Stephen D. Richardson, Ph.D., PE, of GSI Environmental Inc. in Austin, Texas, and his team are presenting research results on baseline sampling of water wells in areas of shale gas development at the NGWA Groundwater Quality and Unconventional Oil and Gas Development: Current Understanding and Science Needs workshop, April 25-26 in Columbus, Ohio.
Upcoming workshop presenter previews findings on baseline sampling of water wells in areas of shale gas development
Below Richardson gives a preview of their presentation as well as what he is looking forward to learning at the conference.
NGWA: Your team is presenting “Recommended Practices for Baseline Sampling of Water Wells in Areas of Shale Gas Development.” Can you give us a short preview of your findings you’ll discuss? What do you hope attendees learn and possibly implement at their job?
Richardson: Our research culminated in several key recommendations for sampling method, purging practices, temporal variations in methane concentrations, and data interpretation that we hope will contribute to the design and implementation of future predrill and postdrill groundwater monitoring programs. Specifically, we found sampling methodology can play an important role in the resulting variability of dissolved methane concentrations, particularly at wells with methane concentrations near or exceeding saturation (effervescing conditions).
Further, we found the natural variability of dissolved methane concentrations during purging or over time, in many cases, correlate well with changes in sodium, specific conductivity, and other geochemical parameters. Finally, for wells with dissolved methane concentrations greater than 1 mg/L in the study area, changes in concentration greater than twofold were not commonly observed. Findings from this study contribute to the design and implementation of predrill and postdrill groundwater monitoring programs by providing practical recommendations for sampling of dissolved gases at residential water wells, highlighting simple relationships for improved data interpretation, and establishing expectations for temporal variations in methane concentrations.
NGWA: Which of the study’s findings surprised you the most?
Richardson: The most surprising observation was the dramatic impact common sampling methods have on resulting dissolved methane results under effervescing conditions. Specifically, the consistency with which the closed system sampling method (i.e., the “IsoFlask”) reported significantly higher dissolved methane concentrations than either the open system or semiclosed system sample collection methods under effervescing conditions was an important finding.
NGWA: What are some of the biggest challenges operators face when conducting baseline sampling of residential water wells in areas of shale gas development?
Richardson: One of the challenges operators face is the lack of downhole access to a water supply wellbore, which leads to limited understanding of well construction and other well dynamics that can influence changes in water quality over time.
Another critical challenge is understanding the extent of natural variability in dissolved methane concentrations for a given region. This variability can confound interpretation of predrill vs. postdrill data comparison and complicate source identification. Most importantly, little guidance is available to operators, regulators, and contractors to support the development of predrill and postdrill sampling programs. Consistent best practices for sampling of water sources is an important step to achieving representative water quality results (especially dissolved gas concentrations) from residential water wells of varying construction and system design.
NGWA: It appears shale gas development will continue to rise in the United States in the coming years. What are your thoughts on the future of baseline sampling residential water wells in these areas?
Richardson: Baseline sampling of residential water wells and other water sources will continue to be an important component of assessing the potential risk to surrounding receptors by oil and gas development. Currently, 13 state agencies in the United States have final regulations for sampling of water sources in areas of shale development, and numerous national and regional organizations representing environmental and oil and gas stakeholders support baseline sampling efforts to better assess risk. As we continue to improve our understanding of natural methane occurrence in the subsurface and its relationship to other geochemical parameters, we anticipate greater consistency will be achieved between state agency-required analytical suites and key parameters that can best alert operators, regulators, and well owners to potential impacts.
NGWA: In addition to presenting your team’s study of findings, which session or sessions are you most looking forward to attending at the conference?
Richardson: I’m looking forward to attending all three sessions. It’s a wonderful opportunity to learn more about cutting-edge research on stray gas migration, monitoring approaches, and chemical fate and transport from top researchers across the United States and Canada. I look forward to sharing findings from our research and to meet with others who are trying to answer some of the same fundamental questions that we are.
NGWA thanks Richardson for his time in answering these questions and in presenting at the workshop. Check back as we’ll post updates from the workshop as they’re made available.