Fully three-dimensional propagation model of horizontal borehole hydraulic fractures in strata under the effect of bedding planes

The bedding plane effect will occur when hydraulic fractures propagate to the bedding plane in sedimentary strata, resulting in the “≠,” “工,” or “/” shaped fracture morphology. Based on previous physical experiments results, this article analyzed the mecroscopic propagation mechanism of tensile failure and the mechanical conditions for main hydraulic fracture and the bedding plane fracture propagating, proposing the criteria for hydraulic fracture to penetrate through the bedding plane. A fully three-dimensional model of hydraulic fracture morphology in horizontal borehole hydraulic fracturing is established with the vertical water flow, water leak-off, and bedding plane effect taken into consideration. Basic equations of continuity, pressure decline, hydraulic fracture morphology, and others are solved. After that, true triaxial hydraulic fracturing experiments with samples containing bedding planes are conducted to verify the aperture, length, width, and height of hydraulic fractures in this model. The model is proved to be accurate and reliable.