HYDROGEOLOGICAL MODELING AND PORE PRESSURE CHARACTERIZATION OF THE DELAWARE BASIN DELAWARE MOUNTAIN GROUP, WEST TEXAS

The Permian-age Delaware Mountain Group (DMG) of the Delaware Basin in west Texas and southeastern New Mexico is the major target for produced water disposal and has taken up a large fraction of the overall water volume produced in the Basin from unconventional operations. Seismic activity in the Delaware Basin has recently increased starting in 2010 and is possibly related to injection operations, which have been increasing in the same time of period. The goal of the study is to determine the historical, current, and future pore pressure in the DMG using a numerical flow model (CMG-STARS software).

To better understand the relationship between seismicity, pre pressure evolution, and produced water disposal, a 3D hydrogeological model of the DMG was constructed with all available static data: well log data, stratigraphic data, petrophysical analysis, and core data. The model was upscaled into 18 layers composing the three major formations of the DMG (Bell Canyon, Cherry Canyon, and Brushy Canyon). Input data for the simulations are the monthly injection rates of 974 saltwater disposal (SWD) wells. The model permeability field was updated with dynamic injectivity information based on surface injection pressures and rates of the SWD wells. Model calibration was achieved comparing model pressures at well locations to bottom-hole pressures computed from field flowing wellhead pressures. Pressure projections (to 2025) were simulated using injection rates based on the average rate of last 6 months of each SWD well. Preliminary simulation results suggest pressure will keep growing at an increased rate. The basin-wide hydrogeological model provides a preliminary view on the pore pressure evolution of the DMG and is of great interest to help in implementing safe SWD management practices in the area.