Characterizing oil field salinization using airborne, surface, and borehole geophysics: An example from the Upper Colorado River Basin, Texas

Multidisciplinary investigations of natural and oil field salinization along the upper Colorado River, Texas, present an opportunity to integrate results from a stream-axis airborne geophysical survey, ground and borehole geophysical surveys, and well drilling and sampling. Airborne electromagnetic (EM) induction measurements along 437 km (272 mi) of river and tributary stream axes identified discrete salinized streambed segments, including several near oil fields. Identification of these salinized streambed segments allowed more intensive and invasive investigations to be focused on the most significant near-river sources of salinity. One of these streambed segments lies adjacent to an oil field, where production began in the 1950s before discharge of coproduced brine into surface pits was prohibited in Texas. Monitor wells drilled after the airborne survey verified groundwater salinization in the oil field but did not adequately delineate salinization nor identify specific salinity source areas. Subsequent ground and borehole geophysical surveys complemented airborne EM induction and well data by establishing lateral and vertical salinization bounds in the oil field, discovering possible salinity source areas, and determining optimal locations for additional wells.