Structural characterization of potentially seismogenic faults in the Fort Worth Basin

Abstract

From 2006 through mid-2018, there have been 125 [Formula: see text] recorded earthquakes within the Fort Worth Basin and the Dallas-Fort Worth metropolitan area. There is general scientific consensus that this increase in seismicity has been induced by increases in pore-fluid pressure from wastewater injection and from cross-fault pore-pressure imbalance due to injection and production. Previous fault stress analyses indicate that many of the faults are critically stressed; therefore, careful consideration should be taken when injecting in close proximity to these structures. Understanding the structural characteristics that control geomechanical aspects of these earthquake-prone faults is vital in characterizing this known hazard. To improve understanding of faults in the system, we have developed a characterization using a new basin-wide fault interpretation and database that has been assembled through the integration of published data, 2D and 3D seismic surveys, outcrop mapping, earthquakes, and interpretations provided by operators resulting in a 3D structural framework of basement-rooting faults. Our results show that a primary fault system trends northeast–southwest, creating a system of elongate horsts and grabens. Fault architectures range from isolated faults to linked and cross-cutting relay systems with individual segments ranging in length from 0.5 to 80 km. The faults that have hosted earthquakes are generally less than 10 km long, trend toward the northeast, and exhibit more than 50 m of normal displacement. The intensity of faulting decreases to the west away from the Ouachita structural front. Statistical analysis of the fault length, spacing, throw, and linkage tendency enables a more complete characterization of faults in the basin, which can be used to mitigate the seismic hazard. Finally, we find that a significant percentage of the total population of faults may be susceptible to reactivation and seismicity as those that have slipped recently.

Pore Pressure Threshold and Fault Slip Potential for Induced Earthquakes in the Dallas‐Fort Worth Area of North Central Texas

“…(2019) and Horne et al. (2020) (Figures 1 and 2). Most earthquakes have produced normal faulting mechanisms with NE‐striking nodal planes (Magnani et al., 2017; Quinones et al., 2018).…”

“…Earthquakes in the FWB occur primarily in discrete spatial sequences (Quinones et al, 2019) on faults recently interpreted by Hennings et al (2019) and Horne et al (2020) (Figures 1 and 2). Most earthquakes have produced normal faulting mechanisms with NE-striking nodal planes (Magnani et al, 2017;Quinones et al, 2018).…”

“…The matrix and facies information are from Smye et al (2019). Fault data are from Hennings et al (2019) and Horne et al (2020) who also point out that the faults are remarkably uniform in their structural characteristics such as strike, dip, and orientation with respect to the in situ stress state. The ΔPp model was calibrated using established reservoir engineering approaches and was thoroughly tested for its sensitivity to key input data.…”

“…The distribution of ΔPp experienced by the seismogenic and non-seismogenic faults is shown in Figure 4. We note however that as per Hennings et al (2019) and Horne et al (2020), this fault dataset is biased to capture all of the seismogenic faults that were interpreted from the ES areas but, due to scarcity of publicly available data with which to interpret faults uniformly throughout the basin, it underrepresents non-seismogenic faults.…”

“…Using diffusion models at regional scale, Gono et al (2015) found that ΔPp may have ranged 2.07-4.14 MPa in close proximity to the first ESs to develop (DA and Ce, Figure 1). Map of the area of interest in the Fort Worth Basin showing saltwater disposal wells and cumulative injected volumes, the entire record of seismicity from SMU NTXES, the earthquake sequences that we study here, traces of basement-rooted faults from Horne et al (2020), and the distribution of the maximum ΔPp at the basement-sediment interface from the Gao et al (2021)…”