TY - JOUR
T1 - Wellbore stability in layered rocks
T2 - A comparative study of strength criteria
AU - Shi, Xiangchao
AU - Zhuo, Xiao
AU - Xiao, Yue
AU - Guo, Boyun
AU - Zhu, Cheng
AU - Li, Jiaxue
N1 - Funding Information:
We gratefully acknowledge the financial support from the National Natural Science Foundation of China (No. 51774248 and No. 51504208), and the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences (No. Z016013).
Publisher Copyright:
Copyright © 2019 by ASME.
PY - 2020/6
Y1 - 2020/6
N2 - Wellbore instability is a critical issue restricting efficient well drilling and successful development of oil and gas field. Most instability problems originate from shale formations because of their distinct laminated structures that cause significant anisotropy and moderate to high clay contents that are prone to shrinkage and swelling. To account for these influences on the mechanical responses of shales, this study aims to identify an appropriate strength criterion for stability analyses. Two anisotropic criteria including single plane of weakness and the modified Hoek-Brown criteria were compared to evaluate their suitability in characterizing the anisotropic strength of layered rocks including shale, schist, and slate under different confining pressures. Comparative case studies indicated that the single plane of weakness criterion overestimates the strength of layered rocks at some orientation angles. The modified Hoek-Brown criterion can fit well with the experimental data of layered rocks. Moreover, wellbore stability analysis models for shale gas wells were built, respectively, for each criterion and applied to in situ scenarios. The single plane of weakness and modified Hoek-Brown criteria provide similar results of collapse pressure, and the shale failure is mainly determined by the bedding plane. This further validates that the modified Hoek-Brown criterion is a good choice for wellbore stability analysis in shale formations with bedding planes. This study shows the potential of using the modified Hoek-Brown criterion to enhance the safety and efficiency of well drilling and operation in shale formations.
AB - Wellbore instability is a critical issue restricting efficient well drilling and successful development of oil and gas field. Most instability problems originate from shale formations because of their distinct laminated structures that cause significant anisotropy and moderate to high clay contents that are prone to shrinkage and swelling. To account for these influences on the mechanical responses of shales, this study aims to identify an appropriate strength criterion for stability analyses. Two anisotropic criteria including single plane of weakness and the modified Hoek-Brown criteria were compared to evaluate their suitability in characterizing the anisotropic strength of layered rocks including shale, schist, and slate under different confining pressures. Comparative case studies indicated that the single plane of weakness criterion overestimates the strength of layered rocks at some orientation angles. The modified Hoek-Brown criterion can fit well with the experimental data of layered rocks. Moreover, wellbore stability analysis models for shale gas wells were built, respectively, for each criterion and applied to in situ scenarios. The single plane of weakness and modified Hoek-Brown criteria provide similar results of collapse pressure, and the shale failure is mainly determined by the bedding plane. This further validates that the modified Hoek-Brown criterion is a good choice for wellbore stability analysis in shale formations with bedding planes. This study shows the potential of using the modified Hoek-Brown criterion to enhance the safety and efficiency of well drilling and operation in shale formations.
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U2 - 10.1115/1.4045735
DO - 10.1115/1.4045735
M3 - Article
AN - SCOPUS:85101733670
SN - 0195-0738
VL - 142
JO - Journal of Energy Resources Technology, Transactions of the ASME
JF - Journal of Energy Resources Technology, Transactions of the ASME
IS - 6
M1 - 063003
ER -