各向异性地层井壁破裂压力预测
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摘要
地层破裂压力对于钻井和水力压裂非常重要,但直井破裂压力预测往往忽略了地层各向异性的影响。考虑岩石各向异性影响,推导直井井壁应力分布模型,建立各向异性地层破裂压力计算方法,并分析层理产状、各向异性程度、地应力及孔隙压力的影响。结果表明:低角度层理对破裂压力几乎无影响,而高角度层理对破裂压力影响显著;向最大水平地应力方向倾斜的层理,其破裂压力最低,极端情况下甚至比各向同性地层低50%,对井壁稳定极为不利;岩石各向异性程度越高,对破裂压力的影响越大;随着水平地应力比值和孔隙压力的增加,破裂压力整体上逐渐减小,而且地应力影响明显高于岩石各向异性,水平地应力比值增加后,岩石各向异性的影响进一步加剧;该模型提高了破裂压力计算的精度。
The fracture pressure of wellbore is very important for drilling and hydraulic fracturing, while the influence of rock anisotropy has been ignored in the prediction of the fracture pressure. In this study, a stress distribution model around a vertical borehole considering the influence of rock anisotropy was deduced, and a computing method was proposed. The influence of the occurrence of bedding planes, the degree of anisotropy, the in-situ stress and pore pressure on the fracture pressure was analyzed. The results indicated that the bedding plane with a small dip angle almost has little influence on the fracture pressure, while the bedding plane with a large dip angle has a significant influence. When the azimuth of the bedding plane is along with the maximum horizontal in-situ stress, the fracture pressure will reach to its lowest value, and it even can be 50% lower than that of an isotropic case, consequently, it is vulnerable to the stability of the borehole. The higher the degree of rock anisotropy, the greater impact on the fracture pressure. In general, the fracture pressure decreases with the increasing of the ratio of horizontal stresses and pore pressure. The influence of the in-situ stress on the fracture pressure is obviously higher than that of the rock anisotropy, while the effect of the anisotropy can be larger when the ratio of the horizontal stresses is high. The present model improved the computational accuracy of the fracture pressure, and it also can provide theoretical guides for drilling and hydraulic fracturing in anisotropic formations.
The fracture pressure of wellbore is very important for drilling and hydraulic fracturing, while the influence of rock anisotropy has been ignored in the prediction of the fracture pressure. In this study, a stress distribution model around a vertical borehole considering the influence of rock anisotropy was deduced, and a computing method was proposed. The influence of the occurrence of bedding planes, the degree of anisotropy, the in-situ stress and pore pressure on the fracture pressure was analyzed. The results indicated that the bedding plane with a small dip angle almost has little influence on the fracture pressure, while the bedding plane with a large dip angle has a significant influence. When the azimuth of the bedding plane is along with the maximum horizontal in-situ stress, the fracture pressure will reach to its lowest value, and it even can be 50% lower than that of an isotropic case, consequently, it is vulnerable to the stability of the borehole. The higher the degree of rock anisotropy, the greater impact on the fracture pressure. In general, the fracture pressure decreases with the increasing of the ratio of horizontal stresses and pore pressure. The influence of the in-situ stress on the fracture pressure is obviously higher than that of the rock anisotropy, while the effect of the anisotropy can be larger when the ratio of the horizontal stresses is high. The present model improved the computational accuracy of the fracture pressure, and it also can provide theoretical guides for drilling and hydraulic fracturing in anisotropic formations.
引文
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[13] 黄荣樽.地层破裂压力预测模式的探讨[J].华东石油学院学报,1984,9(4):335-346.HUANG Rongzun.A model for predicting formation fracture pressure[J].Journal of the University of Petroleum,China,1984,9(4):335-346.
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[15] 马天寿,陈平.页岩地层中孔隙热弹性井眼稳定力学模型[J].岩石力学与工程学报,2015,34(增2):3613-3623.MA Tianshou,CHEN Ping.Porothermoelastic mechanics model of wellbore stability in shale formations[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(sup 2):3613-3623.
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[17] AADNOY B S.Modeling of the stability of highly inclined boreholes in anisotropic rock formations[J].SPE Drilling Engineering,1988,3(3):259-268.
[18] AADNOY B S.Stresses around horizontal boreholes drilled in sedimentary rocks[J].Journal of Petroleum Science and Engineering,1989,2(4):349-360.
