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USGS2014

Borehole geophysical data for the East Poplar oil field area, Fort Peck Indian Reservation, northeastern Montana, 1993, 2004, and 2005

Areas of high electrical conductivity in shallow aquifers in the East Poplar oil field area were delineated by the U.S. Geological Survey (USGS), in cooperation with the Fort Peck Assiniboine and Sioux Tribes, in order to interpret areas of saline-water contamination. Ground, airborne, and borehole geophysical data were collected in the East Poplar oil field area from 1992 through 2005 as part of this delineation. This report presents borehole geophysical data for thirty-two wells that were collected during 1993, 2004, and 2005 in the East Poplar oil field study area. Natural-gamma and induction instruments were used to provide information about the lithology and conductivity of the soil, rock, and water matrix adjacent to and within the wells. The well logs were also collected to provide subsurface controls for interpretation of a helicopter electromagnetic survey flown over most of the East Poplar oil field in 2004. The objective of the USGS studies was to improve understanding of aquifer hydrogeology particularly in regard to variations in water quality.

Montana↗

USGS2006

Helicopter electromagnetic and magnetic survey maps and data, East Poplar oil field area, Fort Peck Indian Reservation, northeastern Montana, August 2004

This report is a data release for a helicopter electromagnetic and magnetic survey that was conducted during August 2004 in a 275-square-kilometer area that includes the East Poplar oil field on the Fort Peck Indian Reservation. The electromagnetic equipment consisted of six different coil-pair orientations that measured resistivity at separate frequencies from about 400 hertz to about 140,000 hertz. The electromagnetic resistivity data were converted to six electrical conductivity grids, each representing different approximate depths of investigation. The range of subsurface investigation is comparable to the depth of shallow aquifers. Areas of high conductivity in shallow aquifers in the East Poplar oil field area are being delineated by the U.S. Geological Survey, in cooperation with the Fort Peck Assiniboine and Sioux Tribes, in order to map areas of saline-water plumes. Ground electromagnetic methods were first used during the early 1990s to delineate more than 31 square kilometers of high conductivity saline-water plumes in a portion of the East Poplar oil field area. In the 10 years since the first delineation, the quality of water from some wells completed in the shallow aquifers in the East Poplar oil field changed markedly. The extent of saline-water plumes in 2004 likely differs from that delineated in the early 1990s. The geophysical and hydrologic information from U.S. Geological Survey studies is being used by resource managers to develop ground-water resource plans for the area.

Montana↗