RU1774025C - Method of treating productive layer - Google Patents

Abstract

The invention relates to mining. The goal is to increase the safety of mining operations by intensively displacing the working agent from the productive stratum and its deep degassing. Drill a well from the surface. They plant it with pipes and plug the annulus. The casing is perforated at the contact levels of the rocks of the main and immediate soil and the roof of the coal seam being developed. Cracks are formed in them by forcing the working agent into the interior of the array by burning powder charges and fixing the cracks obtained. The casing is perforated in the middle of the coal seam thickness with the formation of cracks also by the burning of powder charges. The tubing string is lowered into the well to the lower casing perforation interval. A packer is installed above it and compressed gas is supplied to the central pipe string until the working agent and methane are displaced from the productive layer through the annular space. Remove and install the packer below the upper casing perforation interval. Compressed gas is supplied into the annular space, expelling the working agent and methane from the productive stratum along the central pipe string to the surface. 1 C.p. f-crystals, 2 tab. with

Description

The invention relates to the mining industry and can be used to prepare for safe and efficient mining of coal seams with a capacity of less than 2.5 m in advance and to produce methane before and after the well has been worked-up.

A known method of processing the productive stratum, including drilling a well from the surface, casing it with pipes, grouting the annulus, forming cracks at the level of contact of the rocks of the main and direct soil of the developed coal seam and in the middle of its power by pumping a working agent, washing the sand plug in the well to separate the intervals perforation of the casing string, injection of coarse sand with liquid to preserve the permeability of cracks, erosion of the sand plug in the well, lowering the stake the tubing string into the borehole to the lower casing perforation interval, installing a packer above it, supplying compressed gas to the central pipe string, displacing the gas-liquid mixture and gas from the productive stratum along the annular space, removing and installing the packer below the upper casing perforation interval , the supply of compressed gas into the annular space and the displacement of the gas-liquid mixture from the productive thickness

xj x | Oh y eat

and gas along the central pipe string to the surface.

As the practice of founding hydraulic fracturing wells shows, the formation of cracks directly in the body of a coal seam by injection of fluid is technically and economically impractical due to the blocking of the migration paths of methane from the fractured-pore volume of coal by the fluid due to the low level of its extraction (up to 20 ... 30%) after injection into the formation.

The concept of effective degassing of the developed coal seam, which has been created in recent decades, and, moreover, of preventing its emission by introducing water directly into the body of the seam, is not sufficiently scientifically substantiated. As practice has shown, there are emissions during the drilling of wells and during the injection of water into them. In undeveloped zones of hydraulic influence on a coal seam due to the absence of a catchment reservoir, it is practically impossible to exclude negative side effects in terms of water saturation of the formation roof rocks, loss of stability and complication of its maintenance, as well as water saturation of the formation soil rocks, which are especially prone to heaving and cause deformation of preparatory workings and reduction of rock permeability.

It is known that in most areas of the Donets Basin the gas content of mine workings, starting from a depth of 500-600, is determined by the gas content not so much of the coal seams being developed as of the host rocks. In this regard, the reduction in gas content and outburst hazard of the developed coal seams is effective only when the productive stratum is degassed (the developed coal seam + enclosing rocks). The latter provides along the way methane production before undermining the well with cleaning operations.

The aim of the invention is to increase the safety of mining operations due to intensive pumping of liquid and deeper degassing of the productive stratum using the effect of ejection of injection air into the latter.

 This goal is achieved in that it forms cracks at the contact level of the rocks of the main and direct roofs of the coal seam being developed by injecting the working agent into the rocks of the soil and the roof of the coal seam and form near-surface cracks at the mid-thickness of the coal seam, for example, burning powder charges.

When conducting a patent search, do not

known technical solutions have been identified, therefore, the distinguishing features that are available in comparison with the prototype are significant. The sequence of technological operations for the implementation of the invention. A well is drilled from the day surface onto the soil rocks of the coal seam being developed, cased with pipes, the annulus is plugged, a hydraulic perforator is lowered into the well, and gaps in the casing are cut at the level of the main and direct soil rocks of the developed coal seam, the hydroperforator is lifted, the sand is washed cork to the level of contact of the rocks of the main and direct roofs of the developed coal seam, lower the hydroperforator to the stop and cut holes in the casing, they lift the hydraulic perforator to the surface, wash the sand plug in the well, inject the fluid simultaneously into the soil and roof of the developed coal seam to form cracks, pump coarse sand with fluid to preserve the permeability of the cracks, lower the perforator, and cut the cracks in the casing in the middle of the coal formation and form a borehole fracture in it, for example, by burning a first charge, a tubing string is lowered into the well to the lower interval rforatsii casing above the packer is set,

supply compressed air to the central pipe string, displacing the gas-liquid mixture and gas from the productive stratum along the annular space, remove and install the packer below the upper interval

perforation of the casing string, feed compressed gas into the annular space, displaced from the productive stratum of the gas-liquid mixture, gas through the central pipe string to the surface.