[19] ONG S H,ROEGIERS J C.Influence of anisotropies in borehole stability[J].International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts,1993,30(7):1069-1075.
[20] ONG S H,ROEGIERS J C.Fracture initiation from inclined wellbores in anisotropic formations[J].Journal of Petroleum Technology,1996,48(7):612-619.
[21] GUPTA D,ZAMAN M.Stability of boreholes in a geologic medium including the effects of anisotropy[J].Applied Mathematics and Mechanics,1999,20(8):837-866.
[22] JIN Y,YUAN J,HOU B,et al.Analysis of the vertical borehole stability in anisotropic rock formations[J].Journal of Petroleum Exploration and Production Technology,2012,2(4):197-207.
[23] 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):161-170.LU Yunhu,CHEN Mian,YUAN Jianbo,et al.Borehole instability mechanism of a deviated well in anisotropic formations[J].Acta Petrolei Sinica,2013,34(3):161-170.
[24] 王越之.各向异性地层应力的推算及深孔地层破裂压力的预测[J].岩石力学与工程学报,1998,17(3):322-329.WANG Yuezhi.Determination of in-situ stresses in anisotropic strata and prediction of breakdown pressure acting on deep well-wall[J].Chinese Journal of Rock Mechanics and Engineering,1998,17(3):322-329.
[25] 高坤,陶果,仵岳奇,等.利用多极子阵列声波测井资料计算横向各向同性地层破裂压力[J].中国石油大学学报(自然科学版),2007,31(1):35-39.GAO Kun,TAO Guo,WU Yueqi,et al.Determining breakdown pressures in transversely isotropic formation by multipole array acoustic logs[J].Journal of China University of Petroleum (Edition of Natural Science),2007,31(1):35-39.
[26] LEKHNITSKIJ S G.Theory of the elasticity of anisotropic bodies[M].Moscow:Mir Publishers,1981.
[27] AMADEI B.Rock anisotropy and the theory of stress measurements[M].Berlin:Springer Verlag,1983.
[28] MA Tianshou,CHEN Ping.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.
[29] LI Y F,FU Y Q,TANG G,et al.Effect of weak bedding planes on wellbore stability for shale gas wells[R].IADC/SPE 155666,2012.
[30] YUAN J L,DENG J G,TAN Q,et al.Borehole stability analysis of horizontal drilling in shale gas reservoirs[J].Rock Mechanics and Rock Engineering,2013,46(5):1157-1164.
[31] 杨建,付永强,陈鸿飞,等.页岩储层的岩石力学特性[J].天然气工业,2012,32(7):12-14.YANG Jian,FU Yongqiang,CHEN Hongfei,et al.Rock mechanical characteristics of shale reservoirs[J].Natural Gas Industry,2012,32(7):12-14.
[32] 贾长贵,陈军海,郭印同,等.层状页岩力学特性及其破坏模式研究[J].岩土力学,2013,34(增2):57-61.JIA Changgui,CHEN Junhai,GUO Yintong,et al.Research on mechanical behaviors and failure modes of layer shale[J].Rock and Soil Mechanics,2013,34(sup 2):57-61.
[33] MCLAMORE R,GRAY K E.The mechanical behavior of anisotropic sedimentary rocks[J].Journal of Manufacturing Science and Engineering,1967,89(1),62-73.
[34] 杨迪,刘树根,单钰铭,等.上扬子地区牛蹄塘组黑色页岩的力学性质[J].成都理工大学学报(自然科学版),2013,40(6):677-687.YANG Di,LIU Shugen,SHAN Yuming,et al.Mechanical property of Lower Cambrian Niutitang Formation black shale in upper Yangtze region,China[J].Journal of Chengdu University of Technology (Science & Technology Edition),2013,40(6):677-687.
[35] YAN Chuanliang,DENG Jingen,HU Lianbo,et al.Brittle failure of shale under uniaxial compression[J].Arabian Journal of Geosciences,2015,8(5):2467-2475.
[36] HIGGINS S M,GOODWIN S A,BRATTON T R,et al.Anisotropic stress models improve completion design in the Baxter shale[R].SPE 115736,2008.
[37] MEIER T,RYBACKI E,BACKERS T,et al.Influence of bedding angle on borehole stability:a laboratory investigation of transverse isotropic oil shale[J].Rock Mechanics and Rock Engineering,2015,48(4):1535-1546.
