米桑油田盐岩层定向钻井井壁稳定性研究

文章摘要

米桑油田盐岩层定向钻井井壁稳定性研究

Study on wellbore stability during directional well drilling in salt rock of Missan Oilfield

投稿时间：2018-08-26 修订日期：2018-08-26

DOI：

中文关键词: 盐岩层井壁稳定坍塌压力破裂压力有限元模型

英文关键词: salt rock layer wellbore stability collapse pressure fracture pressure finite element model

基金项目:国家重大专项“海外重点油气田开发钻采关键技术”(2017ZX05032004)。

作者	单位	邮编
吴怡^*	中海油研究总院有限责任公司	100028
卢运虎	中国石油大学北京石油工程学院	102249
刘书杰	中海油研究总院有限责任公司	100028
王名春	中海油研究总院有限责任公司	100028
洪国滨	中国石油大学北京石油工程学院	102249
吴晓冬	中国石油大学北京石油工程学院	102249

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中文摘要:

米桑油田曾多口井斜井段穿越复合盐膏层,溢流、井漏、井塌、阻卡、缩径等钻井复杂情况频发,导致原井眼报废。为分析米桑油田出现的盐岩蠕变缩径、软泥岩流动、泥页岩及石膏地层坍塌等现象,运用瞬时弹性分析法,描述盐岩层井壁应力状态,建立了瞬时弹性坍塌压力和破裂压力。应用有限元分析法,建立描述盐岩层定向井井壁蠕变稳定性模型,从岩石力学的角度重点分析了米桑油田X井盐岩层坍塌压力和破裂压力,建立泥浆密度新公式,给出岩膏层安全钻井液密度窗口范围。研究结果表明,盐膏层水平与垂直方向力学性质差别明显,各向异性突出,弹性模量低,水平方向泊松比高。计算结果表明,盐膏层安全钻井液密度窗口范围2.31～2.50g/cm₃,本研究成果已成功应用于米桑油田钻遇盐岩层时钻井方案设计,有效解决了井壁稳定难题,安全保证了现场作业。

英文摘要:

The inclined shaft section of Missan oilfield passes through the compound salt gypsum layer, and the complicated drilling conditions of overflow, well leak, well collapse, blocking and shrinkage are frequent, which leads to the discarding of the original hole. Aiming at analyzing the phenomenon in Missan oilfield, like salt rock creeping and hole diameter reduction, mud rock flowing, shale and gypsum formation collapsing and so on, the transient elastic analysis method is used to describe the stress state of the wellbore wall of the salt rock layer, and the instantaneous elastic collapse pressure and fracture pressure are established. The finite element analysis method is used to establish the model for describing the creep stability of directional well wall in salt rock. From the perspective of rock mechanics, the collapse pressure and fracture pressure of X well in Missan oilfield are analyzed, a new formula for mud density and window range of safe drilling fluid in rock and gypsum layer was provided. The research results show that the mechanical properties of salt-paste layer differ significantly in horizontal and vertical directions, with prominent anisotropy, low elastic modulus and high poisson’s ratio in horizontal directions. The calculation results show that the salt-paste safe drilling fluid density window ranges from 2.31 to 2.50g/cm3. The research results have been successfully applied to the design of drilling scheme when drilling into salt-rock formation in Missan oilfield, effectively solving the problem of borehole wall stability and ensuring site operation safely.

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