thin-interbedded sandstone-shale, hydraulic fracturing, fracture propagation, 3D discrete lattice method, fracturing process optimization, Science

In this study, a mechanical model of reservoir and interlayer structure is constructed based on three-dimensional discrete lattice method, and the fracture propagation rule and control factors of hydraulic fracturing in sand-mudstone thin interlayer reservoir are systematically discussed. The results show that: 1) the ratio of elastic modulus of the reservoir significantly affects the vertical propagation of fractures. When the ratio is 1, the fracture propagation is promoted; 2) The minimum horizontal ground stress difference between layers is more than 7 MPa, which can effectively inhibit the propagation of cracks through layers; 3) The combination of a high-viscosity fracturing fluid (≥40 mPa·s) and a high injection rate (≥8 m3/min) enhances fracture penetration, while the “high-low viscosity” combined injection strategy collaboratively optimizes primary fracture expansion and weak interzonal surface opening. Therefore, the process optimization scheme is proposed: 60 mPa·s high viscous surface is used when the barrier modulus is