THE PENNSYLVANIA STATE UNIVERSITY SCHREYER HONORS COLLEGE JOHN AND WILLIE LEONE FAMILY DEPARTMENT OF ENERGY AND MINERAL ENGINEERING

Transcription

1 THE PENNSYLVANIA STATE UNIVERSITY SCHREYER HONORS COLLEGE JOHN AND WILLIE LEONE FAMILY DEPARTMENT OF ENERGY AND MINERAL ENGINEERING REDUCING FRESHWATER CONSUMPTION IN THE MARCELLUS SHALE PLAY BY RECYCLING FLOWBACK WITH ABANDONED MINE DRAINAGE MICHAEL CAVAZZA SPRING 2016 A thesis submitted in partial fulfillment of the requirements for a baccalaureate degree in Petroleum and Natural Gas Engineering with honors in Petroleum and Natural Gas Engineering Reviewed and approved* by the following: Li Li Associate Professor of Petroleum and Natural Gas Engineering Thesis Supervisor Turgay Ertekin Professor of Petroleum and Natural Gas Engineering Honors Adviser * Signatures are on file in the Schreyer Honors College.

2 i ABSTRACT The amount of freshwater consumed during development of the Marcellus shale play can be reduced by recycling flowback with an impaired water source: abandoned mine drainage (AMD). To use AMD in hydraulic fracturing, the high sulfate concentrations typical in AMD must be reduced to a level that it is compatible with formation fluid (<100 mg/l). Sulfate levels in the AMD can be reduced by mixing AMD with flowback fluid, which is high in metals ions such as barium and strontium, through barite and celestite precipitation. By utilizing this process, companies operating in the Marcellus shale can contribute to a cleaner Pennsylvania by reducing stream impairment from AMD and reducing freshwater consumption. The main objectives of this study were: (1) characterize AMD discharges and flowback, (2) mix AMD and flowback at various ratios to develop long-term kinetic data (2 weeks) and determine removal efficiency for sulfate, barium, radium and strontium. Eight AMD discharges of varying compositions located across the state and two recently hydraulically fractured wells in southwest PA were sampled and evaluated. Characterization included ph, alkalinity, flow rates, total and dissolved metals and sulfate. Kinetic tests showed that precipitation occurs quickly and does not continue past one day of mixing. As for removal efficiencies, barium, strontium, radium and sulfate were all removed at varying amounts. Barium and radium can be completely removed when an ample amount of sulfate is added. Sulfate can be removed completely when putting less AMD in the mixture. Strontium could only be removed up to 50%. Possible factors affecting precipitation of strontium include lack of celestite formation and the presence of organics. Results show that sulfate can be removed to level that is acceptable for hydraulic fracturing operations.

3 ii TABLE OF CONTENTS LIST OF FIGURES... iii LIST OF TABLES... iv ACKNOWLEDGEMENTS... v Chapter 1 Introduction... 1 Chapter 2 Background... 3 Abandoned Mine Drainage... 4 Flowback... 7 Naturally Occurring Radioactive Elements... 9 Locations of Drilling Activity and AMD Impaired Streams Chapter 3 Previous Studies on AMD and Flowback Water Mixing Chapter 4 Field Sampling and Characterization of AMD and Flowback Waters AMD Characterization Flowback Characterization NORM Analysis Chapter 5 AMD and Flowback Mixing Tests Extended Kinetic Testing Removal Efficiency Radium Removal Discussion of Results Sources of Error Chapter 6 Conclusions Future Work Appendix A Extended Kinetic Testing BIBLIOGRAPHY... 36

4 iii LIST OF FIGURES Figure 1: AMD Discharge (Ernest, PA)... 5 Figure 2: Stream Impairment due to AMD Discharge (Ernest, PA)... 5 Figure 3: Replacing Freshwater with AMD as a Makeup Fluid for Hydraulic Fracturing... 9 Figure 4: (a) Unconventional Wells Drilled in PA as of March 2016 (red dots) (b) AMD Impaired Streams in PA as of October 2013 (red lines) Figure 5: Example of Barite Scale Formation in Pipe Figure 6: Location of AMD Discharges and Wells Sampled for Flowback Figure 7: Photos of AMD Discharges Figure 8: Sulfate Concentration for AMD Discharges Figure 9: Measured Flow Rates for AMD Discharges Figure 10: Variation in Barium and Strontium Concentration between Well 1 and Well Figure 11: Extended Kinetic Testing for Crabtree Discharge (Late Time Flowback) Figure 12: Barium and Strontium Removal Efficiency Figure 13: Sulfate Removal Efficiency Figure 14: Average Removal Efficiencies for both Early and Late Time for Wells 1 and 2 at 1:1 (SO4:Ba+Sr) Figure 15: Sulfate Removal vs. Barium+Strontium for Mixes at 1:1 (SO4:Ba+Sr) Figure 16: Radium Removal Compared to Barium Removal Figure 17: Clyde + Late Flowback Kinetic Testing Figure 18: Ernest + Late Flowback Kinetic Testing... 35

5 iv LIST OF TABLES Table 1: PA DEP Lab Testing Methods Table 2: AMD Discharge Characterization (Spring 2015) Table 3: Early Time Flowback Characterization Table 4: Late Time Flowback Characterization Table 5: PA DEP Methods for Radium Testing Table 6: Radium 228 and 226 Testing Results Table 7: Test 1 AMD and Flowback Mix Nomenclature and Ratios Table 8: Test 2 Mix Nomenclature and Ratios Table 9: Kinetic Testing Methods Table 10: Removal Efficiency for Mixes in Test 1 and Test Table 11: Radium Removed from Precipitation Table 12: AMD Discharges (Fall 2015)... 31

6 v ACKNOWLEDGEMENTS I would like to thank Dr. Li Li and Dr. Ertekin for their support throughout this project. Their help with the planning and execution of this project is very much appreciated. A special thanks to The Department of Environmental Protection, namely Richard Beam and Eric Cavazza, for their time and effort in ensuring the completion of this project. Richard and Eric have provided guidance and expertise that is invaluable. Brent Means of the federal Office of Surface Mining also provided expertise and knowledge on relativity complex problems that enhanced the overall project. Bill Burgos and Nathaniel Warner, of Penn State University, will be working on the project moving forward and will provide XRD analysis. I also need to thank Tom Gray and Terry Smith, of TetraTech, for introducing me to the topic. Dr. Vidic of the University of Pittsburgh deserves recognition for the foundation of this research and is acknowledged for his help in the creation of this project.

