Numerical Analysis on the Optimization of Hydraulic Fracture Networks

Abstract

Abstract:The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of natural fractures. In this work, a real natural fracture network is reconstructed from shale samples. Moreover, a virtual fracture system is proposed to simulate the large number of small fractures that are difficult to identify. A numerical model based on the displacement discontinuity method is developed to simulate the fluid-rock coupling system. A dimensionless stress difference that is normalized by rock strength is proposed to quantify the anisotropy of crustal stress. The hydraulic fracturing processes under different stress conditions are simulated. The most complex fracture configurations are obtained when the maximum principle stress direction is perpendicular to the principle natural fracture direction. In contrast, the worst results are obtained when these two directions are parallel to each other. Moreover, the side effects of the unfavorable geological conditions caused by crustal stress anisotropy can be partly suppressed by increasing the viscous effect of the fluid.

Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models

“…Zou et al presented a 3D distinct element method (DEM)‐based fracturing model to investigate the mechanism of HFN propagation in naturally fractured shale formations . Zhang et al developed a displacement discontinuity method (DDM)‐based numerical model to simulate a fluid‐rock coupling system . Nagel et al used continuum and discrete element modeling approaches to simulate the geomechanical process and investigate the complex nature of the coupled interactions between a propagating hydraulic fracture and the existing natural fractures .…”

“…19 Zhang et al developed a displacement discontinuity method (DDM)-based numerical model to simulate a fluid-rock coupling system. 20 Nagel et al used continuum and discrete element modeling approaches to simulate the geomechanical process and investigate the complex nature of the coupled interactions between a propagating hydraulic fracture and the existing natural fractures. 21 Ju et al investigated the processes of the initiation and the propagation of cracks in a heterogeneous material based on the continuum-based discrete element method (CDEM) algorithm; the results indicated that material heterogeneity has considerable effect on crack initiation, but that crack propagation is controlled primarily by the geostress ratio.…”

The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

“…Given the complexity of the problems, extensive theoretical and numerical studies on the actual kinematics of fractures propagating across interfaces between similar and dissimilar rocks have been performed by researchers all over the world [7,[10][11][12][13][14][15][16][17]. These studies of natural hydro-fractures and man-made hydraulic fractures show that the hydro-fractures are primarily branched, blunted, and/or arrested when they meet discontinuities, stress barriers and/or rock layers of strongly contrasting mechanical properties.…”

Determination of Fracture Initiation Locations during Cross-Measure Drilling for Hydraulic Fracturing of Coal Seams

“…At present, to enhance gas drainage efficiency in a low-permeability coal seam, hydraulic fracturing (HF) is used as a standard practice [1][2][3]. It achieves good results draining coal bed methane in most coal mines.…”