RU2672296C1 - Method of developing adjacent of coal seams - Google Patents

Abstract

FIELD: mining.SUBSTANCE: invention relates to the mining industry and can be used in coal mines. Hydraulic fracturing of the pillars left in the developed space of the working bed is carried out by injecting technical formation water into them at a pressure sufficient for hydraulic pillar break. When hydraulic pillar increase its compliance to values of large limit values of compliance of the pillar, above which the developed layer is discharged from dangerous stresses. Distance from the edge parts of the pillar to the well take less than the depth of distribution in the coal seam of cracks formed during hydraulic fracturing. Distance between the wells take less than twice the depth of distribution in the coal seam of cracks formed during hydraulic fracturing.EFFECT: technical result is to improve the safety of mining operations in the over-developed formations and reduce the volume of excavations.1 cl, 4 dwg

Description

The invention relates to the mining industry and can be used in coal mines to increase the efficiency of mining suites of close seams.

A known method of developing a suite of adjacent coal seams (USSR author's certificate No. 1810545, publ. 04/23/1993), including working out the seams in a descending order, the main preparatory workings on the worked-out (downstream) seam in the unloaded from high stress area of the rock mass that occurs near the edge parts of the coal mass or pillars left on the overworking (upstream) seam, securing the preparatory workings and mining the seams with long working faces. The strata are called close in those cases when mining operations in one stratum have an effect on mining operations in other strata.

The disadvantages of this method are the low stability of the local preparatory workings of the worked-out stratum and the increased danger of mining when they are being redeveloped in areas located in zones of high rock pressure formed in the worked-out stratum under pillars located along the worked-out stratum.

There is a method of developing a suite of adjacent formations (Patent RU No. 2403387, publ. 10.11.2010), including mining the formations in a descending order, sinking preparatory workings on the work-out stratum, attaching preparatory workings and working out the formations with long working faces. The location of the zones with increased rock pressure in the producing layer and the stress values in the massif sections along the preparatory mine route located in the zone of increased rock pressure at different distances from the plane perpendicular to the bedding and passing through the edge of the pillar along the mining layer are determined. For each site, the depth of propagation in the roof rocks of the preparatory excavation of an area with increased crack intensity is determined, the preparatory workings are fixed with an anchor support, the length of the anchors is taken more than the propagation depth in the roof rocks of the region with increased crack intensity, while the preparatory workings of the worked-out formation pass after the completion of treatment associated with the formation of pillars on the overburden.

The disadvantages of this method are significant deformations of the preparatory workings of the produced layer in areas located in areas of high rock pressure occurring under pillars of coal left in the worked out space of the working layers.

There is a method of mining suites of coalesced coal seams with a long pillar mining system (patent RU No. 2339818, publ. 11/27/2008). The method includes drilling from the surface of a directional well, unloading the coal-bearing mass followed by suction of gas from the well using vacuum pumps. The location of the directional well on the surface is chosen between two planned mining pits. In the preparation of the extraction columns for the treatment excavation, stage-by-stage unloading of the coal-bearing massif is carried out. Why do they first mechanically affect the coal-bearing massif through the working parts of a multilateral well, for example, by pumping liquid under pressure in a hydro-pulse mode.

The disadvantage of this method is the low efficiency of unloading the produced strata from increased rock pressure formed under pillars left in the worked out space of the working strata.

There is a method of developing a suite of adjacent coal seams (USSR author's certificate No. 636393, publ. 05.12.1977), adopted as a prototype, including mining seams in a descending order, the preparation of mining columns of minerals paired parallel workings, passed with leaving pillars of coal between these workings, working out of mining columns with long working faces, leaving in the worked out space of the mining bed not entirely destroyed by the pressure of the coal. In order to unload the produced layer from increased stresses arising under the pillars left in the mined-out space of the developed layer, a partial extraction of coal from the pillars is carried out with the subsequent destruction of coal not blown between the furnaces by blasting.

The disadvantages of this method are the increased risk of mining associated with a partial excavation of coal from pillars left in the worked out space of mining layers. This is due to the high concentration of stresses on the pillars left in the worked out space of the mining layer, the level of which can be several times higher than the level of stresses natural for the corresponding depth of mining. In addition, for the implementation of this method, it is required to carry out large volumes of auxiliary workings over the developed space, providing access to the rear sight, which is associated with an increased risk of mining.

The technical result of the method is to increase the safety of mining operations in the produced seams when using development systems with the remaining pillars of coal in the worked out space of the working seams, reducing the volume of auxiliary workings.