7 1 Chapter 1 Introduction In mathematics, the product of two negatives results in a positive. This basic premise can be applied to two of the largest industries in Pennsylvania; coal mining and natural gas production. Undeniably, both industries have been a catalyst for economic growth for both the state and the nation. The coal mining industry powered the nation s industrial revolution. The recent boom in natural gas production from the Marcellus shale has brought jobs and economic growth to the area. However, these industries both have a large environmental footprint. The effects of coal mining can be seen in streams that have been impaired by abandoned mine drainage (AMD). The effects of Marcellus shale development are evident in the large volumes of freshwater required to hydraulically fracture each well. Utilization of AMD hydraulic fracturing in place of freshwater, would indeed be a scenario where two negatives produce a positive. If proven possible, then streams across the state could be restored for future generations and natural gas production could continue without the strain of acquiring freshwater. There is also a potential for companies to reduce costs due to the high price of freshwater when compared to AMD. There are several challenges that must be resolved before implementation, however. For the mixture to be used in hydraulic fracturing, the final product must be compatible with formation fluid. If it is incompatible, there is potential for precipitation in the wellbore leading to loss in productivity. AMD can have upwards of a thousand mg/l of sulfate. These levels must be reduced to an acceptable level, and current practices call for less than 100 mg/l (He,

8 2 Zhang, & Vidic, Use of Abandoned Mine Drainage for the Development of Unconventional Gas Resources, 2013). Also, the concentrations of barium and strontium in the flowback should be reduced if it is to be used in future wells. If AMD and flowback are not mixed at correct ratios, these components will not precipitate out at a surface facility, and when this fluid is injected into a well during subsequent hydraulic fracturing operations, precipitation will occur in the wellbore producing scale. Another challenge involves the creation of technologically (human) enhanced naturally occurring radioactive material (TENORM). Radium, which is present in the flowback fluid, will coprecipitate with Barite and can cause issues when disposing of the sludge (He, Zhang, Zheng, Li, & Vidic, 2014).

9 3 Chapter 2 Background Pennsylvania is a state rich in natural resources. The Appalachian Basin has extensive coal deposits and natural gas baring shale. With the ever-increasing demand for energy, both the coal and natural gas resources have been exploited. Coal mining has been around since the late 1750 s in Pennsylvania. Two and one half centuries of bituminous and anthracite coal extraction has provided Pennsylvania enormous economic rewards. However, this long legacy of mining activities, especially those occurring prior to modern environmental regulations, has resulted in significant damage to land and water resources. In the Bituminous coal region of Pennsylvania the Pittsburgh seam has seen the most activity and the surface area of this deposit was estimated to be 5,000 mi 2 (White, Ashley, & Bownocker, 1927). Bituminous coal fields are common in the western part of the state while anthracite coal is common in the east. Abandoned coal mined lands are present throughout the state of Pennsylvania. The Marcellus shale is one of the most prolific gas plays in the world. The U.S. Energy Information Administration (EIA) recently announced that the estimated ultimate recovery (EUR) for the Marcellus shale is over 300 trillion cubic feet (TCF). U.S. shale gas production accounted for 56% of the total U.S. dry gas production in 2015, up 51% since 2004 (Staub, 2015). According to PA DEP drilling permit information, there have been over 9,500 unconventional gas wells drilled in Pennsylvania (PA DEP, 2016). As the switch from coal to

10 natural gas continues across the country, the Marcellus shale will play a key role in supplying 4 this demand. Abandoned coal mines will continue to pollute the environment until a use is found for the contaminated drainage that flows from many of them. As for the Marcellus shale play, drilling activity will only continue to increase and that means a greater strain on freshwater sources. Before mixing AMD with flowback, it is critical to understand how these fluids form and their typical composition. Abandoned Mine Drainage According to the 2014 Pennsylvania Integrated Water Quality Monitoring and Assessment Report required under the federal Clean Water Act, Section 305(b) Report and 303(d) List, roughly 5,500 miles of streams in Pennsylvania are contaminated or impaired by AMD (PA DEP, 2014). Polluted streams may appear either orange (Iron) or white (Aluminum) in color as a result of the precipitation of dissolved metals associated with AMD. AMD can either be net acidic or net alkaline depending on the local geology and the discharge environment. Figure 1 shows a drift mine opening (a mine entry developed to enter a coal seam along its outcrop) that is discharging AMD that is laden with high concentration of both dissolved iron and aluminum. The AMD discharged will eventually reach a receiving stream (Figure 2). The abandoned mine acts a constant source of pollution for the receiving stream which then transports the contaminants downstream to other streams.

11 5 Figure 1: AMD Discharge (Ernest, PA) Figure 2: Stream Impairment due to AMD Discharge (Ernest, PA) AMD forms when sulfide minerals associated with abandoned coal mines come in contact with atmospheric oxygen and water. The oxygen oxidizes pyrite, a mineral that is rich in coal seams. This reaction results in three main byproducts: iron hydroxide (yellow boy), sulfate, and hydrogen ions (acid) through the following processes (Eq. 1-4).

