BASELINE SAMPLING OF WATER SOURCES IN AREAS OF SHALE OIL AND GAS DEVELOPMENT

Transcription

1 BASELINE SAMPLING OF WATER SOURCES IN AREAS OF SHALE OIL AND GAS DEVELOPMENT John A. Connor, P.E., P.G., BCEE; Ann P. Smith, P.E., BCEE; Stephen D. Richardson, Ph.D, P.E.; Lisa Molofsky, G.I.T. GSI Environmental Inc. January 21, 2016

2 ADVANCED ANALYTICAL METHODS RPSEA Year project in 2 phases (currently in Phase II) $3.5M from DOE/RPSEA, $900k in cost share RESEARCH FOCUS ON THREE KEY ENVIRONMENTAL ISSUES: Baseline Sampling and Stray Gas Investigation Advanced Analytics for Air Emissions Flowback/Produced Water Characterization OBJECTIVE: Develop consistent protocols and guidelines for characterizing groundwater quality, air emissions, and produced water from shale development activities. 2

3 BASELINE SAMPLING OF WATER SOURCES What is it? What is Baseline Sampling? aka: Pre-drill sampling or Pre-alteration survey Sampling of water sources within a defined distance from the proposed location of oil and gas development Why Collect Baseline Samples? Establish water quality of drinking water sources Evaluate whether reported changes in local water quality are naturally occurring or the result of nearby drilling Water Source Proposed Well Pad What Water Sources? Residential water wells, springs, and/or surface waters that are intended for human or livestock consumption 3

4 BASELINE SAMPLING OF WATER SOURCES How Many Residential Wells? 4

5 BASELINE SAMPLING OF WATER SOURCES How Many Residential Wells? Over 1 million domestic water wells in PA (PA DCNR, 2015) 5

6 BASELINE SAMPLING OF WATER SOURCES How Many Unconventional Wells? (PADEP, 2015) 6

7 BASELINE SAMPLING OF WATER SOURCES How Many Unconventional Wells? Total UOG Wells: 9,206 (PADEP, 2015) 7

8 GROUNDWATER ISSUES What s the Problem? 8

9 GROUNDWATER ISSUES Let s talk Methane General Information CAS Number: Chemical Formula: CH 4 Appearance: Colorless gas Odor: Odorless Hazard Properties Flashpoint: -306 F ( C ) Lower Explosive Limit: 4.4 % by volume of air Upper Explosive Limit: 17 % by volume of air Key Properties Molar Mass: g/mol Aqueous Solubility: 22.7 mg/l Density: 0.66 g/l (25 C, 1 atm) Health Effects Non-toxic Reduces the amount of oxygen in air Explosive hazard 9

10 GROUNDWATER ISSUES How can Methane Impact Water Quality? Key Indicators of Fresh Water Impact by Methane: Dissolved Oxidants Decrease O 2 NO 3 - SO4-2 Visible Changes at Tap Dissolved By-Products Increase CO 2 Mn +2 Fe +2 H 2 S Dissolved Fe +2 and Mn +2 become oxidized at the surface, creating dirty or turbid looking water. 10

11 GROUNDWATER ISSUES Methane: Natural or Impact? Naturally Occurring Gas Well Migration Eternal Flame Falls, NY Thermogenic and biogenic Natural seeps Effervescing wells House Explosion, Western PA Casing leak or cement failure Creates pathway for deeper methane into shallow aquifers KEY POINT: A recent baseline study in NE PA reported (Baldassare et al., 2014): 24% of water wells with detectable levels of dissolved methane 12% of wells contained dissolved methane > 7 mg/l 11

12 GROUNDWATER ISSUES Methane: Natural or Impact? (Darrah et al., 2014) 12

13 Methane Conc. (mg/l) BASELINE SAMPLING CHALLENGES Understanding Natural Variability Challenge: Differentiating natural variability in groundwater quality from induced variability (i.e., impacts) Pre-Drill Post-Drill January October 7 mg/l PADEP lower threshold for potential stray gas migration incident response KEY QUESTION: Are observed changes in residential water quality within the range of expected variability or suggestive of an impact? 13

