Abstract
Hydraulic fracturing is a critical process in the development of oil shale reservoirs. The presence of widespread bedding planes and natural fractures significantly influences the propagation of hydraulic fractures. Additionally, the injection point density plays a crucial role in the effectiveness of reservoir reconstruction. The Global Embedded Cohesive Zone Method (FEM-CZM) was employed to model the initiation and propagation of fractures from perforation holes, considering the combined effects of bedding planes and natural fractures. The results indicate the following: (1) the initiation and propagation of fractures from perforation holes lead to the co-propagation of two to four asymmetric main fractures, alongside open bedding planes and natural fractures; (2) larger bedding plane thickness and smaller bedding plane spacing promote hydraulic fractures’ tendency to propagate along the bedding planes, resulting in longer fracture lengths and predominance of tensile failure; and (3) a higher in situ stress difference facilitates the fracture’s penetration of the bedding plane, leading to an initial increase and subsequent decrease in fracture length. Tensile failure remains dominant, while the proportion of shear failure increases. Based on these findings, it is recommended to select fracturing sites with thicker bedding planes, larger bedding plane spacing, and a smaller vertical in situ stress field. Additionally, a perforation scheme with six injection points should be adopted to enhance the formation of high-efficiency seepage and heat transfer channels between hydraulic fractures, bedding planes, and natural fractures.
Published Version
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