12 Oxidation of Pyrite 6 4 FeS 2 (s) + 14 O 2 (g) + 4 H 2 O (l) 4 Fe +2 (aq) + 16 H + 2 (aq) + 8 SO 4 (aq) (1) Oxidation of ferrous iron to ferric ion 4 Fe +2 (aq) + O 2 (aq) + 4 H + (aq) 4 Fe +3 (aq) + 2 H 2 O (l) (2) Hydrolysis of ferric ions 4 Fe +3 (aq) + 12 H 2 O (l) 4 Fe(OH) 3 (aq) + 12 H + (aq) (3) Net Reaction 4 FeS 2 (s) + 15 O 2 (g) + 14 H 2 O (l) 4 Fe(OH) 3 (s) + 16 H + 2 (aq) + 8 SO 4 (aq) (4) Acidity is also generated from the hydrolysis of other metals in coal seams and in the Earth s crust. Dissolved metals in AMD such as aluminum, iron (ferrous and ferric) and manganese can undergo hydrolysis reactions and precipitate as metal hydroxides as indicated in the following chemical equations (Jennings, Neuman, & Blicker, 2008). Aluminum Al H 2 O Al(OH) 3 (s) + 3 H + (5) Ferric Iron Fe H 2 O Fe(OH) 3 (s) + 3 H + (6) Ferrous Iron Fe O H 2 O Fe(OH) 3 (s) + 2 H + (7) Manganese Mn O H 2 O Mn(OH) 3 (s) + 2 H + (8)

13 These products wreak havoc on streams and local wildlife. Depending upon the receiving 7 stream s alkalinity, AMD may cause the ph to drop affecting the aquatic habitat or it may react allowing iron and aluminum hydroxide to precipitate coating the stream bottom and impairing the habitat for bottom dwelling macroinvertebrates. Virtually all life will cease to exist in a stream severely impaired by acid mine drainage (Koryak, 1997). Alkalinity is the natural ability of water to neutralize acids. Coal beds are often located near limestone formations. Limestone, or calcium carbonate, will react with the hydrogen ions and increase the ph of the system. These reactions produce bicarbonate and carbonic acid (Eq. 9 and 10). CaCO 3 (s) + H + Ca + + HCO 3 (9) CaCO 3 (s) + 2 H + Ca + + H 2 CO 3 (10) If the stream is unable to neutralize the acid on its own, passive or active treatment systems can be used to treat AMD discharges. However, these methods can be quite costly and there are not enough resources to treat the 5,500 miles of streams in Pennsylvania currently impaired by acid mine drainage. Flowback Hydraulic fracturing, the process of injecting several million gallons of freshwater, sand and chemical additives at high pressure, is responsible for releasing gas trapped in the Marcellus shale formation. An average Marcellus shale gas well requires between 3 and 5 million gallons of water per hydraulic fracture operation (Penn State Public Broadcasting, 2014). When a well is hydraulically fractured, the well is initially put on what is called flowback. For the first 30 days of production, the well is producing hydraulic fracture fluid, and not formation fluid. However, only 20-40% of the water that was injected returns up the well to the surface. This fluid is

14 8 known as flowback (Our look at Gas Drilling Wastewater, n.d.). The other 60-80% of the fluid injected remains in the shale formation. Flowback contains clays, dissolved solid ions and chemical additives. The clays and dissolved solid ions are a result of the Marcellus shale. The chemical additives are left over from the original hydraulic fracture fluid. It is important to understand hydraulic fracturing fluid as many of the constituents often appear in the flowback. The most common hydraulic fracturing fluid used in the Marcellus shale is slickwater. Slickwater consists of water, proppant (sand) and small amounts of additives. The proppant keeps the fractures open under the high stress conditions to maintain conductivity between the wellbore and reservoir. Typical additives used include: (a) friction reducer, (b) biocide and (c) scale inhibitor. Friction reducers are used to reduce pressure at the surface due to high pump rates. Often times this friction reducer is a polyacrylamide polymer. Biocides are used to reduce microbiological influenced corrosion, formation souring, and microbial growth downhole. The biocide is usually a glutaraldehyde/quaternary ammonium blend. Scale inhibitors are solvents that reduce scale buildup that occur at the wellbore which restricts flow of hydrocarbons. Scales can form from a pressure drop, temperature change, mixing of different waters, and agitation (Range Resources Appalachia, LLC, 2011). There has been a recent push for gas companies to reuse flowback to fracture future wells. However, to reuse flowback a makeup fluid must be used to replace the fluid that was lost in the formation (60-80%). The makeup fluid is usually freshwater. There is an opportunity to use AMD instead of freshwater. Figure 3 illustrates this concept. A certain volume of water is needed for a hydraulic fracture operation (Fig. 3a.). After this operation is completed, some flowback returns to the surface. A makeup fluid is needed to supplement the flowback in order to use it for a future well (Fig. 3b.). This makeup fluid is often times freshwater (Fig. 3c.). This project aims to replace freshwater with AMD as a makeup fluid (Fig. 3d.).

15 9 Figure 3: Replacing Freshwater with AMD as a Makeup Fluid for Hydraulic Fracturing Naturally Occurring Radioactive Elements Naturally occurring radioactive materials (NORM) are present in the Marcellus shale. The Marcellus shale was formed by sediments when Pennsylvania was covered by an inland sea. Seawater contains radioactive elements which eventually make their way into the mud particles and organic materials that comprise the shale. Almost all soils and rock contain some levels of radioactive material. Shales are comprised of four main radioactive elements: uranium (U), thorium (Th), potassium (K), and radium (Ra) (Perry, 2011). The Marcellus is rich in uranium-238 and thorium-232. The decay products of these two radioactive materials are radium-228 and radium-226, respectively. Radium may be released into the formation water as Ra 2+ ions (Vidic, Brantley, Vandenbossche, Yoxtheimer, & Abad, 2013).

