the Wind River Reservation Emissions from Drill Rigs on the Wind River Reservation Emissions from Gas Compressor Engines on the Wind River Reservation Medium-Sized Point Sources on the Wind River Reservation Emission From Minor NO x and VOC Wellhead Processes on the Wind River Reservation Point Sources Emissions for the Colville Reservation (tpy) Data Sources for Navajo Nation (tpy) Point Sources Emissions for Navajo Nation (tpy) Area Source Emissions for Natural Gas Combustion for Navajo Nation (tpy) The Average Depth and Duration of Drilling on the Navajo Nation by Formation Assumptions Used in Developing the CBM Generator Emissions Estimate Oil and Gas Production on the Navajo Nation Emissions for New Mexico Natural Gas Facilities with a PTE Between 25 and 100 tpy Wyoming DEQ Emission Factors for Minor NO x and VOC Wellhead Processes Well-Specific Data Required to Estimate Emissions from Minor NO x and VOC Processes on the Navajo Nation Summary of 2002 NO x Emissions on the Navajo Nation Emissions From Drill Rigs on the Navajo Nation Emissions From Gas Compressor Engines on the Navajo Nation xiii

5 LIST OF TABLES Table Page 5-13 Compressor Engine Emissions on Navajo Lands Double-Counted in the State Oil and Gas Inventory Water Production at CBM Wells on Navajo Lands and Resultant Emissions Emissions from Minor NO x and VOC Wellhead Processes on the Navajo Nation Minor NO x and VOC Wellhead Emissions on Navajo Lands Double-Counted in the State Oil and Gas Inventory Data Provided by XTO and Burlington Resources Ute Mt. Ute 2002 Oil and Gas Production Versus 2004 Production Emissions for New Mexico Natural Gas Facilities with a PTE Between 25 and 100 tpy Wyoming DEQ Emission Factors for Minor NO x and VOC Wellhead Processes Well-Specific Data Obtained From the Oil and Gas Commissions Oil and Gas Production on the Ute Mt. Ute Lands Extracted From State Databases Oil and Gas Sales on the Ute Mt. Ute Lands Recorded by Department of Revenue Summary of 2002 NO x Emissions on the Ute Mt. Ute Lands Emissions From Drill Rigs on the Ute Mt. Ute Lands Emissions From Gas Compressor Engines on the Ute Mt. Ute Lands Compressor Engine Emissions to Subtract From the States Inventory Emissions From Medium-Sized Facilities on the Ute Mt. Ute Lands Emissions From Minor NO x and VOC Wellhead Processes on the Ute Mt. Ute Lands Emissions to Ute Mt.Ute to Subtract From State Inventories Point Sources Emissions for Yakama Nation (tpy) xiv

6 LIST OF FIGURES Figure Page 2-1 Location of Drilling Activity on the Wind River Reservation Wellhead Compressor Engine Wells Plotted on the Wind River Reservation Point Sources Emissions for Yakama Nation (tpy) Location of Drilling Activity on the New Mexico Portion of the Navajo Nation Navajo Nation Overlaid with the Public Land Survey System Grid Location of Drilling Activity on the Utah Portion of the Navajo Nation Oil, Gas and CBM Wells in the NMOCD Databases Plotted Against the Boundaries of the Navajo Nation Diagram of Assumed CBM Well Wellhead Compressor Engine Oil, Gas and CBM Wells in the Arizona, New Mexico, and Utah Databases Plotted Against the Boundaries of the Navajo Nation Location of Drilling Activity on the Ute Mt. Ute Lands Wellhead Compressor Engine Oil, Gas and CBM Wells in the Utah, Colorado, and New Mexico Databases Plotted Against the Boundaries of the Ute Mt. Ute Lands xv

7 PREFACE Regulatory Framework for Tribal Visibility Implementation Plans The Regional Haze Rule explicitly recognized the authority of tribes to implement the provisions of the Rule, in accordance with principles of Federal Indian law, and as provided by the Clean Air Act 301(d) and the Tribal Authority Rule (TAR) (40 CFR ). Those provisions create the following framework: 1. Absent special circumstances, reservation lands are not subject to state jurisdiction. 2. Federally recognized tribes may apply for and receive delegation of federal authority to implement CAA programs, including visibility regulation, or reasonably severable elements of each programs (40 CFR 49.3, 49.7). The mechanism for this delegation is a Tribal Implementation Plan (TIP). A reasonable severable element is one that is not integrally related to program elements that are not included in the plan submittal, and is consistent with applicable statutory and regulatory requirements. 3. The Regional Haze Rule expressly provides that tribal visibility programs are not dependent on the strategies selected by the state or states in which the tribe is located (64 Fed. Reg ), and that the authority to implement 309 TIPs extends to all tribes within the GCVTC region (40 CFR (d)(12). 4. The EPA has indicated that under the TAR tribes are not required to submit 309 TIPs by the end of 2003; rather they may choose to opt-in to 309 programs at a later date (67 Fed. Reg ). 5. Where a tribe does not seek delegation through a TIP, EPA, as necessary and appropriate, will promulgate a Federal Implementation Plan (FIP) within reasonable timeframes to protect air quality in Indian country (40 CFR 49.11). EPA is committed to consulting with tribes on a government to government basis in developing tribe-specific or generally applicable TIPs where necessary (See, e.g. 63 Fed. Reg ). It is our hope that the findings and recommendations of this report will prove useful to tribes, whether they choose to submit full or partial 308 or 309 TIPs, or work with EPA to develop FIPs. The amount of modification necessary will vary considerably from tribe to tribe. The authors have striven to ensure that all references to tribes in the document are consistent with principles of tribal sovereignty and autonomy as reflected in the above framework. Any inconsistency with this framework is strictly inadvertent and not an attempt to impose requirements on tribes which are not present under existing law. Tribes, along with states and federal agencies, are full partners in the WRAP, having equal representation on the WRAP Board as states. Whether Board members or not, it must be remembered that all tribes are governments, as distinguished from the stakeholders (private interest) which participate on Forums and Committees but are not eligible for the Board. Despite this equality of representation on the Board, tribes are very differently situated that states. There xvi

8 are over four hundred federally recognized tribes in the WRAP region, including Alaska. The sheet number of tribes makes full participation impossible. Moreover, many tribes are faced with pressing environmental, economic, and social issues, and do not have the resources to participate in an effort such as the WRAP, however important its goals may be. These factors necessarily limit the level of tribal input into and endorsement of WRAP products. The tribal participants in the WRAP, including Board members Forum and Committee member co-chairs, make their best effort to ensure that WRAP products are in the best interest of the tribes, the environment, and the public. One interest is to ensure that WRAP policies, as implemented by states and tribes, will not constrain the future options of tribes who are not involved in the WRAP. With these considerations and limitations in mind, the tribal participants have joined the state, federal, and private stakeholder interests in approving this report as a consensus document. xvii

9 1.0 INTRODUCTION 1.1 Background To reduce haze, and to meet requirements of the Clean Air Act, the U.S. Environmental Protection Agency (EPA) issued a regional haze rule aimed at protecting visibility in 156 Class I federal areas in Under the Regional Haze Rule, states are required to set periodic goals for improving the visibility in these areas. As they work to reach these goals, states must develop comprehensive emissions inventories in order to design implementation plans for reducing visibility-impairing pollution. The Western Regional Air Partnership (WRAP) is a voluntary organization of western states, tribes and federal agencies. The states included in the WRAP are Alaska, Arizona, California, Colorado, Idaho, Montana, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington, and Wyoming. The purpose of the WRAP is to develop the technical and policy tools needed by western states and tribes to comply with the Regional Haze Rule. The WRAP Tribal Data Development Working Group (TDDWG) is charged with facilitating the collection of data related to air quality on tribal lands in a manner that respects the interests of tribes, including the protection of sensitive information. By developing a more inclusive inventory of air pollution sources located on tribal lands, the TDDWG will improve the accuracy of WRAP s baseline inventory from which modeling, policy evaluations, and emission reduction strategies are being developed. 1.2 Objectives and General Methodology The purpose of this report is to present the findings of the effort made to improve point source and oil and gas emissions inventories. The focus of this work is on all oil and gas sources within the areas of interest, and on other point sources with emissions of at least 50 tons per year (TPY) of sulfur oxides (SO x ) or nitrogen oxides (NO x ) located on Native American Reservations in the WRAP region. With the assistance and direction of staff from the TDDWG and the Institute for Tribal Environmental Professionals (ITEP), tribal personnel from seven reservations in the WRAP region were contacted to identify potential emissions sources, and to identify sources of activity data that could be used to develop point source emissions estimates. The tribes and reservations covered by this project include the following: Arapahoe and Shoshone Tribes of the Wind River Reservation Colville Reservation Confederate Tribes of the Warm Springs Reservation Navajo Nation Tohono O'odham Nation Ute Mountain Ute Yakama Nation 1-1

10 Once potential sources were identified, emission estimates were prepared and the emissions inventory data was formatted to be compatible with EPA s National Emission Inventory (NEI) Input Format (NIF). Once formatted, the data was stored in the WRAP Emissions Data Management System (EDMS) database. In addition to sources meeting the emissions criteria of 50 TPY SO x or NO x, all Title V sources were treated as point sources and entered into EDMS where data was available. 1-2

11 2.0 ARAPAHOE AND SHOSHONE TRIBES OF THE WIND RIVER RESERVATION The Wind River Reservation is located in west-central Wyoming and encompasses approximately 2.3 million acres and is home to 2,500 Eastern Shoshone and more than 5,000 Northern Arapahoe Indians. This section discusses the results of the point source and oil and gas emission inventory development effort for the Arapahoe and Shoshone Tribes of the Wind River Reservation for The point source component is discussed first, followed by the oil and gas source component. A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Point Sources Methodology An existing emissions inventory report Air Quality Assessment Report of the Wind River Indian Reservation served as the starting point for identifying potential point sources located on this reservation. Of the nine point source facilities identified in this report, seven are considered oil and gas sources and are addressed in Section below. The remaining two point sources - Peak Sulfur, Inc and Riverton Dome Gas Plant, Devon SFS Operating Inc. - are both Title V sources and have been included in the point source inventory. The Institute for Tribal Environmental Professionals (ITEP) compiled the emissions inventory for the two Title V sources located on the reservation. The data collected for these facilities came from 2002 reported emissions from fee calculation forms obtained at EPA s Region 8 offices. In order to determine the presence of additional potential point sources meeting the selection criteria, Fernando Roman, the Air Quality Coordinator with the Wind River Environmental Quality Commission, was contacted and interviewed by telephone. Mr. Roman was asked about the presence of industrial and manufacturing activity, power generation sources, and large institutional sources such as hospitals or universities located on the reservation. Outside of the two point sources and the oil and gas activities mentioned above, Mr. Roman was not aware of any potential sources of air emissions located on the reservation (Roman, 2005). Results ITEP compiled the point source information for the two Title V sources present on this reservation into the NIF format, and supplied that information to ERG in March of Subsequently, ERG loaded this data into WRAP s EDMS database. Table 2-1 presents a summary of emissions from these facilities. 2-1

