WO2024103622A1 - Coal-measure gas development method based on horizontal-well methane in-situ combustion explosion fracturing - Google Patents

Abstract

A coal-measure gas development method based on horizontal-well methane in-situ combustion explosion fracturing, comprising steps: S1, enabling a construction vertical well (3) to reach a target coal-measure gas reservoir; S2, constructing a horizontal well section (8) in the target coal-measure gas reservoir; S3, constructing branch wells (9) from the horizontal well section to the two sides; S4, sealing the branch wells by means of packers (10), and monitoring the methane pressure in the branch wells in real time; S5, when the methane pressure reaches a specified value, conveying a combustion improver to the branch wells; S6, fully mixing same and then igniting same so as to construct a fracture network (12) around each of the branch wells; S7, completing combustion explosion fracturing operation of all the branch wells so as to finally form an artificial gas reservoir; and S8, opening the packers to extract methane gas. The method constructs the complex fracture networks in the reservoir via explosion shock waves generated by combustion explosion, so as to improve the recovery rate of coal-measure gas. After combustion explosion fracturing, methane gas in surrounding reservoirs gathers in the artificial gas reservoir, so that coal-measure gas cooperative development can be achieved, avoiding waste of resources.

Description

A coal-measure gas development method based on horizontal well methane in-situ explosion fracturing Technical Field

The invention relates to the field of coal-measure gas reservoir transformation, and in particular to a coal-measure gas development method based on horizontal well methane in-situ explosion fracturing.

Background technique

Coal-measure gas, also known as the "three gases" of coal-measure gas, usually refers to coalbed methane, tight sandstone gas and shale gas that co-exist in coal-bearing strata. This genetic characteristic determines that the direction of efficient development of coal-measure gas is co-exploration and co-production. The characteristic of coal-measure gas co-production is that natural gas of different phases in different lithological reservoirs is co-produced in the same well. Its purpose is to improve the development efficiency of coal-measure gas resources and the output of a single well. Co-exploration and co-production of coalbed methane, tight gas and shale gas and co-production of coalbed methane, tight gas and shale gas are almost necessary technical choices for the commercial development of deep coal-measure gas.

my country has a huge amount of coal-measure gas resources, and achieving efficient and coordinated development of coal-measure gas resources is of great significance to ensuring my country's energy security. Traditional coal-measure gas development technology is mainly based on hydraulic fracturing. However, the cracks produced by hydraulic fracturing are usually relatively single, resulting in a low resource recovery rate. Most of the resources in the reservoir are not extracted, resulting in a serious waste of resources. In addition, during the hydraulic fracturing process, the expansion of the cracks is usually controlled by the ground stress. Whether the cracks can expand in the vertical direction of the reservoir is the key to determining the coordinated development of coal-measure gas. However, the ground stress of the target reservoir is usually unchangeable. It often happens that the hydraulic fracturing cracks expand in the horizontal direction of the reservoir, and it is difficult for the cracks to enter the adjacent rock formations, so it is impossible to achieve efficient development of methane gas in the adjacent reservoir. Therefore, the traditional hydraulic fracturing method has serious shortcomings in the development of coal-measure gas, and it is difficult to achieve efficient development of coal-measure gas.

Therefore, in order to improve the transformation effect of the reservoir, it is urgently necessary to seek a new method that can construct a large-scale three-dimensional fracture network in the coal-bearing strata to increase the recovery rate of coal-bearing gas and realize the coordinated and efficient development of the "three gases" of the coal-bearing strata.

Summary of the invention

The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and to provide a coal-bearing gas development method based on in-situ methane explosion fracturing in horizontal wells. This method constructs a complex fracture network in the reservoir through the explosion shock wave generated by the explosion of methane-combustion aid. Compared with traditional hydraulic fracturing technology, it can form a more complex fracture network, which is beneficial to improving the recovery rate of coal-bearing gas. At the same time, after the explosion fracturing, the reservoir is depressurized, and the methane gas in the surrounding reservoirs converges to the artificial gas storage layer, which can realize the coordinated development of coal-bearing shale gas, sandstone gas and coalbed methane, avoiding the problem of resource waste caused by traditional mining methods.

