Numerical Simulation of Hydraulic Fracture Propagation Characteristics of Low Permeable Coal-Rock Mass

Abstract

Based on the coal-rock mass deformation model, hydraulic pressure descent model in fracture, fracture propagation model and its growth criterion, the mathematical model of hydraulic fracturing of low permeable coal-rock mass is established, and the influencing factors such as injection pressure, elastic modulus of coal-rock mass and in-situ stress, which affect the characteristics of hydraulic fracture propagation, are studied using the ANSYS software. The results show that fracture length presents a linear increase and widest width increases as an exponent function with the increase of injection pressure, and the ability of making fracture width is greater than fracture length during late fracturing; besides, with the increase of Young’s modulus of coal-rock mass and least horizontal stress, fracture length and widest width decrease, which are independent of maximum horizontal stress. The obtained conclusions provide a guiding role for the optimization of operation parameters of field hydraulic fracturing of low permeable coal-rock.

The occurrence state of moisture in coal and its influence model on pore seepage

“…[35][36][37] At present, hydraulic fracturing, hydraulic cutting and hydraulic punching are commonly used as the primary methods to improve the permeability of coal for methane extraction and gas-disaster management. [38][39][40][41][42][43] But the coal seams would be wetted at the same time, which can bring some negative effect, such as occupying the seepage channel, increasing the ow resistance and impacting the gas desorption. [44][45][46] Moisture always coexists with gas in coal at all ve stages of gas recovery, as shown in Fig.…”

Numerical Investigation on Potential Influencing Factors Affecting Drainage Effective Radius of Crossing Borehole

“…In the literature, a pump-less dual-pass mechanical cavitation bit for crossing borehole to improve borehole diameter and bit reliability was designed [8]. The technologies, such as gas drainage by a cluster of holes, hydraulic fracturing through seam boreholes [9], and water-gas two-phase fracturing of coal seams, are based on the arrangement of crossing boreholes [10], so the study of the impact parameters of seam boreholes is helpful for technique optimization.…”