[38] PEI J Y.Strength of transversely isotropic rocks[D].Massachusetts:Massachusetts Institute of Technology,2008.
[2] MA Tianshou,WU Bisheng,FU Jianhong,et al.Fracture pressure prediction for layered formations with anisotropic rock strengths[J].Journal of Natural Gas Science and Engineering,2017,38:485-503.
[3] MA Tianshou,ZHANG Q B,CHEN Ping,et al.Fracture pressure model for inclined wells in layered formations with anisotropic rock strengths[J].Journal of Petroleum Science and Engineering,2017,149:393-408.
[4] 马天寿,杨春和,陈平,等.层状页岩储层水平井破裂压力模型[J].天然气工业,2017,37(增1):161-169.MA Tianshou,YANG Chunhe,CHEN Ping,et al.Fracture pressure model of horizontal wells in layered shale reservoirs[J].Natural Gas Industry,2017,37(sup 1):161-169.
[5] 许玉强,管志川,张洪宁,等.基于含可信度地层压力剖面的精细井身结构设计方法[J].中国石油大学学报(自然科学版),2014,38(6):72-77.XU Yuqiang,GUAN Zhichuan,ZHANG Hongning,et al.Methods for precise casing design based on formation pressure profiles with different credibility[J].Journal of China University of Petroleum (Edition of Natural Science),2014,38(6):72-77.
[6] 杨焕强,王瑞和,周卫东,等.滑套固井压裂起裂压力及影响因素[J].中国石油大学学报(自然科学版),2014,38(6):78-84.YANG Huanqiang,WANG Ruihe,ZHOU Weidong,et al.Fracture initiation pressure and its influencing factors during sliding sleeve fracturing in cemented wells[J].Journal of China University of Petroleum (Edition of Natural Science),2014,38(6):78-84.
[7] 曲占庆,李小龙,李建雄,等.基于扩展有限元法的多径向井压裂裂缝形态[J].中国石油大学学报(自然科学版),2018,42(1):73-81.QU Zhanqing,LI Xiaolong,LI Jianxiong,et al.Crack morphology of multiple radial well fracturing based on extended finite element method[J].Journal of China University of Petroleum (Edition of Natural Science),2018,42(1):73-81.
[8] HUBBERT M K,WILLIS D G.Mechanics of hydraulic fracturing[J].AIME Petroleum Transactions,1957,210:153-168.
[9] MATTHEWS W R,KELLY J.How to predict formation pressure and fracture gradient[J].Oil and Gas Journal,1967,65(8):92-106.
[10] HAIMSON B,FAIRHURST C.Initiation and extension of hydraulic fractures in rocks[J].SPE Journal,1967,7(3):310-318.
[11] EATON B A.Fracture gradient prediction and its application in oilfield operations[J].Journal of Petroleum Technology,1969,21(10):1353-1360.
[12] ANDERSON R A,INGRAM D S,ZANIER A M.Fracture pressure gradient determination from well logs[J].Journal of Petroleum Technology,1973,25(11):1259-1268.
[13] 黄荣樽.地层破裂压力预测模式的探讨[J].华东石油学院学报,1984,9(4):335-346.HUANG Rongzun.A model for predicting formation fracture pressure[J].Journal of the University of Petroleum,China,1984,9(4):335-346.
[14] 陈勉,金衍,张广清.石油工程岩石力学[M].北京:科学出版社,2008.
[15] 马天寿,陈平.页岩地层中孔隙热弹性井眼稳定力学模型[J].岩石力学与工程学报,2015,34(增2):3613-3623.MA Tianshou,CHEN Ping.Porothermoelastic mechanics model of wellbore stability in shale formations[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(sup 2):3613-3623.
[16] AADNOY B S,CHENEVERT M E.Stability of highly inclined boreholes[J].SPE Drilling Engineering,1987,2(4):364-374.
[17] AADNOY B S.Modeling of the stability of highly inclined boreholes in anisotropic rock formations[J].SPE Drilling Engineering,1988,3(3):259-268.
[18] AADNOY B S.Stresses around horizontal boreholes drilled in sedimentary rocks[J].Journal of Petroleum Science and Engineering,1989,2(4):349-360.
[19] ONG S H,ROEGIERS J C.Influence of anisotropies in borehole stability[J].International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts,1993,30(7):1069-1075.
