CN113756775A - Hydraulic permeability increasing process for large-dip-angle low-permeability coal seam - Google Patents
Hydraulic permeability increasing process for large-dip-angle low-permeability coal seam Download PDFInfo
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- CN113756775A CN113756775A CN202111138047.0A CN202111138047A CN113756775A CN 113756775 A CN113756775 A CN 113756775A CN 202111138047 A CN202111138047 A CN 202111138047A CN 113756775 A CN113756775 A CN 113756775A
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/12—Packers; Plugs
- E21B33/122—Multiple string packers
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
Abstract
The invention relates to the technical field of coal seam hydraulic permeability increasing, and discloses a large-dip-angle low-permeability coal seam hydraulic permeability increasing process, which comprises the following steps: drilling, namely drilling a hole in a coal seam to form a fracturing hole; determining a hole sealing process, placing two packers in each fracturing hole, wherein the two packers are distributed at intervals, one side of each fracturing hole is provided with a plurality of branch holes communicated with the fracturing hole, the intersection point between each branch hole and each fracturing hole is a branch point, a fracturing pipe is inserted into each fracturing hole, and a screen pipe section of each fracturing pipe is placed at the position of the branch hole to be fractured; step (3), designing fracturing parameters, including pump injection pressure parameters and injection liquid amount parameters; step (4), fracturing equipment model selection; and (5) fracturing, namely sealing the fractured holes by using a hole sealing material, connecting pipelines and equipment after the hole sealing material is solidified for 12-48h, and pumping to perform water injection fracturing. The hydraulic fracturing hole sealing device can avoid the phenomenon of water leakage caused by poor hole sealing effect in the hydraulic fracturing process.
Description
Technical Field
The invention relates to the technical field of coal seam hydraulic permeability increasing, in particular to a large-dip-angle low-permeability coal seam hydraulic permeability increasing process.
Background
Most of the existing coal resources in China are outburst coal seams, and before the coal seams of the type are mined, gas extraction treatment needs to be carried out on the coal seams according to the regulations to reduce the content of gas in the coal seams so as to ensure the operation safety in the coal mining process.
In order to improve the gas extraction efficiency, the permeability of a coal seam needs to be improved, most of mines adopt a pressure relief permeability-increasing process for improving the permeability of the coal seam, and a hydraulic fracturing technology is adopted for the best effect in the pressure relief permeability-increasing process.
The hydraulic fracturing permeability can reduce the outburst risk of the coal bed: (1) the coal bed physical and mechanical properties are changed: the fracturing fluid has the function of fracturing, can continuously run through and expand cracks through hydraulic fracturing, expands the wetting radius, generates repeated effects of expansion-contraction-expansion, and changes the physical and mechanical properties of a coal bed to the maximum extent; (2) the displacement effect on gas is as follows: water is infiltrated into the cracks and pores with different pore diameters to the maximum extent through hydraulic fracturing, the wettability of the medium is increased to the maximum extent, and gas in different pores can be displaced; (3) law of distribution of varying ground stress: hydraulic fracturing can make the stress in front of the working face more uniform through the transmission action of water pressure, thereby reducing the risk of coal seam outburst caused by nonuniform stress.
After the hydraulic fracturing is carried out on the gas-containing medium layer, the gas concentration and the gas extraction amount in a short time of an extraction drill hole are greatly increased, the extraction speed is increased, the gas content of a coal seam is reduced, and the method is an effective technical means for improving the extraction efficiency.
The pressure process in the prior art is used for remarkably improving the working efficiency when gas extraction is carried out after hydraulic fracturing permeability-increasing treatment is carried out on a coal seam, a hole packer can be used for ensuring that a fracturing drill hole is water-tight in the fracturing process in the process of realizing the permeability-increasing of the coal seam by adopting the hydraulic fracturing technology, but the seat sealing force of the existing hole packer is large, the existing hole packer is only suitable for a cased well or a rock layer open hole well with good homogeneity, the coal seam is soft, and the phenomena of local hole collapse and the like of the drill hole can be caused by the large seat sealing force, so that the hole sealing effect is influenced.
In addition, there are often certain safety issues in implementing hydraulic splitting.
Disclosure of Invention
The invention aims to provide a hydraulic permeability increasing process for a large-dip-angle low-permeability coal seam so as to avoid the phenomenon of water leakage caused by poor hole sealing effect in the hydraulic fracturing process.
