![[Visit Client Website]](/img/gsa/banner.jpg)
Paper No. 201-7
Presentation Time: 9:50 AM
EXPLORING THE POTENTIAL LINKAGES BETWEEN OIL-FIELD BRINE REINJECTION, CRYSTALLINE BASEMENT PERMEABILITY, AND TRIGGERED SEISMICITY FOR THE DAGGER DRAW OIL FIELD, SOUTHEASTERN NEW MEXICO, USA USING HYDROLOGIC MODELING (Invited Presentation)
We used hydrologic models to explore the potential linkages between oil-field brine reinjection and earthquakes (up to Md 3.2) in southeastern New Mexico and to assess different injection management schemes aimed at reducing the risk of triggered seismicity. Our analysis focuses on saline water injection into the basal Ellenburger Group beneath the Dagger Draw Oil field, Permian Basin. Increased seismicity frequency (>Md 2) began in 2001 at an average depth of 11 km within the crystalline basement 15 km to the west of the reinjection wells. There is a 5-year lag between peak injection in 1996 and the onset of increased seismic frequency. Assigning a crystalline basement hydraulic diffusivity between 0.1-1 m2 s-1 produced between 20-50 m of excess heads to depths of 11 km about years after injection started. The lag between injection and seismicity can be explained by the time required for the pressure envelope to propagate laterally 15 km and downward into the crystalline basement 11 km. Several plausible scenarios could account for the pressure increases at 11 km depth including assigning a constant permeability to the crystalline basement of about 10-15 m2 and a specific storage of 10-7 m-1, allowing permeability to decrease with depth (from 10-12.8 to 10-15.3 m2), or including a vertical conductive fault zone (10-12 m2). The presence of a low permeability (10-16 m2) weathered zone at the top of the crystalline basement may prevent significant downward pressure propagation. We tested several injection management scenarios including redistributing injection between various wells and lowering the total volume of injected fluids. The scenarios that significantly reduced excess heads within the crystalline basement was to limit reinjection to 50% to 10% of the total volume of produced fluids.