(1. Faculty of Engineering and Technology，China University of Geosciences(Beijing)，Beijing 100083，China；2. China Institute of Geotechnical Investigation and Surveying Co.，Ltd.，Beijing 100007，China)
Abstract：The problem of instability is more prominent when drilling inclined wells in bedding layers. A new wellbore stability model is established considering the weakening action of bedding plane on rocks on the basis of the traditional borehole stability model. The model takes into account the arbitrary nature of 3D in-situ stress with three Euler angles，and applies Mogi-Coulomb criterion to strengthen the effect of intermediate principal stress，as well as combines the single weak-plane strength theory to fulfill the goal of guided drilling. The method and formula for calculating the collapse and fracture pressure using this model are given. The experimental and calculated results show that the rock gains a minimum strength when the angle between the loading direction and bedding plane is 30°.. Mogi-Coulomb criterion is more effective on the estimation of rock matrix strength because of the consideration of the influence of intermediate principal stress. The collapse area is markedly enlarged under the effect of bedding plane，and the collapse position is changed. The drilling direction for obtaining the minimum collapse pressure is not simply perpendicular to the bedding plane in space. And the boreholes in the symmetry in terms of principle in-situ stress plane underground have the same fracture pressure. The safe mud density window calculated with the model above can provide theoretical basis for the safe drilling and trajectory design of inclined boreholes.
丁立钦1，王志乔1，吕建国1，孙元帝1，2. 基于围岩本体Mogi-Coulomb强度准则的层理性岩层斜井井壁稳定模型[J]. 岩石力学与工程学报, 2017, 36(3): 622-632.
DING Liqin1，WANG Zhiqiao1，LU Jianguo1，SUN Yuandi1，2. A model for inclined borehole stability in bedding rocks based on Mogi-Coulomb criterion of rock matrix. , 2017, 36(3): 622-632.
[1] 陈 勉，金 衍，张广清. 石油工程岩石力学[M]. 北京：科学出版社，2008：110–121.(CHEN Mian，JIN Yan，ZHANG Guangqing. Rock mechanics on petroleum engineering[M]. Beijing：Science Press，2008：110–121.(in Chinese))
[2] 尹 帅，丁文龙，杨文娜，等. 考虑地层各向异性井壁稳定性研究进展[J]. 地球科学进展，2015，30(11)：1 218–1 230.(YIN Shuai，DING Wenlong，YANG Wenna，et al. Progress of borehole stability considering strata anisotropy[J]. Advances in Earth Science，2015，30(11)：1 218–1 230.(in Chinese))
[3] JAEGER J C. Shear failure of anisotropic rocks[J]. Geological Magazine，1960，97(1)：65–72.
[4] CHENEVERT M E. The deformation-failure characteristics of laminated sedimentary rocks[M]. Texas：University of Texas Press，1964：87–123.
[5] AADNOY B S. Modeling of the stability of highly inclined boreholes in anisotropic rock formations[J]. SPE Drilling Engineering，1988，3(3)：259–268.
[6] OKLAND D，COOK J M. Bedding-related borehole instability in high-angle wells[C]// SPE 47285. Trondheim：SPE/ISRM Rock Mechanics in Petroleum Engineering. [S. l.]：[s. n.]，1998：413–422.
[7] 金 衍，陈 勉，柳贡慧，等. 弱面地层斜井井壁稳定性分析[J]. 石油大学学报：自然科学版，1999，23(4)：46–48.(JIN Yan，CHEN Mian，LIU Gonghui，et al. Wellbore stability analysis of inclined wells in weak plane formations[J]. Journal of the University of Petroleum：Natural Science，1999，23(4)：46–48.(in Chinese))
[8] 刘向君，陈一健，肖 勇. 岩石软弱面产状对井壁稳定性的影响[J]. 西南石油学院学报，2001，23(6)：12–14.(LIU Xiangjun，CHEN Yijian，XIAO Yong. The effect of weak plane?s orientation on wellbore stability[J]. Journal of Southwest Petroleum Institute，2001，23(6)：12–14.(in Chinese))
[9] 蔚宝华，闫 伟，李 斌，等. 高陡层理性地层井壁稳定性模拟试验研究[J]. 石油钻采工艺，2009，31(2)：48–50.(YU Baohua，YAN Wei，LI Bin，et al. Mechanical borehole stability test study in highly-dipped laminated formation[J]. Oil Drilling and Production Technology，2009，31(2)：48–50.(in Chinese))
[10] LEE H，ONG S H，AZEEMUDDIN M，et al. A wellbore stability model for formations with anisotropic rock strengths[J]. Journal of Petroleum Science and Engineering，2012，96/97(19)：109–119.