14 BASELINE SAMPLING CHALLENGES Understanding Natural Variability Challenge: Cloudy understanding of the inherent variability in pre- and post-drill sampling results Analytical Methods Purge volume KEY POINT: There are factors unrelated to shale gas extraction that can influence residential water quality results 14

15 BASELINE SAMPLING CHALLENGES Lack of Specific Guidance Numerous national and regional oil & gas and environmental organizations support implementation of baseline sampling programs and provide guidance KEY POINT: Detailed procedures for conducting baseline sampling of water sources are needed to support existing guidance 15

16 BASELINE SAMPLING PROTOCOL What s the Goal? Baseline Sampling of Water Sources Surface Water Water Wells Springs/Seeps Implications & Case Study 5 4 Data Analysis & Management Develop a practical protocol for improved sample collection methods and data interpretation for pre-drill and post-drill sampling programs 3 Sample Collection & Analyses 1 Regulations & Guidance 2 Information Resources 16

17 TODAY S TALK Regulations: Provide a summary of current preand post-drill sampling regulations and guidance Sample Collection: Discuss methods for collecting dissolved gas samples at residential water wells Data Analysis: Discuss key relationships that can be valuable in understanding natural methane occurrence (PA DCNR, 2012) 17

18 BASELINE SAMPLING REGULATIONS What s Out There? 18

19 BASELINE SAMPLING REGULATIONS What s Out There? Alaska California Colorado Idaho Illinois * Final Regulations for Baseline Sampling of Water Sources Michigan Nevada North Carolina * Ohio Pennsylvania * Tennessee West Virginia * Wyoming * Presumption of Liability: The burden of proof remains with the oil and gas operator in cases of alleged water quality impacts to nearby water supplies. 19

20 BASELINE SAMPLING REGULATIONS Presumption of Liability in PA Act Protection of water supplies (c) Presumption. Unless rebutted by a defense established in subsection (d), it shall be presumed that a well operator is responsible for pollution of a water supply if (2) in the case of an unconventional well: i. the water supply is within 2,500 feet of the unconventional vertical well bore 2,500 ft ii. the pollution occurred within 12 months of the later of completion, drilling, stimulation or alteration of the unconventional well Water Source Proposed Well Pad 20

21 BASELINE SAMPLING REGULATIONS Presumption of Liability in PA Act Protection of water supplies (d) Defenses. To rebut the presumption established under subsection (c), a well operator must affirmatively prove any of the following (2) in the case of an unconventional well: i. the pollution existed prior to the drilling, stimulation or alteration activity as determined by a predrilling or prealteration survey; ii. iii. iv. the landowner or water purveyor refused to allow the operator access to conduct a predrilling or prealteration survey; the water supply is not within 2,500 feet of the unconventional vertical well bore; the pollution occurred more than 12 months after completion of drilling or alteration activities; v. the pollution occurred as the result of a cause other than the drilling or alteration activity. 21

22 BASELINE SAMPLING REGULATIONS What do Regulations Include? Location Type of water supply; distance from the production well (sampling radius); number of sampling locations Timeframe Sampling frequency; time period prior to and after production well development Methods Sample location; sampling procedures; well purging practices Analytical Recommended field parameters; analytical suite; established action levels Reporting Operator provides data to state agency and/or water well owner; publically available 22

23 BASELINE SAMPLING REGULATIONS Type of Water Supply DEF N: Water Source or Supply: Residential water wells, springs, and surface waters that are intended for human or livestock consumption and/or other household uses. Residential Wells Springs & Seeps Surface Waters All 13 State Agencies (Wooster, 2012) Colorado Nevada Illinois W. Virginia N. Carolina Wyoming Pennsylvania (Clean-Flo, 2014) California N. Carolina Idaho Illinois Pennsylvania 23

24 BASELINE SAMPLING REGULATIONS Sampling Radius & Number of Locations Radius Water Source Proposed Well Pad KEY POINT: Radial distances range from ¼ mile to 1 mile Distances may be based on extent of horizontal wellbore 24

25 BASELINE SAMPLING REGULATIONS Number of Required Analytes KEY POINT: Wide range in the number and type of analytes required by each state agency 25