In order to achieve the purpose, the invention adopts the following technical scheme: the large dip angle low permeability coal seam hydraulic permeability increasing process comprises the following steps:
drilling, namely drilling a hole in a coal seam to form a fracturing hole;
determining a hole sealing process, placing two packers in each fracturing hole, wherein the two packers are distributed at intervals, one side of each fracturing hole is provided with a plurality of branch holes communicated with the fracturing hole, the intersection point between each branch hole and each fracturing hole is a branch point, a fracturing pipe is inserted into each fracturing hole, and a screen pipe section of each fracturing pipe is placed at the position of the branch hole to be fractured;
step (3), designing fracturing parameters, including pump injection pressure parameters and injection liquid amount parameters;
step (4), fracturing equipment model selection;
and (5) fracturing, namely sealing the fractured holes by using a hole sealing material, connecting pipelines and equipment after the hole sealing material is solidified for 12-48h, and pumping to perform water injection fracturing.
The principle and the advantages of the scheme are as follows:
by adopting the process in the scheme, the gas concentration and the gas extraction amount in the short time of the extraction drill hole can be greatly increased, the extraction speed is effectively accelerated, and the gas content of the coal seam is reduced.
In the hole sealing process in the scheme, two packers distributed at intervals are placed in each fracturing hole, so that the fracturing holes can be ensured to be watertight in the fracturing process, the pressure required in fracturing is ensured, and the normal operation of fracturing is ensured.
Preferably, as an improvement, a pressure sensor is arranged at an orifice of the fracturing hole to detect pressure change of the orifice, a gas concentration sensor is arranged at the air return side of the air return gateway of the coal bed to monitor the gas concentration change condition around the fracturing hole, and a high-pressure valve is arranged at the orifice of the fracturing hole.
Hole sealing material can make the leakproofness in fracturing hole more in this scheme, install connecting line again after the leakproofness in fracturing hole is improved through hole sealing material, equipment, can make whole fracturing process more stable safety, simultaneously in this scheme because install pressure sensor at the drill way in fracturing hole, the pressure variation in this pressure sensor can monitor the drill way, realize the long-distance accurate monitoring of downthehole pressure variation, can observe the unusual of equipment and management in real time through monitoring drill way pressure variation in this scheme, effectual improvement security.
The gas concentration sensor installed on the air return side of the air return crossheading in the scheme can detect the change condition of the gas concentration at the periphery of the pressure hole, and the safety condition can be monitored in real time.
In addition, a high-pressure valve is arranged at the orifice of the fracturing hole, and water injection and drainage are conveniently controlled by the arrangement.
Preferably, as an improvement, when the water injection amount in the step (5) reaches the design requirement, the high-pressure valve at the orifice of the fracturing hole is closed, so that the high-pressure water in the coal body maintains the pressure.
In the scheme, because the water in the medium still has higher pressure after hydraulic fracturing, the high-pressure water can still continue to crack the coal body in the coal body, and the crack generated in the fracturing process is better maintained, so that the high-pressure valve is closed to maintain the pressure of the high-pressure water in the coal body, the development and the maintenance of the crack in the coal body are facilitated, the high-pressure water pressure maintaining is favorable for reducing the gas flow attenuation coefficient after the hydraulic fracturing, and the gas extraction effect after the fracturing is improved.
Preferably, as an improvement, in the determination of the pumping pressure parameter in step (3), the pumping pressure is lower than the rated pressure of the pump, and the power of the pump is at least the product of the pumping pressure and the pumping flow rate.
The whole fracturing effect can be better after the condition of the pump injection pressure of the scheme is met.
Preferably, as an improvement, when the pressure drop of the high-pressure water in the fracturing hole is lower than 0.5MPa for 3 days, the high-pressure valve of the orifice of the fracturing hole is slowly opened to perform slow drainage.
When the pressure decline range in this scheme in 3 days was less than 0.5Mpa, stopped the pressurize, because the downthehole high pressure water of fracturing at this moment no longer has the ability of making the seam or downthehole high pressure water makes the seam ability relatively poor, slowly opens the orifice high pressure valve this moment, slowly the drainage can prevent to block up the fracturing hole because of the too fast a large amount of coal cinder of bringing out of rivers.
Preferably, as an improvement, when the natural outflow of water is small, a pipeline is put into the fracturing hole by using a diaphragm pump, and the residual water in the fracturing hole is pumped and drained.
This scheme can prevent that the nature drainage from having the remaining condition, can avoid producing ponding.