12 Table 2-1. Point Sources Emissions for the Wind River Reservation (tpy) Plant Name CO NO x PM-10 PM SO 2 VOC Riverton Dome Gas Plant, Devon SFS Operating Inc Peak Sulfur Inc Oil and Gas Sources This section describes the base year 2002 emission inventory of oil and gas area sources for the Wind River Reservation. The focus of this inventory effort was to estimate emissions of nitrous oxides (NO x ) from oil and gas production operations. In a related project to address point and area source emissions led by the WRAP Stationary Sources Joint Forum (SSJF), major NO x sources in the oil and gas industry were identified and methodologies defined for estimating emissions from those sources. The major NO x sources were identified as: drill rigs, gas compressor engines, and coal bed methane (CBM) pump engines. Minor NO x and VOC wellhead processes for which emission factors are available were also identified. The methods employed to estimate emissions from these sources on the Wind River Reservation are based on those developed for the SSJF project. Minor modifications have been made to accommodate the sources of data that were specific to the Wind River Reservation. A complete discussion of these methods and the oil and gas emissions inventory produced for the Wind River Reservation are presented in this section. Area Source Oil and Gas Methodology Drill Rigs. The approach used to estimate emissions from drill rig engines was to combine activity data from drilling permits with emissions data from a survey of drill rig operators. Drilling permits were obtained from the Wyoming Oil and Gas Conservation Commission (WYOGCC). The WYOGCC drill permits that applied to activity on the Wind River Reservation were determined with assistance from the Shoshone Oil and Gas Commission. The emission estimate uses several activity indicators from the drill permit data and combines that with emission factors derived from the drilling survey to make the most locally appropriate emission estimate. The WYOGCC was contacted to obtain, amid other information, the activity data afforded by drill permits. The drilling information obtained is as follows: Spud date - the date that drilling commenced Well depth - the depth of the well; total vertical, measured or target depending on availability Completion date - the date well preparation is finalized; occurring with some delay after drilling ceases Well formation - the geologic structure that the well was drilled to 2-2

13 Well field - the legal designation for the area where the well was drilled Well county - the county where the well was drilled; for allocation purposes Well coordinates - latitude and longitude of the well While the State maintained a database containing these fields, every field was not completed for every well. The absence of this information required that some assumptions be made about the duration of drilling. Those assumptions are documented later in this section. Drill permit data was provided for by the WYOGCC (2005) for the entire State of Wyoming, as represented by the geographic boundaries of the State. That this data contained activity on the Wind River Reservation was easily confirmed by plotting the locations of drill permits against a map of the Wind River Reservation. Figure 2-1 shows the location of wells that when plotted were found to be within the Wind River Reservation. Figure 2-1. Location of Drilling Activity on the Wind River Reservation. The question that remained was whether the information provided by the WYOGCC encompassed all drilling activity on the Wind River Reservation or only some fraction of the total. Representatives of both the Wind River Environmental Quality Commission and the Shoshone Oil and Gas Commission (SOGC) confirmed that the WYOGCC oil and gas data 2-3

14 encompassed all oil and gas development on the Wind River Reservation (WREQC, 2005; SOGC, 2005). However, when wells were identified as located on the Wind River Reservation based only on the geographic coordinates, the WREQ responded that many wells had been omitted. This was determined to have resulted from some missing or erroneous geographic coordinates in the well database. The solution to this problem of identifying wells on the Wind River Reservation was arrived at with assistance from the Shoshone Oil and Gas Commission. The SOGC provided a list of the oil and gas fields on the Wind River Reservation and the total 2002 oil and gas production for those fields. Selecting wells based on the field identifier in the WYOGCC data resulting in a selection of wells with a total 2002 production that was within one percent of the production reported by the SOGC. It was thus determined that the most accurate method for identifying wells on the Wind River Reservation was by selecting from the WYOGCC database based on the field identifier. The list of fields on the Wind River Reservation provided by the SOGC is provided in Table 2-2. Table 2-2. Oil and Gas Fields on the Wind River Reservation Field Names Circle Ridge Maverick Springs Muddy Ridge Pavillion Pilot Butte Riverton Dome Riverton Dome East Rolff Lake Sand Mesa Sheldon Sheldon Northwest Steamboat Butte Winkleman Drill permits applicable to the Wind River Reservation were selected from the total set of WYOGCC drill permit data by extracting only those wells drilled in the fields listed in Table 2-2. The WYOGCC drill permit data provided the base level of activity to characterize the number of wells being drilled in an area, the depth of those wells and the amount of time required to construct the wells. What was also needed was information about the drill rigs that could be used to tie this information about the characteristics of the well being drilled to emissions from drill rig engines. Fortunately, using the results of a recent Wyoming Department of Environmental Quality (DEQ) survey of drilling in the Jonah-Pinedale area of Southwest Wyoming it was possible to derive the necessary relationship. 2-4

15 The Jonah-Pinedale area has seen particularly intense drilling activity in recent years and the information provided represents the synthesis of emissions estimates made by ten different drilling companies for a total of 218 wells drilled. The emission factors derived from the WYDEQ (2005) survey are 13.5 tons NO x per well and 3.3 tons SO 2 per well. The emissions from the prime mover on a drill rig for drilling a well are dependent upon the depth of the well, the composition of substrate and the characteristics of the engine. For example, a small rig drilling a relatively shallow well in the Powder River Basin would have different emissions than a large rig drilling a deep well in the Jonah-Pinedale area. Because of this variation in drilling operations, it would not be appropriate to use the same Jonah-Pinedale emission factor for wells drilled on the Wind River Reservation without making some adjustments. To reflect this fact, we employed a methodology developed in the SSJF project that uses information about the characteristics of wells in a specific area to scale the Jonah- Pinedale emission factor for drilling operations in that area. The most specific unit for which well characteristics were available was the formation. Creating formation-specific emission factors offers a good degree of accuracy because the well depths and substrate encountered when drilling the same formation should be consistent. This consistency within a single formation would be irrelevant if it weren t for the absence of duration data for some wells drilled on the Wind River Reservation. Using the methodology developed in the SSJF project, the emissions from the drilling of all wells in one formation are estimated using the average duration of well preparation activities and average well depth within the formation. This is based on the assumption that wells with no information for depth or duration will, on average, be well represented by all those wells in the formation for which depth and duration were available. In addition to the assumption that the depth and duration of drilling activities for wells in a single formation are approximated by the average for the formation, two other important assumptions are inherent to this method. First, it is assumed that the difference between the completion date and the date that drilling ceased is, on average, constant relative to the total duration of preparation activities. This assumption was needed because the actual date that drilling ceased was not available. What this assumption means is that if on average wells with 100 days between spud date and completion actually had a duration of drilling of only 80 days, then on average wells with 50 days between spud date and completion would have 40 days of actual drilling. It was also necessary to assume that the capacity of the equipment used to drill a well is dependent upon the depth of the well. This assumption was made because the data clearly indicated that substantially different rigs were employed in different drilling applications. Some wells in the Powder River Basin had the same approximate drilling duration as wells in Jonah-Pinedale. It was therefore assumed that the capacity of the prime mover would grow proportional to the depth of the well. With those two assumptions, it is then possible to scale the emission factor from the Jonah-Pinedale area to other formations based on the average well depth and drilling duration and in doing so to correct for variations due to well depth, composition of substrate, and engine capacity. 2-5

16 To scale the Jonah-Pinedale emission factor to the formations found on the Wind River Reservation the average well depth and duration was calculated for each formation. Due to the relatively small number of wells drilled in some formations and the absence of duration data for some wells, it was not always possible to determine a formation-specific duration. When no duration information was available for a particular formation, the average duration for all wells drilled on the Wind River Reservation was assumed. The average depths and durations determined for the formations of the Wind River Reservation are shown in Table 2-3. Table 2-3. The Average Depth and Duration of Drilling on the Wind River Reservation by Formation Average Drilling Duration Average Well Depth Formation (Days) (Ft) Fort Union 33 5,674 Fort Union-Wind River 281 4,330 Lance-Meeteetse-Mesaverde ,433 Meeteetse-Mesaverde ,425 Mesaverde 80 12,600 Nugget 21 7,055 Nugget-Phosphoria-Tensleep 20 7,116 Phosphoria 5 7,150 Phosphoria-Tensleep 141 7,215 Wind River 48 4,754 The vast majority of wells drilled in Jonah-Pinedale were drilled to the Lance or Lance- Mesaverde formation. The average well depth and drilling duration for those formations - based on drill permit data obtained from the Wyoming OGC for 2002 and was 11,896 ft and 80.6 days (WYOGCC 2005). Based on this information for Jonah-Pinedale and the data for the Wind River Reservation shown in Table 2-3, formation-specific emission factors were created using Calculation 2-1. Calculation 2-1: EF A = EF J x ( D A / D J ) x ( T A / T J ) where: EF A = The emission factor for another formation EF J = The Jonah-Pinedale emission factor D A = The average depth of wells drilled in another area Dj = The average depth of wells drilled in Jonah-Pinedale T A = The duration of drilling in another area = The duration of drilling in Jonah-Pinedale T j 2-6

17 Emissions for a single formation were then calculated using Calculation 2-2. The emissions for the formations were then summed to determine the total emissions from drill rigs operating on the Wind River Reservation. Calculation 2-2: E = EF x W where: E = The 2002 emission for a given formation EF = The formation specific emission factor W = The number of wells drilled in the formation in CBM Pump Engines. The data obtained from the WYOGCC (2005) did not show any coal bed methane wells on the Wind River Reservation in The Wind River Environmental Quality Commission confirmed that there were no CBM wells on the Wind River Reservation in 2002 (WREQC, 2005). Non-Point Natural Gas Compressor Engine Emissions. For the purposes of this study, natural gas compressor engines have been grouped into three categories. The largest facilities, in terms of potential emissions, are the large natural gas compressor stations on natural gas transmission lines. These are typically Title V facilities and they are dealt with as point sources. The second tier of facilities is the gas gathering compressor station. These medium-sized facilities are included in the area source inventory for the Wind River Reservation and are discussed in the following subsection. The final category of compressor engines, which is the primary focus of this area source compressor engine emission estimate, is the group of relatively small, dispersed wellhead compressor engines. Figure 2-2 presents an example of such an engine. The methodology used to estimate emissions from these engines is presented in this subsection. A methodology to estimate emissions from wellhead compressor engines was developed by ENVIRON for the WRAP SSJF project. In that project a production-based emission factor was derived from local studies of compressor engine emissions. This emission factor was then combined with county level gas production to estimate emissions. For the Wind River Reservation, emissions were determined by combining the production-based emission factor with total gas production on the Wind River Reservation, as reported in well production data obtained from the WYOGCC (2005). 2-7

