阅读说明：本技术 碎软低渗煤层井上下联合压裂区域瓦斯高效抽采方法 (Efficient gas extraction method for broken soft low-permeability coal seam well upper and lower combined fracturing area ) 是由 姜在炳 张群 范耀 刘磊 杜天林 舒建生 庞涛 牟全斌 于 2020-05-08 设计创作，主要内容包括：一种碎软低渗煤层井上下联合压裂区域瓦斯高效抽采方法,先在煤矿井下形成采区大巷或作业巷道,为施工作业和瓦斯抽采提供场所；其次在煤矿井下沿煤层顶板距离煤层顶界或煤层底板距离煤层底界一定距离施工一组能覆盖一个采区多个工作面的定向长钻孔；之后在地面实施透巷井与井下采区大巷或作业巷道贯通,以便地面压裂管汇和地面井-井下长钻孔高压连接装置的连接；后利用地面大型压裂装备对煤矿井下长钻孔交替实施分段压裂施工,分段压裂操作主要在井下巷道完成,最后利用煤矿井下瓦斯专用抽采管路进行并网抽采。本发明有效提高煤矿井下碎软低渗煤层储层改造强度和抽采效果,实现煤矿井下区域化无死角低成本的高效瓦斯抽采。(A method for efficiently extracting gas in an upper and lower combined fracturing region of a broken soft low-permeability coal seam well comprises the steps of firstly forming a mining area main roadway or an operation roadway under a coal mine well, and providing places for construction operation and gas extraction; secondly, constructing a group of directional long drill holes capable of covering a plurality of working faces of one mining area along the coal mine underground along the distance from the coal seam roof to the coal seam top boundary or the distance from the coal seam bottom plate to the coal seam bottom boundary; then, a through roadway well is communicated with an underground mining area main roadway or an operation roadway on the ground so as to facilitate the connection of a ground fracturing manifold and a ground well-underground long drilling high-pressure connecting device; and then, carrying out staged fracturing construction on the long underground drill holes of the coal mine alternately by using large-scale ground fracturing equipment, wherein staged fracturing operation is mainly completed in an underground roadway, and finally carrying out grid-connected extraction by using a special gas extraction pipeline of the coal mine. The method effectively improves the modification strength and the extraction effect of the underground broken soft low-permeability coal seam reservoir of the coal mine, and realizes the underground regional dead-angle-free and low-cost efficient gas extraction of the coal mine.)

1. A method for efficiently extracting gas in an upper and lower combined fracturing region of a broken soft low-permeability coal seam well is characterized by comprising the following steps:

the method comprises the following steps: a mining area main roadway or an operation roadway is formed under the coal mine, a place is provided for construction operation and gas extraction,

step two: constructing a group of long drill holes which can cover a plurality of working faces of a mining area along the coal seam roof or the coal seam floor in the underground coal mine, wherein the long drill holes are preferably drilled in a casing for hole fixing and well completion, or open hole well completion or screen pipe well completion or casing pipe well completion can be selected,

step three: at least 1 through lane well is communicated with a large lane or an operation lane of an underground mining area on the ground so as to connect a ground fracturing manifold with a ground well-underground long drilling hole high-pressure connecting device,

step four: the underground long drill holes of the coal mine are alternatively subjected to fracturing construction by utilizing large-scale ground fracturing equipment, the staged fracturing of each hole is realized, the staged fracturing operation is mainly completed in an underground roadway,

step five: gas is extracted by using a special gas extraction pipeline under a coal mine, and grid-connected gas extraction of a gas extraction hole is realized.

2. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: the mining area main roadway and the operation roadway refer to roadways which are formed in a mining area range and can be used for drilling machine operation, ground well-underground long drilling hole high-pressure connecting device connection and gas extraction.

3. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: the long drilling holes which can cover a plurality of working faces of a mining area are constructed along the coal seam roof or the coal seam floor in the underground coal mine, namely, the drilling hole tracks are controlled to be relatively stable distance from the coal seam top boundary or the coal seam bottom boundary by using a geosteering technology.

4. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: and step two, casing pipe hole fixing and well completion refers to that rock powder in the hole is washed clean, a pipe shoe and a grout stop plug are installed at the front end of the casing pipe, a pipe hoop is sequentially connected with the casing pipe, the casing pipe is driven into a preset depth by mechanical pushing, and then hole sealing and hole waiting solidification are carried out.

5. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: the ground fracturing manifold is connected with the ground well-underground long drilling hole high-pressure connecting device, namely a high-pressure outlet of the ground fracturing equipment is connected through an underground high-pressure fracturing wellhead, and the ground well bottom end is connected with the underground long drilling hole through the high-pressure connecting device, so that a conveying channel for conveying ground high-pressure fluid to the underground long drilling hole of the coal mine is formed, and the safe operation of the underground long drilling hole staged fracturing of the coal mine in an underground roadway is guaranteed.

6. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: the casing cementing well completion long borehole is preferably subjected to directional hydraulic sand blasting perforation annular staged fracturing process technology, and the directional hydraulic sand blasting perforation staged fracturing process technology can also be selected; directional hydraulic sand blasting perforation staged fracturing technology is preferred for long boreholes in open hole completions or screen well completions or cased well completions.

7. The method for efficiently extracting the gas in the underground combined fracturing region of the crushed soft low-permeability coal seam according to claim 1, which is characterized by comprising the following steps: the method is characterized in that the long underground drill holes of the coal mine are alternatively fractured, and the step of realizing the staged fracturing of each hole refers to the step of alternatively fracturing each long drill hole by changing the valve direction of a ground well-underground long drill hole high-pressure connecting device which is arranged in advance in a mining area main roadway or an operation roadway.

Technical Field

The invention belongs to the technical field of coal mine gas extraction, and relates to a method for efficiently extracting gas in an upper and lower combined fracturing region of a broken soft low-permeability coal bed well.

Background

At present, the coal mine gas extraction mode mainly takes ground coal seam gas development and underground drilling negative pressure extraction as main modes, but the broken soft low-permeability high-gas outburst coal seam gas extraction effect is poor, and the extraction cost is high.

The coal mine gas extraction mode mainly based on the development of the ground coal bed gas has the disadvantages of high operation cost, low extraction efficiency, long extraction period, large land occupation, great limitation by landform and the like.

The coal mine gas extraction mode mainly based on underground drilling negative pressure extraction is limited by underground fracturing equipment and construction conditions, and has the defects of small injection capacity of a fracturing pump, high difficulty in implementing sand adding, difficulty in carrying equipment and poor coal seam permeability increasing effect, so that the gas extraction effect is poor.

Disclosure of Invention

The invention aims to provide a method for efficiently extracting gas in an upper and lower combined fracturing region of a broken soft low-permeability coal seam, which can effectively overcome the defects of the prior art, effectively improve the gas extraction efficiency of the broken soft low-permeability coal seam, and realize the gas extraction of the upper and lower combined fracturing region of the well, wherein the gas content and the gas pressure of the coal seam are quickly reduced at low cost.

In order to achieve the purpose, the invention discloses a method for efficiently extracting gas in an upper and lower combined fracturing region of a broken soft low-permeability coal seam well, which is characterized by comprising the following steps of:

the method comprises the following steps: a mining area main roadway or an operation roadway is formed under the coal mine, a place is provided for construction operation and gas extraction,

step two: constructing a group of long drill holes which can cover a plurality of working faces of a mining area along the coal seam roof or the coal seam floor in the underground coal mine, wherein the long drill holes are preferably drilled in a casing for hole fixing and well completion, or open hole well completion or screen pipe well completion or casing pipe well completion can be selected,

step three: at least 1 through lane well is communicated with a large lane of an underground mining area on the ground so as to connect a ground fracturing manifold with a ground well-underground long drilling high-pressure connecting device,

step four: the underground long drill holes of the coal mine are alternatively subjected to fracturing construction by utilizing large-scale ground fracturing equipment, the staged fracturing of each hole is realized, the staged fracturing operation is mainly completed in an underground roadway,

step five: gas is extracted by using a special gas extraction pipeline under a coal mine, and grid-connected gas extraction of a gas extraction hole is realized.

