POTENTIAL TO USE CLASS II WELLS TO DISPOSE OF DESALINATION RESIDUAL FLUIDS IN TEXAS

Procedures are developed to delineate scientifically defensible buffer distances for Class II disposal wells from designated Brackish Groundwater Production Zones (BGPZ) in Texas. Desalination of brackish water is a process that will be used to meet the water needs of the growing Texas population, but the disposal of the residual fluids is an issue. There are over 75,000 Class II wells in Texas designed to inject fluids, but are currently restricted to injecting fluids associated with oil and natural gas production. Class II wells can be disposal wells, enhanced oil recovery (EOR) wells, or hydrocarbon storage wells. Procedures were developed to (1) streamline and automate compilation of injection well data from the Railroad Commission of Texas databases; (2) obtain hydrogeologic and hydrostratigraphic information from available Brackish Resources Aquifer Characterization System (BRACS) studies on Texas Aquifers developed by the Texas Water Development Board; and (3) model the migration of injectate within the BRACS study aquifers to delineate scientifically defensible buffer distances for Class II injection wells from designated BGPZ. Procedures are based on the analytical solutions of Bear and Jacobs (1965} and the EPA (1994). These (1) provide generic and robust solutions for deep well injection analysis; (2) are suitable for regional-scale analyses; and (3) provide efficient screening level assessments that are capable of identifying areas that may require more detailed, site-specific studies. Additionally, the procedures can be readily adopted for analyses of injectate migration for other well classes in various aquifer systems or in computing extraction well capture zones. Class II disposal wells offer potential sites for disposal of desalination residual wells. Class II EOR wells were not analyzed in this study, but offer another potential option.