18 Figure 2-2. Wellhead Compressor Engine The emission factor is derived from a study conducted by the New Mexico Oil and Gas Association (NMOGA). In this study NMOGA compiled an emissions inventory of the unpermitted compressor engines operated by the oil and gas production industry in the New Mexico portion of the San Juan Basin. In the State of New Mexico, the threshold for permitting reported by the New Mexico Environmental Department was a potential to emit 25 tons per year (NMED, 2005b). Thus, the inventory of unpermitted sources included those sources with a potential to emit less than 25 tons per year. The small wellhead compressor engines fall into this category. The NMOGA inventory provided emissions for wellhead compressor engines, which were compared to production statistics for the San Juan Basin to derive an emission factor with units of tons NO x per MCF of gas produced. The result is an emission factor of 2.34x10-5 tons NO x per MCF gas produced. We had previously requested from the WYOGCC well-specific oil and gas production statistics for the entire State of Wyoming. The WREQC and the SOGC reported that the WYOGCC data was expected to include all oil and gas development on the Wind River Reservation. The wells obtained from the WYOGCC were plotted using GIS software to determine which wells were on the Wind River Reservation. The resulting plot is shown in Figure 2-3. The production determined for the wells depicted in Figure 2-3 was submitted to the WREQC for review. WREQC responded that a great deal of production had been omitted. 2-8

19 Figure 2-3. Wells Plotted on the Wind River Reservation A more accurate method of selecting wells on the Wind River Reservation from the WYOGCC database was developed with the assistance of the Shoshone Oil and Gas Conservation Commission. The SOGC recommended selecting wells from the WYOGCC database using the names of the fields on the Wind River Reservation. The SOGC provided a list of oil and gas field names and a summary of 2002 oil and gas production from those fields. When oil and gas wells were selected from the WYOGCC database using that list of fields, the resulting wells had a total production within one percent of the production summaries provided by the SOGC. Total 2002 gas production, determined by summing the gas production at all wells on the Wind River Reservation, was 28,426,554 MCF. Emissions from compressor engines were estimated as the product of gas production and the production-based emission factor. The WREQC was contacted to determine if there were any controls on wellhead compressors. The WREQC responded that the use of wellhead compression was believed to be small, but reported no controls on those engines. Emissions have therefore been estimated without controls. Based on the WREQC comment that the use of wellhead compression is believed to be small, we expect that the emissions estimates produced by this method represent a conservative estimate of emissions from wellhead compressor engines. 2-9

20 Medium-Size Facilities. The production-based emission factor developed from the NMOGA inventory of unpermitted compressor engines in the San Juan Basin is only useful for estimating emissions from compression facilities with a potential to emit less than 25 tons per year. This is due to the nature of the inventory and the permitting requirements in the State of New Mexico. In order to be unpermitted, the compressor engines in the study must have had a potential to emit less than 25 tons NO x per year. Thus by applying the emission factor derived from the NMOGA inventory to gas production we estimated emissions for only those compressor engines on the Wind River Reservation that have a potential to emit less than 25 tons per year. Additional emissions for very large compressor facilities are addressed in the point source emissions. Emissions for a final set of mediumsized facilities - facilities larger with a potential to emit greater than 25 tons per year, but less than 100 tons per year - were determined primarily by contacting the facility operators. Nine point sources were identified for the Wind River Reservation in a previous emission inventory compiled by Advanced GeoEnvironmental (2003). Included in that list of nine sources are the two Title V sources. The emissions reported for each of the oil and gas point sources in that previous inventory effort are shown in Table 2-4. Table Emissions From Point Sources on the Wind River Reservation Reported in a Previous Inventory a Source CO NO x SO 2 PM 10 PM 2.5 VOC Devon SFS Operating, Inc., Riverton Plant Devon SFS Operating, Inc., Beaver Creek Plant Peak Sulfur, Inc West Pavilion Compressor Station Wind River Gas Gathering, Inc Wildhorse Energy, Pavilion Booster Station Hidden Valley Compressor Station Sand Mesa Compressor Station Enervest Riverton Compressor a Advanced GeoEnvironmental, The Riverton Plant and Peak Sulfur are in the point source inventory compiled by ITEP. The WREQC reported that the Beaver Creek Plant is near, but not on the Wind River Reservation. The Wildhorse Energy, Pavilion Booster Station, also referred to as the Pavilion Compressor Station, was included by WYDEQ in the State of Wyoming s 2002 emissions inventory. Plotting the coordinates of the Pavilion Compressor Station confirmed that the facility is located on tribal lands. However, in this inventory effort it was decided to 2-10

21 code facilities based on the entity submitting the data rather than the geographic location of the facility. Because emissions for the Pavilion Compressor Station were submitted by WYDEQ, that source is not included in the Wind River emissions inventory. That left five point sources in this previous inventory that are on the Wind River Reservation but are not in some way already incorporated into this inventory. Only the emissions for the facility operated by Wind River Gas Gathering, Inc. were adopted from the previous inventory effort. The other four facilities all had an estimated NO x emission of 476 tons in the previous inventory. We decided to investigate these facilities individually. The WREQC indicated the operating companies for the Hidden Valley, Sand Mesa and Enervest Riverton facilities. For each of those facilities, we contacted the operator and obtained emissions data. For the remaining facility, the West Pavilion Compressor Station (also known as the West Powerline Compressor Station), we obtained data from the Wyoming Department of Environmental Quality. WYDEQ (2005b) reported that the facility has two Waukesha engines that are controlled to an emission rate of 1.0 g/hp-hr. The permitted NO x emission for the facility is 33 tons per year. The permitted level has been used to approximate actual emissions. Minor NO x and VOC Wellhead Processes. In addition to the area sources identified as potentially major sources of NO x emissions, we have estimated emissions for several other processes occurring at oil and gas wellheads. Emissions were estimated for both NO x and VOC using well-specific production and emission factors provided by the Wyoming Department of Environmental Quality. The sources for which emissions were estimated in this portion of the inventory and the emission factors used are listed in Table 2-5. Table 2-5. Wyoming DEQ Emission Factors for Minor NO x and VOC Wellhead Processes a Gas Wells Emission Factor Oil Wells Source Emission Factor Condensate Tanks 3,271 lbs VOC per year/bpd Heater lbs NO x per barrel 27,485 lbs per Dehydrator year/mmcfd Pneumatic Devices 0.1 tons VOC / well 1,752.0 lbs NO x per lbs VOC per year / Heater year/well Tanks BPD 86.0 tons VOC/well completion Completion 1.75 tons NO x /well completion Pneumatic Devices 0.2 tons VOC per year/well a For documentation of the Wyoming DEQ emission factors, refer to Appendix A. To use these emission factors, it was necessary to obtain well-specific production data from the Wyoming Oil and Gas Conservation Commission. The list of well-specific information obtained from the WYOGCC is presented in Table 2-6. The wells that were on the Wind River Reservation were identified by selecting well records where the field was one of those 2-11

22 in the list of fields on the Wind River Reservation that was provided by the Shoshone Oil and Gas Commission (SOGC) (see Table 2-6). The total oil and gas production from the wells identified by this method is compared with the 2002 oil and gas production summary provided by the Shoshone Oil and Gas Commission in Table 2-7. Table 2-6. Well-Specific Data Obtained From the Oil and Gas Commissions Well-Specific Data Obtained from the Oil and Gas Commissions 2002 oil produced 2002 gas produced 2002 water produced Well location (latitude/longitude) Well field Well formation Well depth Well class (oil/gas) Coal bed methane (yes/no) Completion date Table 2-7. Comparison of Total Oil and Gas Production From the WYOGCC and From the SOGC WYOGCC SOGC Percent Difference 2002 Oil Production (BBL) 2,154,450 2,177, Gas Production (MCF) 28,426,554 28,592, Once obtained, the well data was separated into two categories, oil wells and gas wells, based on the identifier supplied in the WYOGCC data. Because some of the emission factors have units of emissions per well, wells with zero oil and zero gas production and a non-2002 completion date were removed from consideration. This action prevented emissions from being estimated at wells where no activity actually occurred in The fact that records were obtained for all wells that contained each of the fields in Table 2-6 did not mean that for every well all those fields were populated. The most important fields for the purposes of this inventory were those containing the production figures. These appeared to be well maintained. However, in some cases the completion date and the well class, which are also used in this emission estimate, were blank. It did not appear possible to obtain additional data for completion dates, and the assumption is that a blank completion date implies the well was completed some time in the past, prior to The emission factors obtained from WYDEQ contained some assumptions about controls that were adjusted to represent the Wind River Reservation. Although the WREQC did not identify any controls imposed on these wellhead processes, controls on flaring emissions 2-12

23 have been assumed in the emissions estimate. The WYDEQ emission factor for completions includes the assumption that a large volume of the gas released is routed to a flare. This assumption is carried over to the Wind River Reservation emissions inventory because the flaring assumed in the emission factor is not very different from the flaring we would assume based only on safety considerations. The Wyoming DEQ also assumed that condensate tanks with greater than 18.3 barrels per day of condensate production would be controlled with an overall efficiency of 98 percent. For wells with condensate production less than 18.3 barrels per day WYDEQ provided an uncontrolled emission factor (see Table 2-5). To account for the absence of controls on condensate tanks on the Wind River Reservation, emissions were simply estimated for all wells using the uncontrolled emission factor. Emission factors were combined with the well data to estimate emissions following the general procedure shown in Calculation 2-3. For detailed sample calculations for each of these processes, refer to Appendix B. Calculation 2-3. Calculation of wellhead emissions for individual wells Gas Well E = SUM i (P g x EF g,i ) + SUM j (Pc x EF c,j ) + SUM(EF w ) Where: E = The 2002 emission P g = 2002 gas production EF g,i = Emission factor for gas process i P c = 2002 condensate production EF c,j = Emission factor for condensate process j EF w = Per well emission factor Oil Well E = SUM i (P o x EF g,i ) + SUM(EF w ) Where: E = The 2002 emission P o = 2002 oil production EF o,i = Emission factor for oil process i EF w = Per well emission factor Area Source Oil and Gas Emissions Summary A summary of the NO x emissions estimated for the oil and gas processes on the Wind River Reservation is presented in Table 2-8. Wellhead compressor engine emissions are clearly the largest source of NO x, contributing over 50 percent of the area source oil and gas NO x 2-13

