CN114508336A - Drilling, unfreezing and fracturing integrated device and method for soft coal seam - Google Patents

Abstract

The invention provides a drilling, unfreezing and fracturing integrated device and method for a soft coal seam, and the device comprises the following steps: the drill rod is assembled on the drilling machine, the outlet end of the drill rod is provided with a jet flow drill bit, and the inlet end of the drill rod is connected with the outlet of the cryogenic pump; outlets of a plurality of first liquid nitrogen tanks in the first set of liquid nitrogen tank group are connected with an inlet of the cryogenic pump through a first nitrogen supply pipeline; the outlets of a plurality of second liquid nitrogen tanks in the second set of liquid nitrogen tank group are connected with the main nitrogen supply pipeline through second nitrogen supply pipelines; the bottom of the second liquid nitrogen tank is provided with a heater. The method comprises the following steps: determining the drilling position and the permeability-increasing transformation area of the coal seam; arranging a drilling, unfreezing and fracturing integrated device in a rock roadway; liquid nitrogen output by the first set of liquid nitrogen tank group is pressurized by a cryogenic pump and then is conveyed into a jet flow drill bit, and the formed high-speed liquid nitrogen jet flow is utilized to act on the coal bed; and (4) plugging the inlet of the drilled hole, fracturing the coal bed by using high-pressure fluid generated by liquid nitrogen phase change, and forming a crack in the coal bed. The device and the method can integrally realize drilling, unfreezing and fracturing operations.

Description

An integrated device and method for drilling, unlocking and fracturing of soft coal seams

technical field

The invention belongs to the technical field of coal gas extraction and treatment, and in particular relates to an integrated device and method for drilling, unlocking and fracturing of soft coal seams.

Background technique

Because the soft coal seam has many problems such as soft coal quality, poor gas permeability and high gas content, safety accidents such as coal and gas outburst are prone to occur during the mining process. At present, in order to reduce the mining accidents of soft coal seams, the main solution is to carry out gas extraction through drilling holes, so as to reduce the gas pressure. During the drilling process, the coal seam around the borehole is broken under the high-speed impact of the drill bit, and the gas will be released rapidly, which will form a high gas gradient in the borehole, and even lead to the phenomenon of blowholes. At the same time, the cement formed by the mixture of broken pulverized coal and moisture will block the borehole, making it difficult to discharge the slag from the borehole. Drilling accident. In addition, due to the soft texture of the soft coal seam, the phenomenon of hole collapse easily occurs during the drilling process, resulting in problems such as limited extension length of the drilling hole and low porosity, thus failing to meet the gas drainage requirements. In addition, the water-based working fluid used in drilling will also cause the expansion of clay minerals in the soft coal seam, which will block the pores of the coal seam, which further increases the difficulty of gas extraction. In this case, it is necessary to develop a new type of coal seam drilling equipment and anti-penetration technology to solve the technical problems of difficult drilling holes in soft coal seams, poor coal seam anti-penetration effect and low gas drainage efficiency.

SUMMARY OF THE INVENTION

In view of the problems existing in the above-mentioned prior art, the present invention provides an integrated device and method for drilling, unblocking and fracturing of soft coal seams, which can effectively improve the porosity of drilling and the flowback rate of coal slag, And it can easily solve the problem of stuck drill; at the same time, it can ensure the extension of the borehole length, and can improve the anti-penetration effect of the coal seam, which is beneficial to improve the gas extraction efficiency in the later stage; the device has a simple structure, low manufacturing cost, and can be integrated It can realize drilling, unblocking and fracturing operations in a streamlined manner.

The method has simple steps and convenient operation, and can effectively solve the problems of easy sticking, low porosity, difficult slag discharge, and unsatisfactory coal seam enhancement effect in the drilling process of soft coal seams.

In order to achieve the above purpose, the present invention provides an integrated device for drilling, unblocking and fracturing of soft coal seams, including a jet drill bit, a drill pipe, a drilling rig, a first set of liquid nitrogen tanks, a cryogenic pump, a second set of liquid nitrogen Nitrogen tank set and heater;

The jet drill bit is installed on the outlet end of the drill pipe; the drill pipe is assembled on the drilling rig;

The first set of liquid nitrogen tanks is used to provide jet medium for liquid nitrogen jet drilling, which consists of a plurality of first liquid nitrogen tanks; each first liquid nitrogen tank is connected with a first pressure sensor, and its The outlets are all connected with first solenoid valves; the outlets of the plurality of first liquid nitrogen tanks are connected with the inlet of the cryogenic pump through the first nitrogen supply pipeline, and the outlet of the cryogenic pump is connected with the inlet of the drill pipe through the main nitrogen supply pipeline;

The second set of liquid nitrogen tanks is used for liquid nitrogen desorption and phase transition cracking, and is composed of a plurality of second liquid nitrogen tanks; each second liquid nitrogen tank is connected with a second pressure sensor, and its The outlets are all connected with second solenoid valves; the outlets of the plurality of second liquid nitrogen tanks are connected with the main nitrogen supply pipeline through the second nitrogen supply pipeline;

The number of the heaters is the same as the number of the second liquid nitrogen tank, and they are set in one-to-one correspondence. The heaters are correspondingly assembled at the bottom of the second liquid nitrogen tank, and are used for the liquid nitrogen in the second liquid nitrogen tank. heating.

