流固耦合下破碎性煤系地层坍塌规律研究  

Study on the Collapse Law of Fractured Coal StrataUnder Fluid-Solid Coupling

作　　者：邢林庄 周泽南 刘可成 尹泽斌 于永生 王贵[3] XING Linzhuang;ZHOU Zenan;LIU Kecheng;YIN Zebin;YU Yongsheng;WANG Gui(Engineering Technology Department of PetroChina Xinjiang Oilfield Company,Karamay,Xinjiang 834000,China;Engineering Technology Research Institute of PetroChina Xinjiang Oilfield Company,Karamay,Xinjiang 834000,China;Southwest Petroleum University,Chengdu,Sichuan 610500,China)

机构地区：[1]中国石油新疆油田公司工程技术处 [2]中国石油新疆油田公司工程技术研究院 [3]西南石油大学

出　　处：《钻采工艺》2024年第5期24-32,共9页Drilling & Production Technology

基　　金：中国石油集团公司重大项目“复杂超深井安全优快钻完井技术集成与试验”(编号:2020F-46)资助。

摘　　要：破碎性地层广泛存在裂隙结构,其井壁稳定分析一直是研究难点。文章基于流固耦合理论开展了破碎性煤系地层井壁稳定研究,推导了非稳定渗流模型,结合岩石力学实验确定渗流作用对煤岩力学参数的影响,建立了流固耦合下的坍塌压力计算模型,并结合实钻数据完成模型验证与分析。研究结果表明:渗流初期以非稳定渗流为主,当渗流时间超过6 min后,渗流量随渗流时间增加而线性增加,表明已从非稳定渗流转变为稳定渗流;渗流作用下,煤岩内摩擦角降幅较大,内聚力降幅相对较小;渗流作用对轴向应力影响较小,对径向和周向应力影响较大;考虑渗流作用后,坍塌压力当量密度上升了约0.3 g/cm 3;对比分析X01井和X04井煤层段井壁稳定预测结果,文章基于流固耦合理论的井壁稳定预测模型能够准确预测煤系地层的坍塌压力。研究成果有助于保障破碎性地层井壁稳定,为合理确定钻井液密度提供理论依据。Fracture structures are widely present in fractured strata,and its borehole stability analysis is always a difficult point in research.In this paper,the fluid-solid coupling method is used to study the borehole stability of fractured formation,and the unsteady seepage model derived.Combined with rock mechanics experiments,the influence of seepage on rock mechanics parameters is determined,and the collapse pressure calculation model based on fluid-solid coupling is established and verified.The results show that the initial stage of seepage is dominated by unstable seepage.When the seepage time exceeds 6 min,the seepage flow increases almost linearly with the seepage time,indicating that the unstable seepage has changed into stable seepage.Under the action of seepage,the internal friction angle of coal rock changes greatly,and the change of cohesion is relatively small.The seepage effect has little influence on the axial stress,but has great influence on the radial and circumferential stress.After considering the seepage effect,the equivalent density of collapse pressure increases by about 0.3 g/cm 3.By comparing and analyzing the prediction results of borehole stability in coal seam section of X01 well and X04 well,the fluid-solid coupling prediction model of borehole stability established in this paper is more accurate to calculate the collapse pressure of coal strata.The research results are helpful to ensure the borehole stability of fractured formations and provide a theoretical basis for reasonably reducing drilling fluid density.

关 键 词：破碎性地层 流固耦合 坍塌压力 非稳定渗流 煤岩力学参数 

分 类 号：TE21[石油与天然气工程—油气井工程]