24 emissions. As mentioned in the discussion of methodology, this is believed to be a conservative estimate of emissions from wellhead compressor engines. Drill rig emissions and emissions from the minor NO x and VOC wellhead processes make up most of the remaining emissions. Less than 10 percent of the area source oil and gas emissions are contributed by the medium-sized facilities. Table 2-8. Summary of 2002 NO x Emissions on the Wind River Reservation NO x Emissions Process (ton) Drill Rigs 188 Minor NO x and VOC Wellhead Processes 227 Compressor Engines 664 Medium-size Facilities 90 Coal bed Methane Total 1,169 The emissions presented for the Wind River Reservation have not been reconciled with emissions estimated for the State of Wyoming in the related WRAP SSJF project. The following discussion of the results obtained for each emissions source includes guidance on how the area source oil and gas emissions estimated for the Wind River Reservation might be reconciled with the area source oil and gas emissions estimated for the State of Wyoming. Emissions from drill rigs operating on the Wind River Reservation are shown in Table 2-9. There were 21 wells drilled on the Wind River Reservation in In the project for the WRAP SSJF, these 21 wells were included in drill rig emissions estimates for the State of Wyoming. According to the WYOGCC database, all 21 of those wells were drilled in the part of the Wind River Reservation corresponding to Fremont County. Reconciliation with the State emissions inventory could be achieved by reducing the emissions for Fremont County by the amount of emissions estimated for drill rigs on the Wind River Reservation. Table 2-9. Emissions from drill rigs on the Wind River Reservation Wells Drilled Total Emissions (Tons) In 2002 NO x SO The emissions estimate for wellhead compressor engines are presented in Table These emissions exactly duplicate compressor engine emissions estimated for the same set of wells in the State of Wyoming oil and gas area source emissions inventory. In the State inventory, those wells are assigned to Fremont County. The wellhead compression estimates in the two inventories can be reconciled by simply subtracting the wellhead compression estimated for the Wind River Reservation from the total wellhead compression estimated for Fremont County. 2-14

25 Table Emissions From Gas Compressor Engines on the Wind River Reservation Number of Total Gas Emission Factor Emission NO x Wells Production (MCF) (tons NO x /MCF) (tons) ,426, E Emissions determined for the medium-sized facilities and the sources of the emissions data are listed in Table Although the Wyoming DEQ maintains permit data on at least some of the medium-sized facilities found on the Wind River Reservation, none of these facilities were found in the point source inventory submitted by the Wyoming DEQ. No reconciliation of the medium-sized facilities is required. Table Medium-Sized Point Sources on the Wind River Reservation Facility Total 2002 NO x Emission (tons) Source West Pavilion Compressor Station 33 WYDEQ, 2005b Wind River Gas Gathering Inc. 37 Advanced GeoEnvironmental, 2003 Hidden Valley Compressor Station 13.8 Encana, 2005 Sand Mesa < 1 Encana, 2005 Enervest Riverton Compressor 6.0 Peak Energy, 2005 Total 90 Emissions for the minor NO x and VOC wellhead processes are estimated for a total of 472 wells on the Wind River Reservation; 212 gas wells and 260 oil wells. Emissions for the wellhead processes associated with both oil and gas wells are shown in Table The WYOGCC database indicates that all 472 wells are on the portion of the Wind River Reservation that coincides with Fremont County. To eliminate emissions on the Wind River Reservation from the State inventory, the total emissions determined for the Wind River Reservation for each of the minor NO x and VOC processes must be subtracted from Fremont County emissions reported in the State of Wyoming inventory. Table Emissions From Minor NO x and VOC Wellhead Processes on the Wind River Reservation Gas Wells VOC NO x CO tons Total 3, Flashing & Standing/Working/Breathing Dehydration Unit 1, Heater Pneumatic Devices Completion: Flaring and Venting 1,

26 Table Emissions From Minor NO x and VOC Wellhead Processes on the Wind River Reservation (Continued) Oil Wells VOC NO x CO tons Total Flashing & Standing/Working/Breathing Heater Pneumatic Devices Emissions <Under development.> 2-16

27 3.0 COLVILLE RESERVATION The Confederated Tribes of the Colville Reservation are located on a reservation in northcentral Washington that encompasses approximately 1.4 million acres. The Colville Reservation is occupied by over 5,000 residents, both Colville tribal members and their families and other non-colville members, living either in small communities or in rural settings. This section discusses the results of the point source emission inventory development effort for the Colville Tribe for There are no oil and gas sources located on this reservation, and no further discussion of this source category is presented here. A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Point Sources Methodology There was no existing emissions inventory for this reservation to consult prior to initiation of this project. Therefore, in order to identify potential point sources, ERG contacted Byron Woods (Air Resource Specialist - Confederated Tribes of the Colville Reservation) and interviewed him by telephone. Mr. Woods indicated there were two Title V sources located on the reservation, and was unaware of any other potential point sources meeting the selection criteria. ERG reviewed with him the list of facilities identified on the Colville Tribal Enterprise Corporation website ( and with the exception of the Title V facilities, found no sources of interest (Woods, 2005). As noted above, there are two Title V sources located on this reservation that have been included in this inventory - Colville Indian Power and Veneer (CIPV) and Colville Indian Precision Pine (CIPP). ERG contacted EPA Region 10 staff in an effort to obtain 2002 emissions inventory data for these facilities (Flood, 2005). Unfortunately, 2002 emissions data was not available but EPA was able to provide 2003 emissions information. The 2003 emissions data was reviewed to ensure the correct emission factors and emission estimation approaches were used, and in the absence of data for 2002, this information was used to develop the point source inventory for the Colville Reservation. Results ERG compiled the point source information for the two Title V sources present on this reservation into the NIF format, and this data has been loaded into WRAP s EDMS database. Table 3-1 presents a summary of emissions from these facilities. 3-1

28 Table 3-1. Point Sources Emissions for the Colville Reservation (tpy) Plant Name CO NO x PM-10 PM SO 2 VOC Colville Indian Precision Pine Colville Indian Power and Veneer Emissions <Under development.> 3-2

29 4.0 CONFEDERATE TRIBES OF THE WARM SPRINGS RESERVATION The Confederated Tribes of the Warm Springs Reservation is located in central Oregon and encompasses approximately 650,000 acres. The Confederated Tribes of the Warm Springs Reservation is occupied by nearly 4,000 members of the Warm Springs, Wasco, and Paiute tribes. This section discusses the results of the point source emission inventory development effort for the Warm Springs Reservation for There are no oil and gas sources located on this reservation, and no further discussion of this source category is presented here. A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Point Sources Methodology There was no existing emissions inventory for this reservation to consult prior to initiation of this project. Therefore, in order to identify potential point sources, ERG contacted Gerry Shipps (Air Resource Specialist - Confederated Tribes of the Warm Springs Reservation) and interviewed him by telephone. Mr. Shipps indicated there was one Title V source located on the reservation, and was unaware of any other potential point sources meeting the selection criteria (Shipps, 2005). ERG reviewed with him the list of facilities identified on the Business Directory section of the Warm Springs website ( and with the exception of the Title V facility, found no sources of interest. As noted above, there is one Title V source located on this reservation - Warm Springs Forest Products (WSPF). Based on a recommendation from Mr. Shipps, ERG contacted EPA Region 10 staff in an effort to obtain 2002 emissions inventory data for this facility as their Title V permit is currently being prepared by Region 10. Unfortunately, EPA did not have any data for this facility in their records (Flood, 2005). At this point, ERG again consulted with Mr. Shipps who suggested ERG contact the source directly. ERG was able to talk with Darrel Kelly at WSPF, but Mr. Kelly had concerns about providing the 2002 data for this project. After consultation with Mr. Shipps, Mr. Kelly agreed to provide assistance for this effort, but ultimately Mr. Kelly did not have the information available in a format suitable for this project (Kelly, 2005). WSPF is currently attempting to permit an additional unit for their facility, and was unable to devote sufficient resources to this project in order to track down and compile a complete inventory for However, it should be noted that once their Title V permit is issued, WSPF will be required to submit a comprehensive annual emissions inventory, at which time their data should be available to add to the WRAP emissions inventory. 4-1

30 Emissions <Under development.> 4-2

31 5.0 NAVAJO NATION The Navajo Nation is located on a reservation that encompasses 14.2 million acres in the "Four Corners" region and includes lands in Arizona, Utah, and New Mexico. This section discusses the results of the point source and oil and gas emission inventory development effort for the Navajo Nation for The point source component is discussed first, followed by the oil and gas source component. A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Point Sources Methodology There was no existing emissions inventory for this reservation to consult prior to initiation of this project. Therefore, in order to identify potential point sources, ERG contacted Iris Shirley (Senior Environmental Specialist, Navajo Nation) and interviewed her by telephone. Ms. Shirley indicated there were fourteen Title V source located on the reservation, and that there were numerous other fuel-burning sources that might be of interest (Shirley, 2005). Ms. Shirley provided ERG with various literature and background information from which data collection and further inquiries were made. Subsequently, data for estimating the point source emissions for Navajo Nation for the year 2002 were collected from a variety of sources, including Navajo Tribal Utility Authority (NTUA) (NTUA 2005a; NTUA 2005b), telephone interviews with all the major hospitals on the Navajo Reservation, the Navajo Oil and Gas Company (NOGC, 2005), and a telephone interview with Diné College plant operations and maintenance personnel (Dine, 2005). Maintenance staff at 11 hospitals within the Navajo reservation and Diné College at Window Rock were interviewed to collect data about fuel usage, fuel types used and facility heating equipment. The findings from this data collection effort indicated that a majority of these facilities use natural gas as the primary fuel. Diesel fuel and liquefied propane gas (LPG) is also being used by these facilities, but in very small quantities. Based on the estimates of fuel quantities consumed by these sources, it was determined that emissions were well below the cutoff point for inclusion in the point source inventory. Table 5-1 contains a listing of the sources/facilities considered in the data collection effort. 5-1

32 Table 5-1. Data Sources for Navajo Nation (tpy) Site No. Facility Name Fuel Types Used 1 Navajo Tribal Utility Authority Natural Gas 2 Navajo Oil and Gas Company Diesel Fuel 3 Diné College Window Rock Campus Natural Gas and Diesel Fuel 4 Diné College Shiprock Campus Natural Gas 5 Chinle Hospital Natural Gas and Diesel Fuel 6 Crownpoint Healthcare Facility Natural Gas and LPG 7 Fort Defiance Indian Hospital Natural Gas and Diesel Fuel 8 Gallup Indian Medical Center Facility not within Navajo reservation 9 Inscription House Health center No response 10 Kayenta Health Center LPG 11 Northern Navajo Medical Center Natural Gas and Diesel Fuel 12 Sage Memorial Hospital Natural Gas 13 Tsaile Health Center Propane 14 Tuba City Indian Medical Center LPG and Diesel Fuel 15 Winslow Indian Health Center No heating equipment in use Commercial, industrial, institutional, and public buildings natural gas usage data was obtained from the NTUA for nearly 650 discrete units (many facilities have more than one unit). Emissions from none of these types of facilities were above the NO x and SO x cut-off level for inclusion in the point source inventory, and therefore these sources are considered area sources. Telephone conversations with Navajo Oil and Gas company s tribal affairs coordinator revealed that an overwhelming majority of their consumers were gas service stations, which are not classified as point sources for the purpose of this inventory since they do not typically have any combustion equipment and emit primarily volatile organic compounds (VOC). Furthermore, none of Navajo Oil and Gas company's other consumers use fuel in such a quantity so as to emit more than or equal to the cut-off level for inclusion in the point source inventory. During the data collection process, ERG made efforts to collect propane and LPG sales data from distributors such as Ferrelgas, Amerigas and Chief Propane. During telephone conversations with the appropriate supervisor/coordinator for these distributors, it was learned that none of these distributors actually had any fuel refineries or production facilities physically located within the Navajo reservation that would require large, on-site combustion units. Another major finding was that most of their consumers were residential consumers and individual farm owners who would not be expected to have emissions at sufficient levels for them to be categorized as point sources. Results ITEP compiled the point source information for thirteen of the Title V sources present on this reservation into the NIF format, and supplied that information to ERG in May of Emissions data for the Four Corners Steam Electric Station and Navajo Generating Station were 5-2

