Water Issues Associated with Increasing Unconventional Oil Production in the Permian Basin

The Permian Basin is being transformed from a major conventional oil play to the world's largest unconventional play; however, managing water for this transition is critical in this semiarid region. The study included quantifying produced water volumes with oil and gas production along with water demands for hydraulic fracturing using a detailed well-by-well analysis. Our results show that oil wells in conventional reservoirs generate large volumes of produced water relative to oil production with produced water to oil ratios of 13 (i.e. 13 barrels [bbl] of water relative to a bbl of oil). However, produced water from conventional reservoirs has been mostly injected back into the pressure-depleted oil-producing reservoirs for enhanced oil recovery using water flooding. Unconventional horizontal wells use large volumes of water for hydraulic fracturing that has been markedly increasing by factors of 10 - 16 per well and by factors of 7-10 after dividing by lateral well length (2008-2015). Although unconventional wells generate less produced water relative to oil ( 3 bbl of water relative to oil) than conventional wells, the main difference is that this produced water cannot be reinjected into the low permeability shale reservoirs. Instead, the produced water is disposed into non-producing geologic zones that could result in overpressuring and induced seismicity. There is a high potential for reusing produced water from unconventional wells in the Permian Basin because the produced water volumes can support the hydraulic fracturing water demand based on 2014 data. Reusing produced water with minimal water treatment (clean brine) could partially mitigate produced water injection concerns while reducing water demand for hydraulic fracturing.