Further, in order to conveniently seal the annular space between the drill pipe and the borehole, an annular seal block is also included, and the annular seal block is sleeved on the outside of the drill pipe to realize the sealed connection between the drill pipe and the borehole.

Further, in order to help realize the automatic control process, a PLC controller is also included, and the PLC controller is respectively connected with the first pressure sensor, the first solenoid valve, the second pressure sensor, the second solenoid valve, the cryopump and the heater. .

In this technical solution, a jet drill bit is installed at the end of the drill pipe, which can not only effectively avoid the problem that the soft coal seam is easy to collapse under the rotating impact of the mechanical drill bit, but also improve the cinder flowback rate by using the high-speed impact effect of the jet. The first pressure sensor is connected to the first liquid nitrogen tank, and the pressure data in the first liquid nitrogen tank can be acquired in real time; the first solenoid valve is connected to the outlet of the first liquid nitrogen tank, and the first liquid nitrogen can be automatically realized The on-off control of the tank; the second pressure sensor is connected to the second liquid nitrogen tank, and the pressure data in the second liquid nitrogen tank can be obtained in real time; the outlet of the second liquid nitrogen tank is connected to the second solenoid valve, which can be automated The on-off control of the second liquid nitrogen tank is realized; the inlet of the cryopump is connected to each outlet of the first set of liquid nitrogen tank groups through the first nitrogen supply pipeline, so that the released liquid nitrogen can be easily pressurized by the cryopump The high-speed liquid nitrogen jet can be formed with the jet drill bit, and then the continuous impact of the high-speed liquid nitrogen jet and the low temperature cracking effect of the liquid nitrogen can be used to break the coal and rock and form holes. The bottom of each second liquid nitrogen tank in the second set of liquid nitrogen tanks is equipped with a heater, and the liquid nitrogen in the second liquid nitrogen tank can be heated to produce a gasification expansion effect and form high-pressure gas, so that, When the pressure of each second liquid nitrogen tank reaches or exceeds the set value, each second solenoid valve in the second liquid nitrogen tank group can be opened in turn, so that the high-pressure gas in the second liquid nitrogen tank group can quickly enter The drill pipe, the jet drill bit and the drilling annulus can use the formed multiple high-pressure and high-speed air streams to repeatedly impact the coal lumps in the annulus to cause stuck drilling, so as to effectively solve the problem of stuck drilling.

The present invention also provides an integrated method for drilling, unblocking and fracturing of soft coal seams, comprising the following steps:

Step 1: Preparatory work; carry out geological exploration of the coal seam, determine the high gas pressure area of the coal seam, and then determine the location of the coal seam drilling hole and the area for permeability enhancement according to the gas distribution in the coal seam and the geological parameters of the coal seam;

Step 2: Arranging construction equipment; arranging an integrated device for drilling, unlocking and cracking in the rock roadway, and the integrated device for drilling, unlocking and cracking consists of a first set of liquid nitrogen tanks and a second set of cryogenic pumps. The nitrogen tank group, the heater, the jet drill bit, the drill pipe and the drilling machine are composed; the first set of liquid nitrogen tank group is used to provide the jet medium for the liquid nitrogen jet drilling, which is composed of a plurality of first liquid nitrogen tanks, and a plurality of first liquid nitrogen tanks. The outlet of the liquid nitrogen tank is connected to the inlet of the cryogenic pump through the first nitrogen supply pipeline; the outlet of the cryogenic pump is connected to the inlet of the drill pipe through the main nitrogen supply pipeline; Phase transition cracking, which consists of a plurality of second liquid nitrogen tanks, the outlets of the plurality of second liquid nitrogen tanks are connected with the main nitrogen supply pipeline through the second nitrogen supply pipeline; the plurality of heaters are assembled in one-to-one correspondence. The bottom of the second set of liquid nitrogen tanks; the jet drill bit is installed on the outlet end of the drill pipe; the drill pipe is assembled on the drilling rig;

Step 3: liquid nitrogen jet drilling; open each first solenoid valve on the first set of liquid nitrogen tank group, and start the cryogenic pump, so that the liquid nitrogen output from the first set of liquid nitrogen tank group is pressurized by the cryogenic pump and then drilled by the drill. The rod is transported into the jet drill bit, and under the throttling action of the jet drill nozzle, a high-speed liquid nitrogen jet is formed to act on the coal seam; the high-speed impact of the liquid nitrogen jet and the low temperature cracking effect are used to break the coal seam and form holes of a certain size; In the process of jet drilling, the drilling rig is used to push the drill pipe forward to ensure that the coal seam in front of the liquid nitrogen jet is always within the effective rock breaking range of the liquid nitrogen jet, and a borehole with a certain shape and length is formed in the coal seam. Make the broken coal slag flow back into the rock road along with the liquid nitrogen from the annulus between the drill pipe and the borehole;

