Analysis and Numerical Simulation of Hydrofracture Crack Propagation in Coal-Rock Bed

In underground coal mines,hydrofracture can cause the increase of breathability in the fractured coal bed.When the hydrofracture crack propagates to the interface between the coal bed and the roof-floor stratum,the crack may enter roof-floor lithology,thus posing a limit on the scope of breathability increase and making it difficult to support the roof and floor board for subsequent coal mining.In this work,a two-dimensional model of coal rock bed that contains hydrofracture crack was constructed.Then an investigation that combines the fracture mechanics and the system of flow and solid in rock failure process analysis(RFPA2D-Flow)were carried out to study the failure mechanism at the interface between rocks and coals,and critical water pressure that hydrofracture crack propagates.The results indicated that the main factors that affect the direction of hydrofracture crack propagation are the angle of intersection between coal-rock interface and horizontal section,horizontal crustal stress difference,tension-shear mixed crack fracture toughness in coal-rock interface and differences in elasticity modulus of coal-rock bed.The possibility of crack directly entering coal-rock interface would increase with the increase in angle of intersection or horizontal crustal stress difference.The trend that crack propagates along the coal-rock interface will become stronger with the decrease of the fracture toughness at the coal-rock interface and the increase of the elasticity modulus difference between the coal bed and the roof strata.The results of this study was to put forward a method of controlling hydrofracture crack,optimize the fracturing well location provides a certain theoretical basis.

Brief overview and perspective on Advances in CO_(2)Geological Storage and Utilization(CGSU)

1 Introduction All over the world,with the intense longing for carbon emission reduction and the demand for clean energy(Feng et al.,2020;Iddphonce et al.,2020;Zhao et al.,2022),a promising and far-reaching technology called CO_(2) geological storage and utilization(CGSU)has attracted increasing attention(Iddphonce et al.,2020;Ma et al.,2020).This CGSU technique enjoys huge potential and broad prospect,because it usually enables dual rewarding consequences–to sequester CO_(2) and to acquire energy from geological formations,such as geothermal rock,oil and gas reservoirs(Iddphonce et al.,2020;Klewiah et al.,2020;Liu et al.,2020).In fact,the CGSU has been followed by interest of scientists all around world since geological storage was first proposed in the 1970s as a way to dispose of the CO_(2).Meanwhile,the CGSU technique is not mature enough and usually involves a complicated THMC coupled process,making it necessary to deploy more insightful investigations to boost the development of CGUS technique in a robust,safe and cost-effective manner(Liu et al.,2021b;Zhao et al.,2021;Liu et al.,2023).Basically,this theme is expected to enhance the knowledge about the crucial role of CGSU in achieving the carbon emission reduction–an issue concerned to the world(Liu et al.,2021a;Xie et al.,2021;Zhao et al.,2021;Zhao et al.,2022).Therefore,this special issue is organized and tends to present newest achievements regarding the CGSU,such as the theory expansion,economic analysis,experimental investigation and numerical simulation.