CN114412430B - Liquid carbon dioxide circulation fracturing coal bed gas reservoir permeability increasing device and method - Google Patents
Liquid carbon dioxide circulation fracturing coal bed gas reservoir permeability increasing device and method Download PDFInfo
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 211
- 239000007788 liquid Substances 0.000 title claims abstract description 108
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 106
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 103
- 239000003245 coal Substances 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000001965 increasing effect Effects 0.000 title claims abstract description 24
- 230000035699 permeability Effects 0.000 title claims abstract description 24
- 238000002347 injection Methods 0.000 claims abstract description 42
- 239000007924 injection Substances 0.000 claims abstract description 42
- 230000005540 biological transmission Effects 0.000 claims abstract description 23
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000011435 rock Substances 0.000 claims description 47
- 238000007789 sealing Methods 0.000 claims description 42
- 239000002002 slurry Substances 0.000 claims description 30
- 238000005553 drilling Methods 0.000 claims description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 23
- 230000008569 process Effects 0.000 claims description 22
- 238000012544 monitoring process Methods 0.000 claims description 17
- 238000003860 storage Methods 0.000 claims description 13
- 239000002689 soil Substances 0.000 claims description 11
- 230000009977 dual effect Effects 0.000 claims description 9
- 238000000605 extraction Methods 0.000 claims description 7
- 238000001179 sorption measurement Methods 0.000 claims description 7
- 230000009471 action Effects 0.000 claims description 6
- 230000001939 inductive effect Effects 0.000 claims description 3
- 238000009434 installation Methods 0.000 claims description 3
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 10
- 230000008859 change Effects 0.000 abstract description 5
- 230000008014 freezing Effects 0.000 abstract description 3
- 238000007710 freezing Methods 0.000 abstract description 3
- 239000007789 gas Substances 0.000 description 50
- 239000012530 fluid Substances 0.000 description 7
- 238000005516 engineering process Methods 0.000 description 5
- 238000002309 gasification Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 238000010257 thawing Methods 0.000 description 2
- 238000012425 Freezing-thawing process Methods 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000011440 grout Substances 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000037452 priming Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000001932 seasonal effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/2605—Methods for stimulating production by forming crevices or fractures using gas or liquefied gas
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
- E21B36/001—Cooling arrangements
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/006—Production of coal-bed methane
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/2607—Surface equipment specially adapted for fracturing operations
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimising the spacing of wells comprising at least one inclined or horizontal well
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
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Abstract
The invention discloses a permeability increasing device and method for a liquid carbon dioxide circulation fracturing coal bed gas reservoir, wherein an inner pressure-resistant hole packer and an outer pressure-resistant hole packer are both arranged in a fracturing drill hole, and one end of a grouting pipe penetrates through the outer pressure-resistant hole packer to be positioned between the inner pressure-resistant hole packer and the outer pressure-resistant hole packer; the outlet of the air compressor is connected with the inlet of the multistage condenser through a pipeline, the liquid injection pump is connected with one end of the fracturing pipe through a transmission pipe, the other end of the fracturing pipe sequentially penetrates through the outer pressure-resistant hole packer and the inner pressure-resistant hole packer to extend into the fracturing drill hole, the negative temperature shunt and the current limiter are arranged on the transmission pipe, and one port of the current limiter is connected with the pipeline between the air compressor and the multistage condenser through a return pipeline and a return tee joint. The invention can effectively seal the interior of the fracturing drill hole, can continuously realize the double fracturing effects of low-temperature freezing and phase change expansion of the liquid carbon dioxide, and finally effectively improve the permeability of the coal bed methane reservoir.
Description
Technical Field
The invention relates to a permeability increasing device and method for a liquid carbon dioxide circulating fracturing coal bed gas reservoir, which are particularly suitable for fracturing permeability increasing and other works of a compact coal bed gas reservoir rich in bentonite and high in adsorbability, and belong to the field of underground safe and efficient coal bed gas exploitation.
Background
Unconventional energy represented by coal bed gas continuously increases the proportion of energy structures in China, and gradually becomes mainstream resources for future energy consumption in China. However, because the occurrence conditions of the energy are complex, the air permeability of the matrix of the reservoir is poor, and great difficulties exist in large-scale development, such as the reservoir is easily damaged, the exploitation efficiency is low, the cost is high, and the like. At present, a common fracturing permeability-increasing mode is a hydraulic fracturing technology, but the technology has the defects of high water consumption, easy attachment of water lock and water sensitivity effect, large equipment volume and the like, so that the hydraulic fracturing technology taking water-based fracturing fluid as a core cannot meet the exploitation requirements of gas reservoirs with high adsorption and high reservoir bentonite content.
