TIERED APPROACH TO EVALUATION AND MANAGEMENT OF PRODUCED WATER IMPACTS ON GROUNDWATER RESOURCES

Transcription

1 TIERED APPROACH TO EVALUATION AND MANAGEMENT OF PRODUCED WATER IMPACTS ON GROUNDWATER RESOURCES Shawn M. Paquette, P.E., BCEE, John A. Connor, P.E., P.G., BCEE, Lisa J. Molofsky, P.G., Kenneth L. Walker, Jr., P.E. GSI Environmental Inc., Houston, TX

2 WHERE ARE WE TODAY IN CALIFORNIA? DROUGHT SALINE GW USE INJECTION WELLS Oil & Gas Operations Future Water Demand 2

3 EFFICIENT EVALUATION & SUSTAINABLE MANAGEMENT OF PRODUCED WATER IMPACTS Two Key Questions: Is there a produced water impact? How do we manage impact in sustainable manner? 3

4 NATURAL RESOURCE ASSESSMENT: PRINCIPAL ELEMENTS INJURY: Change in the chemical composition, yield, or discharge of GW aquifer BKG LOSS OF SERVICE: DAMAGE: Loss of beneficial use of GW by human users, the ecosystem (e.g., discharge to SW), or other in place services (e.g., prevention of subsidence) Monetary value of the lost or impaired service caused by the injury Restore loss of service, not chemistry $ 4

5 INJURY: Evaluation of Potential PW Impacts Is There an Injury? Is there a salinity impact to the aquifer? Is the impact due to PW or other source(s)? BKG? Tiered Evaluation Approach: TIER 1: Initial Screening Process TIER 2: Basic Geochemical Analyses TIER 3: Advanced Geochemical Analyses 5

6 TIERED EVALUATION APPROACH Why do we need help with impact/injury evaluations? Source(s) of salinity difficult to distinguish Numerous evaluation techniques Best tool dependent on site specific characteristics Multiple lines of evidence may be needed OBJECTIVE: Provide tiered approach for effective and efficient evaluation. 6

7 TIERED EVALUATION APPROACH TIER 1: INITIAL SCREENING PROCESS TIER 2: BASIC GEOCHEMICAL ANALYSIS TIER 3: ADVANCED GEOCHEMICAL ANALYSIS TDS or Cl Below Applicable Criteria TDS Source of Basic No No No or Cl Elevated Geochemical No < Background Salinity Analyses Conclusive Conclusive Advanced Geochemical Analyses Conclusive No Yes Yes Yes Yes Yes NO FURTHER EVALUATION WARRANTED ADDITIONAL DATA/ REVISED METHODS KEY POINT: Match level of effort and complexity of evaluation to site specific conditions and complexity. 7

8 TIER 1: INITIAL SCREENING PROCESS Chloride Conc. BACKGROUND CRITERIA NO INJURY SOURCE CONCLUSIVE SOURCE INCONCLUSIVE NFA MANAGEMENT TIER 2 8

9 TIER 2: BASIC GEOCHEMICAL ANALYSES TO EVALUATE SOURCE OF SALINITY PIPER STIFF HISTOGRAMS SCHOELLER PIE BAR RADIAL BIVARIATE 9

10 TIER 3: MIXING LINE EXAMPLE 1,000 Potassium vs. Chloride Seawater Produced Water Potassium (mg/l) Background ,000 10, ,000 Chloride (mg/l) KEY POINT: Elevated salinity in southern portion of site attributable to seawater intrusion, limiting scope of investigation and corrective action activities. 10

11 NATURAL RESOURCE ASSESSMENT: PRINCIPAL ELEMENTS INJURY: Change in the chemical composition, yield, or discharge of GW aquifer BKG LOSS OF SERVICE: DAMAGE: Loss of beneficial use of GW by human users, the ecosystem (e.g., discharge to SW), or other in place services (e.g., prevention of subsidence) Monetary value of the lost or impaired service caused by the injury Restore loss of service, not chemistry $ 11

12 LOSS OF SERVICE: BASELINE SERVICES OF GROUNDWATER EXTRACTIVE: NON EXT./ DISCHARGE: NON EXT./ STOCK VALUE: OPTION VALUE: Pumping and use of GW as water supply (e.g., potable, irrigation, industrial, geothermal) Natural discharge of GW to SW (e.g., potable SW, ecological habitat, recreational activities) Storage Prevention of subsidence or seawater intrusion Protection of usable water Disposal of waste liquids in saline aquifer Future back up water supply 12

13 NATURAL RESOURCE ASSESSMENT: PRINCIPAL ELEMENTS INJURY: Change in the chemical composition, yield, or discharge of GW aquifer BKG LOSS OF SERVICE: DAMAGE: Loss of beneficial use of GW by human users, the ecosystem (e.g., discharge to SW), or other in place services (e.g., prevention of subsidence) Monetary value of the lost or impaired service caused by the injury Restore loss of service, not chemistry $ 13

14 DAMAGE: VALUATION/SUSTAINABLE REMEDY SELECTION DAMAGE SUSTAINABLE REMEDY SELECTION Value of replacement or restoration of lost service For lower quality GW, Damage is the incremental increase in treatment costs Restore lost service Protect users (i.e., humans, ecosystem, etc.) Preserve other services of GW unit and interconnected units May include: Well head/point of use treatment Relocation of water supply well Use of alternate water supply 14

15 NATURAL RESOURCE ASSESSMENT: EXAMPLE 1 0 ~100 Regional Aquifer Well Injection Well Recovery Well SWD Well Upper Sand Unit Loss of option value in lower quality, lower yield sand unit due to PW impacts Deeper high quality, high yield regional aquifer used for domestic and irrigation needs ~150 Regional Aquifer POTENTIAL REMEDIAL OPTIONS: Option 1: Flush and pump Option 2: Monitor >~3,100 Brine Reservoir 15

16 NATURAL RESOURCE ASSESSMENT: EXAMPLE 1 0 ~100 Regional Aquifer Well Injection Well Recovery Well SWD Well Upper Sand Unit REMEDY EVALUATION: Both meet objective to protect human health & environment Upper Sand Unit has low option value Option 1 consumes large volume of water from regional aquifer ~150 Regional Aquifer Loss of storage Subsidence concerns Option 1 consumes energy and creates waste stream >~3,100 REMEDY SELECTION: Option 2 (monitoring) more sustainable remedial Brine Reservoir alternative. 16

17 NATURAL RESOURCE ASSESSMENT: EXAMPLE 2 Produced water injection into saline aquifer 17

18 NATURAL RESOURCE ASSESSMENT: EXAMPLE 2 KEY QUESTIONS Likely to be used as drinking water? TDS (mg/l) 10,000 3,000 1,000 NO UNLIKELY POSSIBLE YES If used, incremental treatment cost? $ Aquifer Conc. Background Standard Pressure Reverse Osmosis Δ = Damage Adapted from NRC, 2008 Influent TDS 18

19 WRAP UP: TWO KEY QUESTIONS Is there a produced water impact? Tiered Approach to Injury Determination How do we manage impact in sustainable manner? Natural Resource Assessment & Valuation Concepts for Sustainable Management 19

20 CONTACT INFORMATION 2211 Norfolk Suite 1000 Houston, TX O: Shawn M. Paquette, P.E., BCEE 20