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为尝试研究非均匀层状岩层中的复杂水力压裂裂缝延伸行为,以胜利油田某典型砂泥薄互层储层的水平井压裂为背景模型,利用基于有限元的数值模拟软件,开展了一系列水平井压裂裂缝延伸行为的数值模拟研究。在模拟中,表征远场地应力的模型围压、层理(界面)的强度和地层岩性是考虑的主要因素。数值模拟表明,水力压裂裂缝的延伸模式是远场地应力、界面性质及地层岩性的综合作用结果。裂缝延伸过程中遇到层间界面会出现偏转、分叉和钝化终止行为,总体可分为4类延伸模式:直接穿透、钝化、T型扩展、偏转。这些非平面、复杂裂缝并非体积压裂改造裂缝,因此,不但不利于油气的流动,而且也是压裂压力畸高、有效主裂缝长度减少甚至压裂失败的原因之一。数值模拟初步解释了裂缝延伸过程中应力演化及其与层间界面的相互作用机制,可望为水力压裂改造工程相关的设计与机理分析提供参考。
In order to study the fracturing behavior of complex hydraulic fractures in heterogeneous stratigraphic strata, a horizontal well fracturing of a typical sand and thin interbedded reservoir in the Shengli Oilfield was used as a background model. Based on the numerical simulation software based on the finite element method, NUMERICAL SIMULATION STUDY ON THE TENSILE BEHAVIOR OF A SERIES OF HORIZONTAL WELL BORING CRACKS. In the simulation, the model confining pressure in far field, strength of stratification (interface) and lithology of formation are the main factors to be considered. Numerical simulations show that the extension mode of hydraulic fracturing is a combination of far-field stress, interface properties and formation lithology. There are four types of extension modes: deflection, passivation, T-extension and deflexion. These non-planar and complex fractures are not fracturing fractures. Therefore, it is not only not conducive to the flow of oil and gas, but also one of the reasons for the high fracturing pressure, effective primary fracture length reduction and even fracturing failure. The numerical simulation preliminarily explained the stress evolution and the interaction mechanism with the interfacial interface during the process of fracture extension. It is expected to provide a reference for the design and mechanism analysis of the hydraulic fracturing retrofit project.