16 These elements are not likely to be hazards when brought to the surface. However, through 10 repeated treatment and recycling of the flowback water, a concentrated sludge with elevated levels of radium can form. Radium is the element that must be analyzed due to its propensity to coprecipitate with barite. If the radium concentration in the sludge becomes too concentrated, it will have to be disposed of in landfills approved for low level radioactive waste (He, Zhang, Zheng, Li, & Vidic, 2014). The common units for measuring radioactivity are pci/g or pci/l (picocuries per gram or liter). A report by the USGS concluded that radium concentrations in produced water from oil and gas extraction activities in Pennsylvania and New York were as high as 18,000 pcil -1 and had a mean of 2,460 pcil -1. The limit for unrestricted disposal in Resource Conservation and Recovery Act (RCRA-D) nonhazardous landfills ranges form 5-50 pcig-1 depending on state regulations. According to the PADEP s 2004 guidance document on monitoring radioactivity in solid waste, solids containing NORM can be disposed without DEP approval if the following conditions are met: 1. Volume of solid waste is lower than 1 m 3 2. Gamma radiation (Geiger counter) at a distance of 5 cm from any surface is less than 50 μrh Total radium concentration in solid waste is lower than 5.0 pcig -1 NORM is important to measure throughout the process so that the sludge complies with regulations and does not require special handling or disposal at a low-level radioactive waste landfill. Locations of Drilling Activity and AMD Impaired Streams The idea behind using of AMD in hydraulic fracturing has been around for some time. AMD is an abundant water source that could service the gas industry for many years. A key benefit is the general location of AMD discharges in Pennsylvania overlays the same geographic area as the Marcellus shale drilling activity. Figure 4a shows unconventional wells that have been drilled in Pennsylvania as of March 2016 according to the PA DEP. When compared to the AMD impaired stream map (Figure 4b), it

17 11 becomes evident that these locations overlay each other. This means that transportation of AMD to well locations would be minimal, reducing overall costs. Figure 4: (a) Unconventional Wells Drilled in PA as of March 2016 (red dots) (b) AMD Impaired Streams in PA as of October 2013 (red lines) The main drawback to using AMD in hydraulic fracturing is that it generally has high sulfate concentrations. When water with high sulfate is injected down a well, scale formation occurs when the water comes in contact with barium and strontium downhole. When scale forms in the wellbore, the productivity of the well decreases due to a decrease in flow diameter through the casings. Figure 5: Example of Barite Scale Formation in Pipe (Courtesy:

18 12 Chapter 3 Previous Studies on AMD and Flowback Water Mixing Previous work (Beers, Heinrichs, Lane, & Peterson, 2015) has been done to develop a treatment system for AMD to produce a low-sulfate water compatible with hydraulic fracturing operations. This process used liquid-liquid extraction based technology. The tests concluded that sulfate levels could be reduced to below 100 mg/l. However, this process could be costly due to the methods used for sulfate reduction and the continued need to treat the flowback fluid. Reducing sulfate by means of flowback mixing could be a more cost effective option. The idea behind mixing AMD and flowback focuses on reducing the sulfate, barium and strontium to acceptable levels through precipitation reactions in a treatment facility. The sludge created from the mixing can then be disposed of according to state regulations. The equilibrium constants for barite and celestite are relatively high (Eq ). BaSO 4 (s) Ba 2+ + SO 4 2 log(k eq,25c ) = 9.97 (11) SrSO 4 (s) Sr 2+ + SO 4 2 log(k eq,25c ) = 5.68 (12) As for reducing sulfate concentrations through mixing with flowback, two key groups have done testing in this area. Researchers at Duke University and Technion completed a study that evaluated the impact of blending Marcellus flowback with AMD from Pennsylvania (Kondash, Warner, Lahav, & Vengosh, 2013). Three AMD samples were used, two lime-treated (high ph 10-11), and one synthetic blend (low ph 3.4). The results showed that the lime treated, high ph, samples removed more barium, strontium, sulfate and radium than the lower ph samples.

19 13 The other group that has done extensive research in the area of mixing AMD and flowback has been Dr. Radisav D. Vidic and his team at the University of Pittsburgh. The focus and results of their research include: the fate of NORM in the sludge; barite precipitation occurs within the first 30 minutes of mixing AMD and flowback; and an overall treatment system for scaling this project to a treatment facility (He, Li, Liu, Barbot, & Vidic, 2014) (He, Zhang, & Vidic, Use of Abandoned Mine Drainage for the Development of Unconventional Gas Resources, 2013) (He, Zhang, Zheng, Li, & Vidic, 2014). However, further analysis is needed before there is commercial use of this idea. The majority of the research done in this field involves barite precipitation, and NORM formation. Research has shown that strontium removal is less than 40% when mixing low ph AMD and flowback. Hypotheses around the low strontium removal include: (a) lattice poisoning and (b) complexation with organic matter (He, Li, Liu, Barbot, & Vidic, 2014). The objective of this research is to investigate the fate of strontium after mixing so that the removal efficiency can be increased. This study will involve different AMD discharges and actual flowback samples. An extended kinetic test (14 days) was conducted to attempt to reduce strontium concentrations and removal efficiencies were monitored.