33 not included as part of this project since accurate data for these facilities has already been entered into EPA s draft 2002 NEI, and therefore in to WRAP s EDMS database as well. Subsequently, ERG loaded the data for the thirteen Title V sources into WRAP s EDMS database. Table 5-2 presents a summary of emissions from these thirteen facilities. Emissions from the Four Corners Generating Station (Farmington, New Mexico) and the Navajo Generating Station (Page, Arizona) are also included in this table in order to show emissions from all Title V sources located on the Navajo reservation. Table 5-2. Point Sources Emissions for Navajo Nation (tpy) Plant Name CO NO x PM-10 PM SO 2 VOC Texaco Aneth Tank Battery 21 & Recycle Facility El Paso Natural Gas, Gallup Compressor Station El Paso Natural Gas, White Rock Compressor Station El Paso Natural Gas, Window Rock Compressor Station ExxonMobile, McElmo Creek Plant Conoco Wingate Fractionating Plant Transwestern Pipeline Co., Leupp Compressor Station # Transwestern Pipeline Co., Compressor Station No. 4 - Klagetoh ChevronTexaco, Aneth Natural Gas Processing Plant El Paso Natural Gas, Dilkon Compressor Station 95 2 El Paso Natural Gas, Leupp Compressor Station El Paso Natural Gas, Navajo Compressor Station 388 Peabody Western Coal Company, Black Mesa Complex Four Corners Generating Station 2,414 41,577 3,506 32, Navajo Generating Station 2,091 35,569 4,099 4, In addition to the Title V data, ERG has calculated emission estimates for the minor, or area sources, obtained from the NTUA although this information has not been entered into the WRAP EDMS database. Attachment A contains detailed emission estimates for these minor sources, and Table 5-3 presents a summary of the emissions from these sources in aggregate. 5-3

34 Table 5-3. Area Source Emissions for Natural Gas Combustion for Navajo Nation (tpy) Plant Name CO NO x PM-10 PM SO 2 VOC (Multiple Facilities) Oil and Gas Sources This section describes the base year 2002 emission inventory of oil and gas area sources for the Navajo Nation. The focus of this inventory effort was to estimate emissions of nitrous oxides (NO x ) from oil and gas production operations. In a related project to address point and area source emissions led by the WRAP Stationary Sources Joint Forum (SSJF), major NO x sources in the oil and gas industry were identified and methodologies defined for estimating emissions from those sources. The major NO x sources were identified as: drill rigs, gas compressor engines, and coal bed methane (CBM) pump engines. Minor NO x and VOC wellhead processes for which emission factors are available were also identified. The methods employed to estimate emissions from these sources on the Navajo Nation are based on those developed for the SSJF project. A complete discussion of these methods and the oil and gas emissions inventory produced for the Navajo Nation are presented in this section. Area Sources Oil and Gas Methodology Drill Rigs. The approach used to estimate emissions from drill rig engines was to combine activity data from drilling permits with emissions data from a survey of drill rig operators. The Minerals Department of the Navajo Nation was contacted to obtain well production and drilling permit data. The department responded that such information was not available to the public and would not be made available for this effort. However, the department referred us to the data maintained by the BLM or the states, which the department believes to be accurate and in fact sometimes uses for its own purposes (NNMD, 2005). Drilling permits for the Navajo Nation might be found in the data from the State of New Mexico, the State of Arizona or the State of Utah. Drilling permit data from all three States had been previously requested for the related inventory being conducted by the WRAP SSJF. The data they provided were analyzed to determine what portion of the data was applicable to operations on the Navajo Nation. The Arizona Geological Society reported that no wells were drilled in the State of Arizona in 2002 (AZGS, 2005). In contrast, many wells were drilled in the State of Utah and well permit data for each of those wells was obtained from the Utah Division of Oil Gas and Mining (UTDOGM, 2005). There was also a large amount of drilling activity in the State of New Mexico. However, when the New Mexico Oil Conservation Division (NMOCD) was contacted to obtain, amid other information, the activity data afforded by drill permits, the agency refused to provide the data. Although the NMOCD did not directly provide the data, we were able to obtain the necessary information with considerable assistance from the New Mexico Environmental Department (NMED). The NMED obtained a copy of the master well database maintained by the NMOCD and provided both the original database and filtered well production 5-4

35 information for use in this and the SSJF inventory efforts (NMED, 2005). The drilling information obtained is as follows: Spud date - the date that drilling commenced Well depth - the depth of the well; total vertical, measured or target depending on availability Completion date - the date well preparation is finalized; occurring with some delay after drilling ceases Well formation - the geologic structure that the well was drilled to Well field - the legal designation for the area where the well was drilled Well county - the county where the well was drilled; for allocation purposes Well coordinates - latitude and longitude of the well While the NMOCD database contained all these fields, every field was not completed for every well. The absence of this information required that some assumptions be made about the duration of drilling. Those assumptions are documented later in this section. The NMOCD database contains drill permit data for the entire State of New Mexico, as represented by the geographic boundaries of the State. That this data contained the activity on the Navajo Nation was confirmed by plotting the locations of drill permits against a map of the Navajo Nation. Figure 5-1 shows the location of New Mexico well drilling plotted against the boundaries of the Navajo Nation. 5-5

36 Figure 5-1. Location of Drilling Activity on the New Mexico Portion of the Navajo Nation Drill permits applicable to the Navajo Nation were thus selected from the total set of NMOCD drill permit data using GIS software to plot the drill permit locations and then extract only those wells shown to be drilled on the Navajo lands. One additional step was made to improve the accuracy of this selection process. It was observed that many wells in the NMOCD database were missing geographic coordinates. Therefore, it was possible that by simply plotting wells based on geographic coordinates, some wells would be omitted. This problem was solved by using the Public Land Survey System location information to supplement the geographic coordinates. If a well did not have geographic coordinates in the NMOCD database, then it was assigned the coordinates of the center point of the Township-Range in which was drilled. Because the Township-Range data was much more complete, by this process a geographic coordinate was obtained for nearly all wells. Figure 5-2 shows the Navajo Nation overlaid by the Township-Range grid. From the picture it is clear that assigning wells the center point coordinates was a fair predictor of whether a well with no spatial coordinates in the database was drilled on the Navajo Nation. 5-6

37 Figure 5-2. Navajo Nation Overlaid with the Public Land Survey System Grid The drill permit data provided by the Utah DOGM included geographic coordinates for every drill permit. It was thus a relatively simple matter to plot the wells drilled in the State of Utah and determine if any wells were drilled on the Utah portion of the Navajo Nation. As shown in Figure 5-3, there were no wells drilled on the Utah portion of the Navajo Nation in Thus, the entire selection of wells drilled on the Navajo Nation in 2002 was obtained from the NMOCD data. 5-7

38 Figure 5-3. Location of Drilling Activity on the Utah Portion of the Navajo Nation The NMOCD drill permit data provided the base level of activity to characterize the number of wells being drilled in an area, the depth of those wells and the amount of time required to construct the wells. What was also needed was information about the drill rigs that could be used to tie this information about the characteristics of the well being drilled to emissions from drill rig engines. Fortunately, using the results of a recent Wyoming Department of Environmental Quality (DEQ) survey of drilling in the Jonah-Pinedale area of Southwest Wyoming it was possible to derive the necessary relationship. The Jonah-Pinedale area has seen particularly intense drilling activity in recent years and the information provided represents the synthesis of emissions estimates made by ten different drilling companies for a total of 218 wells drilled. The emission factors derived from the WYDEQ (2005) survey are 13.5 tons NO x per well and 3.3 tons SO 2 per well. The emissions from the prime mover on a drill rig for drilling a well are dependent upon the depth of the well, the composition of substrate and the characteristics of the engine. For example, a small rig drilling a relatively shallow well in the Powder River Basin would have different emissions than a large rig drilling a deep well in the Jonah-Pinedale area. Because of this variation in drilling operations, it would not be appropriate to use the same Jonah-Pinedale emission factor for wells drilled on the Navajo Nation without making some adjustments. To reflect this fact, we 5-8

39 employed a methodology developed by the SSJF project that uses information about the characteristics of wells in a specific area to scale the Jonah-Pinedale emission factor for drilling operations in that area. The most specific unit for which well characteristics were available was the formation. Creating formation-specific emission factors offers a good degree of accuracy because the well depths and substrate encountered when drilling the same formation should be consistent. Using the methodology developed in the SSJF project, the emissions from the drilling of all wells in one formation are estimated using the average duration of well preparation activities and average well depth within the formation. In addition to the assumption that the depth and duration of drilling activities for wells in a single formation are approximated by the average for the formation, two other important assumptions are inherent to this method. First, it is assumed that the difference between the completion date and the date that drilling ceased is, on average, constant relative to the total duration of preparation activities. This assumption was needed because the actual date that drilling ceased was not available. What this assumption means is that if on average wells with 100 days between spud date and completion actually had a duration of drilling of only 80 days, then on average wells with 50 days between spud date and completion would have 40 days of actual drilling. It was also necessary to assume that the capacity of the equipment used to drill a well is dependent upon the depth of the well. This assumption was made because the data clearly indicated that substantially different rigs were employed in different drilling applications. Some wells in the Powder River Basin had the same approximate drilling duration as wells in Jonah- Pinedale. It was therefore assumed that the capacity of the prime mover would grow proportional to the depth of the well. With those two assumptions, it is then possible to scale the emission factor from the Jonah-Pinedale area to other formations based on the average well depth and drilling duration and in doing so to correct for variations due to well depth, composition of substrate, and engine capacity. To scale the Jonah-Pinedale emission factor to the formations found on the Navajo Nation the average well depth and duration was calculated for each formation for which data was available. The average depths and durations determined for the formations of the Navajo Nation are shown in Table 5-4. Table 5-4. The Average Depth and Duration of Drilling on the Navajo Nation by Formation Formation Average Well Depth (Ft) Average Drilling Duration (Days) Basin Fruitland Coal (Gas) 1, Gallegos Fruitland Sand Pc, S. Gas 1, Kutz Pictured Cliffs, West (Gas) 1, Twin Mounds Fruitland Sand Pc (Gas) Waw Fruitland Sand Pc (Gas) 1,

