深层泥页岩井壁失稳机理与预测模型研究进展

Research status of the wellbore failure mechanism and predicting model in deep mudstone and shale

深层油气资源开发已成为国家油气发展的重要战略,泥页岩井段井壁失稳是制约深层油气资源安全高效开采的技术“瓶颈”。本文在分析深层泥页岩井壁失稳的力学机理和化学机理基础上,着重论述考虑泥页岩水化作用、弱结构面、各向异性和多场耦合的井壁稳定性预测模型的研究进展和发展趋势。钻井液密度不合理是井壁力学失稳的主要原因,泥页岩水化作用是井壁化学失稳的主要原因;在井壁流-固-化-热四场耦合作用下,考虑弱结构面、各向异性对泥浆安全密度窗口的影响,是目前研究深层泥页岩井壁稳定性的主要趋势和方法。

The exploitation of deep oil and gas resources has become an important strategy of national oil and gas development,and borehole instability in mudstone and shale formations is the technical bottleneck restricting the safe and efficient development of deep oil and gas resources.This paper analyzes the mechanical and chemical mechanisms of deep mudstone shale borehole failure with the focus on the research status and development trend of wellbore stability prediction models for shale hydration,weak structural plane,anisotropy and multi⁃field coupling.Improper mud density is the major cause for mechanical wellbore failure,while mudstone and shale hydrations are the major causes for chemical wellbore failure.Investigation of the effects of the weak plane and anisotropy on the safe density window of drilling mud is the major method to study the wellbore stability in deep mud and shale formations under the action of the fluid-solid-chemical-thermal coupling behavior on the wellbore.