20 14 Chapter 4 Field Sampling and Characterization of AMD and Flowback Waters For this research, samples were collected from eight AMD discharges and two recently hydraulically fractured wells. Figure 6 shows the locations of the AMD discharges (orange circles) and the well locations (blue circles). The eight AMD locations are Clyde (a), Crabtree (b), Ernest (c), Tanoma (d), Falls Creek (e), Long Valley (f), B-Vein (g) and C-Vein (h). These discharges were chosen based on their proximity to drilling activity and their level of treatment. Photos of each discharge can be found in Figure 7. Well 1 and 2 denote the two well locations. Figure 6: Location of AMD Discharges and Wells Sampled for Flowback

21 Figure 7: Photos of AMD Discharges 15

22 16 The AMD discharges and flowback wells were sampled and sent to the PA DEP labs in Harrisburg, PA. Table 1 displays the methods used by the lab to characterize various parameters. Table 1: PA DEP Lab Testing Methods Method Colorimetric Titration using SM 2320B Ion Chromatography (IC) Inductively Coupled Plasma Mass Spectrometry (ICPMS) Parameters Sulfate, Chloride Alkalinity Bromide Other Metals (Barium, Strontium, etc.) AMD Characterization A summary of the key species in the AMD discharges are shown in Table 2. Both total and dissolved constituents were analyzed. For the following tables, total concentrations are reported for sulfate and alkalinity. Dissolved concentrations are reported for all other constituents. Table 2: AMD Discharge Characterization (Spring 2015) Location ph Alk. Na + Ca 2+ Mg 2+ Ba 2+ Sr 2+ Fe Cl - SO 4 2- (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Clyde ND Crabtree Ernest Tanoma Falls Creek Long Valley ND 0.1 ND B-Vein ND C-Vein ND ND: Not Detectable

23 17 Figure 8: Sulfate Concentration for AMD Discharges Figure 9: Measured Flow Rates for AMD Discharges The characteristics of the AMD discharges vary based on geological location, mining methods and treatment options. When it comes to mixing AMD and flowback, two key variables must be analyzed. First, the discharge should have high enough sulfate concentrations to react with the barium

24 18 and strontium in the flowback. Second, the AMD discharge should have a large enough flowrate to be able to supply a treatment facility. However, if the flowrate is not high enough, it may be possible to drill into the mine pool and extract the AMD this way. The latter adds cost to the project, which is why this research will look at high flowrate AMD discharges. It is evident that the sulfate concentration varies greatly between discharges. Three discharges were selected based on high sulfate concentrations, along with high flowrates. The discharges used for this study are Clyde, Crabtree and Ernest. It should be noted that the B-Vein and C-Vein are a potential candidate for hydraulic fracture fluid as they are both already around or below the 100 mg/l cut off for sulfate concentration. Flowback Characterization Two separate companies operating in Southwest PA provided flowback samples. Because flowback is defined by state regulation as the water that returns to the surface for the first 30 days after a well is put online, samples were collected early in the flowback period (Well 1- Day 2, Well 2- Day 1) and then late in the flowback period (Well 1- Day 30, Well 2- Day 29). The water chemistry changes as the flowback period progresses. Tables 3 and 4 display the data from the samples. Table 3: Early Time Flowback Characterization Location ph Alk. Na + Ca 2+ Mg 2+ Ba 2+ Sr 2+ Fe Cl - SO 4 2- (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Well Well

25 Table 4: Late Time Flowback Characterization 19 Location ph Alk. Na + Ca 2+ Mg 2+ Ba 2+ Sr 2+ Fe Cl - SO 4 2- (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Well ND Well ND Figure 10: Variation in Barium and Strontium Concentration between Well 1 and Well 2 Well 1 has a larger concentration of barium than strontium. The opposite is true for Well 2. Also, the concentrations of these metals increased from early to late time in the flowback period. The variance in composition makes it difficult to have a single recommendation on mixing ratios. NORM Analysis The PA DEP lab, using the methods outlined in Table 5, completed radium analysis on the late time flowback samples. The results of the tests are shown in Table 6.

26 Table 5: PA DEP Methods for Radium Testing 20 Method Parameters Brooks and Blanchard Radium 228 EPA Radium 226 Table 6: Radium 228 and 226 Testing Results Flowback Ra-228 Ra-226 (Late Time) (pci/l) (pci/l) Well Well ,012 For the NORM characterization, the values fall within typical ranges for Pennsylvania. A study involving 46 flowback samples found that the average Ra-228 concentration was 120 pci/l while Ra-226 was 623 pci/l (He, Zhang, Zheng, Li, & Vidic, 2014).

27 21 Chapter 5 AMD and Flowback Mixing Tests AMD and flowback mixing tests were performed to evaluate two main objectives: (1) to determine an extended kinetic profile (14 days) for key reactants (2) to identify an optimal mixing ratio that maximizes precipitation of sulfate, barium, and strontium. To distinguish between different mix ratios, the molar ratio of sulfate to barium plus strontium was used (SO 4 : Ba+Sr). This implies that a 1:1 ratio would have just enough sulfate to react with all the barium and strontium to precipitate barite and celestite assuming no other reactions occur. Two key tests were performed to accomplish these objectives. Test 1 was completed to obtain extended kinetic information by mixing AMD discharges with the late time flowback samples (Table 7). The majority of the samples were 1:1 (SO 4 : Ba+Sr). The other samples were either over loaded with sulfate (CL-2L) or only had enough sulfate to form barite, and not celestite (CR-2L and E-2L). Table 7: Test 1 AMD and Flowback Mix Nomenclature and Ratios Mix Tag AMD Location Flowback Sample AMD Volume Flowback Volume (SO 4:Ba+Sr) Ratio ml ml fraction CL-1L Clyde Well 1 - Late 10,709 7, CL-2L Clyde Well 2 - Late 13,707 3, CR-1L Crabtree Well 1 - Late 16,070 1, CR-2L Crabtree Well 2 - Late 16, E-1L Ernest Well 1 - Late 16,497 1, E-2L Ernest Well 2 - Late 15,

