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ORIGINAL RESEARCH article
Front. Earth Sci.
Sec. Geohazards and Georisks
Volume 13 - 2025 | doi: 10.3389/feart.2025.1550266
This article is part of the Research Topic Physical Properties and Mechanical Theory of Rock Materials with Defects View all 12 articles
Evaluating Water-Induced Wellbore Instability in Shale Formations: A Comparative Analysis of Transversely Isotropic Strength Criteria
Provisionally accepted- 1 The University of Chicago, Chicago, United States
- 2 University of Houston, Houston, Texas, United States
- 3 Daqing Oilfield Co., Ltd., Daqing, China
This study addresses wellbore instability in shale formations by conducting mechanical experiments on bedded shale samples with varying hydration times. We fitted experimental data using two anisotropic strength criteria to determine the shale's strength parameters. A transverse isotropic stress model was developed to predict the lower limit of the safe drilling fluid density window, examining the effects of hydration time and anisotropy on wellbore stability. Results indicate that rock strength initially increases and then decreases with bedding angle. Within the β1 to β2 range, both the Jaeger's Plane of Weakness model (JPW) and Plane of Patchy Weakness Model (PPW) accurately predicted shale strength; however, below β1, the JPW criterion overestimated strength, while the PPW criterion better reflected strength variations. Anisotropy due to bedding significantly increased wellbore collapse pressure, shifting the optimal well trajectory from the direction of minimum horizontal stress to maximum horizontal stress, altering collapse pressure contour distributions. The choice of strength criteria had minimal impact on the trend of collapse pressure with well trajectory. While shale hydration can significantly affect wellbore stability and the lower safe drilling mud window with well trajectory, prolonged contact between drilling fluid and rock gradually increased lower safe drilling mud window. Collapse pressure in vertical or horizontal wellbores was minimally affected by soaking time, whereas inclined wellbores showed greater sensitivity. Notably, horizontal wells drilled in the direction of minimum horizontal stress were more responsive to contact time with drilling fluid, leading to a faster increase in collapse pressure.
Keywords: hydration, wellbore stability, Transversely isotropic, Strength criteria, shale
Received: 23 Dec 2024; Accepted: 24 Mar 2025.
Copyright: © 2025 Zhang, Du and Jiang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Xuejia Du, University of Houston, Houston, 77004, Texas, United States
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