40 The vast majority of wells drilled in Jonah-Pinedale were drilled to the Lance or Lance- Mesaverde formation. The average well depth and drilling duration for those formations - based on drill permit data obtained from the Wyoming OGC for 2002 and was 11,896 ft and 80.6 days (WYOGCC 2005). Based on this information for Jonah-Pinedale and the data for the Navajo Nation shown in Table 5-4, formation-specific emission factors were created using Calculation 5-1. Calculation 5-1: EF A = EF J x ( D A / D J ) x ( T A / T J ) Where: EF A = The emission factor for another formation EF J = The Jonah-Pinedale emission factor D A = The average depth of wells drilled in another area Dj = The average depth of wells drilled in Jonah-Pinedale T A = The duration of drilling in another area = The duration of drilling in Jonah-Pinedale T j Emissions for a single formation were then calculated using Calculation 5-2. The emissions for the formations were then summed to determine the total emissions from drill rigs operating on the Navajo Nation. Once emissions were estimated, one final adjustment was made to account for varying nonroad fuel sulfur levels. Because the emission factor for SO 2 was based on fuel sulfur levels in the State of Wyoming. SO 2 emissions from drill rigs operating anywhere in the State of New Mexico, including the Navajo Nation need to be adjusted to correspond to nonroad fuel sulfur levels in the State of New Mexico. This adjustment was accomplished my multiplying the total SO 2 emission by the ratio of the New Mexico fuel sulfur level to the Wyoming fuel sulfur level. That ratio is 0.24 to 0.27 (Sierra Research, 2004). Calculation 5-2: E = EF x W Where: E = The 2002 emission for a given formation EF = The formation specific emission factor W = The number of wells drilled in the formation in

41 Coal Bed Methane Pump Engines. Emissions from coal bed methane (CBM) pump engines operating on the Navajo lands were determined by first estimating engine activity based on water production and then combining that activity with an emission factor for natural gas fired engines. The water production at CBM wells that is required for this calculation was obtained from the oil and gas production database maintained by the New Mexico Oil Conservation Division and provided for use in this study by the New Mexico Environmental Department (NMED, 2005). The emission factor for gas fired engines was obtained from EPA s NONROAD2004 model. The well production data included the oil, gas, and water production, the API number, well location and the producing pool for all wells in the State of New Mexico. As in the case of the drilling data, it was necessary to assign coordinates to some wells based on the Public Land Survey System location information. After assigning geographic coordinates to the wells obtained from the NMOCD database, the well locations were then plotted against the boundaries of the Navajo Nation to determine which wells were located on Navajo lands. The resulting plot is shown in Figure 5-4. Note that Figure 5-4 includes not only CBM wells, but also conventional oil and gas wells. Figure 5-4. Oil, Gas and CBM Wells in the NMOCD Databases Plotted Against the Boundaries of the Navajo Nation 5-11

42 To estimate the activity of CBM engines required isolating only CBM wells. This was accomplished based on the producing pool identifier provided in the NMOCD data. Wells producing from BASIN FRUITLAND COAL (GAS) were identified as CBM wells. Having isolated the water production at CBM wells it was then possible to estimate the activity of pump engines. Engine activity was determined for each well by first determining the water power developed by the dewatering pump. Using an assumption of the pump s efficiency it was then possible to determine the power that must be supplied to the pump. Assuming that losses in the electrical delivery system are negligible, the power supplied to the pump is the same as the power produced by the generator. Then, by estimating the efficiency of the generator system at converting the power at the engine flywheel to electrical power it was possible to estimate the horsepower-hours of the engine. The complete list of assumptions used for this calculation are presented in Table 5-5. A simple diagram of the assumed pumping system that results from this information is provided in Figure 5-5. Table 5-5. Assumptions Used in Developing the CBM Generator Emissions Estimate Assumption Reason Pump efficiency = 0.6 Industry provided estimate (Olson, 2004). Generator efficiency = 0.85 Estimate based on small size of engines. Downhole pressure contribution is negligible Simplification necessary due to lack of data. This leads to a slightly conservative estimate. Power delivered the pump is exactly equal to the The power in lifting the water is undoubtedly much power required to lift water over the depth of the greater than any of the other components. No data well and overcome frictional losses. Minor losses available on minor losses and exit velocity. (joints, flanges, etc...) and exit velocity are assumed to be negligible Diameter of pipe that conducts water to surface is Wyoming OGC provided estimate (Strong, 2005) 0.2 ft Pipe roughness of drawn/plastic tubing (5 x 10-6 ft) Industry contact stated majority of piping is 8760 hours of engine operation and 4380 hours of pumping per year fiberglass (Weatherford, 2005) Industry representative indicated that much of the time the engine is operating, but no water is being pumped (Gantner, 2005). 5-12

43 Figure 5-5. Diagram of Assumed CBM Well With the assumption that minor losses from joints in the pipe or other inconsistencies in the system are negligible and that the exit velocity at the top of the pipe is near zero, then the power imparted to the water by the pump is equal to the power required to overcome the elevation difference and the frictional losses (the energy lost to heat and turbulence at the pipe-water interface). The equation that describes this relationship is shown in Calculation 5-3. Calculation 5-3: H = d + P H L Where: H P = the energy imparted by the pump d = the depth of the wells HL = frictional losses H L is somewhat difficult to calculate due to the dependence of the calculation method on the flowrate. For the same pipe under a certain threshold flowrate, the flow is laminar and it is a 5-13

44 simple matter to determine the frictional loss using the Darcy-Weisbach equation. However, above that threshold flowrate for the same pipe, the flow becomes turbulent and there are several possible methods of estimating the frictional loss. In this study, we have used the Hazen- Williams equation to estimate frictional losses for flowrates that imply a Reynolds Number above 3000 (see Calculation 5-4). Calculation 5-4: Method for calculating the frictional losses (H L ) R = D V ν Where: R = The Reynolds number D = The diameter of the pipe V = The velocity of flow (flowrate divided by cross-sectional area of pipe) ν = The kinematic viscosity of water (assumed = 1.0) If R < 3000 then, 2 L V H L = f (the Darcy-Weisbach equation) D 2g Where: L = The length of pipe D = The diameter of pipe V = The velocity of flow g = The acceleration of gravity and with f 64 = R Else if R > 3000, H L 1.85 = V L (the Hazen-Williams equation) ( C H ) R Where: V = The velocity of flow L = The length of pipe R = The hydraulic radius (cross-sectional area of pipe divided by the wetted perimeter) C H = The Hazen-Williams coefficient, 140 for plastics 5-14

45 The flowrate itself was not a trivial matter to estimate. The information obtained from the NMOCD database is total annual water production. One option was to assume that flow is constant for 8760 hours per year. However, based on information provided the New Mexico Oil and Gas Association (Gantner, 2005), it was clear that pumps are frequently operating without pumping any fluid apart from gases. This would occur when the water level in the well is drawn down low enough that water needs to be pumped only intermittently. Effectively, this signifies that a portion of the time the engines are operating with a very low load when no water is being pumped and the rest of the time are operating at a load sufficient to pump water. At this time, it has not been possible to estimate the fraction of time that the pumps are actually moving water and fifty percent has been assumed. This means that fifty percent of the time engines are assumed to be idling with only ten percent of their loaded horsepower. These idling emissions, discussed below, are added to the emissions resulting from the work performed to lift water from the wells. In terms of the determination of flowrates, this 50 percent operational schedule means that flowrates are determined based on the total annual water production divided by 4,380 hours per year of pumping. As shown in Calculations 5-3 and 5-4, determining the frictional loss and adding that to the depth of the well yields the energy that is imparted by the pump. Then, to determine the power of the pump we applied the equation shown in Calculation 5-5. Calculation 5-5. Determining the pump power P P = H Q γ / 550 Where: P = the power supplied by the pump (hp) H P = the energy supplied by the pump (ft) Q = the flowrate (cfs) γ = specific weight of water (62.4 lb/ft 2 ) Once the power delivered by the pump was determined, determining the power developed by the engine was a matter of applying the pump and generator efficiencies as shown in Calculation 5-6. Calculation 5-6. Determining the engine power P E = P /ε / ε P G Where: P E = the power developed by the engine (hp) P = the power delivered by the pump (hp) ε P = the efficiency of the pump (0.60) ε G = the efficiency of the generator (0.85) 5-15

46 Total annual engine activity due to pumping water at one well was estimated as the product of the power developed by the engine and 4,380 hours per year. To this activity, with units of horsepower-hours, was added the engine activity while not pumping water. Engines that are idling while no water is being pumped are assumed to operate at ten percent of their operational load. Thus, for a single well, the idling engine activity was calculated as ten percent of the pumping horsepower determined in Calculation 7 multiplied by 4,380 hours per year. The total engine activity was thus the sum of 4,380 hours of engine activity while idling plus 4,380 hours of engine activity while pumping. Emissions were then calculated as the product of total engine activity and the 12 g/hp-hr emission factor for natural gas fired engines (SCC ) provided in EPA s NONROAD2004 model. Non-Point Natural Gas Compressor Engine Emissions. For the purposes of this study, natural gas compressor engines have been grouped into three categories. The largest facilities, in terms of potential emissions, are the large natural gas compressor stations on natural gas transmission lines. These are typically Title V facilities and they are dealt with as point sources. The second tier of facilities is the gas gathering compressor station. These medium-sized facilities are included in the area source inventory for the Navajo Nation and are discussed in following subsection. The final category of compressor engines, which is the primary focus of this area source compressor engine emission estimate, is the group of relatively small, dispersed wellhead compressor engines. Figure 5-6 presents an example of such an engine. The methodology used to estimate emissions from these engines is presented in this subsection. Figure 5-6. Wellhead Compressor Engine 5-16

47 A methodology to estimate emissions from wellhead compressor engines was developed by ENVIRON for the WRAP SSJF project. In that project a production-based emission factor was derived from local studies of compressor engine emissions. This emission factor was then combined with county level gas production to estimate emissions. For the Navajo Nation, emissions were determined by combining the production-based emission factor with total gas production on the Navajo Nation, as reported in well production data obtained from the Utah Department of Oil, Gas and Mining (UTDOGM, 2005), the Arizona Geological Survey (AZGS, 2005) and New Mexico Tech s GO-TECH website (NMT, 2005). The emission factor is derived from a study conducted by the New Mexico Oil and Gas Association (NMOGA, 2003). In this study NMOGA compiled an emissions inventory of the unpermitted compressor engines operated by the oil and gas production industry in the New Mexico portion of the San Juan Basin. In the State of New Mexico, the threshold for permitting reported by the New Mexico Environmental Department was a potential to emit 25 tons per year (NMED, 2005b). Thus, the inventory of unpermitted sources included those sources with a potential to emit less than 25 tons per year. The small wellhead compressor engines fall into this category. The NMOGA inventory provided emissions for wellhead compressor engines, which were compared to production statistics for the San Juan Basin to derive an emission factor with units of tons NO x per MCF of gas produced. The result is an emission factor of 2.34x10-5 tons NO x per MCF gas produced. We had previously obtained oil and gas production statistics for the State of New Mexico in the form of a database maintained by the New Mexico Oil Conservation division. Production data was also downloaded from the New Mexico Tech GO-TECH website. The production data obtained from the NMT website was preferred for two reasons. First, the data appeared to be better maintained on the NMT website than in the OCD database. Second, the NMT data is easily accessible by the public, where the NMOCD data was obtained only with assistance from the New Mexico Environmental Department. The NMT data did not include the location information necessary to determine which wells were located on Navajo lands. Instead, well location information was obtained from the NMOCD database. It was possible assign location information present in the NMOCD database to wells in the NMT database based on the API number that identifies wells in both databases. As described in the discussion of the drill rig emissions methodology, it was necessary to assign some wells the geographic coordinates of the Township-Range in which they were located when coordinates were not explicitly stated in the NMOCD database. The wells obtained from the NMT database were plotted with the coordinates derived from the NMOCD database. The same was done for the well data obtained from the Utah DOGM. The Utah data included geographic coordinates for all wells, so it was not necessary to go through the intermediate step of assigning coordinates based on Township-Range locations. GIS software was then used to determine which of the wells in the Utah and New Mexico databases were on the Navajo Nation. All wells submitted by the Arizona Geological Survey were added to the Navajo Nation. The Arizona Geological Survey reported that all wells in the State of Arizona were found on the 5-17