For stratification, i.e. in order to form a horizontal crack in the plan, it is necessary to create a pressure Рр in the porous space, which exceeds the mountain pressure by the value of the temporary rock resistance to rupture ap, since the cohesive forces of the rock particles must be overcome

RR Rg + Ohr,

(D

where Rg is rock pressure, MPa;

Rg / 9pdN, (2)

gderp - density of rocks, kg / m3;

81 m / s2;

N - depth of the bed, m.

According to Prof. V.I. Shchurov, the rock resistance to rupture is usually small and lies within the range of 1.5 ... 3 MPa, therefore it does not significantly affect Pp. Approximate fracture pressures for shallow wells (N 1000 m) are recommended.

RR (1.74-2.57) Rsg,

where RST is the hydrostatic pressure of the liquid column, the height of which is equal to the depth of the formation,

Pct / ezdN cos /,

(4)

where hl is the density of the fluid in the well, kg / m3;

ft is the angle of curvature (averaged), deg.

Based on the foregoing, it was established that the energy costs of creating cracks in the productive stratum depend on the strength characteristics of the rocks of the main and immediate roofs and soil of the developed coal seam and the strength of their contact. The values of the mechanical properties of the rocks and coals during compression tests are given in Table 1.

If we take the tensile strength perpendicular to the layer as 100%, then the tensile strength parallel to the layers is expressed by the data given in Table 2.

An analysis of the data in Tables 1 and 2 indicates that the ultimate strength of the rocks of the main roof, soil in compression exceeds the ultimate strength of rocks of the immediate roof, the soil in compression, firstly, the ultimate strength of rocks in compression parallel to the layer (except limestone) 64-89% lower than the compressive strength of the rocks perpendicular to their bedding, and secondly, the difference in the values of the strength of the rocks and the compression angle is very significant, thirdly.

It should also be noted that the tensile strength of the main and immediate roofs during compression is higher than that of the rocks of the main and direct soils.

In addition, it was found that the compressive strength of the rocks is higher than the tensile strength of the rocks under tension (rupture).

It is known that the tensile strength at break of the contacts is substantially less than the tensile strength at break of the rock in adjacent layers. The tensile strength at breaking the contact of the rocks is recommended to be taken from the condition

(4)

Opi 1 0.4 C1,

where C1 is the coefficient of adhesion (for example), for coal shales: mudstone

15 0.006 ... 0.039; siltstone 0.006 ... 0.243; sandstone 0.027 ... 1.86; for plant residues: 0.009 ... 0.48; 0.006 ... 1.14; 0.45 ... 1.8; for small plant detritus: 1.9 ... 2.4; 0.92-4.32 (respectively), MPa. For mirrors

20 slip values of the coefficient of adhesion are on average 0.012 (mudstone) and 0.015 (siltstone), i.e. below the values of the coefficient of adhesion in the presence of the listed 25 inclusions on the contact.

A comparative analysis of the data shows that the difference in the values of the tensile strength of the rocks of the main and immediate roofs, soil

30 and the ultimate strength of the rocks at their contact exceeds one or two orders of magnitude.

Liquid injection at a rate exceeding the natural injectivity of the rock contacts of the immediate and main

35 soils and roofs, it is aimed at the formation of not only main cracks in them, but also many vertical and horizontal cracks in the developed coal seam and mainly coal

40 stratum and rocks of the immediate soil and roof. The latter is explained by the fact that the compressive strength of sandstone, siltstone in comparison with coal is almost an order of magnitude higher.

45 Example. Suppose it is necessary to reduce the gas content and outburst hazard of the Kyu Felix layer and host rocks in the Karaganda basin in the mine field named after Kostenko. The thickness of the Kyu formation varies from 1.5 to 2.5 m. The latter is separated by mudstone beds with a thickness of 0.01 to 0.05 m. Formation characteristic: gas content - 15.6 m3 / t; expected gas mobility - 31 m / t; volatiles yield 55 25%. The top of the formation is represented by raw, weakly clayey mudstones with a thickness of 2.5-8 m, then gray, fine-grained, strong sandstone, the soil of the reservoir is represented by mudstone, slightly carbonized with a thickness of 4-6 m, more sandstone. Plast Kyu

It is classified as hazardous in the GZZ (mine is super-categorical) and dust and is conditionally classified as outburst hazardous.