Preferably, as an improvement, after the drainage of the fractured hole is finished, the pipeline is connected with an extraction system, a flowmeter is installed, the concentration of methane in the drilled hole is monitored, the concentration of gas in the drilled hole and the gas extraction amount are inspected, a mathematical model of gas extraction data and extraction time is established, and the gas pre-extraction rate in the fractured region is calculated.
The gas pre-pumping rate of the fracturing area is calculated in the scheme, so that the fracturing effect is convenient to examine, and the fracturing construction parameters are convenient to change according to actual conditions.
Preferably, as an improvement, a camera is installed at the opening of the fracturing hole.
The state of drill way can be observed in real time in the setting of camera, and can observe the condition in fracturing hole drill way through the camera at the in-process of fracturing, pay close attention to pressure variation, further improved the security.
Preferably, as an improvement, when the pressure fluctuation exceeds 10MPa or the pumping pressure continues to be more than 40MPa, the pump is stopped to relieve the pressure for checking.
Dangerous condition can in time be investigated in this scheme, can in time handle when the discovery has the anomaly.
Preferably, as an improvement, the packer includes top connection, lower clutch, center tube and packing element, the both ends of center tube are connected with top connection and lower clutch respectively, the packing element cover is in the center tube outside, the feed liquor hole has been seted up on the center tube, the feed liquor hole is the through-hole, the packing element includes interior packing element and outer packing element, be equipped with the strengthening rib between interior packing element and the outer packing element, threaded connection has the anchoring piece on the center tube, the anchoring piece compresses tightly the periphery of packing element.
According to the scheme, the rubber sleeve comprises an inner rubber sleeve and an outer rubber sleeve, the reinforcing ribs are arranged between the inner rubber sleeve and the outer rubber sleeve, the rigidity and the strength of the shoulder part of the rubber sleeve can be enhanced, the anchoring part is further arranged, the rubber sleeve can be compressed through the anchoring part, and meanwhile, the reinforcing ribs can be clamped and fixed, so that the combination strength of the reinforcing ribs and the anchoring part can be enhanced.
In the scheme, the consolidation of the whole packer is effectively enhanced under the matching action of the reinforcing ribs and the anchoring pieces, so that the hole sealing can be effectively supported, and the problem that partial holes are easily broken when the traditional packer is used for fracturing and sealing the hole in a coal mine is greatly reduced.
Drawings
FIG. 1 is a schematic diagram of a hole sealing process in an embodiment of the hydraulic permeability increasing process for a large-dip-angle low-permeability coal seam according to the invention.
FIG. 2 is a semi-sectional view of an packer in a second embodiment of the hydraulic permeability-increasing process for a high-dip-angle low-permeability coal seam according to the present invention.
FIG. 3 is a partial cross-sectional view of the packer in a second embodiment of the hydraulic permeability-increasing process for a steep-dipping low-permeability coal seam according to the present invention.
Detailed Description
The following is further detailed by way of specific embodiments:
reference numerals in the drawings of the specification include: the fracturing device comprises a fracturing hole 1, a fracturing pipe 2, a packer 3, a steel wire 4, a branch hole 5, an upper joint 6, a sealing ring 7, a rubber sleeve 8, an outer rubber sleeve 801, an inner rubber sleeve 802, a liquid inlet hole 9, a central pipe 10, a lower joint 11, an annular piston 12, a reinforcing rib 13, an anchoring piece 14 and a liquid guide hole 15.
Example one
The large dip angle low permeability coal seam hydraulic permeability increasing process comprises the following steps:
drilling, namely drilling a coal seam to form a fracturing hole 1;
step (2), determining a hole sealing process, placing two packers 3 in each fracturing hole 1, wherein the two packers 3 are distributed at intervals, one side of each fracturing hole 1 is provided with a plurality of branch holes 5 communicated with the fracturing hole 1, the intersection point between each branch hole 5 and each fracturing hole 1 is a branch point, a fracturing pipe 2 is inserted into each fracturing hole 1, and a screen pipe section of each fracturing pipe 2 is placed at the position of each branch hole 5 needing fracturing;
as shown in fig. 1, a guide shoe is provided at the front end of the fracturing pipe 2, so that the fracturing pipe 2 can be ensured to be smoothly lowered into the fracturing hole 1, in this embodiment, two branch holes 5 are provided at one side of the fracturing hole 1 as an example, intersection points between the two branch holes 5 and the fracturing hole 1 are a first branch point and a second branch point from left to right, a packer 3 is lowered to a position of about 10m in the direction of an orifice of the first branch point, and two sets of packers 3 keep a certain distance.
