Preliminary Hydrogeological Modeling of Deep Injection in the Delaware Basin for Pore Pressure Characterization with Application to Induced Seismicity

Abstract:

The Delaware Basin of west Texas and southeastern New Mexico is now one of the world’s most productive petroleum provinces. Within the basin the earthquake rate has accelerated significantly alongside recent petroleum development. Many of these earthquakes have been spatiotemporally linked to petroleum operations including deep injection of oilfield wastewater (SWD). Since February of 2020, series of earthquakes have occurred near Mentone, TX including a M5.0. It is possible that this new earthquake sequence has been caused by increasing reservoir pores pressure associated with SWD in formations between basement and the intervals targeted for petroleum production.

To assess the potential for SWD-inducement in the Mentone area and in southern New Mexico we have constructed screening-level 3D geological and hydrogeological models of the entire northern Delaware Basin in Texas and New Mexico that span the formations used for SWD between basement and the intervals targeted for petroleum development. Our geological model was constructed using Petrel with geometric control from ~7,300 wells and spanning the Cambrian through Pennsylvanian strata used for SWD. The thickness of the model varies from 1,000 to 11,000 ft following the structure of the basin and it is partitioned into 15 layers following generalized lithology. Our hydrogeologic uses model uses CMG STARS and incorporates 189 SWD wells, mainly in New Mexico, which were active from January 1989 to January 2020. The reservoir properties are derived from data from the Fort Worth Basin of northcentral Texas which contains closely analogous strata and better quantitative control. The model is calibrated using injection pressure constraints while honoring injection volume history using 37 SWD injection wells.

Preliminary results indicate that the pore pressures have increased regionally by 150 to 300 psi in some areas (please refer to the picture: pressure increase in psi from 1989 to 2020). The impacted area is mainly in New Mexico, including areas with new earthquake sequences. In addition, the model predicts a corridor of elevated pore pressure that extends southward to the Mentone area in Texas and, with the observation that the earthquakes in the general area are also deep, provides a justification that the region may be experiencing seismicity induced from deep SWD.