Wherein: the mining area main roadway and the operation roadway refer to roadways which are formed in a mining area range and can be used for drilling machine operation, ground well-underground long drilling hole high-pressure connecting device connection and gas extraction.

Wherein: the long drilling holes which can cover a plurality of working faces of a mining area are constructed along the coal seam roof or the coal seam floor in the underground coal mine, namely, the drilling hole tracks are controlled to be relatively stable distance from the coal seam top boundary or the coal seam bottom boundary by using a geosteering technology.

Wherein: and step two, casing pipe hole fixing and well completion refers to that rock powder in the hole is washed clean, a pipe shoe and a grout stop plug are installed at the front end of the casing pipe, a pipe hoop is sequentially connected with the casing pipe, the casing pipe is driven into a preset depth by mechanical pushing, and then hole sealing and hole waiting solidification are carried out.

Wherein: the ground fracturing manifold is connected with the ground well-underground long drilling hole high-pressure connecting device, namely a high-pressure outlet of the ground fracturing equipment is connected through an underground high-pressure fracturing wellhead, and the ground well bottom end is connected with the underground long drilling hole through the high-pressure connecting device, so that a conveying channel for conveying ground high-pressure fluid to the underground long drilling hole of the coal mine is formed, and the safe operation of the underground long drilling hole staged fracturing of the coal mine in an underground roadway is guaranteed.

Wherein: the casing cementing well completion long borehole is preferably subjected to directional hydraulic sand blasting perforation annular staged fracturing process technology, and the directional hydraulic sand blasting perforation staged fracturing process technology can also be selected; directional hydraulic sand blasting perforation staged fracturing technology is preferred for long boreholes in open hole completions or screen well completions or cased well completions.

Wherein: the method is characterized in that the long underground drill holes of the coal mine are alternatively fractured, and the step of realizing the staged fracturing of each hole refers to the step of alternatively fracturing each long drill hole by changing the valve direction of a ground well-underground long drill hole high-pressure connecting device which is arranged in advance in a mining area main roadway or an operation roadway.

Therefore, compared with the prior art, the method for efficiently extracting the gas in the underground combined fracturing region of the broken soft low-permeability coal bed has the following effects:

1. the underground long drill hole of the coal mine is arranged in a coal seam top plate or a coal seam bottom plate, so that the problems that a broken soft coal seam is easy to collapse and bury a drill, a casing is difficult to lower, the broken soft coal seam is directly fractured in a relatively plastic broken soft coal seam, the fracture expansion and extension are not long, the improvement and yield increase effect is poor and the like are well solved, the length of the long drill hole is increased, the coal seam damage is reduced, the construction difficulty and risk are reduced, and the processing workload of the coal seam screen pipe (casing pipe) before coal mining is reduced.

2. The ground fracturing equipment is adopted for construction, the defects of small discharge capacity, high sand adding difficulty, difficulty in equipment carrying and poor coal bed permeability increasing effect of the underground fracturing equipment are overcome, the low-cost and high-discharge sand adding staged fracturing transformation can be realized, and the effective yield increasing transformation of the coal bed is realized.

3. By adopting a casing well cementation and completion mode, the annular staged fracturing process technology with directional hydraulic sand blasting and perforation can be matched and optimized, and the staged effect, the fracturing scale, the fracturing effect and the like are greatly improved.

4. The staged fracturing construction is carried out on the underground long drilled hole by adopting the idea of factory operation and the alternate construction method, the staged fracturing of all holes is reasonable in connection, the time waiting caused by stratum depressurization, blowout, fracturing pipe column dragging and the like is avoided, and the fracturing construction time and cost are greatly shortened.

