页岩储层体积压裂裂缝扩展数值模拟

发布时间：2018-11-11 14:30

【摘要】：水力压裂的启裂与扩展是一个复杂非平衡、非线性的演化过程:一方面,研究水力压裂裂缝的启裂与扩展对于压裂设计和压后产能评价有着重要的理论意义;另一方面,地下岩体是非透明、非均质的材料,给岩石内部裂缝扩展和实现破坏的观察带来了非常大的困难。论文基于2013年研发的一套水力压裂裂缝缝网模拟程序(SVFN)进行研究,该软件应用边界元的位移不连续法进行计算,解决了有限元在模拟过程中不能有效处理裂缝尖端奇异性的问题,能模拟多条人工裂缝与大量天然微裂缝的互作用,及形成复杂裂缝缝网的动态过程。在论文的撰写过程中,用C++编程语言编程对SVFN的部分子程序进行了编译和程序调试。论文介绍了边界元的位移不连续法,推导了多裂缝情况下应力强度因子的求取并且给出了裂缝的开裂和延伸准则。以数值模拟为主要研究方法,对体积压裂过程中人工裂缝、天然微裂缝、人工裂缝与天然微裂缝的延伸、裂缝间的扩展形态,缝宽变化,互作用关系以及裂缝相交等方面进行了研究。通过数值模拟及分析,总结了体积压裂过程中裂缝破裂和转向机理以及体积压裂裂缝网络形成的控制因素,体积压裂效果的好坏受到地应力大小,人工主裂缝和天然裂缝的长度、宽度、在地层中的方位、间距、密度、开启或闭合等多重因素的影响。天然裂缝在30°时最容易开裂。人工裂缝内压力以及杨氏模量对裂缝宽度影响程度较大,其他如泊松比、水平地应力、裂缝倾角对其影响相对较小。这为更好地进行体积压裂效果评价奠定了基础。
[Abstract]:Fracture initiation and expansion of hydraulic fracturing is a complex and nonlinear evolution process. On the one hand, the study of fracture initiation and expansion of hydraulic fracturing is of great theoretical significance for fracturing design and post-fracturing productivity evaluation. On the other hand, the underground rock mass is non-transparent and heterogeneous, which brings great difficulties to the crack propagation and failure observation. This paper is based on a set of hydraulic fracturing fracture mesh simulation program (SVFN) developed in 2013. The software is calculated by discontinuous displacement method of boundary element. It solves the problem that the finite element method can not deal with the singularity of crack tip effectively, and can simulate the interaction between multiple artificial cracks and a large number of natural micro-cracks, and the dynamic process of forming complex fracture network. In the process of writing the thesis, some subprograms of SVFN are compiled and debugged by C programming language. In this paper, the displacement discontinuity method of boundary element is introduced, the stress intensity factor is derived in the case of multiple cracks, and the crack cracking and extension criteria are given. Taking numerical simulation as the main research method, this paper deals with the extension of artificial fracture, natural microfracture, artificial fracture and natural microfracture, the extension form of fracture and the variation of fracture width in the process of volume fracturing. The interaction relationship and fracture intersection are studied. Through numerical simulation and analysis, the fracture and turning mechanism during volume fracturing and the controlling factors of formation of volume fracturing fracture network are summarized, and the effect of volume fracturing is subjected to the magnitude of in-situ stress. The length, width, azimuth, spacing, density, opening or closing of the artificial and natural fractures are affected by many factors. Natural cracks are most likely to crack at 30 掳. The influence of pressure and Young's modulus on fracture width is greater than that of Poisson's ratio, horizontal in-situ stress and fracture dip angle. This lays a foundation for better evaluation of volume fracturing effect.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE357.1

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