26 BASELINE SAMPLING REGULATIONS Analytical Suite > 75% of States 25-75% of States < 25% of States Water Quality TDS ph Turbidity Alkalinity Bubbles Sediment Color Sp. Cond. Temp. Hardness Effervesc. ORP Odor DO Major Cations Anions Chloride Sulfate Calcium Iron Bromide Fluoride Nitrate Nitrate Magnesium Manganese Potassium Sodium Ammonium Phosphorus Iodide InOrgs / Trace Elements Barium Arsenic Lithium Boron Selenium Lead Strontium Chromium Aluminum Cadmium Mercury Silicon Silver Uranium Zinc Organics Dissolved Gases BTEX TPH DRO PAHs GRO TOC VOCs Detergents Surfactants Methane Ethane Propane Butane Hydrogen Sulfide 26

27 BASELINE SAMPLING REGULATIONS Action Limits Consider Dissolved Methane If a dissolved methane concentration greater than 1 mg/l 5 mg/l 7 mg/l 10 mg/l Alaska Colorado N. Carolina Wyoming Pennsylvania Nevada is detected in a sample, gas compositional analysis and stable isotope analysis of methane ( 12 C, 13 C, 1 H, 2 H) shall be performed to determine the gas type. KEY POINT: In addition to methane, some state agencies have established action limits for BTEX, TPH, chloride, and other parameters. 27

28 BASELINE SAMPLING REGULATIONS Sample Collection: Well Purging DEF N: Well Purging: practice to collect samples that are representative of the surrounding formation, rather than stored water within the wellbore. Parameter Stability 3 Casing Volumes California Colorado North Carolina Wyoming In a typical well this could be: hundreds of gallons! California Colorado North Carolina Ohio Wyoming 28

29 BASELINE SAMPLING REGULATIONS Sample Collection Only two state agencies offer comprehensive guidance on pre-drill and postdrill sampling of water sources Colorado and Wyoming Other states reference general USGS and USEPA sampling guidance for monitoring wells and surface waters Selection of sampling methodology is often at the operator s discretion 1 Open System Direct Fill Method (40 ml VOA vials) Three Common Sampling Methods for Dissolved Gases 2 Semi-Closed System Inverted Bottle Method (40 ml VOA vials) 3 Closed System In-Line Sampling Device (IsoFlask ) RESEARCH QUESTION: What is the effect of different sample collection methods on dissolved methane concentrations? 29

30 BASELINE SAMPLING METHODS

31 BASELINE SAMPLING CHALLENGES Residential Wells are not Monitoring Wells Majority of baseline sampling efforts focus on residential water wells: Well construction details are limited Open hole completions Water has mixed aquifer conditions (different fractures supply water) Sampling is conducted at the surface from the water well system (e.g., outlet of the pressure tank) Existing guidance for sampling of monitoring wells does not apply to residential water wells (e.g., dissolved gas sampling) KEY POINT: Residential water wells create additional complications for environmental sampling 31

32 BASELINE SAMPLING CHALLENGES Residential Wells are not Monitoring Wells Majority of baseline sampling efforts focus on residential water wells: Well construction details are limited Open hole completions Water has mixed aquifer conditions (different fractures supply water) Sampling is conducted at the surface from the water well system (e.g., outlet of the pressure tank) Existing guidance for sampling of monitoring wells does not apply to residential water wells (e.g., dissolved gas sampling) KEY POINT: Residential water wells create additional complications for environmental sampling 32

33 BASELINE SAMPLING METHODS Where are Samples Typically Collected? (Clean Water Store, 2014) KEY POINT: It is generally recommended that samples be collected as close to the well as possible prior to treatment devices 33

34 BASELINE SAMPLING METHODS Where are Samples Typically Collected? (Clean Water Store, 2014) KEY POINT: It is generally recommended that samples be collected as close to the well as possible prior to treatment devices 34

35 BASELINE SAMPLING METHODS Common Dissolved Gas Sampling Methods Direct-Fill Method w/ 40 ml VOA Vials Two upright 40 ml VOA vials were filled directly from the faucet (or via ¼ tubing connected to the faucet) after the pressure tank. Inverted Bottle Method w/ 40 ml VOA Vials Two 40 ml VOA vials were inverted and submerged in a 5 gallon bucket filled with well water, and subsequently filled through ¼ tubing attached to the faucet after the pressure tank. RESEARCH QUESTION: In-line Sampling Device w/ IsoFlask A single 750 ml IsoFlask sample was collected directly from the tubing attached to the faucet after the pressure tank. What is the effect of different sample collection methods on dissolved methane concentrations? 35 35