The front end (i.e. the right end in the attached drawing 1) of the fracturing pipe 2 is a screen pipe section, the screen pipe section is put to the branch mouth feel needing fracturing, and the distance of the right end of the screen pipe section of the fracturing pipe 2 exceeds the first branch point. In this embodiment, it is fixed with fracturing pipe 2 through steel wire 4 at the left end in fracturing hole 1 to play spacing fixed effect to fracturing pipe 2.
Step (3), designing fracturing parameters, including pump injection pressure parameters and injection liquid amount parameters;
step (4), fracturing equipment model selection;
and (5) fracturing, namely sealing the fractured holes by using a hole sealing material, connecting pipelines and equipment after the hole sealing material is solidified for 12-48h, and pumping to perform water injection fracturing.
In the determination of the pumping pressure parameter in step (3) in this embodiment, the pumping pressure is smaller than the rated pressure of the pump, and the power of the pump is at least the product of the pumping pressure and the pumping flow rate. In the embodiment, the coal seam initiation pressure is about 15MPa, and the pumping pressure is about 20 MPa.
And (3) designing parameters of the injection liquid amount:
first, a pre-stage
For a certain coal bed, in order to enhance the fracturing effect, a surfactant and a fire retardant with proper proportion can be designed and added to enter a fracturing hole along with the fracturing fluid.
Displacement stage
When the amount of the front liquid reaches the designed amount, the displacement liquid is calculated, and the displacement time and the displacement liquid amount are accurately calculated without reducing or increasing the displacement liquid amount.
In the embodiment, the water injection rate of the hydraulic fracturing directional long drill hole is 1500m3。
And (4) fracturing equipment model selection:
in the process of carrying out a coal mine underground hydraulic fracturing permeability-increasing test, equipment and consumables such as a pump set, a fracturing hole sealing pipe, a high-pressure rubber pipe, a high-pressure valve, a high-concentration optical gas detector, a DGC gas content tester, a drilling machine and the like are required to be prepared.
The related parameters of the fracturing pump set are shown in the table I:
The concrete fracturing implementation process in the step (5) comprises the following steps:
1) fracturing process and safety protection
After the hole sealing material is used for sealing the fractured holes, pipelines and equipment are connected after the hole sealing material is solidified for 12-48h, and a pump is started for water injection fracturing, wherein the hole sealing material is solidified for 48h in the embodiment.
The pressure sensor is arranged at the orifice of the fracturing hole to detect the pressure change of the orifice, the gas concentration sensor is arranged at the air return side of the air return gateway of the coal bed to monitor the gas concentration change condition around the fracturing hole, and the high-pressure valve is arranged at the orifice of the fracturing hole.
Installing a camera at the orifice of the fracturing hole, and observing the condition of the orifice of the fracturing hole in real time;
in the fracturing process, the condition of the opening of the fracturing hole is observed through the camera, the pressure change is closely concerned, when the pressure fluctuation exceeds 10MPa or the pumping pressure lasts more than 40MPa, the pump is stopped to release the pressure for checking, and other abnormal conditions are timely treated.
And (5) stopping the pump and closing the high-pressure valve at the orifice for pressure relief after the water injection amount in the fracturing process reaches the design requirement in the step (5), checking equipment and pipelines, closing the high-pressure valve at the orifice of the fracturing hole to keep the pressure of the high-pressure water in the coal body, determining the pressure maintaining time on site according to the change condition of the pressure of the high-pressure water in the hole, and closing the high-pressure valve at the orifice for pressure maintenance for seven days in the embodiment.
2) Fracturing hole drainage
After the injection amount reaches the design requirement, closing the orifice high-pressure valve to perform pressure maintaining, when the pressure drop amplitude of high-pressure water in the fracturing hole lasting for 3 days is lower than 0.5MPa, the high-pressure water no longer has the capability of making a seam (or the capability of making a seam by the high-pressure water in the hole is poor), stopping the pressure maintaining, slowly opening the high-pressure valve at the orifice of the fracturing hole to perform slow drainage, preventing the fracturing hole from being blocked by a large amount of coal dust brought out due to too fast water flow, and opening the orifice high-pressure valve by using a long-arm tool in the drainage process to prohibit personnel from passing through the area to prevent people from being injured.