5. Compared with the development of the ground coal bed gas, the land occupation, the drilling cost and the gas extraction cost are greatly reduced.

6. In conclusion, the technical method is an important breakthrough in the technical field of coal mine gas extraction, can quickly reduce the gas content and the gas pressure of the broken soft low-permeability coal seam, realizes the aim of coal mine regionalization low-cost high-efficiency gas extraction, and solves the problem of unbalance of coal mine excavation-extraction.

Drawings

FIG. 1 is a front view of efficient gas extraction in an upper and lower combined fracturing area of a broken soft low-permeability coal seam well (a long drill hole is positioned on a top plate).

FIG. 2 is a front view of efficient gas extraction in the upper and lower combined fracturing regions of a broken soft low-permeability coal seam well (a long drill hole is positioned on a bottom plate).

FIG. 3 is a top view of efficient gas extraction in the upper and lower combined fracturing regions of a broken soft low-permeability coal seam well (a long drill hole is positioned on a top plate).

Reference numerals:

1-operating a roadway; 2-a gas extraction pipeline; 3-high pressure manifold in the roadway; 3-1-high pressure pipeline in the roadway; 3-2-pressure valve in the tunnel; 4-fracturing the wellhead at the bottom of the ground well; 5-fracturing the wellhead by long drilling; 6-coal bed; 7-coal seam roof; 8-a coal seam floor; 9-long underground drilling; 10-ground penetrating roadway well.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The method for efficiently extracting the gas in the upper and lower combined fracturing regions of the broken soft low-permeability coal seam well comprises the following steps:

the method comprises the following steps: and determining a gas extraction target area, forming a mining area main roadway and an operation roadway 1, and meeting the requirements of long drilling 9 drilling operation and fracturing construction operation.

Specifically, in order to meet the requirements of long-drilling 9 drilling operation and fracturing construction operation, the operation roadway generally has a width of 5m and a height of 4 m.

Step two: and constructing a plurality of groups of coal seam roof or bottom plate long drill holes 9 to cover the whole gas extraction area.

Specifically, the drilling adopts an accurate geosteering technology to control the relatively stable distance of the perforation track at the top boundary or the bottom boundary of the coal seam, so that the directional perforation communication drilling in the later period and the stratum can be conveniently fractured, and the preferred distance between the perforation track of the long drilling hole and the coal seam is 0.2m-2.0 m.

Specifically, a boundary detection technology is applied to long-drilling while-drilling geological guidance, and the distance between the perforation track and the coal bed is detected in real time by measuring parameters such as resistivity and natural gamma of coal and rock layers in a certain range around the coal and rock layers and according to the characteristic that the resistivity and natural gamma of the coal bed and the top plate rock of the coal bed are obviously different, so that the perforation track is controlled to be within a certain range of a vertical distance from the coal bed.

In particular, the long drilling is preferably completed by casing fixed hole, and open hole completion or screen pipe (casing) completion can be selected. The method comprises the following steps of drilling a hole, drilling a hole.

Step three: and (5) constructing a ground through roadway well.

Specifically, 1 or more ground wells 10 are accurately butted with a preset target area of a roadway on the ground, and casing cementing operation is completed.

Specifically, the ground through roadway well is specifically designed into a vertical well or a directional well according to ground topography and construction conditions.

Specifically, 1 or more ground through roadway wells are designed according to the sizes of a plurality of working faces of a mining area and the construction capacity of ground fracturing equipment.

