An Assessment of the Probability of Subsurface Contamination of Aquifers from Oil and Gas Wells in the Wattenberg Field, Modified for Water Well Location

Abstract

AbstractThe United States National Science Foundation has funded a Sustainability Research Network (SRN) focused on natural gas development in the Rocky Mountain region of the United States. The objective of this specific study is the assessment of the use of existing water wells to monitor the risk of the contamination by the migration of fracturing fluids or hydrocarbons to fresh water aquifers. An additional objective of the study is to modify existing risk estimates using the spacial relationships between the existing water wells and producing oil wells. This will allow estimates of single barrier failure and multiple barrier failure resulting in contamination to be projected for oil and gas wells in areas without surrounding water wells to detect migration, based on well construction type.Since 1970, the Wattenberg Field in Colorado has a large number of oil and gas wells drilled. These wells are interspaced tightly with agricultural and urban development from the nearby Denver Metropolitan area. This provides a setting with numerous water wells that have been drilled within this area of active petroleum development. Data from 17,948 wells drilled was collected and analyzed in the Wattenberg field, allowing wells to be classified by construction type and analyzed for barrier failure and source of aquifer contamination. The assessment confirms that while natural gas migration has occurred in poorly constructed wellbores is infrequent, it can happen and that the migration risk is determined by the well construction standards. The assessment also confirms that there has been no occurrence of hydraulic fracturing fluid contamination of fresh water aquifers through wellbores. The assessment determines both the spacial proximity of oil and gas wells and surface casing depth to water wells to determine the utility of water wells to monitor migration in oil wells.