RU2571464C1 - Preliminary degassing of coal series and worked-out area - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to mining. Claimed process comprises the drilling of wells for perforated casing to fit therein for hydrofracturing to be performed there through. Note here that the coal seam is subjected to overworking/underworking for release and creation the pore-fracture massif of hard and low-permeability rocks. Inclined wells with horizontal ends are drilled in the rock coal seam and, further, into worked-out space to allow drilling gasifying entries to the seam by smaller-diameter bore-holes. Lengthwise fractures are produced via perforated casing in the order following from the face to well mouth and crosswise fractures to release the massif of horizontal tectonic rock pressure component. Fluid with surfactant is forced therein for soil and roof disintegration. Proppant plug is set to prevent a premature methane removal. Thereafter, said plug is washed off. Note here that, first, methane is driven through injection wells to production wells while at cycle termination methane is driven via production wells to injection wells. To acquire the comprehensive data on the massif relieving and on safety, control monitoring measures are taken.

EFFECT: increased face efficiency owing to efficient degassing and unloading of series of worked seams.

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Description

The invention relates to the mining industry, namely to underground coal mining, and is intended for preliminary degassing of the zone of high rock pressure from the extinguished lava, as well as for mining a suite of gas-bearing formations with a strong low-permeable roof and soil and the worked out space.

In the practice of underground coal mining, there is a known method of unloading by advancing overtime or undermining of adjacent seams, including the preparation of excavation columns (AE) by conducting and securing conveyor (AE) and ventilation openings, leaving a coal pillar between the AE of the developed AE and the ventilation opening to be worked out by the AE with conducting ventilation interruptions between them and methane removal using a methane-air mixture flow created by air leaks carried out from the face through the exhaust country (Patent RU 2282030 C1, published August 20, 2006, Bull. No. 23 (analogue)). However, in the presence of difficult (strong and poorly permeable) roof and soil rocks, a large amount of methane remains in the formation and massif even when the protective layers are advanced and the roof rocks are torpedoed from the side of the extinguished lava.

There is also known a method of intensification of hydraulic fracturing of rocks through a perforated casing, including drilling a well and supplying it with a suspension containing liquid carbon dioxide and finely divided material; hydraulic fracturing is carried out by creating a transition of carbon dioxide from liquid to gaseous state (Patent RU 2280163 C1, published July 20, 2006, Bull. No. 20). This method is technically the closest to the proposed invention and is taken by the authors as a prototype. The disadvantage of this method is that the use of carbon dioxide has a detrimental effect on the environment, because when reacted with water, an acid is formed as a result of the reaction of the compound, which leads to acid rain when it comes to the surface.

The technical result consists in increasing the productivity of the lava due to the effective underground degassing and unloading of the retinue of the worked seams in the conditions of strong and poorly permeable inter-bedded rocks and increasing the safety of mining operations.

The proposed method allows to provide a comprehensive impact on a coal seam based on its degassing through wells and unloading by underworking and underworking to remove methane from the seam and worked out space created, including due to the formation of longitudinal cracks and transverse unloading cracks, of the pore-crack volume of the solid and poorly permeable roof and soil rocks with its subsequent extraction through boreholes, there is no interference with the main underground processes, since the development of the formation is foreseen from the mine workings ahead of the treatment work, the use of the same wells and holes to remove methane from the reservoir and the worked out space of the existing and extinguished lavas, as well as to carry out works in stages with their combination. Degassing wells are inclined drilled from specially designed workings of the well with horizontal endings of a larger diameter, turning into small-diameter degassing bore-holes on a coal seam. To prevent premature methane removal, a proppant plug is provided, which is subsequently eroded by water. With methane recovery, work cycles are respected. First, methane is pushed through water to the production wells through injection wells; at the end of the cycle, the order is changed to intensify - methane is pushed through production wells to injection wells.

The implementation of the method is shown in FIG. 1, FIG. 2 and FIG. 3. In FIG. 1 presents a proposed scheme for mining a formation suite in a vertical section, in FIG. 2 - the same diagram, top view, with the application of theoretical positions, in FIG. 3 - section along the line aa.

