VNIMI’s Division in Kemerovo, Kemerovo, Russia

P. V. Grechishkin, Director, Candidate of Engineering Sciences, pv_grechishkin@mail.ru

In hydraulic splitting of coal seams, it is important to recognize the influence exerted by particular geological and geotechnical factors on the morphology and size of widened fractures. The study of the fracture morphology in hydraulic splitting of samples manufactured from a natural material was carried out. In the study, the condition of similarity rather than equality of deformations in model and in nature was fulfilled. For that reason, it was proposed to study the mechanism of fracture widening using equivalent materials and the main theoretical provision of oil reservoir mechanics. Modeling on artificial materials provides a functional dependence of the extension, propagation rate and opening of fractures created by hydraulic splitting. The possible natural morphology of fractures created in in-situ hydraulic splitting is not modeled in this case as a model is incapable to reproduce the structure and texture of a coal seam which is a nonuniform and anisotropic body. The combination of two types of modeling enables transference of lab-scale data to natural conditions and allows engineering analysis with regard to field observations. The implemented modeling of opening of hydraulic split fractures makes it possible to draw a conclusion that creation of fractures of substantial length (100–200 m) and width requires increasing flow rates of water used as breaking fluid, or using fluids of increased viscosity. For reaching comparable fracture parameters, the rate of water injection is to be 3–4 times higher than in case of injection of viscous fluids.

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