The technical result is achieved by the fact that wells are drilled from the surface, including sections of wells drilled on empty rocks, and sections of wells drilled on pillars of coal, sections of wells drilled on pillars of coal are parallel to the longitudinal axes of the pillars, technical wells are injected into the pillars through the wells water at a pressure sufficient to hydraulically fracture the pillar and thereby increase its compliance to values that are large limiting values of the compliance of the pillar, above which the worked-out formation it is unloaded from dangerous stresses, the distance from the marginal parts of the pillar to the nearest well is taken less than the depth of spread over the coal seam in the vicinity of the well drilled in whole coal, cracks formed during hydraulic fracturing, and the distance between the wells in the sections of wells drilled in whole coal, take less than twice the depth of propagation over a coal seam in the vicinity of a well section drilled entirely of coal, cracks formed during hydraulic fracturing.

The method is illustrated by the following figures:

FIG. 1 is a diagram of the mutual arrangement of adjacent (mining and mining) formations and wells;

FIG. 2 is a diagram of the location in the vicinity of a well drilled entirely of coal, cracks formed during hydraulic fracturing;

FIG. 3 is a diagram of the mutual arrangement of wells drilled in the whole coal;

FIG. 4 is a diagram explaining the effect of increasing the flexibility of the pillar located in the worked-out space of the mining reservoir, on the stress state of the mining reservoir, where:

1 - the earth's surface;

2 - a pillar of coal located in the worked out space of the mining layer;

3 - underworked formation;

4 - well;

5 - a vertical section of the well drilled through waste rocks of the overburden;

6 is a horizontal section of the well drilled entirely on coal;

7 - interdimensional power;

8 - the depth of spread over the coal seam in the vicinity of the well, cracks formed during hydraulic fracturing;

9 - the distance from the edge parts of the pillar of coal to the nearest well;

10 - the distance between the wells in the sections of wells drilled on the whole coal;

11 - the width of the pillar;

12 - the edge of the pillar of coal;

13 - worked out space

14 - the level of natural stresses in the produced layer before the start of mining in adjacent formations;

15 - the level of maximum permissible (dangerous) stresses in the produced reservoir in the zone of influence of the pillar;

16 - stress distribution in the produced layer in the zone of influence of the pillar before fracturing of the pillar;

17 - stress distribution in the produced reservoir in the zone of influence of the pillar after its fracturing;

The method is as follows. The whole coal left in the mined-out space of the mining layer has a rectangular shape in plan. The smaller side of this rectangle is equal to the width of the rear sight 11 (Fig. 3), the larger side is equal to the length of the excavation column. The width of the pillars left between the extraction columns is usually 20 - 40 m, the length of the excavation columns is up to 4000 m or more. The longitudinal axis of the rear sight is parallel to the larger side of the rear sight (edge parts of the rear sight 12, Fig. 3).

Coal seams are mined in a descending order. The preparation of mining columns of minerals on the mining bed is carried out by paired parallel workings, passed with the leaving of a pillar of coal between these workings. The excavation columns are worked out by long working faces with the remaining in the worked-out space of the producing layer not being destroyed by the rock pressure of the pillars of coal 2 (Fig. 1) with a width of 11 (Fig. 3). Under pillars left in the worked-out space of the overburden, zones are formed with high stresses 16 (Fig. 4), significantly exceeding the level of maximum permissible (dangerous) stresses in the underburden 15, when exceeded which there is an increased intensity of manifestations of rock pressure in the treatment and preparatory workings underwork reservoir. As a result, the risk of mining in these workings increases. The use of well-known methods for unloading the produced formation from increased stresses formed under pillars left in the worked out space of the working formation, in addition to the increased danger of mining, is associated with large amounts of work on conducting preparatory workings on the developed space.

When using the proposed method for unloading the produced formation from increased stresses forming under the pillars, wells 4 are drilled from the earth's surface 1 (Fig. 1). Each well 4 consists of two sections: a vertical section 5 drilled over empty rocks of the overburden, and a section wells 6 drilled entirely on coal. A section of the well 6 drilled in the rear of the coal is arranged parallel to the longitudinal axis of the pillar (edge parts of the pillar 12, (Fig. 3).

The distance 10 (Fig. 3) between the wells in the areas drilled on the whole of coal, take less than twice the depth of spread over the coal seam in the vicinity of the section of the wells drilled on the whole of coal, cracks formed during hydraulic fracturing. The distance 9 from the edge parts of the pillar 12 (Fig. 3) to the nearest well is less than the depth 8 (Fig. 2) of the spread along the coal seam in the vicinity of the well drilled over the whole coal, cracks formed during hydraulic fracturing. When these two conditions are met, the pillar will be fractured over its entire width 11 (Fig. 3).

Hydraulic fracturing of the pillar is carried out by injection through the wells into the coal seam of the working fluid at a pressure sufficient for hydraulic fracturing of the pillar.

As the working fluid of hydraulic fracturing, for example, technical formation water, hydrochloric acid solutions, etc. are used.

The essence of hydraulic fracturing during the implementation of the proposed method consists in the creation in the pillar of artificial cracks and the destruction of the pillar. With hydraulic fracturing of the pillar, its compliance under the influence of external loads increases: the greater the degree of destruction of the pillar, the greater its compliance.

