STRUCTURAL CHARACTERIZATION AND SEISMOGENIC ASSOCIATION OF BASEMENT-ROOTED FAULTS OF THE DELAWARE BASIN, WEST TEXAS

The Permian Basin of Texas and New Mexico is an important petroleum province that has experienced an increased number of earthquakes (EQs) beginning in 2009 with the rate of seismicity accelerating from 2016 through to present. Many of these EQs have been spatiotemporally linked to oilfield operations, however, the identification and characteristics of EQ hosting faults has remained elusive. This research leverages a new interpretation of basement-rooted faults in the Delaware Basin and associates geometric characteristics and fault surface stress states with well-located events from the TexNet Earthquake Catalog to determine which faults may be seismogenic, and the uncertainties to these qualifications.

Seismicity within the Delaware Basin occurs in both spatiotemporally isolated and diffuse clusters that are generally restricted to the southern Delaware Basin. This impacted area contains 240 fault surfaces, 35% of which trend NNW-SSE, 55% trend E-W and 10% trend NNE-SSW. This compares to the 650 faults mapped regionally where 63% of segments trend NNE-SSW, 34% trend E-W and only 2% of segments are oriented NNE-SSW.

To understand the relationship between EQs and basement-rooted faults, distance to EQ hypocentral locations were calculated for each fault segment, and a series of maps were generated to show spatial relationships of well-located EQ events at different lateral search radii for the analyzed faults. An updated regional stress model based on published and new inputs was used to calculate the static stress observed on these fault surfaces. When combined, these analyses show that fault surfaces range from stable to critically stressed, and many of the the critically stressed faults are proximal to recent EQs. Specifically, E-W trending and NNE-SSW faults have the closest association to observed seismicity, and NNE-SSW faults are most well-oriented for slip. Furthermore, EQs are more common at the conjuncture of these multiple-oriented fault groups creating a high degree of structural complexity.

As EQ rates continue to increase and the seismogenic region grows, it essential to characterize and identify faults of importance. The results of this study can be applied more broadly across the Permian Basin, in conjunction with other analyses, to be more predictive about the locations of future seismicity.