Study on the Influence of Bedding Density on Hydraulic Fracturing in Shale

Abstract

Natural fractures and weak bedding planes are important for forming complex fracture networks in shale reservoirs. There are many sets of shale layers with different bedding densities in Sichuan, China. In this paper, three typical drilling cores with different bedding densities were collected. The shale rock mechanical properties and fracture morphology are investigated. Bedding density affects the strength and deformation characteristics. A fracture characterization model is proposed, and the hydraulic fracturing effects are evaluated. It is shown that with decreasing bedding density, the peak strength and elastic modulus increase, and Poisson’s ratio decreases gradually. The effect of natural fractures on hydraulic fracturing is investigated by analyzing the expansion of hydraulic fracture. The research shows that natural fractures have a significantly induced effect on the initiation and propagation of hydraulic fracture. According to the results of physical simulation of hydraulic fracturing, three types fracture extension models are established: a strong extended complex fracture model, a weak bedding extended complex fracture model, and a natural fracture crack propagation model. Natural fractures with different bedding structural properties may result in different propagation types of hydraulic fracture.