SPATIAL AND TEMPORAL TRENDS IN UNDERGROUND INJECTION CONTROL WELL VOLUMES, OKLAHOMA

Water and other fluids have been injected into oil and gas reservoirs for decades to allow for secondary recovery or enhanced oil recovery (EOR) of petroleum. Flowback water from well completion and water co-produced with oil and gas are commonly disposed of via saltwater disposal (SWD) wells. Recent research has suggested a link between these fluid injections and seismicity in several regions of the United States. In some parts of the mid-continent, such as Oklahoma, there is limited published information regarding volumes of fluids injected, formation or injection pressures and the variability of those parameters in space and time. As a result of this data gap it is difficult to separate induced from natural seismicity or to manage seismic risk associated with subsurface fluid injection. The objectives of this research were to create and summarize Class II underground injection control (UIC) well data for Oklahoma from 2000 to present. Well completion data from various sources were compiled to determine the zone into which fluids are injected for the more than 11,000 UIC wells in the state. Spatial and temporal trends in EOR and SWD volumes and pressures were examined and analyzed. The most complete dataset compiled thus far is for the year 2011 which indicates that the Desmoinesian, Missourian, and Atokan-Morrowan zones receive the greatest volumes of EOR fluids with a statewide total EOR volume estimated to be 1427 million barrels. Saltwater is disposed predominantly into the Arbuckle Group, Multiple-Undifferentiated, and Devonian to Middle Ordovician zones with a statewide total SWD volume estimated to be 1018 million barrels. Spatial and temporal trends in fluid injection volumes are related to development of water-saturated emerging plays such as the Mississippian or to cycles of dewatering projects and secondary recovery activity.