From the development 1, inclined wells are drilled, turning into horizontal endings and going into the worked-out space 2 (Figs. 1 and 2). In this case, the wells are not placed in the coal seam, but in the host rocks, as the most stable and shape-preserving. By purpose, the wells are distinguished between injection and production. To intensify methane recovery in injection horizontal wells 3, a phased linear hydrodisintegration of strong and poorly permeable soil and roof rocks separately in the direction from the lava through a perforated casing is provided (Fig. 3). With a retreating procedure of work through perforation under pressure necessary for the destruction of the enclosing rocks, a fluid is fed into the massif, the component composition of which includes water and surface-active substances (surfactants) in order to increase the efficiency of penetration of the formed crack 4 into the pore volume of the massif. Immediately after hydro-cleavage is carried out, air is supplied through the same perforation to drain the cracks. Next, the crack is plugged with a proppant plug (plug). The pressure of the fluid stream depends on the physical properties of the rocks. In this case, the plug does not allow methane to escape into free space, but temporarily delays it in the crack. Due to the unloading action, the maximum development of hydrocracking cracks occurs when they are orthogonal to the direction of action of the maximum horizontal tectonic components of rock pressure 5 when they are present in the mine field (Kurlenya M.V., Seryakov V.M., Eremenko A.A. Technogenic geomechanical fields stresses. - Novosibirsk: Nauka, 2005. - 264 p., p. 40; Romashov AN, Tsygankov SS About the nature of tectonic stresses in the earth's crust // Mountain Journal. - 1996. - No. 7-8. - S. 41-44, p. 44). Thus, a system of longitudinal and transverse cracks is created, as shown in FIG. 2 and 3.

To ensure additional gas unloading of the coal seam 7 and the worked-out space 8, at the same time as the creation of deviated wells, calls 6 are made into the formation in the form of holes of smaller diameter.

Then, by alternating method, water is injected through injection wells 3, which dissolves and erodes the plug and pushes methane to production wells 9, through which it is extracted to the earth's surface. The alternation method implies a change in order after the first cycle, namely that methane is subsequently pushed back to the injection wells through production wells. The location of the wells is determined taking into account the action of the overhanging rock consoles 10 from the side of the working and quenched lavas, thereby achieving the efficiency of unloading from the reference rock pressure 11 created by these consoles (Fig. 2), both from the side of the quenched and from the side of the active lava.

In order to increase the safety of mining operations, zones of influence of the underwork and part-time 12 from neighboring layers are determined. Why do they carry out control measures in these zones - drill wells and install sensors 13, drill a degassing well 14 from a conveyor belt, monitor 15 by submitting information about rock pressure to a recording computer, which saves data and sends them for processing to the operator and via the Internet - to the designer.

Carrying out a set of measures described in the presented invention helps to increase the productivity of lava and the “absolute” safety of work, as opposed to the safety principle existing at enterprises based on “acceptable risk”.

An example of the implementation of the described method can be the development of a suite of shallow formations of the Vorkutskoye field. The volumetric weight of coal γ and the compressive strength are 1.22 t / m ³ and 14 MPa, respectively, low-permeable sandstones of the roof and soil have a density of 2.7 t / m ³ , the compressive strength is 114 MPa, and M. M strength . Protodyakonov f = 11, permeability - less than 0.01 μm ² . The average natural methane content is 25 m ³ / t. For an array composed of rocks and coal with reduced physical properties, the maximum value of the reference rock pressure at a depth of about 1000 m from the side of the working lava is 1.3 γH, from the quenched side - 1.6 γH. Due to a decrease in gas content of less than 8 m ³ / t, we can expect an increase in the load on the lava by approximately 4 times, and the degassing efficiency is more than 90%.

If the host rocks are less stable and well permeable, for the implementation of measures, we recommend that if there is an underwork, a part-time job, deviated wells with horizontal endings should be drilled exclusively in the soil or only in the roof, respectively.

Claims (1)

A method for preliminary degassing of a coal seam suite and a mined-out space, including the fact that wells are drilled from an advanced underground mine, a perforated casing pipe is passed through them, through which hydrocracking is carried out, characterized in that the coal seam is pre-worked / worked out for unloading and creating a pore the fractured volume of the array of strong and poorly permeable rocks, deviated wells with horizontal endings are drilled into the rocks containing the coal seam and then into the worked out With the provision of drilling degassing penetrations into the formation with smaller bore holes, they form longitudinal cracks and cross cracks that unload the mass from the horizontal tectonic component of the rock pressure through a perforated pipe when retreating in the direction from the lava to the wellhead, supply fluid with a surfactant for splitting rocks of the soil and the roof and install a proppant plug, thereby preventing premature methane removal, subsequently the plug is washed out with water, first, methane is pushed to production wells through injection wells, at the end of the cycle, methane is pushed through production wells to injection wells, and control and monitoring measures are taken to obtain objective information about the discharge of the massif and safety.

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