In the process of liquid nitrogen jet drilling, if there is a situation of sticking due to large coal pieces falling off the coal body, first remove the large coal pieces causing the sticking, and then continue the liquid nitrogen jet drilling operation to complete the scheduled drilling. length of drilling operations;

Step 4: Liquid nitrogen phase transition causes cracking; when the borehole reaches a predetermined length, stop the jet drilling operation, and use an annular seal to block the borehole entrance, forming a closed space in the drill pipe, the jet drill bit and the annulus ; Turn on multiple heaters at the bottom of the second set of liquid nitrogen tanks in turn to heat multiple second liquid nitrogen tanks, so that the pressure in the multiple second liquid nitrogen tanks continues to rise. When the pressure exceeds the fracture pressure of the coal seam and is lower than the fracture pressure of the rock layer, each second solenoid valve in the second set of liquid nitrogen tank group is opened in turn, and the high-pressure fluid generated by the phase change of liquid nitrogen is used to fract the coal seam, and the coal seam is broken. Cracks formed inside.

In step 3, the large coal lumps causing the sticking are removed by liquid nitrogen to dissolve the sticking. The specific method is as follows: firstly close the first solenoid valve and the cryogenic pump, and at the same time, turn on a plurality of heaters in turn, and make the first The liquid nitrogen in the second liquid nitrogen tank produces a gasification expansion effect and forms a high-pressure gas; in this process, the pressure signal corresponding to the second liquid nitrogen tank is collected in real time through the second pressure sensor; when the pressure of each second liquid nitrogen tank is After reaching or exceeding the set value, open each second solenoid valve in the second set of liquid nitrogen tank group in turn, so that the high-pressure gas in the second set of liquid nitrogen tank group quickly enters the drill pipe, jet drill bit and drilling annulus. Inside, the formed multiple high-pressure and high-speed airflows impact the coal lumps in the annulus for many times, until the large coal lumps causing the sticking are broken and removed;

Further, in order to prevent the wall of the borehole from breaking and to ensure the integrity of the borehole, in step 3, during the liquid nitrogen gas dissolving operation, the internal pressure of the second set of liquid nitrogen tanks is lower than the fracture pressure of the coal seam.

Further, in order to effectively promote the continuous extension of cracks, in step 4, as the amount of liquid nitrogen in the second liquid nitrogen tank continues to decrease, the power of the heater is continuously increased, and the second liquid nitrogen tank continues to be heated to ensure that the second set of The pressure in the liquid nitrogen tank group is always higher than the extension pressure of coal seam fractures.

In the method proposed by the invention, both liquid nitrogen gasification and phase transformation are carried out in a closed container, rather than in a borehole. This is mainly because when liquid nitrogen is gasified in the borehole, it is affected by various factors such as coal seam permeability, ambient temperature, borehole pressure and liquid nitrogen volume, the pressurization rate of liquid nitrogen gasification and the maximum gasification/phase The variable pressure is uncertain, especially when the permeability of the coal seam around the borehole is high, the gasification and pressurization rate in the borehole will be very low, and the gas infiltrates into the coal seam, it is difficult to establish a high pressure environment in the borehole. The present invention adopts the method of liquid nitrogen gasification/phase transition in a specific container, and uses a heating device to adjust the gasification/phase transition rate during the gasification/phase transition process, which can not only accurately control the liquid nitrogen gasification/phase transition process It can also prevent the loss of fluid energy during the gasification/phase change process, which can ensure that the fluid energy can be released into the borehole in a short time, and concentrated for impact crushing coal lumps or cracking caused by sticking. The coal seam around the borehole can greatly improve the success rate of cracking and cracking.

The present invention fully combines the coal seam drilling, unblocking and cracking and anti-penetration technology in one set of procedures, and selects high-pressure jet instead of the mechanical drill bit for rock-breaking drilling, which can not only effectively prevent the soft coal seam from being impacted by the rotation of the mechanical drill bit The problem of borehole collapse is easy to occur, and the high-speed impact effect of the jet can be used to improve the cinder flowback rate. The invention uses low-temperature liquid nitrogen as the jet medium, which can effectively prevent the water phase intrusion from causing damage to the pore structure of the soft coal seam, and can avoid the occurrence of coal seam pore throat blockage caused by the expansion of clay minerals in contact with water. During the liquid nitrogen jet drilling process, with the continuous injection of liquid nitrogen, the temperature of the coal seam around the borehole decreases continuously, forming a low temperature freezing zone. The enhanced cementitiousness is beneficial to inhibit the collapse of the borehole and significantly improve the porosity of the soft coal seam. In the process of slag discharge, as the temperature of liquid nitrogen continues to rise, the volume expands continuously, and the fluid flowback velocity in the annulus continues to increase, which is beneficial to further promote the flowback of coal slag.

