Using discrete element numerical simulation to determine effect of persistent fracture morphology on permeability stress sensitivity

Abstract

The stress sensitivity of coal seams with different fracture structures affects gas migration characteristics in the fracture zone. In this study, permeability stress experiments for intact and persistent fracture coal samples are carried out. A discrete element method numerical simulation that adopts the changing joint stiffness method is proposed. Based on the experimental data, the corresponding parameters of persistent fractures and elastic joints for fluid-solid coupling simulations are determined. Subsequently, the internal influence mechanisms of fracture morphology on axial and confining stress sensitivities are determined. The simulation results show that sectional fractures with different dip angles in the persistent fracture control the sensitivity to axial and confining stresses. The horizontal segment fracture aperture decreases with an increase in axial stress, which reduces its flow capacity. This results in a decrease in the flow rates in the persistent fracture. When the confining stress increases, the vertical fracture aperture is significantly reduced, considerably reducing the flow rate in the persistent fracture.

Research on the Mechanism and Control Technology of Coal Wall Sloughing in the Ultra-Large Mining Height Working Face

“…According to Xu et al [1], who investigated the form of coal wall instability under various constraints using the pressure bar model, weak coal seams are susceptible to shear failure and slip instability, while hard and medium coal seams are susceptible to shear failure and slip instability. Hard coal seams frequently experience collapsing failure and bending instability; Wang et al [2][3][4] proposed three types of coal wall failure modes: compression shearing, pulling shearing, and pulling cracking; Yin et al [5] analyzed the form and depth of the coal wall in the large mining height working face by using the stability principle of the pressure bar; Liu et al [6,7] analyzed the rib mechanism of stepped coal cutting using numerical simulation. Suorineni et al [8] found that the joint action of the active high stress area and the tensile stress area during the operation led to the collapse of the working face.…”

Evolution Characteristics of the Microstructure with Different Fracturing Fluids: An Experimental Study of Guizhou Bituminous Coal

“…Affected by the shortage of fossil energy and the greenhouse effect, all countries in the world are actively exploring new energy. , Coalbed methane is a new type of clean energy with broad application prospects, which has attracted the attention of governments all over the world. , According to the data of the International Energy Agency (IEA), the total global coalbed methane resources buried at a depth of less than 2000 m can reach 260 trillion m 3 , which is more than twice the proven reserves of conventional natural gas . However, the coal seams are less permeable and need to be hydraulically fractured to increase the permeability before the drainage of coalbed methane, especially in China. , Fracturing fluid is a key factor affecting the hydraulic fracture morphology and coal microstructure and plays an important role in the process of hydraulic fracturing. − …”

Implementation and validation of effective thermal conductivity model of coal‐rock mass with rough capillary pore structure under CT three‐dimensional reconstruction

“…Deep mining will become the new normal of sustainable development of the coal industry and resource development, which brings both opportunities and challenges. [1][2][3] The mining of deep coal resources will face a severe high-temperature environment, but at the same time, the geothermal resources contained in the deep can be used as symbiotic resources for mining and utilization. 4,5 The common problem involved is the heat transfer inside or between the coal rock mass and its exchange medium.…”

“…With the long‐term high‐intensity mining of shallow coal resources in China, coal mining has gradually extended to the deep. Deep mining will become the new normal of sustainable development of the coal industry and resource development, which brings both opportunities and challenges 1–3 . The mining of deep coal resources will face a severe high‐temperature environment, but at the same time, the geothermal resources contained in the deep can be used as symbiotic resources for mining and utilization 4,5 .…”