36 BASELINE SAMPLING METHODS Sampling Variability Study 9 residential water wells in Susquehanna and Bradford Counties, NE Pennsylvania All wells were >2,500 ft from the nearest existing or proposed gas well location Adaptor 6 Casing Well Completion Well Depths Casing Volumes Methane Concentrations Open hole; completed in Catskill Formation, Lock Haven Formation, and glacial till ft btoc gallons Low: < 5 mg/l Medium: 5 15 mg/l High: > 15 mg/l 6 Bedrock Hole 1 Discharge Pipe Troll 4 Pump General Well Schematic 36

37 BASELINE SAMPLING METHODS Effect of Sample Collection Question What is the effect of different sample collection methods on dissolved methane concentrations? Open System Direct Fill Method (40 ml VOA vials) Closed System In-Line Sampling Device (IsoFlask ) 37

38 BASELINE SAMPLING METHODS Effect of Sample Collection Question What is the effect of different sample collection methods on dissolved methane concentrations? Open System Direct Fill Method (40 ml VOA vials) Semi-Closed System Inverted Bottle Method (40 ml VOA vials) KEY POINT: Sampling method can impact resulting dissolved methane concentrations, particularly at higher methane wells 38

39 BASELINE SAMPLING METHODS Effect of Well Purging Challenge Procedure 3 consecutive readings of: ph = ± 0.2 SU Spec. Cond = ± 5% Temp. = ± 0.2 C Determine how purge volume affects variability in dissolved gas concentrations and water quality at domestic water wells At three events, samples were collected after 5 successive purge volumes: Zero purge (1 min = ~0.5 gallons) Purge to parameter stability 0.5 casing volumes 1 casing volume 3 casing volumes Analyses Dissolved gases, isotopic composition of methane, water, and DIC, water quality parameters 39

40 BASELINE SAMPLING METHODS Effect of Well Purging Question What is the effect of purge volume on dissolved methane concentrations? Change from No Purge to 3 Casing Volumes Purged typically 30% KEY POINT: No clear advantage to purging larger volumes of water to produce more consistent dissolved gas concentration results. 40

41 BASELINE SAMPLING METHODS Well Purging: Field Parameter Stabilization? Question Do field parameters remain stable after initial stabilization? Stabilization Criterion: ±5% 41

42 BASELINE SAMPLING METHODS Well Purging: Field Parameter Stabilization? Question Do field parameters remain stable after initial stabilization? Stabilization Criterion: ±0.2 KEY POINT: Parameters don t necessarily remain stable indicating that water source can continue to evolve throughout purging process. 42

43 DATA ANALYSIS & INTERPRETATION

44 Methane Conc. (mg/l) BASELINE SAMPLING CHALLENGES Methane: Natural vs. Impact Challenge: Differentiating natural variability in groundwater quality from induced variability (i.e., impacts) Pre-Drill Post-Drill January October 7 mg/l PADEP lower threshold for potential stray gas migration incident response KEY QUESTION: Are observed changes in residential water quality within the range of expected variability or suggestive of an impact? 44

45 BASELINE SAMPLING DATA ANALYSIS Lines of Evidence: Isotopic Signature Gas Shows Throughout (Molofsky et al., 2013) KEY POINT: Isotopic analysis may enable methane source identification but it s not always a silver bullet 45

46 BASELINE SAMPLING DATA ANALYSIS Other Lines of Evidence Topography Upland Well Water Type Redox State Valley Well Ca- Rich Na- Rich Oxidized Reduced Key Research Question How do these factors help us understand the occurrence of natural methane, and differentiate between natural methane and that originating from a stray gas incident? 46

47 BASELINE SAMPLING DATA ANALYSIS Understanding Natural Methane Occurrence RESIDENCE TIME SHORT (Younger) LONG (Older) Water Type CaHCO 3 NaHCO 3 Cation Exchange Ca 2+ & Mg 2+ Na + Mineral Dissolution Lower TDS Higher TDS Mixing with Na-Cl Water Low Cl - Higher Cl - Redox State More Oxidized More Reduced KEY POINT: Elevated methane occurrence may be associated with older groundwater with longer residence times. 47