In addition, since there is no water phase in the drilling, the broken cinders will not be cemented with each other, and will flow back into the roadway with nitrogen or liquid nitrogen in a discrete state, which is beneficial to greatly reduce the sticking during the drilling process. probability of an accident. Especially when a sticking accident occurs, high-pressure gas is generated by heating liquid nitrogen, and then the coal blocks that cause the sticking accident in the drilling hole are repeatedly impacted and broken, which can effectively remove the stuck point and enable the drilling operation to continue. Ensure drilling efficiency. Since the coal seam around the borehole is in contact with liquid nitrogen for a long time, some natural cracks in the coal body are opened when cooled. When the borehole reaches a predetermined length, the high pressure generated by the phase change of liquid nitrogen can continue to impact the coal seam around the borehole. At the same time, it promotes the expansion and extension of open natural fractures, increases the scope of drilling penetration, and improves the efficiency of coal and gas drainage in the later stage.

This method realizes the integrated operation of liquid nitrogen jet drilling, gasification solution stuck, and phase transition cracking, and overcomes the technical problems such as easy collapse of soft coal seam holes, easy drilling sticking and easy expansion of clay in coal seams in conventional coal seam drilling technology. At the same time, it can effectively solve the accident of sticking during the drilling process. After the drilling is completed, it can also conduct high-pressure cracking on the coal seam around the drilling hole, which can significantly improve the penetration enhancement range of the drilling hole. It is an integrated method for enhancing the permeability of soft coal seams.

Description of drawings

Fig. 1 is the schematic diagram of liquid nitrogen jet drilling state in the present invention;

Fig. 2 is the schematic diagram of the accident state of pipe string drilling in the present invention;

Fig. 3 is the schematic diagram of the liquid nitrogen dissolving card dissolving process in the present invention;

FIG. 4 is a schematic diagram of the liquid nitrogen phase change cracking process in the present invention.

In the picture: 1. Coal seam, 2. Jet drill bit, 3. Drill pipe, 4. Drilling rig, 5. Cryogenic pump, 6. First set of liquid nitrogen tank group, 7. Second set of liquid nitrogen tank group, 8. Heater , 9, drilling, 10, large coal, 11, annular seal block, 12, cracks, 13, the first nitrogen supply pipeline, 14, the second nitrogen supply pipeline, 15, the main nitrogen supply pipeline.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 1 , the present invention provides an integrated device for drilling, unblocking and fracturing of soft coal seams, including a jet drill bit 2, a drill pipe 3, a drilling rig 4, a first set of liquid nitrogen tanks 6, a low temperature Pump 5, second set of liquid nitrogen tank group 7 and heater 8;

The jet drill bit 2 is installed on the outlet end of the drill rod 3; the drill rod 3 is assembled on the drill rig 4;

The first set of liquid nitrogen tanks 6 is used to provide jet medium for liquid nitrogen jet drilling, which is composed of a plurality of first liquid nitrogen tanks; each first liquid nitrogen tank is connected with a first pressure sensor, and Its outlets are all connected with a first solenoid valve; the outlets of the plurality of first liquid nitrogen tanks are connected to the inlet of the cryopump 5 through the first nitrogen supply pipeline 13, and the outlet of the cryopump 5 is connected to the drill pipe through the main nitrogen supply pipeline 15. 3 inlet connections;

The second set of liquid nitrogen tank group 7 is used for liquid nitrogen to dissolve the card and to cause cracking by phase transition, and it is composed of a plurality of second liquid nitrogen tanks; each second liquid nitrogen tank is connected with a second pressure sensor, and The outlets are all connected with second solenoid valves; the outlets of the plurality of second liquid nitrogen tanks are connected with the main nitrogen supply pipeline 15 through the second nitrogen supply pipeline 14;

The number of the heaters 8 is the same as the number of the second liquid nitrogen tank, and they are set in one-to-one correspondence. The heaters 8 are correspondingly assembled at the bottom of the second liquid nitrogen tank, and are used for the liquid nitrogen in the second liquid nitrogen tank. Nitrogen is heated.

In order to conveniently seal the annular space between the drill rod and the borehole, an annular sealing plug 11 is also included.

In order to help realize the automatic control process, a PLC controller is also included, and the PLC controller is respectively connected with the first pressure sensor, the first solenoid valve, the second pressure sensor, the second solenoid valve, the cryopump 5 and the heater 8 . As a preference, the PLC controller can also be connected to the drilling rig 4 .

The first pressure sensor is used to obtain the first pressure signal in the first liquid nitrogen tank in real time, and send it to the PLC controller, and the PLC controller obtains the first pressure signal in the first liquid nitrogen tank according to the received first pressure signal. The first pressure value of The second pressure value in the second liquid nitrogen tank; the PLC controller is used to control the on-off action of the first solenoid valve and the second solenoid valve, to control the start and stop actions of the cryopump 5, and to control the start and stop of the heater 8. It is used to control the power change of the heater 8 , and of course, it can also control the start-stop action of the drilling rig 4 .

