New initiative to examine the impacts of oil and gas operations on fault stability and earthquake processes in the Los Angeles basin, CA

Josimar Alves da Silva, Franklin D. Wolfe, Annika Huprikar, Andreas Plesch, Ruben H. Juanes, & John H. Shaw

Published August 14, 2021, SCEC Contribution #11406, 2021 SCEC Annual Meeting Poster #116

We have initiated a new effort to explore how nearly a century of oil and gas production and associated wastewater injection have impacted the state of stress on tectonically active faults in the Los Angeles basin. We begin with a study of the Wilmington oil field, which is the largest in the basin and has been associated with induced seismicity and significant ground surface subsidence (up to 10 m). We do so using coupled flow and geomechanics modeling with detailed production and injection information from 1936 to present day.

We have developed a detailed geological model of the Wilmington oil field using industry seismic reflection and more than 5000 wells that penetrate the reservoir. Our geological model includes the main upper Miocene and Pliocene stratigraphic intervals, which encompass the reservoirs, as well as the top of the basement. Additionally, we use published cross-sections and available 3D seismic data to map several normal faults that compartmentalize the Wilmington anticline. These faults exert important hydraulic control over the pore pressure and subsidence distribution at the Wilmington oil field. Our structural model also includes two main regional faults: the Wilmington blind-thrust fault and the strike-slip Newport-Inglewood fault.

We first process and analyze the historical production information of the Wilmington oil field. There are several wells in the historical production database that do not have well coordinates. We therefore design a cross-correlation method to estimate the well coordinates based on its production and the production of nearby wells in the field that have coordinates. We assess our updated well coordinates by analyzing the consistency of the spatiotemporal evolution of fluid production/injection in the field. We also gathered and compiled publicly available reservoir pressure information available at the California Department of Conservation. Initial reservoir simulation results show that reservoir pressure decrease significantly during the early periods of production in the field (from 1936 to 1950). This result is in agreement with the idea that reservoir pressure depletion caused reservoir compaction and significant ground subsidence during first 20 years of production. These substantial changes in pressure likely have a direct impact on the stability of faults in the region, and we are planning to examine how this may affect the prospects for induced or triggered seismicity in the region.

Key Words
induced seismicity, oil and gas production, LA basin

Citation
Alves da Silva, J., Wolfe, F. D., Huprikar, A., Plesch, A., Juanes, R. H., & Shaw, J. H. (2021, 08). New initiative to examine the impacts of oil and gas operations on fault stability and earthquake processes in the Los Angeles basin, CA. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)