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.
Highlights
In the extraction of coal bed methane, the relationship between the production well and the natural network of cracks in the coal seam is crucial
The total sample fracture surface was maintained in the plane specified by fracture nucleus
There is every reason to assert that, under the fracture over-compression, the adhesion and friction forces and at the interface of the opposite edges will be significant and the fracture will intersect with the natural crack to the experiments with inhomogeneities in the form of separate solid inclusions with uneven surfaces
Summary
In the extraction of coal bed methane, the relationship between the production well and the natural network of cracks in the coal seam is crucial. In order to create an artificial fracture intersecting the natural cleavage in coal seams, hydraulic fracturing technology is used [1,2,3]. Further fracture propagation in the rock mass is possible only due to an additional energy supply, which is ensured by the fluid velocity. It can be concluded that in a homogeneous medium with certain mechanical and filtration properties, the propagation of the fracture in a specified direction is completely determined by the technical characteristics of the injection means and the fluid properties
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