In this technical solution, a jet drill bit is installed at the end of the drill pipe, which can not only effectively avoid the problem that the soft coal seam is easy to collapse under the rotating impact of the mechanical drill bit, but also improve the cinder flowback rate by using the high-speed impact effect of the jet. The first pressure sensor is connected to the first liquid nitrogen tank, and the pressure data in the first liquid nitrogen tank can be acquired in real time; the first solenoid valve is connected to the outlet of the first liquid nitrogen tank, and the first liquid nitrogen can be automatically realized The on-off control of the tank; the second pressure sensor is connected to the second liquid nitrogen tank, and the pressure data in the second liquid nitrogen tank can be obtained in real time; the outlet of the second liquid nitrogen tank is connected to the second solenoid valve, which can be automated The on-off control of the second liquid nitrogen tank is realized; the inlet of the cryopump is connected to each outlet of the first set of liquid nitrogen tank groups through the first nitrogen supply pipeline, so that the released liquid nitrogen can be easily pressurized by the cryopump The high-speed liquid nitrogen jet can be formed with the jet drill bit, and then the continuous impact of the high-speed liquid nitrogen jet and the low temperature cracking effect of the liquid nitrogen can be used to break the coal and rock and form holes. The bottom of each second liquid nitrogen tank in the second set of liquid nitrogen tanks is equipped with a heater, and the liquid nitrogen in the second liquid nitrogen tank can be heated to produce a gasification expansion effect and form high-pressure gas, so that, When the pressure of each second liquid nitrogen tank reaches or exceeds the set value, each second solenoid valve in the second liquid nitrogen tank group can be opened in turn, so that the high-pressure gas in the second liquid nitrogen tank group can quickly enter The drill pipe, the jet drill bit and the drilling annulus can use the formed multiple high-pressure and high-speed air streams to repeatedly impact the coal lumps in the annulus to cause stuck drilling, so as to effectively solve the problem of stuck drilling.

The present invention also provides an integrated method for drilling, unblocking and fracturing of soft coal seams, comprising the following steps:

Step 1: Preparatory work; carry out geological exploration of coal seam 1, determine the high gas pressure area of coal seam 1, and then determine the drilling position of coal seam 1 and the area of enhanced permeability transformation according to the distribution of gas in coal seam 1 and the geological parameters of coal seam 1;

Step 2: Arrange construction equipment; as shown in Figure 1, a drilling, jam-releasing and cracking integrated device is arranged in the rock roadway, and the drilling, jam-releasing and cracking integrated device is composed of a first set of liquid nitrogen tank groups , cryogenic pump 5, second set of liquid nitrogen tank group 7, heater 8, jet drill bit 2, drill pipe 3 and drilling rig 4; the first set of liquid nitrogen tank group 6 is used to provide jet medium for liquid nitrogen jet drilling, It consists of a plurality of first liquid nitrogen tanks, and the outlets of the plurality of first liquid nitrogen tanks are connected with the inlet of the cryopump 5 through the first nitrogen supply pipeline 13; the outlet of the cryopump 5 is connected with the drill through the main nitrogen supply pipeline 15. The inlet of the rod 3 is connected; the second set of liquid nitrogen tank group 7 is used for liquid nitrogen to dissolve the card and phase change cracking, which is composed of a plurality of second liquid nitrogen tanks, and the outlets of the plurality of second liquid nitrogen tanks pass through the second supply. The nitrogen pipeline 14 is connected with the main nitrogen supply pipeline 15; a plurality of heaters 8 are assembled on the bottom of the second set of liquid nitrogen tanks 7 in one-to-one correspondence; the jet drill bit 2 is installed on the outlet end of the drill pipe 3; the drill pipe 3 Assembled on the drilling rig 4;

The drilling rig 4 is used to drive the drill rod 3 to move forward, so as to push the jet drill bit 2 to continuously perform the drilling operation, so as to form a borehole 9 with a certain length in the coal seam 1 .

Step 3: Drilling with liquid nitrogen jet; in view of the problems such as the easy collapse of the drilled hole 9 during the mechanical drilling of the soft coal seam 1 and the expansion of the clay caused by the water in the coal seam 1, the high-pressure jet method is used to drill the coal-breaking hole 9, and low-temperature liquid nitrogen is used. as a jet medium. As shown in Figure 1, open each first solenoid valve on the first set of liquid nitrogen tank group 6, and start the cryopump 5, at this time, keep the second solenoid valve closed, so that the first set of liquid nitrogen tank group 6 The output liquid nitrogen is pressurized by the cryogenic pump 5 and then transported by the drill pipe 3 to the jet drill bit 2. Under the throttling action of the nozzle of the jet drill bit 2, the high-pressure liquid nitrogen flows out from the nozzle, and the pressure decreases rapidly and the speed increases rapidly, forming a The high-speed liquid nitrogen jet acts on the coal seam 1; the high-speed impact of the liquid nitrogen jet and the low temperature cracking effect of the liquid nitrogen are used to break the coal seam 1 and form holes of a certain size; during the drilling process of the liquid nitrogen jet, at the same time, the drilling rig 4 is used to push The drill pipe 3 moves forward to ensure that the coal seam 1 in front of the liquid nitrogen jet is always within the effective rock breaking range of the liquid nitrogen jet, and a drill hole 9 with a certain shape and length is formed in the coal seam 1. The annulus between drill pipe 3 and borehole 9 is flowed back into the rock tunnel together with liquid nitrogen; during the cinder flowback process, the liquid nitrogen will continue to gasify and expand, resulting in a continuous increase in volume and a continuous increase in the flow velocity in the annulus. large, which is conducive to enhancing the efficiency of cinder flowback, and can reduce the probability of sticking accidents in drilling holes 9;