28 22 Test 2 was completed by mixing AMD discharges with the early time flowback samples at ratios equivalent to 1:1 (Table 8). These samples were sent to the PA DEP labs and analyzed using the methods outlined in Table 1. These samples were mixed and then analyzed two weeks after the initial mix was completed. Table 8: Test 2 Mix Nomenclature and Ratios Mix Tag AMD Location Flowback Sample AMD Volume Flowback Volume (SO 4:Ba+Sr) Ratio ml ml fraction CL-1E Clyde Well 1 - Early 1,417 1, CL-2E Clyde Well 2 - Early 1,262 1, CR-1E Crabtree Well 1 - Early 2, CR-2E Crabtree Well 2 - Early 2, E-1E Ernest Well 1 - Early 3, E-2E Ernest Well 2 - Early 2, Extended Kinetic Testing Concentrations for alkalinity, barium, strontium, calcium and sulfate were measured once every day for 14 straight days. The goal of the testing was to determine if strontium could completely precipitate out if ample time was allowed. The samples were sent to Geochemical Testing (Somerset, PA) for kinetic testing. Table 9 shows the methods used by Geochemical Testing to characterize the mixes. Only the six Test 1 samples were used (Table 7). Figure 11 shows the results for the Crabtree discharge. Others kinetic profiles can be found in Appendix A. Table 9: Kinetic Testing Methods Method ASTM D EPA / Parameters Alkalinity Metals

29 23 Figure 11: Extended Kinetic Testing for Crabtree Discharge (Late Time Flowback) The testing concluded that precipitation does not occur after the initial mixing period of one day. As mentioned earlier, tests have shown that barite precipitates out within 30 minutes of mixing. All tests showed that the concentrations of barium, strontium and sulfate did not change after the first day.

30 Removal Efficiency 24 Both Test 1 and Test 2 were used in evaluating removal efficiencies. In both cases, removal efficiencies were calculated by dividing final 14 day mix concentrations and the initial concentrations. Barium, strontium and sulfate removal efficiencies are shown in Table 10. Calcium was also monitored but did not show any removal. Table 10: Removal Efficiency for Mixes in Test 1 and Test 2 Mix Tag (SO 4:Ba+Sr) Ratio Barium Removal Strontium Removal fraction (%) (%) (%) Sulfate Removal CL-1E CL-2E CL-1L CL-2L CR-1E CR-2E CR-1L CR-2L E-1E E-2E E-1L E-2L Plotting this data as a function of (SO 4:Ba+Sr) will show trends for removal analysis (Figures 12 and 13). There is a cluster of points around the ratio of 1:1 because samples were sent to the lab in batches and it was assumed that this would be the optimal mix ratio. After analysis showed that strontium was only being removed at around 50%, two extremes were tested. Two mixes were done at a ratio much lower than 1:1. One mix was completed with 4 times as much sulfate needed to precipitate out 100% of the barium and strontium.

31 25 Figure 12: Barium and Strontium Removal Efficiency Figure 13: Sulfate Removal Efficiency Key takeaways from Figure 12 are that barium can be removed at 100% efficiency with at 1:1 ratio. However, when there is only enough sulfate in the mix to react with all the barium, the removal efficiency was found to be roughly 63%. This could be due to a phenomenon called ion shielding.

32 26 Because we are dealing with high ionic strength waters, it may be difficult for the sulfate to find and react with the barium due to the high strength of other charges in the water. Virtually no strontium was precipitated with a low (SO 4:Ba+Sr) ratio. At a ratio around 1:1, the strontium was removed at efficiencies between 25-50%. These results show that strontium can coexist in the mix with excess sulfates and not precipitate. In an attempt to reduce more strontium, a sample was overloaded with sulfate to form more celestite. The conclusion was that the strontium not removal was not increased over 1:1 ratio mix. This implies that celestite precipitation is not occurring. X-Ray diffraction (XRD) analysis done in previous work showed that strontium precipitates as Sr Barite (75% barium, 25% strontium) (Kondash, Warner, Lahav, & Vengosh, 2013). Figure 13 confirms this observation that celestite may not be forming but rather strontium is coprecipitating with barium. As for the sulfate, 100% removal can be achieved at ratios under 1:1. As for ratios around 1:1, there is a large range of removal efficiencies. To determine why this is, average values for each well were calculated to see if the variance in water chemistry between wells is the reason (Figure 14). Figure 14: Average Removal Efficiencies for both Early and Late Time for Wells 1 and 2 at 1:1 (SO4:Ba+Sr)

33 There are two hypotheses as to why Well 2 has only half the removal efficiency as Well 1: (1) 27 barium and strontium are precipitating out as carbonate minerals, (2) complexation from organic material in Well 2 is greater than Well 1. Witherite and strontianite are carbonate minerals that could possibly form from mixing. The equilibrium constants are as follows: BaCO 3 (s) Ba 2+ + CO 3 2 log(k eq,25c ) = 3.00 (12) SrCO 3 (s) Sr 2+ + CO 3 2 log(k eq,25c ) = 0.32 (13) When comparing these equilibrium constants to that of barite and celestitie, and respectively, the equilibrium constants for the carbonate minerals are quite small and therefore are less likely to precipitate. The concentrations for barium, strontium and sulfate were converted from mg/l to mol/l. Because barium and strontium have a two plus charge, and sulfate has a two minus charge, they react at a 1:1 ratio. By plotting the amount of sulfate removed vs. the amount of barium plus strontium removed, and comparing to a unit slope, conclusions can be made regarding carbonate precipitation. Figure 15 shows that the removal of these minerals fall on the unit slope line. This implies that all barium and strontium is removed by sulfate, and not carbonate. There are a few points on the plot that fall to the right of the unit slope line, which could indicate that a very small amount was precipitated out as another mineral (possibly carbonates). However, this would be too small of an amount to account for the 50% reduction in sulfate removal between Well 1 and Well 2.

