Effect of matching relation of multi-scale, randomly distributed pores on geometric distribution of induced cracks in hydraulic fracturing

Abstract

Reservoir rock contains many multi-scale, unevenly distributed pores, and the pore structures of shale in different reservoirs and geological environments vary greatly. Because the seepage velocity and pressure field are related to the pore spatial variations, the inhomogeneity of the seepage is superimposed on the anisotropy of the rock’s physical properties, which will affect the distribution of the induced cracks. A method for calculating the pore size in the bonded particle model, based on Delaunay triangulation, is proposed. A modeling approach capable of simulating the multi-scale pore distribution of actual rock is presented based on the proposed method. To understand how microcracks connect micropores in the process of fracturing, several bonded particle model samples with different pore structures were established, and numerical experiments were conducted based on the coupling calculation of the discrete seepage algorithm and discrete element method. The focus of this study was on the interactions between the distribution characteristics of multi-scale pores, the specific physical properties of the fracturing fluid, and the distribution differences of the induced cracks caused by the special seepage characteristics when using different fracturing fluids. The numerical results showed that the advantages of supercritical CO2 fracturing are maximized in deep reservoirs (high in-situ stress) and that a suitable in-situ stress condition is required (i.e. a stress ratio close to 1).

Energy dissipation mechanisms in fluid driven fracturing of porous media

“…0 | WZA = 10 4 × 0 = 10 −11 m 2 /Pa s. The WZA zone represents the presence of a zone that has a different geomaterial with a close mechanical stiffness, but a much larger permeability. The presence of such inhomogenieties within the reservoir, at various scales, has been previously discussed in various studies (Peng 2020;Yang et al 2018;Baykin and Golovin 2016;Legarth et al 2005). • Weak Zone B (WZB): The weak zone in this modeling case has an initial degraded stiffness of one percent of the intact material stiffness and a higher initial permeability that is three order of magnitudes higher than the rest of the domain , i. the weak zone has a high permeability, the high fluid flow intensity in the damage zone forced the evolution of damage of the WZA zone.…”

Applying Circular Economy to Construction Industry through Use of Waste Materials: A Review of Supplementary Cementitious Materials, Plastics, and Ceramics

“…Classification of pores within cementitious and composite materials is the basis for understanding the multi-functionality of additives and the type of adopted curing. Pore classification is generally based on their shapes, such as geometric pores [180], or their type, such as 1. open pores, 2. through pores (pores open from two sides), and 3. closed pores [181]. In size, however, they are generally categorized as micropores (below 1 nm), mesopores (1-25 nm), macropore (25-50 nm), and fracture (above 50 nm [182][183][184].…”

Fracture Propagation Modes of Lower Cambrian Shale Filled with Different Quartz Contents under Seepage-Stress Coupling

“…Hydraulic fracturing is considered one of the most effective fracking techniques for shale gas extraction today and has been widely recognized and applied in engineering [15][16][17][18]. Shale gas reservoirs are highly inhomogeneous and anisotropic, and reservoir-geomechanics-fracturing simulations are used to investigate the effect of subsequent parent well injection on interwell fracture disturbance and changes in induced stresses [19,20].…”