CO-PRODUCTION AND MANAGEMENT OF SALTWATER FROM PETROLEUM RESOURCE PLAYS IN OKLAHOMA

Water and energy resources are fundamentally connected and have created what some refer to as the energy-water or water-energy nexus. A common goal of water and energy management is to maximize the supply of one while minimizing the use of the other. Saltwater management has become an important issue in the water-energy nexus, for example, because recent seismic activity in Oklahoma has far exceeded historic seismicity and is reportedly correlated to underground injection control wells. Therefore, there is an urgent need to understand saltwater production, management, and disposal practices while quantifying volumes and pressures by geologic zones from which saltwater is produced or injected.

Oklahoma’s statewide co-produced water volumes were estimated to range from 811–925 million barrels (MMbbl) from 2000–2011. Compilation of annual fluid injection report data indicates that statewide saltwater disposal (SWD) volumes were 878, 990, 1067, and 1193 MMbbl from 2010–2013, respectively, and are increasing at a rate that is similar to statewide petroleum production. In the last few years, an estimated 40–60% of Oklahoma’s co-produced saltwater volumes originated from oil and gas wells in the Mississippian play where median fluid production ratios of H2O:oil and H2O:gas were 7.4 and 9.8, respectively. Other widespread practices, such as dewatering operations in the Hunton of central Oklahoma, have resulted in high volumes of co-produced saltwater and subsequently high volumes for SWD. This paper summarizes Oklahoma’s injection well data on county- and annual- scales by geologic zone of completion. SWD volumes injected into the Arbuckle basal sedimentary strata increased most in Alfalfa, Grant, and Woods Counties of northern Oklahoma from 2010–2013, while SWD volumes in some central Oklahoma counties have decreased in that same time period.

Because co-production of saltwater varies in space and time, it is important to continue documenting recent trends and anticipating saltwater production rates in developing petroleum resource plays. When saltwater management plans includes a component of co-produced water recycle and reuse, we can develop jointly sustainable water and energy resources, while minimizing other geologic and environmental hazards.