The pliability of the pillar during its hydraulic fracturing is increased to values that are larger than the limiting values of the pliability of the pillar, upon exceeding which the produced layer is unloaded from dangerous stresses. Hazards are voltages in excess of 15 (Fig. 4).

Using the proposed method allows, in comparison with known methods:

- to increase the safety of mining operations in the produced strata when using development systems with the remaining pillars of coal in the worked out space of the working strata;

- reduce the volume of auxiliary workings.

The parameters necessary for the implementation of the proposed method (the pressure is sufficient for hydraulic fracturing of coal; the limiting value of the pillar compliance, above which the worked-out formation is unloaded from dangerous stresses; the depth of propagation along the coal formation in the vicinity of the borehole of cracks formed during hydraulic fracturing, etc.) , in each case, is determined by using well-known methods of mine, laboratory or analytical studies, taking into account specific mining and geological and mining technical conditions for the development of converged coal seams.

The scope of the proposed method are mines working off the adjacent coal seams. Such mines include most of the promising mines of the Kuznetsk basin, as well as many mines in China, Australia, Poland, and other countries developed in the field of mining.

The method is illustrated by the following example. The Kotinskaya mine works off formation 52 (mining), below which at a distance of 32-39 m, formation 51 (underworking) lies. During mining of seam 52 over a distance equal to the length of the lava, 30 m wide coal pillars that are not destroyed by rock pressure are left in the worked out space throughout the mine field, which causes 51 areas with increased stresses to form in the seam to be mined. Stresses 16 (Fig. 4) in these zones in the conditions of this mine exceed the level of natural stresses 14 (Fig. 4) by 1.7 -2.0 times or more. The total area of the hazardous zones of PGD in the overburden formation 51 is about 30% of the area of the mine field.

To unload the produced layer from the increased stresses forming under the pillars, wells 4 are drilled from the earth's surface 1 (Fig. 1). The length of the section 6 of the hole 4 drilled in the whole coal is 400 m. The section of the well 6 drilled in the whole coal is located parallel to the edge portions of the rear sight 12, FIG. 3.

For hydraulic fracturing, water is used. Depth 8 (Fig. 2) of spreading over a coal seam in the vicinity of a section of a well drilled about the whole of coal, cracks formed during hydraulic fracturing, is 6 m. In total, three wells are drilled entirely. The distance 10 (Fig. 3) between the wells in the sections of the wells drilled on the whole coal is taken equal to 10 m. The distance from the edge parts of the pillar 12 (Fig. 3) to the nearest well is taken to be 5 m.

Under the mining and geological and mining conditions under hydraulic fracturing of the pillar, its compliance is increased to 1.5 m, which is 0.3-0.5 m higher than the marginal compliance of the pillar (1.0-1.2 m), above which the workable the formation is unloaded from dangerous stresses.

The level of dangerous (15, Fig. 4) stresses in the overburden formation 51 in the zone of influence of the pillar, when exceeded which there is an increased intensity of manifestations of rock pressure in the workings of the underburden formation, in the conditions of the Kotinskaya mine, 1.3–1.4 magnitudes of natural stress in an underworked stratum before mining operations in adjacent strata.

Stresses in the overburden 51 after hydraulic fracturing of the pillar left in the worked out space of the overburden 52 are reduced from 1.7 -2.0 to 1.1-1.2 the magnitude of the natural stresses in the underburden before the start of mining operations in adjacent layers.

The use of the proposed method for mining the adjacent seams 52 and 51 in the conditions of the Kotinskaya mine makes it possible to reduce the intensity of rock displacements in the preparatory mine workings of the mining seam 51 located under coal pillars left in the mine space of the mining seam 52 by 3-4 times and to increase mountain safety works.

Claims (1)

A method of developing converging coal seams, including mining the coal beds in descending order, preparing excavation columns of minerals in parallel paired excavations, leaving a pillar of coal between these excavations, mining excavation columns with long mining faces, leaving coal pillars that are not destroyed by rock pressure, which differs the fact that wells are drilled from the surface, including sections of wells drilled over empty rocks, and sections of wells drilled over pillars coal, well sections drilled along the pillars of coal are placed parallel to the longitudinal axes of the pillars, technical formation water is pumped through the wells at a pressure sufficient to hydraulically fracture the pillar and thereby increase its compliance to values that exceed the maximum limiting compliance of the pillar, above which the worked-out seam is unloaded from dangerous stresses, the distance from the edge parts of the pillar to the nearest well is taken less than the depth of propagation in the coal seam in the vicinity of the importance of the whole drilled hole, the cracks formed during hydraulic fracturing, and the distance between the wells in the sections of the wells drilled whole, take less than twice the depth of propagation in the coal seam in the vicinity of the well section drilled, the fractures formed during the hydraulic fracturing.

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