In order to solve the above technical problems, the technical solution adopted by the present invention is:

A method for developing coal-measure gas based on horizontal well methane in-situ explosive fracturing, specifically comprising the following steps:

S1: A vertical well is constructed from the surface through a drilling platform, and the vertical well passes through the cap rock and enters the target coal-measure gas-bearing reservoir;

S2: Considering the compressibility, gas content, self-supporting capacity of artificial fractures, the impact range of explosive fracturing, and the influence of the distance from the adjacent gas-bearing reservoir, the horizon is selected in the target coal-bearing gas-bearing reservoir and a horizontal well section is constructed, which is connected to the vertical well;

S3: construct several evenly distributed branch wells from the horizontal well section to both sides;

S4: Starting from the end of the horizontal well section far away from the vertical well, a packer is used to isolate the branch well against high pressure, and the methane pressure in the branch well is monitored in real time through a methane pressure sensor installed on the packer;

S5: When the methane pressure in the branch well reaches a specified value, the combustion-supporting agent is transported into the branch well through the combustion-supporting agent transport channel;

S6: After the methane and the combustion aid are fully mixed, the methane-combustion aid mixture system in the branch well is ignited by an ignition gun to construct a complex fracture network around the branch well;

S7: After the explosive fracturing of the first branch well is completed, the above steps S4 to S6 are repeated in the order of construction in the vertical well direction, and the explosive fracturing operations of other branch wells are completed one by one, and finally a large-scale artificial gas storage layer is formed around the horizontal well;

S8: Drilling the drill bit opens the packer and starts extracting methane gas from the target coal-bearing gas reservoir.

Further preferably, the target coal-bearing gas-bearing reservoir described in S1 includes shale gas reservoirs, tight sandstone gas reservoirs and coalbed methane reservoirs, and the shale gas reservoirs, tight sandstone gas reservoirs and coalbed methane reservoirs are randomly and alternately distributed.

Further preferably, the length of the horizontal well section described in S2 is 400 to 1000 m.

Further preferably, the branch wells described in S3 are arranged in an alternating manner, and the spacing between adjacent branch wells on the same side is 20 to 50 m, which is specifically determined by the compressibility of the reservoir and the initial methane pressure in the branch wells; the minimum distance L between the branch well closest to the vertical well and the vertical well is 20 to 30 m, so as to ensure the stability of the vertical well.

Further preferably, the packer described in S4 is composed of a coiled tubing and a packer quick interface, a methane pressure sensor, an oxidant input channel, a one-way valve, an ignition gun and a packer housing.

The combustion aid is transported from the surface to the horizontal well section through the continuous tubing, and then the continuous tubing is connected to the packer through a quick interface and then transported to the branch well through the combustion aid input channel; a one-way valve is installed in the combustion aid input channel to prevent leakage of methane and the combustion aid; the transmission device of the methane pressure sensor and the ignition gun is transported through the continuous tubing, and the methane pressure is monitored and ignited after being connected to the packer through the continuous tubing and the quick interface of the packer.

The vertical distance l between the installation position of the packer and the horizontal well section is 10 to 15 m, thereby forming a protective rock column with a width of 2l around the horizontal well section to maintain the stability of the horizontal well section.

Further preferably, the specified methane pressure in S5 is 2-10 MPa; and the combustion aid is pure oxygen.

The present invention has the following beneficial effects:

1. The present invention utilizes the methane desorbed from the coal-bearing gas reservoir itself as an explosive, thus avoiding the need for explosives to be transported into the reservoir. The dangerous process of explosion is prone to occur, ensuring the safety of the reservoir transformation process.

2. The present invention constructs a complex fracture network in the reservoir through the explosion shock wave generated by the combustion of methane-combustion aid. Compared with the traditional hydraulic fracturing technology, it can form a more complex fracture network, which is beneficial to improving the recovery rate of coal-bearing gas. At the same time, after the explosion fracturing, the reservoir is depressurized, and the methane gas in the surrounding reservoirs converges to the artificial gas storage layer, which can realize the coordinated development of coal-bearing shale gas, sandstone gas and coalbed methane, avoiding the problem of resource waste caused by traditional mining methods.

3. The present invention adopts the form of horizontal wells and branch wells to carry out methane in-situ explosive fracturing, which can greatly increase the range of fracturing and construct a large-scale fracture network. The fractures can expand in the vertical direction of the reservoir and enter the adjacent rock formations, thereby increasing the coal-bearing gas production capacity of a single well. At the same time, explosive fracturing in branch wells can avoid damage to horizontal wellbores and vertical wellbores, thereby ensuring the structural stability of the gas flow channel.

4. The packer in the present invention not only has the function of isolating branch wells and resisting the overflow of explosion shock waves, but also realizes the integrated functions of gas pressure monitoring, ignition and combustion-aiding agent transportation. The process flow is simple and easy to operate.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view of a horizontal well and a combustion and explosion layer according to the present invention.

FIG. 2 is a schematic diagram of the branch well and the packer structure of the present invention.

