基于构型力学理论的井壁损伤失稳研究

The project is close to undertake the former project that was supported by the National Natural Science Foundation of China in 2011,which focuses on complex microstructure and many defects evolution inside the borehole rock. However, these problems were hardly got through by traditional fracture mechanics and damagement mechanics, which are based on continuous media theory. According to configurational forces theory, the new ideas and methods are put forward that will describe complex microstructure and many defects evolution inside the borehole rock by mechanical chemical coupling effect, i.e. discontinuity, heterogeneity and anisotropy and so on. Through the microscopic test of complex microstructure and many defects configuration changes inside borehole wall rock, the basic physical test method of configuration theory will be obtained; the casing damage constitutive model of instability will be established on the basis of configuration theory; the casing damage evolution equation of instability and casing strength criterion will be worked out; as well as.the simulative calculation of casing damage instability.At last, the research new system of casing damage instabilitywill be formulated based on configurational force theory. The project will further reveal evolution process and deep mechanism of the gradual deterioration deformation of the borehole wall rock, which will results in destruction failure. And the deformation is aroused by complex microstructure and many defects cumulation damage inside borehole wall rock. With providing new understanding that complex microstructure and many defects evolution have an effect on its rigidity and strength, and providing more scientific evidences for borehole wall stability assessment and fracture prediction of instability, there will be theoretical and practical significance for effectively solving the problem of borehole wall instability.

本项目紧密承接前一个国家自然科学基金资助项目，针对以往基于连续介质理论的传统断裂力学、损伤力学难以处理的井壁岩石内部复杂微结构多缺陷演化问题，提出了运用构型力学理论来描述力学化学耦合作用下井壁岩石内部非连续、非均质和各向异性等复杂微结构多缺陷演化规律的新思路、新方法。通过微观分析测试井壁岩石内部复杂微结构多缺陷的构型改变，建立构型力学基本物理量测定方法、基于构型力学的井壁损伤失稳本构方程、井壁损伤失稳演化模型和井壁岩石强度准则，以及对井壁损伤失稳变化过程进行仿真计算与模拟等，形成基于构型力学理论的井壁损伤失稳研究新体系。项目将进一步揭示井壁岩石内部复杂微结构多缺陷损伤累积造成井壁岩石逐渐劣化变形屈服到破坏失效的演化过程和深层机理，为井壁岩石内部复杂微结构多缺陷演化对其刚度和强度的影响提供新认识，为井壁稳定性评估和断裂失稳预测提供更科学的依据，对有效解决井壁失稳问题有着重要的理论和实际意义。

井壁失稳是困扰钻井工程的复杂难题，主要有井眼缩径、垮塌、破裂和储层破坏等问题，事故的产生会给石油工业生产带来巨大的经济损失，滞后生产进程，而井壁失稳主要发生在泥页岩地层，大约有90%的井眼垮塌事故都与泥页岩的不稳定有关，所以对泥页岩井壁岩石的失稳问题进行研究非常有必要。本课题力图在现有理论与实验研究的基础上，将以物质质量粒子及其连续体作为研究对象的传统连续介质力学理论与以缺陷为研究对象的构型力学理论相结合，通过从微/细观尺度分析井壁岩石的损伤结构特征以及非连续、非均质缺陷结构在力学化学耦合作用下的构型改变，建立了构型力学基本物理量测定方法、基于构型力学的井壁损伤失稳本构方程、井壁损伤失稳演化模型和井壁岩石强度准则，以及对井壁损伤失稳变化过程进行仿真计算与模拟等。最终形成了基于构型力学理论的井壁损伤失稳研究新体系，为有效解决钻井过程中的井壁失稳问题提供更为可靠的科学依据。