34 28 Figure 15: Sulfate Removal vs. Barium+Strontium for Mixes at 1:1 (SO4:Ba+Sr) Another possible reason for poor removal efficiencies for strontium and sulfate could be due to complexation in the mix. When strontium complexes with OH -, HCO 3-, Cl -, and organics, it can be difficult for it to react with sulfate. Organics, in particular, can make it very difficult to precipitate celestite. The purpose of organics in hydraulic fracture fluid, or anticipants, is to prevent precipitation of minerals. In a previous study where both synthetic and actual flowback samples were used, the actual flowback samples had less removal of constituents due to complexation in the water, due mainly to organics. It is believed that the organic matter will adsorb to active sites, preventing crystal growth and overall removal efficiency (He, Li, Liu, Barbot, & Vidic, 2014). If this is the case, Well 2 may have more organic matter present than Well 1.

35 Radium Removal 29 Precipitate from three of the samples was sent to the PADEP lab to be tested for radium. Table 11 shows the amount of Ra-228 and Ra-228 removed from mixing along with the removal efficiencies. Table 11: Radium Removed from Precipitation Mix Tag (SO 4:Ba+Sr) Ratio Ra-228 Removed Ra-228 Removal Ra-226 Removed fraction (pci/l) (%) (pci/l) (%) Ra-226 Removal CL-2L CR-1L E-2L Because radium co-precipitates with barium, it is worth comparing the removal efficiencies. Figure 16 displays the removal efficiency for Ra-228, Ra-226 and barium for the three samples. Ra-226 was removed completely in almost all three samples. The percentage of Ra-228 and barium was virtually the same for CR-1L and E-2L. CL-2L was much less, which may be due to ion shielding. Figure 16: Radium Removal Compared to Barium Removal

36 Discussion of Results 30 The removal efficiency analysis and extended kinetic test provided a window to observe reactions during the mixing of AMD and flowback. The extended kinetic test demonstrated that the removal of barium, strontium and sulfate is not a function of time after one day. Although strontium reduction cannot be achieved through time, it is a positive for the project s economics. This means that companies will not have to spend a lot of time, and money, waiting for precipitation to occur. Removal efficiency test concluded that 100% of barium and radium could be achieved at ratios above 1:1 (SO 4:Ba+Sr). Sulfate could be removed at 100% efficiency at values around 0.2:1 (SO 4:Ba+Sr). Strontium could be removed at 50%. By analyzing Figures 12 and 13, it is evident that the optimal mix ratio is located between somewhere less than 1:1 (SO 4:Ba+Sr). As the addition of more sulfate to the system did not result in an increase in strontium removal, it should not be a priority to remove strontium in the form of celestite or Sr-barite. By reducing the amount of organic material in the flowback, it may be possible to increase the amount of strontium and sulfate reduction. Methods other than sulfate removal should be considered for strontium removal. The study completed by Duke University and Technion achieved strontium removal as high as 70% when using lime-treated AMD. By increasing the ph and alkalinity of the water, it may be more favorable for strontianite to form. Sources of Error Potential sources of errors involved in the characterization of the fluids, and the initial mix concentration calculations. The mixing of these two fluids produces a high ionic strength water. This makes analysis difficult, as the samples must be diluted prior to characterization. The dilution factors for strontium for the kinetic testing ranged from 10 to 500. This may account for the oscillating curves for the extended kinetic data. In addition, the initial mix

37 31 concentrations of some ions increase. This may be due to the initial characterization of the fluids being calculated by the PA DEP lab, and the extended kinetic testing being done by Geochemcial Testing. The collection of the AMD and flowback samples were completed in the spring of Test 2 was completed using this AMD fluid. For Test 1, new samples of the AMD discharges were collected. Due to long lead times for the characterization of the AMD, the values from spring 2015 were used to set up the mixing ratios. Since then, the more recent samples were analyzed by the PA DEP lab and the results are shown in Table 12. The concentrations changed slightly, but not enough affect the results of the extended kinetic tests. The sulfate values for the spring AMD samples were 3,870 mg/l, 614 mg/l, and 448 mg/l for Clyde, Crabtree and Ernest, respectively. Table 12: AMD Discharges (Fall 2015) Location ph Alk. Na + Ca 2+ Mg 2+ Ba 2+ Sr 2+ Fe Cl - SO4 2- (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Clyde ND 6.3 ND Crabtree ND Ernest ND

38 32 Chapter 6 Conclusions The characteristics of AMD vary by location and should be sampled prior to mixing with flowback. It was determined that the discharges in the bituminous region (southwest PA) had higher concentrations of sulfate than those of the anthracite region (northwest PA). Clyde, Crabtree and Ernest discharges were selected based on high sulfate concentrations and high flowrates. The B-Vein and C- Vein discharge, located in Sullivan County have a low enough sulfate concentration that they could be used in hydraulic fracturing even without mixing with flowback. As for the flowback samples, both had very high concentrations of dissolved metals. However, barium and strontium varied greatly between Well 1 and Well 2. This implies that the flowback should be tested prior to mixing to ensure that the mixing ratios calculated match the flowback composition. Kinetic data shows that precipitation reactions are not a function of time after the first day of mixing. Retention times for mixing will thus be smaller, lowering the cost of the project. Removal efficiencies varied based on mixing ratios, and flowback characteristics. Barium is completely removed when an ample amount sulfate is added. Sulfate can be removed completely when putting less AMD in the mixture (0.2:1 SO 4:Ba+Sr). Strontium could only be removed up to 50%. Possible factors affecting precipitation of strontium include lack of celestite formation and the presence of organics. It may be possible to increase strontium removal if organics are removed, or the AMD is treated with lime to increase the ph. The results are promising that AMD could one day be used in hydraulic fracturing operations. Mixing of AMD and flowback may be the most cost effective way of utilizing AMD and could result in a cleaner environment in Pennsylvania.