Among them are: 1. Surface; 2. Drilling platform; 3. Vertical well; 4. Cap rock; 5. Shale gas reservoir; 6. Tight sandstone gas reservoir; 7. Coalbed methane reservoir; 8. Horizontal well section; 9. Branch well; 10. Packer; 101. Continuous tubing and packer quick interface; 102. Methane pressure sensor; 103. Combustion aid input channel; 104. One-way valve; 105. Ignition gun; 106. Packer shell; 11. Protective rock column; 12. Fracture network.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

As shown in FIG1 , a method for developing coal-measure gas based on in-situ methane explosion fracturing in horizontal wells specifically includes the following steps:

S1: A vertical well 3 is constructed from the ground surface 1 through a drilling platform 2, and the vertical well 3 passes through the cap rock 4 and enters the target coal-bearing gas reservoir; the target coal-bearing gas reservoir includes a shale gas reservoir 5, a tight sandstone gas reservoir 6 and a coalbed methane reservoir 7, and the shale gas reservoir 5, the tight sandstone gas reservoir 6 and the coalbed methane reservoir 7 are randomly and alternately distributed.

S2: Considering the compressibility and gas content of the reservoir, the self-supporting capacity of the artificial fractures, the impact range of the explosive fracturing and the influence of the distance from the adjacent gas-bearing reservoir, a layer is selected in the target coal-bearing gas-bearing reservoir and a horizontal well section 8 is constructed. The horizontal well section 8 is connected to the vertical well 3, and the length of the horizontal well section 8 is 400 to 1000 m.

S3: Several evenly distributed branch wells 9 are constructed from the horizontal well section 8 to both sides. The branch wells 9 are arranged in an alternating manner up and down. The spacing between adjacent branch wells 9 on the same side is 20 to 50 m, which is specifically determined by the compressibility of the reservoir and the initial methane pressure in the branch wells 9; the minimum distance L between the branch well 9 closest to the vertical well 3 and the vertical well 3 is 20 to 30 m, so as to ensure the stability of the vertical well 3.

S4: Starting from the end of the horizontal well section 8 away from the vertical well 3, the branch well 9 is isolated against high pressure by using a packer 10, and the methane pressure in the branch well 9 is monitored in real time by a methane pressure sensor 102 installed on the packer 10.

As shown in FIG. 2 , the packer 10 is composed of a coiled tubing and packer quick interface 101 , a methane pressure sensor 102 , an oxidant input channel 103 , a one-way valve 104 , an ignition gun 105 and a packer housing 106 .

The combustion aid is transported from the surface 1 to the horizontal well section 8 through the continuous oil pipe, and then the continuous oil pipe is connected to the packer 10 through the quick interface 101, and then the combustion aid is transported to the branch well through the combustion aid input channel 103; a one-way valve 104 is installed in the combustion aid input channel 103 to prevent leakage of methane and the combustion aid; the transmission device of the methane pressure sensor 102 and the ignition gun 105 is transported through the continuous oil pipe, and the methane pressure is monitored and ignited after the continuous oil pipe is connected to the packer 10 through the quick interface 101 of the packer.

The vertical distance l between the installation position of the packer 10 and the horizontal well section 8 is 10 to 15 m, thereby forming a protective rock column 11 with a width of 2l around the horizontal well section 8 to maintain the stability of the horizontal well section 8.

The packer not only has the function of isolating branch wells and resisting the overflow of explosion shock waves, but also realizes the integrated functions of gas pressure monitoring, ignition and combustion-aid delivery. The process is simple and easy to operate.

S5: When the methane pressure in the branch well 9 reaches a specified value, the specified methane pressure is 2-10 MPa; a combustion aid is transported into the branch well 9 through the combustion aid transport channel 103. The combustion aid generally refers to pure oxygen, but can also be other highly oxidizing gases, liquids and solid powders.

S6: After the methane and the combustion aid are fully mixed, the methane-combustion aid mixture system in the branch well 9 is ignited by the ignition gun 105 to construct a complex fracture network 12 around the branch well 9.

S7: After the explosive fracturing of the first branch well 9 is completed, the above steps S4 to S6 are repeated in the order of construction in the direction of the vertical well 3, and the explosive fracturing operations of other branch wells 9 are completed one by one, and finally a large-scale artificial gas storage layer is formed around the horizontal well.

The use of horizontal wells and branch wells for in-situ methane explosion fracturing can greatly increase the range of fracturing and build A large-scale fracture network can expand vertically along the reservoir and enter adjacent rock formations, increasing the coal-bearing gas production capacity of a single well. At the same time, explosive fracturing in branch wells can avoid damage to horizontal and vertical wellbores, ensuring the structural stability of the gas flow channel.

S8: The packer 10 is opened by drilling with a drill bit, and the methane gas in the target coal-bearing gas reservoir is started to be extracted.