In this embodiment, after the water natural outflow is less, through using the diaphragm pump to transfer the pipeline in the fracturing hole, the downthehole surplus water of pump drainage fracturing, if the downthehole water yield of fracturing is less, can be to the downthehole quartering pipe of putting into of fracturing, use the pressure wind to blow off the downthehole ponding.
And finally, carrying out fracturing effect investigation: and after the drainage of the fractured hole is finished, connecting the pipeline with an extraction system, installing a flowmeter, monitoring the methane concentration of the drilled hole, inspecting the gas concentration and the gas extraction amount of the drilled hole, establishing a mathematical model of gas extraction data and gas extraction time, and calculating the gas pre-extraction rate of the fractured region.
Example two
As shown in fig. 2, the packer 3 in this embodiment includes an upper joint 6, a lower joint 11, a central tube 10 and a packing element 8, the upper joint 6 of the packer 3 is connected to the fracturing pipe 2, two ends of the central tube 10 are respectively connected to the upper joint 6 and the lower joint 11, two ends of the central tube 10 in this embodiment are respectively formed integrally with the upper joint 6 and the lower joint 11, and the packing element 8 is sleeved outside the central tube 10.
The central tube 10 in this embodiment is provided with a liquid inlet hole 9, and the liquid inlet hole 9 is a through hole. Referring to fig. 3, the glue cylinder 8 includes an inner glue cylinder 802 and an outer glue cylinder 801, and in this embodiment, an inner cavity is formed in the glue cylinder 8, so as to form structures of the inner glue cylinder 802 and the outer glue cylinder 801, in this embodiment, a reinforcing rib 13 is disposed in the inner cavity between the inner glue cylinder 802 and the outer glue cylinder 801, and the reinforcing rib 13 in this embodiment is a steel strip.
There are anchoring elements 14 in the central tube 10, anchoring elements 14 are used for compressing tightly the periphery of rubber sleeve 8, anchoring elements 14 are two in this embodiment, two anchoring elements 14 are located the both ends of rubber sleeve 8 respectively, the internal diameter of two anchoring elements 14 is less than the external diameter of rubber sleeve 8, the one end that two anchoring elements 14 are just right each other all is the flaring form, thereby make anchoring elements 14's tip cross section be the wedge, thereby make anchoring elements 14 be the taper sleeve structure, can make like this and improve the consolidation of rubber sleeve 8 shoulder between anchoring elements 14 and the rubber sleeve 8 depending on mechanical wedging effect.
As shown in fig. 2, in the present embodiment, the annular pistons 12 are fixed at the left and right portions of the central tube 10, and the two anchoring members 14 are respectively in threaded connection with the two annular pistons 12, so that the two anchoring members 14 can press the outer rubber sleeve 801 after the threads of the two anchoring members 14 are screwed to the annular pistons 12, thereby clamping the reinforcing ribs 13. In the embodiment, a sealing ring 7 is arranged between the anchor 14 and the annular piston 12, and the sealing ring 7 can enhance the sealing property between the anchor 14 and the annular piston 12. Finally, the rubber sleeve 8, the central tube 10 and the anchoring piece 14 are vulcanized as a whole, so that the rubber sleeve 8 and the anchoring piece 14 are integrally vulcanized and fixed together, and the bonding strength among the reinforcing ribs 13, the rubber sleeve 8 and the anchoring piece 14 is further improved, specifically: in this embodiment, the anchoring member 14 is provided with the liquid guiding hole 15, the liquid guiding hole 15 is a through hole, when the anchoring member 14 and the annular piston 12 are screwed and connected, the reinforcing rib 13 is clamped between the inner rubber sleeve 802 and the outer rubber sleeve 801, and then the epoxy resin is extruded through the liquid guiding hole 15 to further extrude the layer of the reinforcing rib 13, so as to increase the clamping force on the rubber sleeve 8, and the epoxy resin is filled in the gap between the reinforcing rib 13 and the anchoring member 14, so as to further improve the bonding strength between the anchoring member 14 and the rubber sleeve 8.
The packing element 8 in this implementation designs longer, packer 3 after the improvement design effectively seals length and is 800mm, make the expansion bigger like this, be applicable to various open hole wells, in this embodiment when fracturing, the cooperation is current fracturing pipe 2 uses, fracturing fluid is in fracturing pipe 2 gets into the center tube 10 of packer 3 by top connection 6, the fracturing fluid that has certain pressure this moment enters into the inner chamber of packing element 8 through feed liquor hole 9 on the center tube 10, make packing element 8 expand outside protruding, thereby play the effect of hole sealing. After the fracturing fluid of the central pipe 10 is relieved of pressure, the rubber cylinder 8 is retracted inwards to be unsealed.
