Brine Contamination from Oil and Gas Development in the Williston Basin, Montana
Since the 1950s, billions of barrels of brine have been produced with oil from deep formations (>5,500 feet) in the Williston Basin. This brine is some of the most saline water in the nation and can contain chloride concentrations that are near saturation. Brine disposal and handling methods use storage tanks and wells connected by a network of pipelines that include pits and injection into subsurface geologic units. These disposal and handling methods have resulted in contamination of surface water and shallow groundwater at multiple locations throughout the Williston Basin.
Using a combination of geophysical and geochemical methods, the U.S. Geological Survey (USGS) has delineated brine contamination in and near the East Poplar oil field along the western flank of the Williston Basin. Results of this effort show the brine is present throughout the shallow saturated zone in contaminated areas. The brine contamination has been documented for several decades and has not only affected the water quality of privately owned wells, but also the City of Poplar’s public-water supply wells.
The USGS, the Montana Bureau of Mines and Geology, and the U.S. Fish and Wildlife Service have identified brine contamination at multiple locations throughout the Medicine Lake National Wildlife Refuge, located in the northwestern portion of the Williston Basin. The source of the brine may be from buried storage pits that were installed in the mid- to late 1960s.
Concerns about current energy development of the Bakken Formation in the Williston Basin often focus on the hydraulic fracturing component and the associated chemical additives. Lessons from previous energy development in the Williston Basin indicate that concerns should also focus on the large volumes of brine that can inadvertently cause serious effects to water resources from oilfield infrastructure.
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