各向异性地层中斜井井壁失稳机理  

Borehole instability mechanism of a deviated well in anisotropic formations

作　　者：卢运虎[1,2] 陈勉[1] 袁建波[1] 金衍[1] 滕学清[1,2] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]中国石油塔里木油田公司博士后科研工作站,新疆库尔勒841000

出　　处：《石油学报》2013年第3期563-568,共6页Acta Petrolei Sinica

基　　金：国家重点基础研究发展计划(973)项目(2010CB226700);国家重大科技专项(2011ZX05031-004-005HZ);国家自然科学基金项目(No.51074171和No.51204191);中国博士后科学基金(2013M520549)资助

摘　　要：深部层理性地层井壁稳定性必须考虑地层物理力学性质的各向异性,然而目前井壁稳定设计方面仍粗略地将其近似为各向同性体,使得预测的维持井壁稳定的坍塌压力和破裂压力不能满足安全钻井的需要。笔者在研究层理地层岩石力学特性的基础上,获得了一种考虑地层方向特性的井壁围岩应力分布公式,分析了横观各向同性地层的井壁应力分布特征,建立了新的斜井地层井壁稳定分析模型。研究结果表明,岩石的弹性模量、地应力和地层倾斜度的变化对井壁围岩的应力分布和坍塌、破裂压力均会产生影响,克服了常规各向同性井壁稳定分析模型不能准确预测层理性地层斜井井壁稳定的难题。因此在钻井施工设计当中,须根据地层特性选择合适的分析模型,以更好地指导现场实践。Borehole stability in deep laminar formations is in connection with anisotropy of formation mechanical behaviors, but forma dons are roughly identified as an approximately isotropic body in the current borehole stability design, which makes the predicted fracture pressure and collapse pressure for maintaining borehole stability incapable of meeting the need of drilling safety. Based on the investigation of bedding rock mechanics of formations, a formula was deduced for the stress distribution of borehole surrounding rocks, which takes directional characteristics of formation into consideration, and built up a new analytical model for borehole stabili ty of a deviated well by means of examining borehole stress distributions of transversely isotropic formations. The result showed that variations in rock elastic modulus, crustal stress and inclination of formations may all have an impact on stress distributions, fracture pressure and collapse pressure of borehole surrounding rocks, and this model solves the problem that conventional analytical models for borehole stability of isolropic formations can not exactly forecast the horehole stability of a deviated well in laminar formations. Therefore, it is necessary to choose a proper analytical model according to formation characteristics in designing drilling constructions so as to guide field practice more effectively.

关 键 词：井壁稳定 横观各向同性 拉伸破坏 剪切破坏 各向异性度 

分 类 号：TE21[石油与天然气工程—油气井工程]