48 Navajo Nation and plotting the well locations confirmed that assertion. Thus the complete set of wells on the Navajo Nation was determined as the subset of Utah and New Mexico wells with coordinates placing them on the Navajo Nation and all Arizona wells. The total oil and gas production determined for wells on the Navajo Nation is presented in Table 5-6. Emissions from compressor engines were estimated as the product of the total gas production and the productionbased emission factor. Before determining production on the Navajo Nation using the state production databases, we had first contacted the Navajo Nation Minerals Department to obtain well production data for use in this and other portions of the inventory. Though the department was unable to provide data for this effort, the production data that was ultimately obtained from the state databases was submitted to the department for review. Both the maps of well locations created and the production totals for oil and gas wells on the Navajo Nation were submitted to the Minerals Department for review. The Department responded that the map of well locations appeared to accurately depict oil and gas development on the Navajo Nation (NNMD, 2005). Also, the production figures developed, presented in Table 5-6, were reported to be within the expected range for total production on the Navajo Nation. The Department cannot be sure of the exact production totals because some wells on Navajo Nation lands actually produce from federal mineral rights and are not required to report production to the tribe (NNMD, 2005b). Table 5-6. Oil and Gas Production on the Navajo Nation Number of Wells Oil Production (BBL) Gas Production (MCF) 1,572 5,162,770 24,162,522 Medium-Size Facilities. The production-based emission factor developed from the NMOGA inventory of unpermitted compressor engines in the San Juan Basin is only useful for estimating emissions from compression facilities with a potential to emit less than 25 tons per year. This is due to the nature of the inventory and the permitting requirements in the State of New Mexico. In order to be unpermitted, the compressor engines in the study must have had a potential to emit less than 25 tons NO x per year. Thus by applying the emission factor derived from the NMOGA inventory to gas production we estimated emissions for only those compressor engines on the Navajo Nation that have a potential to emit less than 25 tons per year. Additional emissions for very large compressor facilities are addressed in the point source emissions inventory. Emissions for a final set of medium-sized facilities - facilities with a potential to emit greater than 25 tons per year, but less than 100 tons per year - represent a small portion of total oil and gas emissions. However, the Navajo Nation oil and gas inventory would not have been complete without incorporating emissions from this group of facilities. The Navajo Nation Air Quality Program reported that facilities that fall below Title V permitting thresholds had not been previously inventoried and are not permitted (NNAQP, 2005). Thus there was no existing data for these medium-size facilities. A similar lack of data was encountered in some states in the related SSJF project. To estimate emissions from these facilities a method was developed that utilizes gas production data. By this method the subset of point source facilities are selected from the New Mexico point source inventory that have a 5-18

49 potential to emit between 25 and 100 tons per year. Emissions from those facilities are then related to New Mexico gas production and scaled based on gas production to describe emissions from similar facilities on the Navajo Nation. Using the information in the New Mexico point source emissions inventory, it was possible to separate the oil and gas facilities having a PTE between 25 tons per year and 100 tons per year into two categories: gas compression and gas processing. The total emissions in each of these categories were then summed to determine the State total emissions. By dividing those totals by the State total gas production we arrived at the production-based emission factors shown in Table 5-7. Table 5-7. Emissions for New Mexico Natural Gas Facilities with a PTE Between 25 and 100 tpy Type of Facility Gas Processing Gas Transmission Total Emissions (tons NO x ) 2,715 4,195 Total Gas Production (MCF) 1,624,225,738 Emission Factor (ton NO x /MCF) 1.67x x10-6 By combining the emission factors in Table 5-7 with the total gas production on the Navajo Nation, we estimated emissions for the medium-sized gas processing and transmission facilities on Navajo lands. Minor NO x and VOC Wellhead Processes. In addition to the area sources identified as potentially major sources of NO x emissions, we have estimated emissions for several other processes occurring at oil and gas wellheads. Emissions were estimated for both NO x and VOC using well-specific production and emission factors provided by the Wyoming Department of Environmental Quality. The sources for which emissions were estimated in this portion of the inventory and the emission factors used are listed in Table 5-8. Table 5-8. Wyoming DEQ Emission Factors for Minor NO x and VOC Wellhead Processes a Gas Wells Emission Factor Oil Wells Source Emission Factor Condensate Tanks 3,271 lbs VOC per year/bpd Heater lbs NO x per barrel Dehydrator 27,485 lbs per year/mmcfd Pneumatic Devices 0.1 tons VOC / well lbs VOC per year / Heater 1,752.0 lbs NO x per year/well Tanks BPD 86.0 tons VOC/well completion Completion 1.75 tons NO x /well completion Pneumatic Devices 0.2 tons VOC per year/well a For documentation of the Wyoming DEQ emission factors, refer to Appendix A. 5-19

50 To use these emission factors, it was necessary to determine well-specific production for wells on the Navajo Nation. The source of production data and the procedure used to identify wells on the Navajo Nation was the same for the minor NO x and VOC emissions estimate as for the compressor engine estimate. Well production data obtained from the NMT online database was assigned geographic coordinates from the NMOCD database and those coordinates were plotted against the boundaries of the Navajo lands. The wells contained in the Utah DOGM database were also plotted against the tribal boundaries. Wells in the New Mexico or Utah database that plotted inside the boundaries of the tribe s lands are included in this inventory. Also included are all wells submitted by the Arizona Geological Survey. Figure 5-7 shows the resulting plot of well locations used to determine which wells were on the Navajo Nation. Figure 5-7. Oil, Gas and CBM Wells in the Arizona, New Mexico and Utah Databases Plotted Against the Boundaries of the Navajo Nation Similar to the well location information, to determine the well class and the completion date for the New Mexico wells it was necessary to extract additional data from the NMOCD database. This was done by relating the well API number provided in the NMT database to the API numbers included in the NMOCD database. In many cases the completion date was not provided 5-20

51 in the NMOCD database. It did not appear possible to obtain additional data for completion dates, and the assumption is that a blank completion date implies the well was completed some time in the past, prior to The data obtained from the AZGS and UTDOGM did not present the same obstacles. The complete list of well-specific data elements ultimately obtained for all wells on the Navajo Nation is shown in Table 5-9. Table 5-9. Well-Specific Data Required to Estimate Emissions from Minor NO x and VOC Processes on the Navajo Nation Well-Specific Data Required to Estimate Emissions from Minor NO x and VOC Processes on the Navajo Nation 2002 oil produced 2002 gas produced Well location (latitude/longitude) Well class (oil/gas) Coal bed methane (yes/no) Completion date Once obtained, the well data were separated into two categories, oil wells and gas wells, based on the identifiers extracted from the AZGS, UTDOGM and NMOCD databases. Because some of the emission factors have units of emissions per well, wells with zero oil and zero gas production and a non-2002 completion date were removed from consideration. This action prevented emissions from being estimated at wells where no activity actually occurred in The emission factors obtained from WYDEQ contained some assumptions about controls. The Navajo Nation Air Quality Program reported that the minor oil and gas sources are not permitted and the department maintains no data on the sources (NNAQP, 2005). We have therefore assumed that there are no controls applied to minor oil and gas sources. The Wyoming DEQ assumed that condensate tanks with greater than 18.3 barrels per day of condensate production would be controlled with an overall efficiency of 98 percent. For wells with condensate production less than 18.3 barrels per day WYDEQ provided an uncontrolled emission factor (see Table 5-8). Condensate tanks on the Navajo Nation are not expected to be controlled and emissions were simply estimated for all wells using the uncontrolled emission factor. The WYDEQ emission factor for completions includes the assumption that a large volume of the gas released is routed to a flare. This assumption is carried over to the Navajo Nation emissions inventory because the flaring assumed in the emission factor is not very different from the flaring we would assume based only on safety considerations. Emission factors were combined with the well data to estimate emissions following the general procedure shown in Calculation 5-7. For detailed sample calculations for each of these processes, refer to Appendix B. 5-21

52 Calculation 5-7. Calculation of wellhead emissions for individual wells Gas Well Where: Oil Well E = SUM i (P g x EF g,i ) + SUM j (Pc x EF c,j ) + SUM(EF w ) E = The 2002 emission P g = 2002 gas production EF g,i = Emission factor for gas process i P c = 2002 condensate production EF c,j = Emission factor for condensate process j EF w = Per well emission factor E = SUM i (P o x EF g,i ) + SUM(EF w ) Where: E = The 2002 emission P o = 2002 oil production EF o,i = Emission factor for oil process i EF w = Per well emission factor Area Source Oil and Gas Emissions A summary of the NO x emissions estimated for the oil and gas processes on the Navajo Nation is presented in Table Wellhead compressor engine emissions are the largest source of NO x, contributing nearly 50 percent of the area source oil and gas NO x emissions. The combined contribution of the minor NO x and VOC emissions sources contributes most of the remaining emissions. That drill rigs and CBM engines compose a very small portion of the inventory is not surprising. The relatively minor emissions from drill rigs confirms information provided by the Navajo Minerals Department that very little drilling occurred in 2002 (NNMD, 2005). The small emissions contribution from CBM pump engines is consistent with the results determined for the entire WRAP region. 5-22

