Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Arts (MA)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Duke Ophori

Committee Member

Joshua Galster

Committee Member

Huan Feng

Subject(s)

Groundwater--Pollution--Wyoming-- Pavillion, Groundwater flow--Computer simulation, Hydraulic fracturing--Environmental aspects--Wyoming--Pavillion, Gas well drilling--Environmental aspects --Wyoming-- Pavillion

Abstract

This thesis uses the GIS-conceptual model approach to create groundwater models investigating groundwater contamination near Pavillion, Wyoming. This area was part of a study by the US Environmental Protection Agency (EPA) in 2009 that claims domestic water well contamination originated from hydraulically fractured natural gas wells. Hydraulic fracturing is the process of injecting water, sand, and chemicals into gas and oil wells in order to stimulate well production. This has caused concern over groundwater contamination. The models show natural groundwater flow systems generally move from west to east, however, a recharge area near the center of the model locally disrupts that pattern. Fivemile Creek is the primary discharge zone, located towards the northern end of the model. Once gas production is included in the model, the groundwater flow systems change drastically; injection wells induce areas of high head that cause groundwater to flow away from them, while extraction wells draw groundwater towards them. This flow system alteration affects where advective groundwater transport carries dissolved methane. Groundwater flow patterns change direction in response to varying monthly extraction and injection rates, however proper well casing can mitigate these effects by isolating the flow occurring within a well from the surrounding groundwater flow systems. The resulting models support the EPA’s conclusion that hydraulic fracturing was the most likely cause of water contamination in the area by showing that deep contaminants found at the EPA monitoring well can be traced back to a gas development well, while shallower contaminants could have originated from other areas that are not within the vicinity of natural gas wells. Proper casing is crucial for minimizing the disturbance and anthropogenic methane contamination of natural groundwater flow systems. The methodology of this thesis can be used to create groundwater models of any area where enough data is available to create realistic groundwater models.

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