Abstract:

Hydraulic fracturing is one of the main technologies to realize the efficient development of shale gas，and bedding plane is the key factor affecting the distribution of the three-dimensional geometry of hydraulic fractures. At present，scholars at home and abroad have explored the impact of shale reservoir bedding on the vertical propagation of hydraulic fractures，but there is less understanding on the vertical propagation pattern of hydraulic fractures in sand-shale interbedded reservoirs. Based on the theory of linear elastic fracture mechanics，a multi-bedding hydraulic fracture propagation model of coupled stress - damage - filtration loss is established in this study，and the impacts of change in reservoir stress field，formation dip angle and tensile strength of bedding plane on the vertical propagation of hydraulic fractures are analyzed. Compared with the microseismic monitoring results，accuracy of the model can reach more than 95%. The simulation results show that propagation of hydraulic fracture can be divided into three stages in the process of penetrating through the bedding plane of sand-shale interbedding，and the propagation direction of hydraulic fracture in the third stage is determined by the change in reservoir stress field，formation dip angle and tensile strength of bedding plane. Reservoirs with low stress difference and low dip angle are favorable to the opening of bedding plane，while reservoirs with high stress difference and high dip angle are favorable to the vertical propagation of hydraulic fracture. As the tensile strength of bedding plane decreases，the opening degree of bedding plane increases. This is mainly because that the lower the tensile strength of bedding plane is，the less the energy consumption for opening the bedding plane is.

Key words:

"> sand-shale interbedding, bedding plane, vertical stress, formation dip angle, interaction, hydraulic fracturing

摘要：

水力压裂是实现页岩气高效开发的主要技术之一，而层理面是影响水力裂缝三维几何形态展布的关键因素。目前国内外学者已经探究了页岩储层层理面对水力裂缝纵向扩展的影响，但是对砂泥岩互层条件下水力裂缝纵向扩展规律缺乏认识。基于线弹性断裂力学理论，构建了耦合应力-损伤-滤失的多层理水力压裂裂缝扩展模型，并分析了储层应力场变化、地层倾角和层理面抗张强度对水力裂缝纵向扩展的影响。对比微地震监测结果，该模型的准确率可达95%以上。模拟结果表明，水力裂缝在贯穿砂泥岩层理面过程中的扩展动态可划分为三个阶段，储层应力场变化、地层倾角和层理面抗张强度决定了第三阶段水力裂缝的延伸方向；低应力差和低地层倾角储层有利于层理面开启，高应力差和高地层倾角储层有利于水力裂缝纵向扩展；随着层理面抗张强度的降低，层理面开启程度也随之增加，主要是由于层理面抗张强度越低，打开层理面耗费能量越小。

关键词:

"> 砂泥岩互层, 层理面, 垂向应力, 地层倾角, 相互作用, 水力压裂