BEG Friday Seminar Series
||April 3, 2015 at 9:00 am
||April 3, 2015 at 10:00 am|
| ||Location:||BEG Main Conference Room; Building 130; PRC Campus|
| ||Contact:||Sophia Ortiz, email@example.com, 512.475.9588|
| ||URL:||Event Link|
Bureau of Economic Geology
The Environmental Protection Agency’s (EPA) drilling and sampling of two deep-monitoring wells in the Pavillion, Wyoming gas field resulted in a draft report hailed by many as the first compelling evidence that hydraulic fracturing had contaminated freshwater aquifers. Consultants for the gas industry provided the EPA with reports highly critical of the well-completion techniques used and the EPA’s interpretation of the data. The United States Geological Survey (USGS) resampled the wells but did not provide any interpretation of its data. Soon afterward, the EPA dropped the project. This paper provides a new, independent analysis of the extensive data set available for these wells. Using previously ignored stable-isotope data on the water produced from the well, it can be demonstrated that the samples from both wells were contaminated by surface water used for grouting cement. The leached cement water introduced into the wells included most of the contaminants used by the EPA to support its fracturing-fluid contamination theory. Water samples taken from one of the wells was progressively purged and showed systematic decrease in key contaminant concentration with a decreasing percentage of surface water, given the oxygen-isotope values (and increasing purge volumes). As the portion of surface water in each sample decreases, so does the pH and the concentration of potassium, glycol compounds, 2-BE, and phenols. All these compounds are known components of the leachate from the portland cement of the type used. The issues with the EPA’s Pavillion study provide important lessons for any future attempts to carry out baseline or post-drilling monitoring of unconventional-gas development.