AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Developing Water Budgets for Unconventional Oil and Gas Production: A Study in the Williston Basin, Montana and North Dakota
(1) USGS, Denver, CO.
(2) US Geological Survey, Helena, MT.
(3) US Geological Survey, Reston, VA.
New technologies have expanded domestic oil and gas production to include low-permeability formations once considered to be inaccessible. Hydrocarbon production from these formations commonly requires considerable quantities of fresh water (surface and/or groundwater) to increase conductivity through hydraulic fracturing (fracing). This water must be removed prior to resource extraction (flowback water); it generally contains salts and minerals from the formation in addition to the additives used to increase fracing efficiency. The volumes of water involved in these practices have already led to supply and disposal problems in some areas. To address such issues and to help stakeholders prepare appropriately, we are developing water-budget methods for oil and gas production. Standard USGS energy assessments provide estimates of technically recoverable resources and facilitate estimation of future hydrocarbon production scenarios. We extend these results to project the volume of water needed for hydrocarbon production.
The Williston Basin in Montana and North Dakota is the area of our initial focus due to (1) the large quantity of oil present in the Bakken Formation, and (2) the potential for impacts on the Prairie Pothole wetlands that host large numbers of migrating waterfowl. Current, rapidly escalating production of Bakken Formation oil requires a million or more gallons of fresh water per well for fracing. Historic and ongoing conventional oil production from other Williston Basin formations has resulted in large volumes of highly saline co-produced waters; in the past, some of these waters escaped into shallow aquifers and have impacted wetlands. We estimate the quantities of water (frac, flow-back, and co-produced) that would be involved in a range of future hydrocarbon production scenarios and compare these quantities with estimated total water budgets for the region. This allows for an evaluation of water-related impacts of oil and gas production for a range of possible future production scenarios.