During the drilling process of the liquid nitrogen jet, after the liquid nitrogen jet impinges on the surface of the coal seam 1, the fluid returns from the annulus between the drill pipe 3 and the borehole 9. Under the continuous impact of the jet, the natural cracks in the coal seam 1 are added. Due to the influence of , coal lumps often fall off from the coal body, and together with the liquid nitrogen, flow back into the rock tunnel from the annulus between the borehole 9 and the drill pipe 3 . As shown in Fig. 2, if the size of the falling coal is large and cannot be removed from the annulus in time, it is easy to get stuck in the vicinity of the jet drill bit 2 or the drill rod 3, and the drill rod 3 and the jet drill bit 2 cannot continue to move forward. It cannot even be recovered from the borehole 9, thus causing a sticking accident, making it impossible to continue the operation of the borehole 9, and at this time, it is necessary to perform a jam removal operation.

If the large coal block 10 falling off the coal body causes the drill to be stuck, first remove the large coal block 10 that causes the drill to stick, and then continue the liquid nitrogen jet drilling operation to complete the predetermined length of drilling operation. In this process, the large coal lumps 10 that cause stuck drills are removed by liquid nitrogen to dissolve the sticking. The specific method is as follows: as shown in FIG. The heater 8 makes the liquid nitrogen in the second liquid nitrogen tank produce a gasification and expansion effect by heating, and forms a high-pressure gas; in this process, the second pressure sensor collects the pressure signal corresponding to the second liquid nitrogen tank in real time; when After the pressure of each second liquid nitrogen tank reaches or exceeds the set value, each second solenoid valve in the second set of liquid nitrogen tank group 7 is opened in turn, so that the high-pressure gas in the second set of liquid nitrogen tank group 7 quickly enters. In the annulus of drill pipe 3, jet drill bit 2 and borehole 9, the formed multiple high-pressure and high-speed airflows are used to impact the coal lumps in the annulus for many times; Repeat the liquid nitrogen gas removal operation until the stuck drill is broken and removed; during the liquid nitrogen gas removal operation, the pressure in the second set of liquid nitrogen tank group 7 is lower than the coal seam rupture pressure to prevent the wall surface of the drill hole 9 Fracture to ensure the integrity of drilled hole 9.

Step 4: The liquid nitrogen phase transition causes cracking; when the borehole 9 reaches the predetermined length, stop the jet drilling operation, and use the annular plug 11 to seal the entrance of the borehole 9. A closed space is formed inside, as shown in Figure 4; the plurality of heaters 8 at the bottom of the second set of liquid nitrogen tank groups 7 are turned on in turn, and the plurality of second liquid nitrogen tanks are heated, so that the plurality of second liquid nitrogen tanks are heated. The pressure keeps rising. When the pressure of each second liquid nitrogen tank exceeds the fracture pressure of the coal seam and is lower than the fracture pressure of the rock formation, each second solenoid valve in the second set of liquid nitrogen tank group 7 is opened in turn, and the liquid nitrogen The high-pressure fluid generated by the nitrogen phase transition fracts the coal seam 1, and forms a certain length of cracks 12 in the coal seam 1, so as to effectively increase the penetration enhancement range of the borehole 9.

In this process, as the amount of liquid nitrogen in the second liquid nitrogen tank continues to decrease, it is necessary to continuously increase the power of the heater 8 to continue heating the second liquid nitrogen tank to ensure that the pressure in the second set of liquid nitrogen tank groups 7 is always higher than the fracture propagation pressure of the coal seam, thereby promoting the continuous extension of the fracture 12.

In the method proposed by the invention, both liquid nitrogen gasification and phase transformation are carried out in a closed container, rather than in a borehole. This is mainly because when liquid nitrogen is gasified in the borehole, it is affected by various factors such as coal seam permeability, ambient temperature, borehole pressure and liquid nitrogen volume, the pressurization rate of liquid nitrogen gasification and the maximum gasification/phase The variable pressure is uncertain, especially when the permeability of the coal seam around the borehole is large, the gasification and pressurization rate in the borehole will be very low, and the gas infiltrates into the coal seam, it is difficult to establish a high pressure environment in the borehole. The present invention adopts the method of liquid nitrogen gasification/phase transition in a specific container, and uses a heating device to adjust the gasification/phase transition rate during the gasification/phase transition process, which can not only accurately control the liquid nitrogen gasification/phase transition process It can also prevent the loss of fluid energy during the gasification/phase change process, which can ensure that the fluid energy can be released into the borehole in a short time, and concentrated for impact crushing coal lumps or cracking caused by sticking. The coal seam around the borehole can greatly improve the success rate of cracking and cracking.