53 Table Summary of 2002 NO x Emissions on the Navajo Nation Process NO x Emission (ton) Drill Rigs 7.92 Minor NO x and VOC Wellhead Processes Gas Compressor Engines CBM Pump Engines 9.43 Medium-sized Facilities Total 1, The emissions presented for the Navajo Nation have not been reconciled with emissions estimated for the State of Arizona, the State of Utah or the State of New Mexico in the related WRAP SSJF project. The following discussion of the results obtained for each emissions source includes guidance on how the area source oil and gas emissions estimated for the Navajo Nation might be reconciled with the area source oil and gas emissions estimated for the states. Emissions from drill rigs operating on the Navajo Nation are shown in Table There were 3 wells drilled on the Navajo Nation in In the project for the WRAP SSJF, these 3 wells were included in drill rig emissions estimates for the State of New Mexico. According to the locations given by the NMOCD database, the 3 wells were drilled in the part of the Navajo Nation corresponding to San Juan County, New Mexico. Reconciliation with the State emissions inventory could be achieved by reducing the emissions for San Juan County by the amount of emissions estimated for drill rigs on the Navajo Nation. Table Emissions From Drill Rigs on the Navajo Nation Wells Drilled in Total Emissions (tons) 2002 NO x SO The emissions estimated for wellhead compressor engines are presented in Table These emissions duplicate compressor engine emissions estimated for the same set of wells in the state oil and gas area source emissions inventory. In the state inventory, those wells are assigned to several different counties in three different states. The wellhead compression estimates in the two inventories can be reconciled by subtracting the wellhead compression estimated for the Navajo Nation from the total wellhead compression estimated in each of those counties. The portion to subtract from each county was determined based on the fraction of the gas production that occurred in the portion of the Navajo lands coincident with each county. Those figures are presented in Table

54 Table Emissions from Gas Compressor Engines on the Navajo Nation Number of Wells Total Gas Production (MCF) Emission Factor (tons NO x /MCF) Emission NO x (tons) 1,572 24,162, E Table Compressor Engine Emissions on Navajo Lands Double-Counted in the State Oil and Gas Inventory State County NO x (tons) AZ Apache 7.11 McKinley 0.36 NM Rio Arriba 0.79 Sandoval 2.92 San Juan UT San Juan The New Mexico Oil Conservation Division s production database contained 236 coal bed methane wells with coordinates that indicated they were on Navajo Nation lands. All 236 wells are on the portion of the Navajo Nation that coincides with San Juan County. The total water produced by the wells and the resulting emissions estimate is presented in Table In this case, the State of New Mexico and Navajo Nation inventories can be reconciled by simply subtracting the emissions estimated for these pump engines in the Navajo Nation from the emissions estimated for pump engines in San Juan County, New Mexico. Table Water Production at CBM Wells on Navajo Lands and Resultant Emissions Water Produced (bbl) Active Engine NO x Emission (ton) Total NO x Emission (ton) Idle Engine NO x Emission (ton) 881, Emissions for the minor NO x and VOC wellhead processes are estimated for a total of 1,325 wells on the Navajo Nation; 523 conventional gas wells and 802 oil wells. Emissions for the wellhead processes associated with both oil and gas wells are shown in Table Emissions for wellhead processes corresponding to these 1,325 wells were previously included in the state oil and gas emissions inventory for six different counties in three different states. To 5-24

55 eliminate emissions on the Navajo Nation from these states inventories, the emissions determined for the Navajo Nation must be subtracted from the appropriate counties in the state inventories. One method for doing so would be to subtract from each county s emissions based on the fraction of total production on the Navajo lands that occurred in the portion of Navajo lands coincident with each of the counties. The emissions determined to be double counted in each county based on such an assessment are shown for each process in Table Table Emissions from Minor NO x and VOC Wellhead Processes on the Navajo Nation Gas Wells Oil Wells VOC NO x CO Tons Total 1, Flashing & Standing/Working/Breathing Dehydration Unit Heater Pneumatic Devices Completion: Flaring and Venting Total 1, Flashing & Standing/Working/Breathing 1, Heater Pneumatic Devices

56 Table Minor NO x and VOC Wellhead Emissions on Navajo Lands Double-Counted in the State Oil and Gas Inventory Process Gas Oil Apache, AZ McKinley, NM Rio Arriba, NM VOC NOx CO VOC NOx CO VOC NOx CO F S/W/B Dehydration Heater Pneumatic Completion Total F S/W/B Heater Pneumatic Total Process Gas Oil Sandoval, NM San Juan, NM San Juan, UT VOC NOx CO VOC NOx CO VOC NOx CO F S/W/B Dehydration Heater Pneumatic Completion Total F S/W/B , Heater Pneumatic Total , Emissions <Under development.> 5-26

57 6.0 TOHONO O ODHAM NATION The Tohono O odham Nation is located on four non-contiguous reservations in south-central Arizona that encompass approximately 2.8 million acres. The Tohono O odham Nation is comprised of over 24,000 residents, with Sells as its capital and largest community. This section discusses the results of the point source emission inventory development effort for the Tohono O odham Nation for There are no oil and gas sources located on this reservation, and no further discussion of this source category is presented here. A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Point Sources Methodology There was no existing emissions inventory available for the Tohono O odham Nation. Therefore, in order to identify potential point sources, ERG contacted Cornelius Antone (Environmental Specialist - Tohono O odham Nation) and interviewed him by telephone. Mr. Antone indicated there was one Title V source located on the reservation, and there were possible sources of interest located in the San Xavier Business Park and at the Hospital in Sells (Antone, 2005). ERG contacted maintenance personnel at the Sells Hospital, and based on an estimated consumption of 60,000 gallons of propane per year, emissions from this facility are less than one ton per year of NO x (Pulshiper, 2005). Telephone interviews with the Solid Waste inspector for the Business Park as well as personnel at the Empire/Caterpillar Machinery facility indicated there were no combustion sources of interest at the San Xavier Business Park (Roscoe, 2005). As noted above, there is one Title V source located on this reservation that has been included in this inventory - the Asarco, Mission Mine Complex (Pima Mine). ITEP compiled the emissions inventory for this source based on data collected for 2002 from compliance reports submitted to EPA Region 9. Results ITEP compiled the point source information for the Asarco, Mission Mine Complex (Pima Mine) in the NIF format, and supplied that information to ERG in April of Subsequently, ERG loaded this data into WRAP s EDMS database. Table 6-1 presents a summary of emissions from this facility. 6-1

58 Table 6-1. Point Sources Emissions for (tpy) Plant Name CO NO x PM-10 PM SO 2 VOC Asarco, Mission Mine Complex - San Xavier (AKA Pima Mine) Emissions <Under development.> 6-2

59 7.0 UTE MOUNTAIN UTE The Ute Mountain Ute Reservation is located in Colorado, Utah, and New Mexico and encompasses approximately 570,000 acres. This section discusses the results of the oil and gas emission inventory development effort for the Ute Mountain Ute Reservation for A placeholder has been included to discuss projected emissions for the year 2018 (currently under development) Emissions Oil and Gas Sources This section describes the base year 2002 emission inventory of oil and gas area sources for the Ute Mt Ute tribal lands. The focus of this inventory effort was to estimate emissions of nitrous oxides (NO x ) from oil and gas production operations. In a related project to address point and area source emissions led by the WRAP Stationary Sources Joint Forum (SSJF), major NO x sources in the oil and gas industry were identified and methodologies defined for estimating emissions from those sources. The major NO x sources were identified as: drill rigs, gas compressor engines, and coal bed methane (CBM) pump engines. Minor NO x and VOC wellhead processes for which emission factors are available were also identified. The methods employed to estimate emissions from these sources on the Ute Mt Ute lands are based on those developed for the SSJF project. Modifications to those methods have been made to accommodate the sources of data that were specific to the Ute Mt Ute lands. A complete discussion of these methods and the oil and gas emissions inventory produced for the Ute Mt Ute lands are presented in this section. Area Source Oil and Gas Methodology Drilling Rigs. The approach used to estimate emissions from drill rig engines was to combine activity data from drilling permits with emissions data from a survey of drill rig operators. Efforts were made to obtain both drilling and production data from the Ute Mt Ute Energy Department, but the department declined to provide any information beyond the names of the two major production companies (UMUED, 2005). Instead, drilling data was obtained from the Colorado Oil and Gas Conservation Commission (CO OGCC) and from the New Mexico Oil Conservation Commission (NMOCD). The data obtained from the state agencies was analyzed to determine what portion of drilling activity was applicable to operations on the Ute Mt Ute lands. Many wells were drilled in 2002 in the State of Colorado and the State of New Mexico. Data for the State of Colorado was obtained directly from the CO OGCC (2005). In contrast, when the New Mexico Oil Conservation Division (NMOCD) was contacted to obtain the activity data afforded by drill permits, the agency refused to provide the data. Although the NMOCD did not directly provide the data, we were able to obtain the necessary information with considerable assistance from the New Mexico Environmental Department (NMED). The NMED obtained a copy of the master well database maintained by the NMOCD and provided both the original 7-1

60 database and filtered well production information for use in this and the SSJF inventory efforts (NM ED, 2005). The drilling information that was ultimately obtained for both Colorado and New Mexico is as follows: Spud date - the date that drilling commenced Well depth - the depth of the well; total vertical, measured or target depending on availability Completion date - the date well preparation is finalized; occurring with some delay after drilling ceases Well formation - the geologic structure that the well was drilled to Well field - the legal designation for the area where the well was drilled Well county - the county where the well was drilled; for allocation purposes Well coordinates - latitude and longitude of the well Wells drilled on Ute Mt Ute lands were selected from the complete set of wells in each state using GIS software to plot the drill permit coordinates and then extract only those wells shown to be on the Ute Mt Ute lands. One additional step was made to improve the accuracy of this selection process. It was observed that many wells in the NMOCD database were missing geographic coordinates. Therefore, it was possible that by simply plotting wells based on geographic coordinates, some wells would be omitted. Using the Public Land Survey System location information to supplement the geographic coordinates solved this problem. If a well did not have geographic coordinates in the NMOCD database, then it was assigned the coordinates of the center point of the Township-Range in which was drilled. Because the Township-Range data was much more complete, by this process a geographic coordinate was obtained for nearly all wells. Figure 7-1 shows the results of this selection process. 7-2

61 Figure 7-1. Location of Drilling Activity on the Ute Mt Ute Lands The question that remained was whether the information provided by the state databases encompassed all drilling activity on the Ute Mt Ute lands or only some fraction of the total. Representatives of both the Ute Mt Ute Environmental Department and Energy Department were contacted to confirm the data derived from the state drilling data. The Energy Department did not provide a response and the Environmental Department was unable to obtain information on the number of wells drilled in The Environmental Department did, however, express that the state oil and gas data should generally be accurate (UMUENV, 2005). In the absence of an alternative source of drilling data, we proceeded with the data extracted from the state databases. The NMOCD database showed no wells drilled on Ute Mt Ute lands and the CO OGCC data showed only one well drilled. The CO OGCC drilling data provided the base level of activity to characterize the well drilled, the depth of the well and the amount of time required to construct the well. What was also needed was information about the drill rig that could be used to tie this information about the characteristics of the well to emissions from drill rig engines. Fortunately, using the results of a recent Wyoming Department of Environmental Quality (DEQ) survey of drilling in the Jonah-Pinedale area of Southwest Wyoming it was possible to derive the necessary relationship. 7-3