各向异性对页岩地层钻井液安全密度窗口的影响  

Effect of Anisotropy on Safe Density Window of Drilling Fluid in Shale Formation

作　　者：吴德胜[1] 李渊 武兴勇 胡开利[1] 甘一风[1] WU Desheng;LI Yuan;WU Xingyong;HU Kaili;GAN Yifeng(PetroChina Xinjiang Oilfield Company,Karamay,Xinjiang 834000,China)

机构地区：[1]中国石油新疆油田分公司,新疆克拉玛依834000

出　　处：《西安石油大学学报（自然科学版）》2023年第6期24-32,共9页Journal of Xi’an Shiyou University（Natural Science Edition）

摘　　要：为揭示页岩储层井壁失稳机理,开展了不同层理倾角页岩的抗压强度实验,采用Jaeger弱面准则拟合页岩强度实验数据,为井壁稳定分析模型提供输入参数;评估了各向异性对井周应力集中的影响,并基于横观各向同性介质井周应力模型,建立了钻井液安全密度窗口分析模型,研究安全密度窗口对各向异性的敏感性。结果表明:随着原地应力异性的增加,破裂压力与坍塌压力的差值减小,即钻井液安全密度窗口变窄,与地应力各向同性时的情况相比,地应力异性导致井筒失稳风险增大;随着页岩弹性模量异性度的增加,井壁破裂压力和坍塌均逐渐减小,因此维持井壁稳定的钻井液安全密度窗口迅速变窄。泊松比异性度对井壁破裂压力和坍塌压力的敏感性分析表明,泊松比各向异性对维持井壁稳定的安全密度窗口的影响十分有限;而弹性模量是引起钻井液安全密度窗口变化的关键因素。To reveal the mechanism of wellbore instability in shale reservoirs,compressive strength experiments were conducted on shale with different bedding angles.The shale strength experimental data were fitted using Jaeger weak surface criterion,providing input parameters for the wellbore stability analysis model;The impact of anisotropy on wellbore stress concentration was evaluated and a safe density window analysis model of drilling fluid was established based on a transverse isotropic medium wellbore stress model to study the sensitivity of the safe density window to anisotropy.The results show that with the increase of in-situ stress anisotropy,the difference between fracture pressure and collapse pressure decreases,which means that the safe density window of drilling fluid narrows.Compared with the situation when the in-situ stress is isotropic,the in-situ stress anisotropy increases the risk of wellbore instability.As the anisotropy of the elastic modulus of shale increases,both the wellbore fracture pressure and collapse pressure gradually decrease,thus the safe density window of drilling fluid that maintains wellbore stability rapidly narrows.The influence of Poisson's ratio anisotropy on the safe density window of drilling fluid is very limited.The elastic modulus of shale is a key factor causing changes in the safe density window of drilling fluid.

关 键 词：横观各向同性 钻井液 安全密度窗口 各向异性 页岩储层 敏感性分析 

分 类 号：TE328[石油与天然气工程—油气田开发工程]