Geomechanical Assessment of the Effect of Inhomogeneities on the Propagation of Hydrofractures in Coal Seams

Abstract

The article gives a theoretical propagation of the development of hydrofractures in coal seams from the position of geomechanics, including the possibilities and conditions for the fracture to intersect a natural crack. A technique is proposed for carrying out experimental studies of the effect of inhomogeneities on the extension of hydraulic fractures by physical modeling on samples of equivalent materials and the facility for their conduct. The results of experiments based on the proposed technique on samples made on the basis of cement, sand, fly ash, and water are presented, with modeling of inhomogeneities of various types. The results made it possible to conclude that when the closed cavities intersect in the form of gaping cracks of limited prevalence, their rupture fluid envelops with the preservation of the rupture plane. It is noted that when crossing unbounded gaping cracks, the established enveloping phenomenon will obviously occur along the “bridge” at the points of contacts of the opposite banks of cracks that take place in a real massif, and the very intersection of the fracture of the natural crack, mainly, depends on its deformation properties, the magnitude of the angle between the planes of the fracture and the crack, and also the fluid pressure.