Numerical simulation of hydraulic fracture height layer-through propagation based on three-dimensional lattice method

Abstract

Unconventional reservoirs such as shale and coal rock are generally well-bedded, with significant differences in the interlayer stress and rock physical parameters. The change law of the fracture morphology is difficult to predict after the layer-through propagation of the fracture height during the fracturing operation. Existing studies have widely used multilayered two-dimensional fracture height models, which are not suitable for fracture propagation simulation in unconventional reservoirs under complex geological conditions. This study established a fracture height propagation model based on the three-dimensional (3D) discrete lattice method and used the Xsite software to simulate the layer-through propagation in layered strata under the influence of in-situ stress, rock physical properties, and construction parameters. The effects of different factors on the fracture height and fracture morphology are described. Sensitivity analysis for different model cases revealed that, when the fractures entered a formation with high in-situ stress and fracture toughness, the growth of the fracture height was restrained. As the elastic modulus of the rock increased, the fracture width significantly decreased and the fracture height increased. Increasing the fracturing fluid displacement benefits the growth of the fracture height and width, and accelerates the passage of hydraulic fracture through the interlayer interface to achieve deep penetration reconstruction in the longitudinal direction of the reservoir. Higher fracturing fluid viscosity increases the fracture width and reduces the fracture reconstruction volume, and the fracture morphology changes under different fracturing fluid viscosity. This study is useful for improving and supplementing unconventional reservoir fracture height simulation technology.