The present invention constructs a complex fracture network in the reservoir through the explosion shock wave generated by the combustion of methane-combustion aid. Compared with the traditional hydraulic fracturing technology, it can form a more complex fracture network, which is beneficial to improving the recovery rate of coal-bearing gas. At the same time, after the combustion and fracturing, the reservoir is depressurized, and the methane gas in the surrounding reservoirs converges to the artificial gas storage layer, which can realize the coordinated development of coal-bearing shale gas, sandstone gas and coalbed methane, avoiding the problem of resource waste caused by traditional mining methods.

The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical scheme of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims (6)

A method for developing coal-measure gas based on horizontal well methane in-situ explosive fracturing, characterized in that it specifically comprises the following steps: S1: A vertical well (3) is constructed from the surface (1) through a drilling platform (2), and the vertical well (3) passes through the cap rock (4) and enters the target coal-bearing gas reservoir; S2: Considering the compressibility and gas content of the reservoir, the self-supporting capacity of the artificial fractures, the impact range of the explosive fracturing, and the influence of the distance from the adjacent gas-bearing reservoir, a layer is selected in the target coal-bearing gas-bearing reservoir and a horizontal well section (8) is constructed, and the horizontal well section (8) is connected to the vertical well (3); S3: constructing a number of evenly distributed branch wells (9) from the horizontal well section (8) to both sides; S4: Starting from the end of the horizontal well section (8) far from the vertical well (3), a packer (10) is used to isolate the branch well (9) against high pressure, and a methane pressure sensor (102) installed on the packer (10) is used to monitor the methane pressure in the branch well (9) in real time; S5: When the methane pressure in the branch well (9) reaches a specified value, a combustion-supporting agent is transported into the branch well (9) through the combustion-supporting agent transport channel (103); S6: After the methane and the combustion aid are fully mixed, the methane-combustion aid mixture system in the branch well (9) is ignited by an ignition gun (105), so as to construct a complex fracture network (12) around the branch well (9); S7: After the first branch well (9) is completed by explosive fracturing, the above steps S4 to S6 are repeated in the order of construction in the direction of the vertical well (3), and the explosive fracturing operations of other branch wells (9) are completed one by one, and finally a large-scale artificial gas storage layer is formed around the horizontal well; S8: The packer (10) is opened by drilling with a drill bit, and the extraction of methane gas in the target coal-bearing gas reservoir begins. According to the method for coal-measure gas development based on horizontal well methane in-situ explosive fracturing as described in claim 1, it is characterized in that: the target coal-measure gas-bearing reservoir described in S1 includes shale gas reservoir (5), tight sandstone gas reservoir (6) and coalbed methane reservoir (7), and the shale gas reservoir (5), tight sandstone gas reservoir (6) and coalbed methane reservoir (7) are distributed alternately. According to the method for coal-measure gas development based on horizontal well methane in-situ explosive fracturing as described in claim 1, it is characterized in that the length of the horizontal well section (8) described in S2 is 400 to 1000 m. According to the method for coal-based gas development based on in-situ methane explosive fracturing in horizontal wells as described in claim 1, it is characterized in that: the branch wells (9) described in S3 are arranged in an upper and lower alternating manner, and the spacing between adjacent branch wells (9) on the same side is 20 to 50 meters; the minimum distance L between the branch well (9) closest to the vertical well (3) and the vertical well (3) is 20 to 30 meters, so as to ensure the stability of the vertical well (3). The method for developing coal-measure gas based on in-situ explosion fracturing of methane in horizontal wells according to claim 1 is characterized in that: the packer (10) described in S4 is composed of a coiled tubing and a packer quick interface (101), a methane pressure sensor (102), an oxidant input channel (103), a one-way valve (104), an ignition gun (105) and a packer housing (106); The combustion aid is transported from the surface (1) to the horizontal well section (8) through a continuous oil pipe, and then the continuous oil pipe is connected to the packer (10) through a quick interface (101) and then the combustion aid is transported to the branch well through a combustion aid input channel (103); a one-way valve (104) is installed in the combustion aid input channel (103) to prevent the leakage of methane and the combustion aid; the transmission device of the methane pressure sensor (102) and the ignition gun (105) are transported through the continuous oil pipe, and after the continuous oil pipe is connected to the packer (10) through the quick interface (101) of the packer, the methane pressure is monitored and ignited; The vertical distance l between the installation position of the packer (10) and the horizontal well section (8) is 10 to 15 m, thereby forming a protective rock column (11) with a width of 2l around the horizontal well section (8) to maintain the stability of the horizontal well section (8). According to the method for coal-measure gas development based on horizontal well methane in-situ explosive fracturing according to claim 1, it is characterized in that: the specified methane pressure described in S5 is 2 to 10 MPa; and the combustion aid is pure oxygen.