流-固-化-热耦合的陆相页岩井壁稳定力学模型及应用
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摘要
由于钻井液浸泡,陆相页岩中的黏土矿物发生水化膨胀,页岩力学强度会发生弱化,诱发井壁坍塌现象。为探讨陆相页岩井壁稳定机理,假设井壁页岩为多孔弹性介质,考虑页岩基质和层理随着钻井液浸泡时间的水化过程,构建了流-固-化-热耦合的井壁应力场模型,再结合剪切破坏准则,形成了陆相页岩井壁坍塌压力评价模型。以泌阳凹陷陆相页岩油藏A水平井基础参数为例进行计算,揭示了A井井壁失稳原因,并优选了钻井液密度。结果表明:水平井若沿着最小水平主地应力方向布置,则井壁坍塌风险最小;在井斜角为45～70°的造斜段内,可采用水基钻井液,但其密度应高于1. 35 g/cm~3,在井斜角为70～90°的高造斜段内,应采用油基钻井液;研究结果与A井钻井情况吻合。该研究结果可应用于指导陆相页岩井壁坍塌压力预测和钻井设计。
The drilling fluid immersion usually leads to the hydration and swelling of the clay minerals in the continental shale,which will reduce the mechanical strength of shale and induce wellbore collapse. In order to explore the wellbore stability mechanism of continental shale,it is assumed that the shale of borehole wall is a porous elastic medium. The fluid-solid-chemical-thermal coupling wellbore stress field model was established by considering the hydration process of shale matrix and bedding with drilling fluid immersion. A collapse pressure evaluation model for continental shale was provided by combining with the shear failure criterion. The basis parameters of horizontal well A in the continental shale reservoir of Biyang Depression was taken as a calculation case to reveal the causes of wellbore instability and optimize the drilling fluid density. Research indicates that the wellbore collapse risk can be greatly reduced by deploying the horizontal wellbore along the minimum horizontal principle geo-stress. Water-based drilling fluid can be adopted in the section with an inclination angle of 45 ～ 70°,and its density should be higher than 1.35 g/cm~3. Oil-based drilling fluid should be adopted in the high-inclination section with an inclination angle of 70 ～ 90°. The prediction shows a favorable agreement with actual drilling data of Well A. This research can be applied to guide the wellbore collapse pressure prediction and drilling design in the continental shale.
The drilling fluid immersion usually leads to the hydration and swelling of the clay minerals in the continental shale,which will reduce the mechanical strength of shale and induce wellbore collapse. In order to explore the wellbore stability mechanism of continental shale,it is assumed that the shale of borehole wall is a porous elastic medium. The fluid-solid-chemical-thermal coupling wellbore stress field model was established by considering the hydration process of shale matrix and bedding with drilling fluid immersion. A collapse pressure evaluation model for continental shale was provided by combining with the shear failure criterion. The basis parameters of horizontal well A in the continental shale reservoir of Biyang Depression was taken as a calculation case to reveal the causes of wellbore instability and optimize the drilling fluid density. Research indicates that the wellbore collapse risk can be greatly reduced by deploying the horizontal wellbore along the minimum horizontal principle geo-stress. Water-based drilling fluid can be adopted in the section with an inclination angle of 45 ～ 70°,and its density should be higher than 1.35 g/cm~3. Oil-based drilling fluid should be adopted in the high-inclination section with an inclination angle of 70 ～ 90°. The prediction shows a favorable agreement with actual drilling data of Well A. This research can be applied to guide the wellbore collapse pressure prediction and drilling design in the continental shale.
引文
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[15]GAO J,DENG J,LAN K,et al.Porothermoelastic effect on wellbore stability in transversely isotropic medium subjected to local thermal non-equilibrium[J].International Journal of Rock Mechanics&Mining Sciences,2017(96):66-84.
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[18]MA T,CHEN P.A wellbore stability analysis model with chemical-mechanical coupling for shale gas reservoirs[J].Journal of Natural Gas Science and Engineering,2015(26):72-98.
[2]梁利喜,丁乙,刘向君,等.硬脆性泥页岩井壁稳定渗流-力化耦合研究[J].特种油气藏,2016,23(2):140-144.
[3]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):33-35.
[4]刘志远,陈勉,金衍,等.多弱面地层水平井裸眼井壁垮塌量计算模型[J].石油勘探与开发,2014,41(1):102-107.
[5]DING Y,LUO P,LIU X,et al.Wellbore stability model for horizontal wells in shale formations with multiple planes of weakness[J].Journal of Natural Gas Science and Engineering,2018(52):334-347.
[6]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):109-119.
[7]CHENG W,JIANG G,ZHOU Z,et al.Numerical simulation for the dynamic breakout of a borehole using boundary element method[J].Geotechnical and geological engineering,2019(18):1-9.
[8]卢运虎,陈勉,袁建波,等.各向异性地层中斜井井壁失稳机理[J].石油学报,2013,34(3):563-568.
[9]张明明,梁利喜,刘向君.页岩储层各向异性对水平井坍塌压力的影响[J].应用数学和力学,2017,38(3):295-409.
[10]刘向君,曾韦,梁喜利,等.龙马溪组页岩地层井壁坍塌周期预测[J].特种油气藏,2016,23(5):130-135.
[11]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.
[12]LIU M,JIN Y,LU Y,et al.A wellbore stability model for a deviated well in a transversely isotropic formation considering poroelastic effects[J].Rock Mech Rock Eng,2016,49(9):3671-3686.
[13]EKBOTE S,ABOUSLEIMAN Y.Porochemothermoelastic solution for an inclined borehole in a transversely isotropic formation[J].Journal of Engineering Mechanics,2005,131(5):522-533.
[14]EKBOTE S,ABOUSLEIMAN Y.Porochemoelastic solution for an inclined borehole in a transversely isotropic formation[J].Journal of Engineering Mechanics,2006,132(7):754-763.
[15]GAO J,DENG J,LAN K,et al.Porothermoelastic effect on wellbore stability in transversely isotropic medium subjected to local thermal non-equilibrium[J].International Journal of Rock Mechanics&Mining Sciences,2017(96):66-84.
[16]GAO J,DENG J,LAN K,et al.A porothermoelastic solution for the inclined borehole in a transversely isotropic medium subjected to thermal osmosis and thermal filtration effects[J].Geothermics,2017(67):114-134.
[17]曹文科.力学-化学-耦合作用对各向异性页岩井壁稳定性影响规律研究[D].北京:中国石油大学(北京),2017.
[18]MA T,CHEN P.A wellbore stability analysis model with chemical-mechanical coupling for shale gas reservoirs[J].Journal of Natural Gas Science and Engineering,2015(26):72-98.