3D reconstruction of low-permeability heterogeneous glutenites and numerical simulation of hydraulic fracturing behavior

Abstract

Based on microfocus computed tomography ( μ CT) imaging and X-ray diffraction techniques, a three-dimensional (3D) reconstruction model for heterogeneous glutenites was established by taking into account the mineral compositions and distribution characteristics of gravel particles. We employed the continuum-based discrete element method (CDEM) to simulate and analyze the initiation and propagation behavior of hydrofracturing cracks of heterogeneous glutenites subjected to various horizontal geostresses. The influences of various horizontal stress ratios and the characteristics of gravel particles on the initiation, growth, geometry, and spatial distribution of hydrofracturing cracks in heterogeneous glutenites were evaluated by comparing the properties of fractures with the simulation results of homogeneous sandstones. Additionally, we conducted a series of hydrofracturing experiments with physical models of the heterogeneous glutenites and homogeneous sandstones and compared the experimental data to the simulation results. Findings showed that the heterogeneity of glutenites significantly affects the hydrofracturing crack initiation and growth behavior. For identical geostress, the initiation pressure for hydrofracturing of heterogeneous glutenites was lower than that of homogeneous sandstones. The difference in initiation pressure between the heterogeneous glutenites and homogenous sandstones gradually decreased with an increase in the horizontal stress ratio, but overall, the change in the horizontal stress ratio had little effect on the initiation pressure for hydrofracturing of heterogeneous glutenites. The data from this investigation also indicate that for both heterogeneous glutenites and homogeneous sandstones, changes in the horizontal stress ratio can have an apparent impact on the spatial distribution and morphology of hydrofracturing cracks.