【摘要】 二氧化碳地质封存技术是一种减少二氧化碳排放量的有效方式。砂岩透镜体具有良好的储-盖组合,是较为理想的二氧化碳封存场址。砂岩透镜体中注入超临界二氧化碳引起的裂缝萌生、扩展、演化等一系列复杂问题直接决定着封存的安全性。利用ABAQUS数值模拟软件,基于扩展有限元法(XFEM)建立流-固耦合模型,通过将超临界二氧化碳注入砂岩透镜体,观察透镜体内部砂岩储层裂缝破裂过程。数值模拟研究得出结论:在透镜体产状不同的条件下,倾斜透镜体相对于水平透镜体封存能力较差,不适宜进行二氧化碳封存;将二氧化碳以3种不同的流速充注到砂岩透镜体中,流速增加不利于封存的安全性,但是裂缝长度和形态没有发生明显变化;裂缝在扩展过程中裂缝首先变宽成为导流通道,然后变长扩展,裂缝尖端应力先增大达到峰值然后逐渐降低,最终裂缝停止扩展。更多还原

【Abstract】 Carbon dioxide geological storage technology is an effective way to reduce carbon dioxide emissions. The sandstone lens is an ideal site for carbon dioxide storage because of its good combination of reservoir cover. Duringthe supercritical carbon dioxide injected into sandstone lens,a series of complex problems including fracture initiation,extension and evolution directly determine the safety of storage. The numerical simulation software ABAQUS that is based on the extended finite element method( XFEM) is used in this study. The study uses the changes of the main keywords to set up fluid-solid coupling model. Then the process of injecting supercritical carbon dioxide into sandstone lens is observed to find out the fracture failure process in the internal sandstone lens reservoir. Several conclusions are drawn from the simulation as follows. Under the condition of different lens shapes,the velocity of the inclined lens is faster than that of the horizontal lens,and the pore pressure at fracture initiation is much larger. The propagation time is short,and the CO2 storage ability is poor. As three different kinds of CO2 injection flowing rates increase,the pressure increase is more obvious,the initiating cracking time is shorter,the fracture propagation time is shorter and the speed of propagation is faster. However,the length and shape of the fracture do not change significantly. In the process of the fracture propagation,the fracture widens firstly and becomes the diversion channel,and then grows. The stress at the fracture tip increases first and then decreases gradually. The fracture stops expanding at last.更多还原