三维地应力状态下钻孔岩石压裂方位及扩展研究

发布时间：2018-05-22 08:39

本文选题：岩石 + 水力压裂　；参考：《燕山大学》2016年硕士论文

【摘要】：在岩石工程、石油天然气工程及水利工程中,钻孔岩石裂缝开裂方位裂缝扩展特征的研究是一个热门课题,历来受到学者们的关注。以往的研究大多局限于二维平面裂缝,三维地应力状态下的岩石钻孔裂缝的研究一直处于初级阶段。本文采用有限元法对三维地应力状态下钻孔岩石裂缝开裂演化征进行了系统的分析,研究结论可指导岩石压裂工程实践,论文主要工作如下。本文给定了十二种三维地应力状态,基于岩石的弹塑性特征,运用有限元法计算出各种应力状态下的开裂方位角,并与基于弹性理论计算结果进行对比。分析表明考虑岩石弹塑性特征的有限元方法计算得出的钻孔岩石开裂方位角更加符合实际的压裂状况,其结果更为准确。采用XFEM(扩展有限元)法,在计算出的开裂方位角的基础上分别对二维平面应变状态下、三维竖直井地应力状态下和三维斜井地应力状态下的预制裂缝进行裂缝的扩展模拟计算,并从裂缝扩展路径、裂尖应力变化、裂缝穿过单元的应力应变曲线、裂缝扩展过程中的能量变化等方面对计算结果进行了详细的分析,得出了相应的裂缝扩展特征。
[Abstract]:In rock engineering, petroleum and natural gas engineering and water conservancy engineering, the research on the crack propagation characteristics of borehole rock crack orientation is a hot topic, which has always been concerned by scholars. Most of the previous studies are confined to two-dimensional plane fractures, and the study of rock borehole fractures under three-dimensional in-situ stress is always in the primary stage. In this paper, finite element method is used to systematically analyze the evolution of fracture cracking in borehole rock under three dimensional in-situ stress. The research conclusions can guide the practice of rock fracturing engineering. The main work of this paper is as follows. In this paper, twelve three dimensional stress states are given. Based on the elastoplastic characteristics of rock, the crack azimuth under various stress states is calculated by finite element method, and the results are compared with those based on elastic theory. The analysis shows that the azimuth angle of rock crack calculated by the finite element method considering the elastoplastic characteristics of rock is more consistent with the actual fracturing condition and the results are more accurate. Based on the calculated crack azimuth, the prefabricated fractures in 3D vertical well under ground stress state and in three dimensional inclined well in-situ stress state are simulated by using XFEM (extended finite element) method, and the fracture propagation simulation is carried out on the basis of the calculated crack azimuth angle, respectively, under the condition of 2D plane strain, 3D vertical well in-situ stress state and 3D inclined well geostress state. The calculation results are analyzed in detail from the aspects of crack propagation path, stress change of crack tip, stress-strain curve of fracture through element, energy change during crack propagation, and the corresponding crack propagation characteristics are obtained.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU45

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