The well is drilled to a depth of 512 m, cased with pipes, for example, 146 mm in diameter with a wall thickness of 8 mm, the annulus is plugged with cement. The installation of a hydraulic perforator at the beginning at a depth of 501 and then 491 m is ensured by a careful measurement of the length of the pipes during tripping and determining the depth of the winch. To more accurately set the punch against the desired interval, a sleeve coupling is used in the tubing string. After the AP-6 m unit is lowered into the well, its mouth tied up and pumping units connected to it, the system is compressed by a pressure that exceeds the working one by 1.5 times. Before pressure testing of the tubing, the sealing of the system is checked in a known manner, and then perforation is carried out by pumping sandy mixture into the tubing. The concentration of sand in water is usually 80-100 kg / m3.

In sandblasting perforation (GSP), the creation of holes in a column, a cement stone of a channel in a rock is achieved by imparting a sand-water jet of several hundred meters per second.

The lower limit of the permissible difference in the nozzles, which ensures the effective destruction of the casing string, cement stone rock should not be less than 12-14 MPa (for 6 mm nozzles). With the strength of the rocks (7szh 20-30 MPa), the lower limits, as experience shows, it is advisable to increase to 18-20 MPa.

The time of effective impact on the barrier should not exceed 15-20 minutes.

In sandblasting, the same equipment is used as in fracturing. The wellhead is equipped with standard 1AU-700 fittings designed for an operating pressure of 70 MPa. Pumping units 4AN-700 are used to pump the water-sand mixture, developing a maximum pressure of up to 70 MPa, and cementing aggregates at lower pressures.

The water-sand mixture is prepared in a sand mixing unit (2PA, ZPA, etc.), which is a sand bunker with a capacity of Yumek with a conical bottom.

Injection of 4000.,. 5000 m3 of fluid with a flow rate of 40 .., 60 l / s and at a pressure of 15 ... 25 MPa into the perforation slots of the casing of the well at the rock level of the main and immediate roofs and soils of the developed coal seam is performed by the group (8 pcs.) 4AN-700 units. To weaken the rock mass, additives may be added to the water.

If necessary, increase

the size of the hydrotreatment zones through the borehole to force water along the main fractures of the rocks of the immediate and main soil and the formation

the depth of the array on the cable into the well to the design level (491 and 501 m) is lowered by two standard ADS-b shells. The distances between the shells and the zones of the perforations of the well are 10 m. At the same time, spirals are turned on - igniters of the latter. A relatively quick combustion of powder charges in 3.3 s allows the creation of a pressure of 30-100 MPa due to the fact that the fluid in the well and in the main fractures of the rocks plays the role of a sealing piston, which does not have time to quickly move from its place due to its inertia. In this combustion process, a mechanical effect is exerted on the productive stratum, leading to the formation of new cracks in it and the expansion of existing ones. Such an effect is similar to hydraulic fracturing, but without fixing the formed cracks with filler.

It is also possible to stepwise push water into the interior of the massif with a constant increase in the mass of the powder charge and not earlier than 2 hours after the previous burning of the latter.

To prevent fluid spills, cable tugs and casing ruptures, it is necessary to keep the fluid level below the mouth by about 50 m and seal the mouth with a special seal.

In this case, the space above the liquid level acts as a shock absorber or air compensator.

The indicated types of work on the use of ADS-6 shells are carried out by geophysical offices or trusts with the necessary equipment, apparatus, and trained personnel.

After forcing the water deep into the massif, a sand carrier is pumped in order to fix the cracks formed in the rocks in the open state. For hydraulic fracturing, for example, pure silica sand with a grain size of from 0.5 to 1.2 mm is used.

The amount of sand injected during a single break (into each perforation zone) is 2-6 tons. 180-350 kg of sand (density 2650 kg / m3) per 1 m3 of liquid is injected.

At a mark of 496 m, the casing of the well is perforated in the mid-plane of the thickness of the coal seam being developed and a borehole crack is formed in it, for example, by blasting ADS-6 three times at intervals every 2 hours after the previous blast. Moreover, the mass of each subsequent powder charge is recommended to be increased.

The operation of thermogasochemical effects on the productive stratum is simple. 6-9 hours of time are spent on its implementation, while 2-3 days are spent on conventional hydraulic fracturing.