Specifically, when the stratum condition is better, and no aquifer exists and other complex conditions, a two-opening well body structure is generally adopted, a phi 311.1mm drill bit is adopted to drill to a surface casing pipe with the diameter of 20m below bedrock and the diameter of 244.5mm below the bedrock in the first opening, and the well cementation cement slurry returns to the ground; and a drill bit with the diameter phi of 215.9mm is communicated with the roadway, and a technical sleeve with the diameter phi of 139.7mm is put into the roadway. For the conditions that the stratum condition is complex, the water-bearing stratum is contained above a roadway and the like, a three-opening well body structure is generally adopted, a drill bit with the diameter of phi 444.5mm is adopted to drill to the position 20m below bedrock, a surface casing with the diameter of phi 339.7mm is arranged below the bedrock, and well cementing cement slurry returns to the ground; secondly, drilling a drill bit with the diameter of 311.1mm to the position 5-10m above the roadway, and putting a technical sleeve with the diameter of 244.5mm into the drill bit to seal the aquifer; and three-opening a roadway by drilling with a drill bit with the diameter phi of 215.9mm, and putting a technical sleeve with the diameter phi of 139.7 mm.

Step four: and the ground fracturing manifold and the ground well-underground long drilling high-pressure connecting device are connected.

Particularly, a high-pressure outlet of the ground fracturing equipment is connected with an underground high-pressure fracturing well head through an aboveground high-pressure fracturing well head, the ground well bottom end is connected with the underground long drill hole through a high-pressure connecting device (comprising a ground well bottom fracturing well head 4, a long drill hole fracturing well head 5, a high-pressure manifold 3 in a tunnel and the like), a conveying channel of ground high-pressure fluid to the underground long drill hole of the coal mine is formed, and the safe operation of the underground long drill hole staged fracturing of the coal mine in the underground tunnel is guaranteed.

Step five: and performing staged fracturing construction on the underground long drill hole by adopting an alternate construction method.

Specifically, alternate staged fracturing construction is performed on each long drilling hole by changing the valve direction of a ground well-underground long drilling hole high-pressure connecting device arranged in advance in a mining area main roadway or an operation roadway.

The method comprises the following specific steps:

(1) and (5) sequentially constructing the fracturing of the first section of the underground long drilling hole.

According to the design of a fracturing scheme, staged fracturing construction (a first section and an nth section of a second section … …) is sequentially carried out on the underground long drilling hole from inside to outside. Firstly, opening a ground fracturing wellhead, a ground well bottom fracturing wellhead 4 and a pressure-resistant valve 3-2 in a roadway for controlling planned construction of long drilling, closing a long drilling fracturing wellhead 5, starting ground fracturing equipment to perform a pipeline test, wherein the pressure test is 40MPa, the pressure test time is not less than 5min, and the ground fracturing manifold and the ground well-underground long drilling high-pressure connecting device have no puncture and leakage, no obvious drop of pressure and qualified pressure test; and then opening a long drilling fracturing wellhead 5 to perform sand fracturing construction, wherein the sand fracturing construction generally comprises injecting a pad fluid, injecting a sand mixing fluid and injecting a displacement fluid, after the fracturing construction of the first section of the first long drilling hole is finished, closing a ground fracturing wellhead, controlling a pressure-resistant valve 3-2 in the roadway of the long drilling hole and the long drilling fracturing wellhead 5 to naturally reduce the formation pressure, opening a control valve in a high-pressure manifold 3 in the roadway to lead to the pressure-resistant valve 3-2 in the roadway of the next long drilling hole and the fracturing wellhead 5 of the next long drilling hole to realize the connection of fracturing channels, developing the fracturing of the first section of the second long drilling hole, and then successively developing the fracturing of the first section of the later long drilling hole according to the same method.

(2) And naturally depressurizing the fractured drilled hole, open-flowing and lifting the fractured string.

And during fracturing, observing the natural depressurization condition of the fractured drill hole, opening a blowout prevention valve of a fracturing wellhead 5 of the long drill hole to blow out after the blowout prevention requirement is met until the fracturing of the wellhead is displayed as 0, and then lifting the fracturing string to the next fracturing position by adopting a down-hole tunnel drilling machine.

