Hydraulic fracturing practices in shaly unconsolidated sandstone reservoirs readily result in complex fractures due to high shale content, strong plasticity, and fracture toughness. This paper introduces a new method for manufacturing shaly unconsolidated sandstone that is supported by experimental results. In addition to the laboratory experiment, a Particle Flow Code (PFC) numerical model was established based on the relevant physical properties, mechanical parameters, and fluid-solid coupling theory. The fracture propagation law of shaly unconsolidated sandstone was comprehensively assessed. Shale content was found to significantly influence fracture propagation. Straight fractures tend to transform into circuitous pinnate fractures accompanied by seepage fracture zones as shale content increases. There is clear stress chain directivity accompanied by uneven distribution of stress after stress field loading, which produces shear stress as the fractures expand. The shear force created by shale can exceed easily the shear strength, leading to shear failure, uneven stress distribution and uneven compaction. The results of this study may provide a workable basis for optimizing the hydraulic fracturing process in shaly unconsolidated sandstone reservoirs.
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