[11] 马天寿，陈 平. 层理页岩水平井井周剪切失稳区域预测方法[J]. 石油钻探技术，2014，42(5)：26–36.(MA Tianshou，CHEN Ping. Prediction method of shear instability region around the borehole for horizontal wells in bedding shale[J]. Petroleum Drilling Techniques，2014，42(5)：26–36.(in Chinese))
[12] CHEN X，TAN C P，DETOURNAY C. A study on wellbore stability in fractured rock masses with impact of mud infiltration[J]. Journal of Petroleum Science and Engineering，2003，38(3/4)：145–154.
[13] 闫传梁，邓金根，蔚宝华，等. 页岩气储层井壁坍塌压力研究[J]. 岩石力学与工程学报，2013，32(8)：1 595–1 602.(YAN Chuanliang，DENG Jingen，YU Baohua，et al. Research on collapsing pressure of gas shale[J]. Chinese Journal of Rock Mechanics and Engineering，2013，32(8)：1 595–1 602.(in Chinese))
[14] 温 航，陈 勉，金 衍，等. 硬脆性泥页岩斜井段井壁稳定力化耦合研究[J]. 石油勘探与开发，2014，41(6)：748–754.(WEN Hang，CHEN Mian，JIN Yan，et al. A chemo-mechanical coupling model of deviated borehole stability in hard brittle shale[J]. Petroleum Exploration and Development，2014，41(6)：748–754.(in Chinese))
[15] LESK M. On the calculation of Euler angles from a rotation matrix[J]. International Journal of Mathematical Education in Science and Technology，1986，17(3)：335–337.
[16] BRADLEY W B. Failure of inclined boreholes[J]. Journal of Energy Resources Technology，1979，101(4)：232–239.
[17] 赵文瑞. 泥质粉砂岩各向异性强度特征[J]. 岩土工程学报，1984，6(1)：32–37.(ZHAO Wenrui. Strength properties of anisotropic rock of an argillaceous siltstone[J]. Chinese Journal of Geotechnical Engineering，1984，6(1)：32–37.(in Chinese))
[18] 陈天宇，冯夏庭，张希巍，等. 黑色页岩力学特性及各向异性特性试验研究[J]. 岩石力学与工程学报，2014，33(9)：1 772–1 779. (CHEN Tianyu，FENG Xiating，ZHANG Xiwei，et al. Experimental study on mechanical and anisotropic properties of black shale[J]. Chinese Journal of Rock Mechanics and Engineering，2014，33(9)：1 772–1 779.(in Chinese))
[19] 侯振坤，杨春和，郭印同，等. 单轴压缩下龙马溪组页岩各向异性特征研究[J]. 岩土力学，2015，36(9)：2 541–2 550.(HOU Zhenkun，YANG Chunhe，GUO Yintong，et al. Experimental study on anisotropic properties of Longmaxi formation shale under uniaxial compression[J]. Rock and Soil Mechanics，2015，36(9)：2 541–2 550. (in Chinese))
[20] 衡 帅，杨春和，张保平，等. 页岩各向异性特征的试验研究[J]. 岩土力学，2015，36(3)：609–616.(HENG Shuai，YANG Chunhe，ZHANG Baoping，et al. Experimental research on anisotropic properties of shale[J]. Rock and Soil Mechanics，2015，36(3)：609–616.(in Chinese))
[21] JAEGER J C，COOK N G W，ZIMMERMAN R W. Fundamentals of rock mechanics，4nd Edition[M]. Chicester：John Wiley and Sons Ltd.，2007：65–79.
[22] VERNIK L，ZOBACK M D. Estimation of maximum horizontal principal stress magnitude from stress-induced well bore breakouts in the Cajon Pass scientific research borehole[J]. Journal of Geophysical Research Atmospheres，1995，97(97)：5 109–5 119.
[23] SONG I，HAIMSON B C. Polyaxial strength criteria and their use in estimating in situ stress magnitudes from borehole breakout dimensions[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1997，34(3)：498.
[24] AL-AJMI A M，ZIMMERMAN R W. Stability analysis of vertical boreholes using the Mogi-Coulomb failure criterion[J]. International Journal of Rock Mechanics and Mining Sciences，2006，43(8)：1 200–1 211.
[25] HASHEMI S S，TAHERI A，MELKOUMIAN N. Shear failure analysis of a shallow depth unsupported borehole drilled through poorly cemented granular rock[J]. Engineering Geology，2014，183(1)：39–52.
[26] RAHIMI R，NYGAARD R. Comparison of rock failure criteria in predicting borehole shear failure[J]. International Journal of Rock Mechanics and Mining Sciences，2015，79(1)：29–40.
2017, Vol. 36 