(3) And (4) constructing the second section, the third section and the fourth section of the underground long drill hole in sequence until the full-hole staged fracturing is completed according to the design requirement.

The setting and the spacing of the long drilling fracturing sections mainly consider factors such as the volume modification range of a coal seam, the stress interference of cracks, construction safety and the like, and the preferred spacing of the fracturing sections is 50-80 m.

When the fracturing construction of the first section of the underground long drilled hole is completed, the natural depressurization, open flow and lifting of the fractured drilled hole can be completed successively, so that the connection in time is formed, at the moment, the construction processes of the step (1) and the step (2) are repeated, the fracturing of the second section of the underground long drilled hole is constructed in sequence, and by analogy, the third section and the fourth section are completed in sequence until the full-hole staged fracturing is completed according to the design requirement.

Specifically, the directional hydraulic sand blasting perforation annular staged fracturing technology is preferred for the long drilling hole of the casing well cementation completion, and the directional hydraulic sand blasting perforation staged fracturing technology can also be selected; directional hydraulic blast perforating staged fracturing techniques are preferred for long boreholes in open hole completions or screen (casing) down completions. The selection principle of the perforation section is as follows: the influence diameter of the fracturing crack in the direction of the perforation is taken as a selected length, perforation sections are sequentially and uniformly arranged for perforation, and the aim of coal seam regional overall transformation is achieved.

Specifically, the hydraulic sand-blasting perforation annular staged fracturing technology utilizes the Bernoulli principle, utilizes the throttling effect of a hydraulic jet nozzle to convert high-pressure perforating fluid into high-speed perforating fluid to erode and cut a sleeve, a hole-fixing cement ring and a stratum so as to realize perforation, and then carries out sand-adding fracturing through an oil sleeve annulus. The construction process mainly comprises the following steps: (1) lowering the sand blasting perforation tool to the design position; (2) lifting and lowering the pipe column to set the packer; (3) injecting a sand carrying liquid containing abrasive into the pipe column, carrying out sand blasting perforation and perforating to penetrate through the casing pipe, and communicating the perforation with the stratum; (4) injecting a displacement liquid; (5) carrying out oil sleeve annulus sand fracturing construction according to design; (6) and (5) unsealing the packer and lifting the pipe column to the next construction section.

Specifically, the directional hydraulic sand blasting perforation staged fracturing technology is a novel production increasing measure integrating directional perforation, fracturing and isolation. The construction process mainly comprises the following steps: (1) lowering the sand blasting perforation tool to the design position; (2) injecting a sand carrying liquid containing abrasive materials into the pipe column, wherein the sand carrying liquid passes through a jetting tool to complete hydraulic perforation; (3) and fracturing the oil pipe, supplementing liquid in an annular space, and fracturing the stratum at the top end of the perforation channel by utilizing the superposition of injection fluid pressurization and annular space pressure to exceed the stratum fracture pressure.

The sand-blasting perforation liquid adopts clean water with the thickness not less than 1m³Injecting sand carrying liquid at the discharge rate of/min, wherein the perforating grinding material is quartz sand of 40-70 meshes, and the sand ratio of the quartz sand is 5-8%.

Specifically, for the case of multiple ground wells, after the staged fracturing of the underground long drill hole of the coal mine controlled by 1 ground well is completed, the staged fracturing construction of the underground long drill hole of other coal mines is completed through other ground wells in succession.

Step six: and performing grid-connected extraction by using the special extraction pipeline for the gas in the underground coal mine.

Specifically, gas negative pressure extraction is carried out on each long drill hole 9 by using the coal mine underground gas special extraction pipeline 2, and the gas extracted from each long drill hole 9 is intensively conveyed into the coal mine underground special gas extraction main pipeline, so that grid-connected gas extraction of the gas extraction holes is realized.

Finally, it should be noted that: it is to be understood that the above-described embodiments are merely examples provided for clarity of explanation and are not intended to limit the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this type are intended to be covered by the present invention.