Hydraulic fracturing modelling of glutenite formations using an improved form of SPH method

Abstract

Due to the low permeability and high heterogeneity properties of glutenite formations, the hydraulic fracture morphologies are extremely distorted during hydraulic fracturing operations, which is difficult to predict by traditional numerical method. Based on the existing limitations (i.e., the mesh re-division problems in FEM, complex parameter calibrations in DEM), an improved Smoothed Particle Hydrodynamics (SPH) method for modelling the hydraulic fracturing of glutenite formations was proposed. The interaction modes between the liquid and solid particles were first defined and the transformation algorithms of liquid, particles and damaged particles were also proposed. Then, the fracture mark ξ was introduced and the traditional kernel function in SPH was improved to simulate the hydraulic fracturing process. The “random gravel generation” algorithm combined with the “searching radius method” were proposed to well reproduce the meso-structures of glutenite. After that, the SPH model of glutenite was established, based on which, the influence of factors such as gravel size, content, strength as well as confining pressure were investigated. Results show that the crack patterns mainly include: 1) Propagating through the gravel; 2) Propagating around the gravel; 3) Stopping inside the gravel; 4) Crack bifurcation. The research results can provide some references for the comprehensive understandings of the internal mechanisms of glutenite hydraulic fracturing processes as well as the applications of SPH method into the simulations of glutenite hydraulic fracturing.