The packer 3 in the embodiment has good rigidity and strength, and can effectively reduce the problem that partial hole collapse easily occurs when the traditional packer 3 is used for underground coal mine fracturing hole sealing.
The foregoing is merely an example of the present invention and common general knowledge in the art of designing and/or characterizing particular aspects and/or features is not described in any greater detail herein. It should be noted that, for those skilled in the art, without departing from the technical solution of the present invention, several variations and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (10)
1. The large dip angle low permeability coal seam hydraulic permeability increasing process is characterized in that: the method comprises the following steps:
drilling, namely drilling a hole in a coal seam to form a fracturing hole;
determining a hole sealing process, placing two packers in each fracturing hole, wherein the two packers are distributed at intervals, one side of each fracturing hole is provided with a plurality of branch holes communicated with the fracturing hole, the intersection point between each branch hole and each fracturing hole is a branch point, a fracturing pipe is inserted into each fracturing hole, and a screen pipe section of each fracturing pipe is placed at the position of the branch hole to be fractured;
step (3), designing fracturing parameters, including pump injection pressure parameters and injection liquid amount parameters;
step (4), fracturing equipment model selection;
and (5) fracturing, namely sealing the fractured holes by using a hole sealing material, connecting pipelines and equipment after the hole sealing material is solidified for 12-48h, and pumping to perform water injection fracturing.
2. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 1, characterized by comprising the following steps: a pressure sensor is arranged at an orifice of the fracturing hole to detect pressure change of the orifice, a gas concentration sensor is arranged at the air return side of an air return gateway of the coal bed to monitor the change condition of gas concentration at the periphery of the fracturing hole, and a high-pressure valve is arranged at the orifice of the fracturing hole.
3. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 1, characterized by comprising the following steps: and (5) after the water injection amount in the step (5) meets the design requirement, closing a high-pressure valve at the orifice of the fracturing hole, and keeping the pressure of the high-pressure water in the coal body.
4. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 1, characterized by comprising the following steps: and (4) in the determination of the pump injection pressure parameter in the step (3), the pump injection pressure is smaller than the rated pressure of the pump, and the power of the pump is at least the product of the pump injection pressure and the pump injection flow.
5. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 3, characterized by comprising the following steps: and when the pressure drop amplitude of the high-pressure water in the fracturing hole is lower than 0.5MPa after the high-pressure water lasts for 3 days, slowly opening a high-pressure valve at the orifice of the fracturing hole to slowly drain water.
6. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 5, characterized by comprising the following steps: after the natural outflow of water is less, through using the diaphragm pump to transfer the pipeline in the fracturing hole, pump drainage fracturing is downthehole remaining water.
7. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 6, characterized by comprising the following steps: and after the drainage of the fractured hole is finished, connecting the pipeline with an extraction system, installing a flowmeter, monitoring the methane concentration of the drilled hole, inspecting the gas concentration and the gas extraction amount of the drilled hole, establishing a mathematical model of gas extraction data and gas extraction time, and calculating the gas pre-extraction rate of the fractured region.
8. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 1, characterized by comprising the following steps: and a camera is arranged at the orifice of the fracturing hole.
9. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 8, characterized in that: when the pressure fluctuation exceeds 10MPa or the pumping pressure continues to be more than 40MPa, stopping the pump to release the pressure for checking.
10. The hydraulic permeability-increasing process for the high-dip-angle low-permeability coal seam according to claim 1, characterized by comprising the following steps: the packer includes top connection, lower clutch, center tube and packing element, the both ends of center tube are connected with top connection and lower clutch respectively, the packing element cover is in the center tube outside, the feed liquor hole has been seted up on the center tube, the feed liquor hole is the through-hole, the packing element includes interior packing element and outer packing element, be equipped with the strengthening rib between interior packing element and the outer packing element, threaded connection has the anchoring piece on the center tube, the anchoring piece compresses tightly the periphery of packing element.
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| CN114607340A (en) * | 2022-03-25 | 2022-06-10 | 中煤科工集团重庆研究院有限公司 | Triggered hole sealing fracturing structure and fracturing method |
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