39 Future Work 33 Questions remain surrounding the precipitation of strontium. XRD will be conducted on the sludge produced from the samples to determine what is actually precipitating. This test will conclude whether or not celestite or stontianite is precipitating. In addition, it will determine if any carbonate minerals are forming in the mix. Preliminary test results show that only barite and Sr-barite are forming in the mixes (along with some halite and quartz). Geochemical models will be used to determine what may be hindering precipitation, and where the optimal mix ratio is. Geochemist s Workbench has already been used to model the mixes and has proven to predict mix results accurately. CrunchFlow will be also be used to model how organics are contributing to the inhibition of strontium precipitation. Lastly, more mixes will be completed at ratios less that 1:1 to try to find the ratio that produces the highest removal of both barium and sulfate. Strontium will need to be removed by other means when using low ph AMD sources. Through these tests an optimal mixing ratio will be recommended.

40 Appendix A 34 Extended Kinetic Testing Figure 17: Clyde + Late Flowback Kinetic Testing

41 Figure 18: Ernest + Late Flowback Kinetic Testing 35

42 36 BIBLIOGRAPHY Beers, T., Heinrichs, M. R., Lane, A. E., & Peterson, R. K. (2015). Treating Acid Mine Drainage for Use as Source Water: A Pilot Study. Society of Petroleum Engineers, 1-7. He, C., Li, M., Liu, W., Barbot, E., & Vidic, R. D. (2014). Kinetics and Equilibrium of Barium and Strontium Sulfate Formation in Marcellus Shale Flowback Water. Journal of Environmental Engineering, 1-9. He, C., Zhang, T., & Vidic, R. D. (2013). Use of Abandoned Mine Drainage for the Development of Unconventional Gas Resources. Disruptive Science and Technology, 1-8. He, C., Zhang, T., Zheng, X., Li, Y., & Vidic, R. D. (2014). Managemnt of Marcellus Shale Produced Water in Pennsylvania: A Review of Current Strategies and Perspectives. Energy Technology, Jennings, S. R., Neuman, D. R., & Blicker, P. S. (2008). Acid Mine Drainage and Effects on Fish Health and Ecology: A Review. Bozeman, MT.: Reclamation Research Group Publication. Kondash, A. J., Warner, N. R., Lahav, O., & Vengosh, A. (2013). Radium and Barium Removal through Blending Hydraulic Fracturing Fluids and Acid Mine Drainage. Environmental Science & Technology, Koryak, M. (1997, September). Origins and ecosystem degredation impacts of acid mine drainage. Retrieved February 10, 2016 Our look at Gas Drilling Wastewater. (n.d.). Retrieved February 13, 2016 PA DEP. (2014). Integrated Water Quality Report. Annual Report, Harrisburg. PA DEP. (2016, March). Oil and Gas Reports. Retrieved from PA DEP: ud_external_data

43 Penn State Public Broadcasting. (2014, August). Explore Shale. Retrieved February 13, Perry, S. A. (2011). Understanding Naturally Occuring Radioactive Material in the Marcellus Shale. Marcellus Shale, 1-8. Range Resources Appalachia, LLC. (2011, Feb 24). Hydraulic Fracturing Fluid Consideratoins in Marcellus Shale Completions. Staub, J. (2015). The Growth of U.S. Natural Gas: An Uncertain Outlook for U.S. and World Supply. Washington, D.C.: U.S. Energy Information Administration. Vidic, R. D., Brantley, S. L., Vandenbossche, J. M., Yoxtheimer, D., & Abad, J. D. (2013). Impact of Shale Gas Development on Regional Water Quality. Science, 826. White, I. C., Ashley, G. H., & Bownocker, J. A. (1927). The Pittsburgh coal bed: Transactions of the American Institute of Mining and Metallurgical Engineers

44 ACADEMIC VITA Academic Vita of Michael Cavazza Education: The Pennsylvania State University University Park, PA Honors Petroleum and Natural Gas Engineering Graduating May 2016 Experience: Present Tetra Tech, Inc. Pittsburgh, PA Engineer Intern Researching the feasibility of using abandoned coal mine drainage to treat flowback from hydraulic fracturing to decrease fresh water consumption Reviewing well permit locations in areas around mine pools that could be potential pilot study locations ConocoPhillips Company Houston, TX Summer 2015 Reservoir Simulation Engineer Intern Evaluated using evolutionary algorithms to optimize the history matching process and produced 30 year forecasts to influence reserves booking Learned unconventional reservoir modeling techniques Summer 2014 Drilling Engineer Intern Analyzed the potential cost savings and surface footprint reduction in moving to multi-well pads and multilateral wellbores in the Delaware Basin in west Texas Worked on several emerging drilling technology projects Summer 2013 Dominion Resources, Inc. Clarksburg, WV Project Engineer Intern Created a construction cost database for transmission projects since 2008 Observed project management on jobs such as compressor stations, pipelines, treatment facilities and LNG exporting Penn State Chemistry Lab New Kensington, PA Research Lab Assistant Conducted research on various polymer development projects Developed skills relating to mechanical analysis, kinetics, calorimetry, and spectroscopy Selected Accomplishments: Petroleum Engineering Merit Award, Spring 2015 Given to PNGE student with highest GPA SPE STAR Scholar, Fall 2013 Two students selected from Eastern North America Region SPE Pittsburgh Petroleum Section Scholarship Spring 2014 and Spring 2015 SPE Student Paper Competition Spring 2015 Second Place at regional competition BP Scholarship in Petroleum and Natural Gas Engineering Fall 2014 Chevron Corporation PNGE Scholarship Fall 2013 Activities: Student member of Society of Petroleum Engineers, Phi Kappa Phi Academic Honor Society and Tau Beta Pi Engineering Honor Society Penn State THON Committee An effort to raise money for pediatric cancer Enjoy golfing, baseball, football and basketball