48 BASELINE SAMPLING DATA ANALYSIS Temporal Variability Analyte Concentration (mg/l) Question Do dissolved methane concentrations correlate with other water quality parameters over time? KEY POINT: Methane variability is strongly correlated with total dissolved solids and other water quality parameters 48

49 BASELINE SAMPLING DATA ANALYSIS Well Purging: Key Relationships Question Do dissolved methane concentrations correlate with other water quality parameters over time? ± 30% KEY POINT: Continuous purging of the well can drive differential input from fractures that feed the wellbore. More sodium-rich water = higher dissolved methane. 49

50 BASELINE SAMPLING DATA ANALYSIS Advanced Redox State Methane Conc. (µg/l) NO 3, SO Mixed High NO 3 - Low NO 3 - Low SO 4-2 Redox Classification KEY POINT: Elevated methane concentrations are associated with sulfatedepleted conditions. 50

51 BASELINE SAMPLING DATA ANALYSIS Water Type: Calcium- vs. Sodium-Rich Waters Methane Conc. (µg/l) Water Type KEY POINT: Elevated methane concentrations are associated with sodium-rich water types. 51

52 BASELINE SAMPLING DATA ANALYSIS Topography: Upland vs. Valley Wells Molofsky et al, 2011,

53 BASELINE SAMPLING DATA ANALYSIS Understanding Natural Methane Occurrence Median Methane Conc. (µg/l) All Samples (1514) Na-rich Water (174) Na-rich Water + Valley Wells (101) Na-rich Water + Valley Wells + Low SO 4 (57) KEY POINT: In combination, these three risk factors provide remarkable predictive power for natural methane. 53

54 STRAY GAS IMPLICATIONS How can we use this information? 1 2 Pre-Drill Condition Higher number of natural risk factors Lower number of natural risk factors Interpretation Post-drill elevated methane more likely to be natural. Post-drill elevated methane less likely to be natural. 54

55 STRAY GAS IMPLICATIONS How can we use this information? Methane (ug/l) Ca-Rich Water, High NO 3-10,000 1, Post-Drill Sample Is methane within the natural range for relevant conditions? 10 Pre-Drill Sample

56 BASELINE SAMPLING PROTOCOL Key Elements Important Design Elements Regulatory requirements Regional water quality information Consistent and applicable sampling methods Robust analyte list with end-goal in mind Knowledge of temporal, sampling, and lab variability Key relationships in water quality parameters Database management 56

57 SOME TAKE-HOME MESSAGES Baseline Sampling Regulations Need for consistency among state agency regs/guidelines Sample Bottle and Collection Method Sampling method can impact resulting dissolved methane concentrations, particularly at higher methane wells Effect of Purge Volume Based on the wells tested, there appears to be no real benefit to purging larger volumes of water Key Relationships with Methane Key associations with methane can be used to better understand natural methane occurrence in the subsurface 57

58 REFERENCES Fun Night Time Reading! Molofsky, L.J., Richardson, S.D., Gorody, A.W., Baldassare, F.; McHugh, T.E.; and J.A. Connor (accepted). Effect of Different Sampling Methodologies on Measured Methane Concentrations in Groundwater Samples, Groundwater. Molofsky, L.J., Connor, J.A., McHugh, T.E., Richardson, S.D., Woroszlyo, C., P.A. Alavarez (accepted). Environmental Factors Associated with Natural Methane Occurrence in the Appalachian Basin, Groundwater. Molofsky, L.J., Connor, J.A., Wylie, A.S., Wagner, T., and S.K. Farhat (2013). Evaluation of Methane Sources in Groundwater in Northeastern Pennsylvania, Groundwater, Vol. 51, Issue 3: Molofsky, L.J., Connor, J.A., Wylie, A.S., Wagner, T., and S.K. Farhat (2011). Methane in Pennsylvania water wells unrelated to Marcellus Shale fracturing, Oil and Gas Journal, Dec. 5, 2011:

59 Stephen D. Richardson, Ph.D, P.E. GSI Environmental Inc. (512) Ann P. Smith, P.E., BCEE GSI Environmental Inc. (512)

60 BASELINE SAMPLING REGULATIONS Analytical Suite 60