[20] ONG S H,ROEGIERS J C.Fracture initiation from inclined wellbores in anisotropic formations[J].Journal of Petroleum Technology,1996,48(7):612-619.
[21] GUPTA D,ZAMAN M.Stability of boreholes in a geologic medium including the effects of anisotropy[J].Applied Mathematics and Mechanics,1999,20(8):837-866.
[22] JIN Y,YUAN J,HOU B,et al.Analysis of the vertical borehole stability in anisotropic rock formations[J].Journal of Petroleum Exploration and Production Technology,2012,2(4):197-207.
[23] 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):161-170.LU Yunhu,CHEN Mian,YUAN Jianbo,et al.Borehole instability mechanism of a deviated well in anisotropic formations[J].Acta Petrolei Sinica,2013,34(3):161-170.
[24] 王越之.各向异性地层应力的推算及深孔地层破裂压力的预测[J].岩石力学与工程学报,1998,17(3):322-329.WANG Yuezhi.Determination of in-situ stresses in anisotropic strata and prediction of breakdown pressure acting on deep well-wall[J].Chinese Journal of Rock Mechanics and Engineering,1998,17(3):322-329.
[25] 高坤,陶果,仵岳奇,等.利用多极子阵列声波测井资料计算横向各向同性地层破裂压力[J].中国石油大学学报(自然科学版),2007,31(1):35-39.GAO Kun,TAO Guo,WU Yueqi,et al.Determining breakdown pressures in transversely isotropic formation by multipole array acoustic logs[J].Journal of China University of Petroleum (Edition of Natural Science),2007,31(1):35-39.
[26] LEKHNITSKIJ S G.Theory of the elasticity of anisotropic bodies[M].Moscow:Mir Publishers,1981.
[27] AMADEI B.Rock anisotropy and the theory of stress measurements[M].Berlin:Springer Verlag,1983.
[28] MA Tianshou,CHEN Ping.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.
[29] LI Y F,FU Y Q,TANG G,et al.Effect of weak bedding planes on wellbore stability for shale gas wells[R].IADC/SPE 155666,2012.
[30] YUAN J L,DENG J G,TAN Q,et al.Borehole stability analysis of horizontal drilling in shale gas reservoirs[J].Rock Mechanics and Rock Engineering,2013,46(5):1157-1164.
[31] 杨建,付永强,陈鸿飞,等.页岩储层的岩石力学特性[J].天然气工业,2012,32(7):12-14.YANG Jian,FU Yongqiang,CHEN Hongfei,et al.Rock mechanical characteristics of shale reservoirs[J].Natural Gas Industry,2012,32(7):12-14.
[32] 贾长贵,陈军海,郭印同,等.层状页岩力学特性及其破坏模式研究[J].岩土力学,2013,34(增2):57-61.JIA Changgui,CHEN Junhai,GUO Yintong,et al.Research on mechanical behaviors and failure modes of layer shale[J].Rock and Soil Mechanics,2013,34(sup 2):57-61.
[33] MCLAMORE R,GRAY K E.The mechanical behavior of anisotropic sedimentary rocks[J].Journal of Manufacturing Science and Engineering,1967,89(1),62-73.
[34] 杨迪,刘树根,单钰铭,等.上扬子地区牛蹄塘组黑色页岩的力学性质[J].成都理工大学学报(自然科学版),2013,40(6):677-687.YANG Di,LIU Shugen,SHAN Yuming,et al.Mechanical property of Lower Cambrian Niutitang Formation black shale in upper Yangtze region,China[J].Journal of Chengdu University of Technology (Science & Technology Edition),2013,40(6):677-687.
[35] YAN Chuanliang,DENG Jingen,HU Lianbo,et al.Brittle failure of shale under uniaxial compression[J].Arabian Journal of Geosciences,2015,8(5):2467-2475.
[36] HIGGINS S M,GOODWIN S A,BRATTON T R,et al.Anisotropic stress models improve completion design in the Baxter shale[R].SPE 115736,2008.
[37] MEIER T,RYBACKI E,BACKERS T,et al.Influence of bedding angle on borehole stability:a laboratory investigation of transverse isotropic oil shale[J].Rock Mechanics and Rock Engineering,2015,48(4):1535-1546.
[38] PEI J Y.Strength of transversely isotropic rocks[D].Massachusetts:Massachusetts Institute of Technology,2008.