深层脆性页岩力学性能及井壁稳定性研究  

Research on the Mechanical Properties and Borehole Stability of Deep Brittle Shale

作　　者：韩正波 刘厚彬 张靖涛[3] 杨华建 沈欣宇 阳强 Han Zhengbo;Liu Houbin;Zhang Jingtao;Yang Huajian;Shen Xinyu;Yang Qiang(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu,Sichuan 610500,China;Southwest Petroleum University,Chengdu,Sichuan 610500,China;PetroChina Changqing Oilfield Company,Qingyang,Gansu 745000,China;PetroChina Southwest Oil and Gas Field Company,Chengdu,Sichuan 610017,China;Sichuan Shale Gas Exploration and Development Co.,Ltd.,Chengdu,Sichuan 610051,China)

机构地区：[1]油气藏地质及开发工程国家重点实验室,四川成都610500 [2]西南石油大学,四川成都610500 [3]中国石油长庆油田分公司,甘肃庆阳745000 [4]中国石油西南油气田分公司,四川成都610017 [5]四川页岩气勘探开发有限责任公司,四川成都610051

出　　处：《特种油气藏》2020年第5期167-174,共8页Special Oil & Gas Reservoirs

基　　金：国家科技重大专项“页岩气三维丛式水平井优快钻井技术试验与应用”(2016ZX05062-003);中国石油西南油气田公司科研项目“自201井区3500m以深页岩气水平井优快钻井技术研究”(20180302-08-01)。

摘　　要：四川盆地中部龙马溪组页岩地层硬度高、脆性强,钻井过程中井壁坍塌严重,阻卡频发。为解决钻井过程中井壁坍塌问题,测试了以四川盆地自201井为代表的深层页岩微细观组构、水理化性能及力学性能参数各向异性特征,并考虑井眼轨迹、层理缝产状、井筒-地层耦合渗流效应、层理缝力学弱面效应等因素,建立了深层脆性页岩水平井井壁稳定理论模型。实验结果表明:深层页岩脆性矿物含量高达70%,水化膨胀性极低,页岩基质力学强度高,但层理缝间强度低,页岩容易沿层理缝滑移崩落。模型计算结果表明:层理缝力学弱面效应影响明显,当井眼轨迹与层理缝面法向之间夹角满足一定角度,井壁倾向沿层理缝剪切滑移垮塌;井筒-地层间渗流效应不可忽略,压力穿透效应降低钻井液的有效径向支撑力,诱发层理缝起裂、延伸至崩落,合理的钻井液密度及有效封堵性可提高深层页岩水平井井壁稳定性。研究成果揭示了深层脆性页岩井壁坍塌作用机理,可为深层脆性页岩水平井关键工程参数设计提供理论依据。The shale strata of Longmaxi Formation in the central part of Sichuan Basin are highly hard and strongly brittle.During the drilling process,the borehole wall collapses seriously and the pipe is stuck frequently.In order to solve the problem of borehole collapse during drilling,the anisotropy characteristics of deep shale,such as microstructure,physical and chemical properties of water,and mechanical properties,were tested,which was represented by Well Zi201 in Sichuan Basin.Theoretical model of horizontal well borehole stability in deep brittle shale was established considering the factors such as wellbore trajectory,bedding fracture occurrence,wellbore-stratum coupling seepage effect,and the mechanical weak plane effect of bedding fracture.The experimental results show that the content of brittle minerals in deep shale is as high as 70%,the hydration expansibility is extremely low,and the mechanical strength of shale matrix is high.While the strength among bedding fractures is low,so the shale is easy to slip and fall along the bedding fracture.The calculation results of the model show that the influence of mechanical weak plane effect of bedding fracture is obvious.When the angle between the wellbore trajectory and the normal direction of the bedding fracture surface meet a certain degree,collapse and shear slip of the wellbore will tend to occur.The wellbore-stratum effect cannot be ignored.The pressure penetration effect will reduce the effective radial support force of the drilling fluid,which may cause the initiation,extension and even collapse of bedding fracture.So reasonable drilling fluid density and effective plugging property can improve horizontal wellbore stability in deep shale.The research results reveal the collapse mechanism of deep brittle shale wellbore,which can provide a theoretical basis for the design of key engineering parameters of deep brittle shale horizontal wells.

关 键 词：深层脆性页岩 井壁稳定 各向异性 弱面效应 龙马溪组 四川盆地 

分 类 号：TE142[石油与天然气工程—油气勘探]