Fault Stability and Pore Pressure Thresholds for Seismogenic Rupture in the Midland Basin
Description:
Beginning in late 2020, the rates of seismicity in the Midland Basin (MB) increased significantly to an average of ~5 ML3.0+ events per month and a very notable ML5.4 earthquake occurred in December of 2022. Like what was experienced in the injection-induced seismicity cycle in the Ft. Worth Basin, the earthquakes in the MB occur in the igneous and metamorphic basement and are organized in localized sequences that exhibit well-defined onset timing and abrupt rate decline behavior. In the Midland Basin it is widely assumed that stressing of strata due to wastewater injection beneath oil- and water-productive Wolfcamp shales is the causal agent. Using a globally-calibrated model of pore pressure evolution (dPp) derived from a comprehensive geologic characterization, we assess the spatial and temporal relationship of Pp to earthquake sequence onset and behavior for 18 sequences. We use dPp as sampled from the deepest model layer in the Ellenburger into which the causative injection has occurred. We find that earthquake sequence onset occurred at dPp ranging from 63 to 513 psi with a mean of 224 psi. Pp gradient at onset ranged from 0.456 to 0.532 psi/ft. Earthquake sequence onset and evolution in the basin occurred in a wide range of stressing (dPp and ddPp) behavior. Some cases, such as Gardendale 1 and 4 and Midway experienced earthquake onset at low dPp, during a steady ramp-up in dPp, and during a period with a low degree of ddPp complexity. Faults reactivated under these conditions must be the most sensitive, natively. At the other extreme, several cases such as Stanton experienced earthquake onset associated with higher dPp, during a rapid increase in dPp, and during a period with a high degree of ddPp complexity. Faults reactivated under these conditions must be inherently more stable. By the end of 2015, ~40 km of fault trace length had dPp from injection of >150 psi above rupture stability which increased to ~320 km as the earthquakes studied developed by the early 2021.
Session: Advances in Characterizing Seismic Hazard and Forecasting Risk in Hydrocarbon Systems [Poster]
Type: Poster
Date: 4/18/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Peter Hennings
Student Presenter: No
Invited Presentation:
Authors
Peter Hennings Presenting Author Corresponding Author peter.hennings@beg.utexas.edu University of Texas at Austin |
Jun Ge jun.ge@beg.utexas.edu University of Texas at Austin |
Elizabeth Horne lily.horne@beg.utexas.edu University of Texas at Austin |
Jean-Philippe Nicot jp.nicot@beg.utexas.edu University of Texas at Austin |
Katie Smye katie.smye@beg.utexas.edu University of Texas at Austin |
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Fault Stability and Pore Pressure Thresholds for Seismogenic Rupture in the Midland Basin
Category
Advances in Characterizing Seismic Hazard and Forecasting Risk in Hydrocarbon Systems