The present invention fully combines the coal seam drilling, unblocking and cracking and anti-penetration technology in one set of procedures, and selects high-pressure jet instead of the mechanical drill bit for rock-breaking drilling, which can not only effectively prevent the soft coal seam from being impacted by the rotation of the mechanical drill bit The problem of borehole collapse is easy to occur, and the high-speed impact effect of the jet can be used to improve the cinder flowback rate. The invention uses low-temperature liquid nitrogen as the jet medium, which can effectively prevent the water phase intrusion from causing damage to the pore structure of the soft coal seam, and can avoid the occurrence of coal seam pore throat blockage caused by the expansion of clay minerals in contact with water. During the liquid nitrogen jet drilling process, with the continuous injection of liquid nitrogen, the temperature of the coal seam around the borehole decreases continuously, forming a low temperature freezing zone. The enhanced cementitiousness is beneficial to inhibit the collapse of the borehole and significantly improve the porosity of the soft coal seam. In the process of slag discharge, as the temperature of liquid nitrogen continues to rise, the volume expands continuously, and the fluid flowback velocity in the annulus continues to increase, which is beneficial to further promote the flowback of coal slag.

In addition, since there is no water phase in the drilling, the broken cinders will not be cemented with each other, and will flow back into the roadway with nitrogen or liquid nitrogen in a discrete state, which is beneficial to greatly reduce the sticking during the drilling process. probability of an accident. Especially when a sticking accident occurs, high-pressure gas is generated by heating liquid nitrogen, and then the coal blocks that cause the sticking accident in the drilling hole are repeatedly impacted and broken, which can effectively remove the stuck point and enable the drilling operation to continue. Ensure drilling efficiency. Since the coal seam around the borehole is in contact with liquid nitrogen for a long time, some natural cracks in the coal body are opened when cooled. When the borehole reaches a predetermined length, the high pressure generated by the phase change of liquid nitrogen can continue to impact the coal seam around the borehole. At the same time, it promotes the expansion and extension of open natural fractures, increases the scope of drilling penetration, and improves the efficiency of coal and gas drainage in the later stage.

This method realizes the integrated operation of liquid nitrogen jet drilling, gasification solution stuck, and phase transition cracking, and overcomes the technical problems such as easy collapse of soft coal seam holes, easy drilling sticking and easy expansion of clay in coal seams in conventional coal seam drilling technology. At the same time, it can effectively solve the accident of sticking during the drilling process. After the drilling is completed, it can also conduct high-pressure cracking on the coal seam around the drilling hole, which can significantly improve the penetration enhancement range of the drilling hole. It is an integrated method for enhancing the permeability of soft coal seams.

Claims (7)

