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压裂液返排动态是影响页岩气井水力压裂后产能效果的重要因素。从页岩气井压后压裂液流动机理出发,讨论了压裂液分布区域和特征,利用数值模拟手段描述了压裂液在裂缝系统中的流动,并深入分析了压裂液滞留在裂缝和地层中的机理。根据页岩气水力压裂可能产生的裂缝形态,压裂液分布在高导流主缝、分支缝及压裂液侵入裂缝面周围的页岩基质,在返排过程中,裂缝与基质之间的渗流能力级差、重力分异造成在高导流裂缝的压裂液滞留,气水两相相对渗透率差异为影响分支缝压裂液返排的主要因素,而基质毛管压力则是阻碍基质侵入带压裂液流动的主要原因。开展对页岩气井压后返排动态研究,对于认识页岩气井压后返排率与裂缝系统形态特征的关系极为重要,同时,也为制定合理的返排制度提供了相应的理论指导。
Fracturing fluid back to the dynamic state of shale gas wells is affecting the productivity after hydraulic fracturing an important factor. Based on the mechanism of fracturing fluid flow after shale gas well fracturing, the distribution area and characteristics of fracturing fluid are discussed. The flow of fracturing fluid in fracturing system is described by means of numerical simulation and the influence of fracturing fluid on fracture and Mechanism in the formation. According to the possible fractures of shale gas hydraulic fracturing, the fracturing fluid distributes in the shale matrix around the fractured surface where the high-conductivity main seam, branch seam and fracturing fluid intrude, The gravitational differentiation caused the retention of fracturing fluid in the high-conductivity fractures. The relative permeability difference between gas and water was the main factor that affected the fracturing fluid flowback in the branch fractures. However, the capillary pressure of the matrix hindered the matrix invasion The main reason for the flow of fracturing fluid. It is very important to study the relationship between the backflow rate of shale gas well and the morphological characteristics of the fracture system after it has been pressed. It also provides corresponding theoretical guidance for formulating a reasonable return system.