Abstract. The commercial coalbed methane production success is majorly defined by the effectiveness of the use of special gas inflow stimulation methods. The necessity of using of such methods is subject to the aspects of searching and displacement of methane within the coal compound. The analysis of the ways of methane production stimulation from virgin coal formations is given. The description of the process of hydraulic fracturing (fracturing) as the most common stimulation method during the commercial coalbed methane production as well as its major advantages are presented. The present work provides data about the initiated laboratory research of sands collected from Kemerovo region deposits for the purpose of finding of the most prospective samples by means of anchoring of fractures. The prospectivity and ability to implement the hydraulic fracturing with the use of locally available sands acting as proppants are shown. The influence of the strain-stress state of the rock massif on the alteration of permeability and the necessity of its extension study with respect to different technological features of hydraulic fracturing is shown.
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.
The paper presents a method of choosing the design of horizontal coalbed methane well by estimation of a coal seam permeability on the results of one-dimensional and two-dimensional geomechanical modeling. The differences in the preparation of one-dimensional geomechanical models of coalbed methane fields from models for conventional oil and gas fields are noted. The results of preparation of one-dimensional geomechanical model based on data from one of the vertical exploration coalded methane wells and two-dimensional geomechanical modeling of coal seam for three common designs are presented. The obtained results allow us to conclude that geomechanical modeling is a suitable tool for estimation of coal seam permeability changes and choosing the most effective well design for the considered mining and geological conditions. In particular, in the coal seam under study, a multilateral well can cause the greatest increasing of permeability.
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