1. An integrated device for drilling, unlocking and fracturing of a soft coal seam, comprising a jet drill bit (2), a drill pipe (3) and a drilling rig (4); it is characterized in that, also comprises a first set of liquid nitrogen tanks group (6), cryogenic pump (5), second set of liquid nitrogen tank group (7) and heater (8); The jet drill bit (2) is installed on the outlet end of the drill rod (3); the drill rod (3) is assembled on the drilling rig (4); The first set of liquid nitrogen tanks (6) is used to provide jet medium for liquid nitrogen jet drilling, and is composed of a plurality of first liquid nitrogen tanks; each first liquid nitrogen tank is connected with a first pressure sensor , and its outlets are all connected with first solenoid valves; the outlets of the plurality of first liquid nitrogen tanks are connected to the inlets of the cryopump (5) through the first nitrogen supply pipeline (13), and the outlets of the cryopump (5) pass through the main The nitrogen supply pipeline (15) is connected with the inlet of the drill pipe (3); The second set of liquid nitrogen tanks (7) is used for liquid nitrogen to dissolve jams and to cause cracking by phase transition, and is composed of a plurality of second liquid nitrogen tanks; each second liquid nitrogen tank is connected with a second pressure sensor , and its outlets are all connected with second solenoid valves; the outlets of the plurality of second liquid nitrogen tanks are connected with the main nitrogen supply pipeline (15) through the second nitrogen supply pipeline (14); The number of the heaters (8) is the same as the number of the second liquid nitrogen tank, and they are set in one-to-one correspondence. The liquid nitrogen in the tank is heated. 2. An integrated device for drilling, unblocking and fracturing of soft coal seams according to claim 1, characterized in that it further comprises an annular sealing plug (11), wherein the annular sealing plug (11) is sleeved on The outside of the drill rod (3) is used to realize the sealed connection between the drill rod (3) and the bore hole (9). 3. An integrated device for drilling, unblocking and fracturing of soft coal seams according to claim 1 or 2, characterized in that, further comprising a PLC controller, the PLC controller is respectively connected with the first pressure sensor , the first solenoid valve, the second pressure sensor, the second solenoid valve, the cryogenic pump (5) and the heater (8) are connected. 4. An integrated method for drilling, unlocking and fracturing of a soft coal seam, characterized in that it comprises the following steps: Step 1: Preparatory work; perform geological exploration on the coal seam (1) to determine the high gas pressure area of the coal seam (1), and then determine the coal seam (1) drilling holes according to the distribution of gas in the coal seam (1) and the geological parameters of the coal seam (1). Location and area of AR modification; Step 2: arranging construction equipment; arranging a drilling, unblocking and cracking integrated device in the rock roadway, and the drilling, unblocking and cracking integrated device consists of a first set of liquid nitrogen tank group (6), a cryogenic pump ( 5.) The second set of liquid nitrogen tank group (7), heater (8), jet drill bit (2), drill pipe (3) and drilling rig (4); the first set of liquid nitrogen tank group (6) is used for A jet medium is provided for the liquid nitrogen jet drilling, which consists of a plurality of first liquid nitrogen tanks, and the outlets of the plurality of first liquid nitrogen tanks are connected with the inlet of the cryopump (5) through the first nitrogen supply pipeline (13); The outlet of the cryogenic pump (5) is connected with the inlet of the drill pipe (3) through the main nitrogen supply pipeline (15); the second set of liquid nitrogen tank group (7) is used for liquid nitrogen to dissolve the stuck and phase transition and cause cracking, which is composed of A plurality of second liquid nitrogen tanks are formed, and the outlets of the plurality of second liquid nitrogen tanks are connected with the main nitrogen supply pipeline (15) through the second nitrogen supply pipeline (14); the plurality of heaters (8) correspond one-to-one It is assembled on the bottom of the second set of liquid nitrogen tank group (7); the jet drill bit (2) is installed on the outlet end of the drill pipe (3); the drill pipe (3) is assembled on the drilling rig (4); Step 3: liquid nitrogen jet drilling; open each first solenoid valve on the first set of liquid nitrogen tank group (6), and start the cryogenic pump (5), so that the liquid nitrogen output by the first set of liquid nitrogen tank group (6) After being pressurized by the cryogenic pump (5), nitrogen is transported by the drill pipe (3) to the jet drill bit (2), and under the throttling action of the nozzle of the jet drill bit (2), a high-speed liquid nitrogen jet is formed to act on the coal seam (1); The high-speed impact of the nitrogen jet and the low-temperature cracking effect cause the coal seam (1) to be broken and form holes of a certain size; during the drilling process of the liquid nitrogen jet, the drilling rig (4) is used to push the drill pipe (3) forward to ensure that the liquid nitrogen The coal seam (1) in front of the nitrogen jet is always within the effective rock breaking range of the liquid nitrogen jet, and a drill hole (9) with a certain shape and length is formed in the coal seam (1), and at the same time, the broken coal slag is removed from the drill pipe ( 3) The annulus between the borehole (9) is flowed back into the rock roadway together with the liquid nitrogen; During the liquid nitrogen jet drilling process, if the large coal block (10) falling off the coal body causes the drill to stick, first remove the large coal block (10) causing the sticking, and then continue the liquid nitrogen jet Drilling operations to complete the drilling operations of a predetermined length; Step 4: liquid nitrogen phase transition causes cracking; when the drill hole (9) reaches a predetermined length, the jet drilling operation is stopped, and the annular plug (11) is used to block the entrance of the drill hole (9), and the drill pipe (3) ), the jet drill bit (2) and the annular space form a closed space; turn on the plurality of heaters (8) at the bottom of the second set of liquid nitrogen tank groups (7) in turn, and heat the plurality of second liquid nitrogen tanks to make the The pressure in the plurality of second liquid nitrogen tanks is continuously rising. When the pressure of each second liquid nitrogen tank exceeds the fracture pressure of the coal seam and is lower than the fracture pressure of the rock layer, open the second liquid nitrogen tank group (7) in turn. Each of the second solenoid valves utilizes the high-pressure fluid produced by the liquid nitrogen phase transition to fracturing the coal seam (1), and forms cracks (12) in the coal seam (1). 5 . An integrated method for drilling, unstuck and cracking for soft coal seam according to claim 4, characterized in that, in step 3, the large coal that causes stuck drilling is treated by liquid nitrogen to dissolve the stick. The block (10) is removed, and the specific method is as follows: firstly close the first solenoid valve and the cryopump (5), and at the same time, turn on a plurality of heaters (8) in turn, and make the liquid nitrogen in the second liquid nitrogen tank generate gas by heating In this process, the pressure signal corresponding to the second liquid nitrogen tank is collected in real time through the second pressure sensor; when the pressure of each second liquid nitrogen tank reaches or exceeds the set value, the Open each second solenoid valve in the second set of liquid nitrogen tank groups (7), so that the high-pressure gas in the second set of liquid nitrogen tank groups (7) quickly enters the drill pipe (3), the jet drill bit (2) and the drilling hole (9) In the annulus, the formed multiple high-pressure and high-speed airflows are used to impact the coal lumps in the annulus for many times until the large coal lumps (10) causing the drill are broken and removed. 6 . An integrated method for drilling, unlocking and fracturing of soft coal seams according to claim 5, characterized in that, in step 3, during the operation of liquid nitrogen dissolving and unlocking, the second set of liquid nitrogen The pressure in the tank group (7) is lower than the fracture pressure of the coal seam. 7. An integrated method for drilling, unblocking and fracturing of soft coal seams according to claim 6, characterized in that, in step 4, as the amount of liquid nitrogen in the second liquid nitrogen tank decreases continuously, The power of the heater (8) is continuously increased, and the second liquid nitrogen tank is continuously heated to ensure that the pressure in the second set of liquid nitrogen tank groups (7) is always higher than the extension pressure of the coal seam crack.

Images