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<p>The instability of wellbores in horizontal wells significantly hinders the development of coalbed methane. Currently, the understanding of the impact of partings in coal seams on wellbore stability is limited. In this study, a model for evaluating wellbore stability in coal seams containing partings has been developed. Rock mechanics parameters of both the coal seam and partings were obtained through experiments, and a fluid–solid coupling numerical model was constructed, incorporating the Mohr–Coulomb damage function. This study analyzes the effects of parting position, thickness, and properties on wellbore stability. Results indicate that the compressive strength of parting core is three times that of normal coal cores. The presence of partings leads to a maximum reduction of 7.16&#xa0;MPa in circumferential stress, contributing to wellbore stability. As the thickness of the parting increases from 50 to 200&#xa0;mm, circumferential stress decreases by approximately 5&#xa0;MPa. However, with increasing thickness, a fractured zone forms between the parting and the wellbore, thereby increasing the risk of wellbore collapse. The optimal distance between the wellbore and the parting is identified as between 100 and 150&#xa0;mm. If the distance is too small, failure is likely to occur; otherwise, the parting provides no support.</p>

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Numerical and Experimental Investigation on the Wellbore Stability for Horizontal Drilling in Deep Coal Seams with Partings

  • 期刊论文

  • 发表日期：

    2025年10月28日

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  • Qiqi Yang,
  • Xuyue Chen,
  • Pu Huang,
  • Gengchen Li,
  • Xiaohua Cao

摘要

The instability of wellbores in horizontal wells significantly hinders the development of coalbed methane. Currently, the understanding of the impact of partings in coal seams on wellbore stability is limited. In this study, a model for evaluating wellbore stability in coal seams containing partings has been developed. Rock mechanics parameters of both the coal seam and partings were obtained through experiments, and a fluid–solid coupling numerical model was constructed, incorporating the Mohr–Coulomb damage function. This study analyzes the effects of parting position, thickness, and properties on wellbore stability. Results indicate that the compressive strength of parting core is three times that of normal coal cores. The presence of partings leads to a maximum reduction of 7.16 MPa in circumferential stress, contributing to wellbore stability. As the thickness of the parting increases from 50 to 200 mm, circumferential stress decreases by approximately 5 MPa. However, with increasing thickness, a fractured zone forms between the parting and the wellbore, thereby increasing the risk of wellbore collapse. The optimal distance between the wellbore and the parting is identified as between 100 and 150 mm. If the distance is too small, failure is likely to occur; otherwise, the parting provides no support.