Coupled Poroelastic Modeling of Hydraulic Fracturing-Induced Seismicity: Implications for understanding the post shut-in ML 2.9 earthquake at the Preston New Road, UK

Wenzhou Cao*, James P Verdon, Ming Tao

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

8 Citations (Scopus)
37 Downloads (Pure)

Abstract

Post-injection seismicity associated with hydraulic stimulation has posed great challenges to hydraulic fracturing operations. This work aims to identify the causal mechanism of the post shut-in ML 2.9 earthquake in August 2019 at the Preston New Road, UK, amongst three plausible mechanisms, that is, the post shut-in pore pressure diffusion, poroelastic stressing on a non-overpressurized fault, and poroelastic stressing on an overpressurized fault. A 3D fully coupled poroelastic model that considers the poroelastic solid deformation, fluid flow in both porous rocks and fracture structures, and hydrofracturing-induced pressure perturbations was developed to simulate the hydromechanical response of the shale reservoir formation to hydraulic fracturing operations at the site. Based on the model results, Coulomb stress changes and seismicity rate were further evaluated on the PNR-2 fault responsible for the earthquake. Model results have shown that increased pore pressure plays a dominant role in triggering the fault slippage, although the poroelastic stress may have acted to promote the slippage. Amongst the three plausible mechanisms, the post shut-in pore pressure diffusion is the most favored in terms of Coulomb stress change, seismicity rate, timing of fault slippage and rupture area. The coupled modeling results suggested that the occurrence of the post shut-in ML 2.9 earthquake was a three-staged process, involving first propagation of fracture tips that stimulated surrounding reservoir formations, then hydraulic connection with and subsequent pore pressure diffusion to the conductive PNR-2 fault, and eventually fault activation primarily under the direct impact of increased pore pressure.
Original languageEnglish
Article numbere2021JB023376
Number of pages24
JournalJournal of Geophysical Research: Solid Earth
Volume127
Issue number3
Early online date20 Feb 2022
DOIs
Publication statusPublished - 24 Feb 2022

Bibliographical note

Funding Information:
The first author would like to thank the Open Research Fund of the Key Laboratory of Deep Earth Science and Engineering, Sichuan University (Grant No: DESE 202101) for their support of this research. The second author is supported by the NERC UK Unconventional Hydrocarbon Challenge Grants (Grant No: NE/R018006/1 and NE/R018162/1). The authors gratefully acknowledge the constructive reviews by Jeremy Maurer, an anonymous reviewer and an anonymous Associate Editor which improved the quality of this manuscript.

Publisher Copyright:
© 2022. The Authors.

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