Perforation of a well at the mid-thickness level of a developed coal seam and formation of near-hole cracks in it by, for example, staged burning of powder charges has a multi-purpose purpose: removing the potential energy accumulated by a coal seam in the form of elastic stresses under conditions of two-sided compression of the seam while simultaneously injecting a working agent into the soil and roof rocks and pushing the latter into the interior of the massif, displacing the gas-liquid mixture and gas from supra- and subsurface cracks, self-flow m coal bed ethane, etc.

A tubing string is lowered into the well to 501 m and a packer is placed above it to isolate the upper part of the annular space. The compressor pumps air into the central pipe string, first displacing the gas-liquid mixture and gas from the fractures of the productive stratum to the surface. The compressor shutdown at the first stage is associated with the termination of the removal of the gas-liquid mixture to the surface, and subsequently with the termination of the removal of methane to the surface. The number of cycles of air injection into the well according to the above-mentioned gas lift model is established experimentally mainly by the volume of pumped water.

After pumping out 50-60% of the volume of water previously pumped into the perforation zone, the packer is reinstalled at 492-493 m to isolate the lower part of the annular space. According to the generally accepted technique, air is pumped by a compressor into the annular space of the well, displacing the gas-liquid mixture and methane from the fractures of the productive stratum into the cracks of the coal seam and soil rocks and to the surface. The compressor shutdown and the number of air injection cycles according to the above gzzlift elevator scheme are similar to the above.

When air is injected both in the central pipe string and in the annular space, it is necessary to control the composition of the gases leaving the well and their

temperature to prevent the ignition of coal.

Subsequently, for the purpose of deeper degassing of the coal-bearing stratum and increasing the flow rate of the well, the latter is connected to a vacuum pump station. Methane is produced through a well before mining is commenced in the zone of technogenic impact on the productive stratum, while undermining a well by refining operations - from the mined-out lava space and the caving collapse dome.

The advantages of the proposed method

processing of the productive stratum compared with the prototype are as follows:

reduced degassing times of the productive stratum due to branched fracturing in the latter;

there is a radical decrease in gas content and outburst hazard of the productive sequence;

the flow rate (specific productivity) of the wells increases prior to the start of mining operations and upon their entry into the area of technogenic impact;

more fully utilized the technical capabilities of mining equipment and vehicles to increase coal production and the pace of preparatory workings;

potential energy accumulated by the coal seam in the form of elastic decreases

stresses under conditions of two-sided compression of a coal seam due to the injection of fluid simultaneously into the soil and roof rocks of the developed coal seam and possible forcing fluid into

the depth of the array.

The proposed method for processing the productive stratum is aimed at improving the safety of mining operations, i.e. has a social character. Region

applications - coal industry: drilling by specialized divisions, which have oil gauging equipment and trained personnel, of ground wells in a high-gas, outburst hazardous productive stratum, the basis of which is the developed coal seam with a thickness of at least 2.5 m and containing rocks.

Claims (2)

SUMMARY OF THE INVENTION 1. A method of treating a productive formation, including drilling a well from a surface, casing it with pipes, grouting the annulus, perforating the casing string at the contact levels of the main and direct soil of the coal seam being developed, the middle of its thickness, and the coal seam roofing rocks, formation of cracks in the contact rocks of the main and direct soil of the coal seam, in the middle of its thickness, and in the rocks of the roof of the coal seam of cracks by the introduction of a working agent with their subsequent closure heating, lowering the tubing string into the well to the lower perforation interval of the casing, installing a packer above it, supplying compressed gas to the central string of pipes, displacing the working agent and methane from the productive stratum along the annular space, removing and installing packer below the upper perforation interval of the casing string, supply of compressed gas to the annular space, displacement of the working agent and methane from the productive stratum central pipe string to the surface, characterized in that, in order to increase the safety of mining operations by intensively displacing the working agent from the productive layer and its deeper degassing, at the first stage of work, the casing is perforated at the contact levels of the main and direct rocks soils and roofs of the developed coal seam and at the same time produce cracks in them; at the second stage of work, the casing is perforated in the middle of the coal seam thickness and the formation of cracks in the near-well zone of the formation is carried out by the burning of powder charges. 2. The method according to p. 1, characterized in that, in order to increase the size of the force impact zone, the working agent is simultaneously pressed through cracks into the interior of the array by burning powder charges placed in the well at the contact levels of the rocks of the main and direct soil and coal seam roofs. Table 1