The anhydrous fracturing technology changes the mode of the traditional water-based fracturing fluid, adopts carbon dioxide or nitrogen and the like in different phases as the fracturing fluid, and utilizes gas or high-pressure gas formed by vaporization to fracture a reservoir. The liquid carbon dioxide temperature is-37 ℃ and there is a liquid-to-gas volume ratio of 1:557 at 0 ℃ so that a greater gas pressure can be generated. The adoption of liquid carbon dioxide as the fracturing fluid has the following advantages: 1. the liquid carbon dioxide has lower liquid temperature than the coal rock, and can generate obvious heat exchange with the coal rock when contacting the coal rock, so that the temperature of the coal rock is reduced, and the higher temperature distribution in the coal rock can form a temperature gradient in a certain range around a drill hole, so that temperature stress can be induced; 2. in the process of reducing the temperature of the coal rock, if the coal rock contains free water, the free water can be solidified into ice under the condition of negative temperature, 9% volume expansion occurs in bedding or pores, and the formed ice body is wedged into a weak surface of the coal rock to cause the nucleation, expansion and extension of microcracks in the coal rock; 3. high-pressure gas formed by liquid carbon dioxide in liquid-gas phase change can cause high-pressure gas impact on coal rocks under the high-sealing condition of drilling, and when the high-pressure gas exceeds the compressive strength of the coal rocks, large cracks can be formed; 4. the carbon dioxide has high adsorbability, can displace the coal bed gas in an adsorption state, has a good displacement effect, and can realize dual functions of fracturing and displacement. However, the existing liquid carbon dioxide fracturing technology is limited to single high-capacity injection, and the aim of fracturing is fulfilled by means of instantaneously formed high-pressure gas. The mode is not suitable for coal mines in frozen soil or frozen rock areas in plateau cold regions, because the frozen soil or frozen rock in plateau cold regions is influenced by seasonal alternation, water in soil bodies or rocks is frozen into ice in autumn and winter, ice body thawing occurs under the action of high temperature in spring and summer, the self strength in the medium is greatly weakened by a freezing-thawing action process in a certain period, so that the medium is seriously degraded, and the crushing degree of the medium is finally increased. And the action period of the frozen soil in the cold region is too long, and the medium damage needs a longer time spatial and temporal evolution process. Therefore, more cracks exist in the coal seam, in the process of cracking the liquid carbon dioxide, the coal seam drilled holes cannot be effectively sealed at present, further, the gasified carbon dioxide gas injected into the drilled holes can escape from some existing cracks, the gasification pressure in the drilled holes is reduced, and finally the instant gasification impact fracturing effect on the coal seam at the deep part of the drilled holes cannot be realized, and the existing mode only carries out single large-capacity injection, and due to the characteristics of frozen soil or frozen rock in a plateau cold region, the existing mode cannot realize poor sealing effect of the drilled holes, and simultaneously only carries out the instant fracturing process of single injection to realize better coal seam permeability increasing effect, so how to provide a method can effectively seal the inside of the fractured drilled holes, and simultaneously can continuously realize the dual cracking effects of low-temperature freezing and phase change expansion of the liquid carbon dioxide, finally, the permeability of the coal bed gas reservoir is effectively improved, and the method is one of research directions of the industry.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a permeability increasing device and method for a coal bed gas reservoir by circulating and fracturing liquid carbon dioxide, which can effectively seal the inside of a fracturing drill hole, can continuously realize the double fracturing effects of low-temperature freezing and phase change expansion of the liquid carbon dioxide, and finally effectively improve the permeability of the coal bed gas reservoir.
In order to achieve the purpose, the invention adopts the technical scheme that: a liquid carbon dioxide circulation fracturing coal bed gas reservoir permeability increasing device comprises an inner pressure-resistant hole packer, an outer pressure-resistant hole packer, a grouting pipe, a fracturing pipe, a current limiter, a negative temperature current divider, a grouting pump, a slurry tank body, a liquid injection pump, a return pipeline, a liquid carbon dioxide storage tank, a multi-stage condenser and an air compressor;
the inner pressure-resistant hole packer and the outer pressure-resistant hole packer are both arranged in the fracturing drill hole, one end of the grouting pipe penetrates through the outer pressure-resistant hole packer and is positioned between the inner pressure-resistant hole packer and the outer pressure-resistant hole packer, the other end of the grouting pipe is connected with an outlet of a grouting pump, and an inlet of the grouting pump is connected with the slurry tank body through a pipeline;
the outlet of the air compressor is connected with the inlet of the multistage condenser through a pipeline, the outlet of the multistage condenser is connected with the inlet of a liquid carbon dioxide storage tank through a pipeline, the outlet of the liquid carbon dioxide storage tank is connected with the inlet of a liquid injection pump through a liquid carbon dioxide pipeline, the outlet of the liquid injection pump is connected with one end of a transmission pipe, the other end of the transmission pipe is connected with one end of a fracturing pipe through a pipe hoop, the other end of the fracturing pipe sequentially penetrates through an outer pressure-resistant hole packer and an inner pressure-resistant hole packer to extend into a fracturing drill hole, a negative temperature shunt and a current limiter are arranged on the transmission pipe, and one port of the current limiter is connected with the pipeline between the air compressor and the multistage condenser through a return pipeline and a return tee joint; one port of the negative temperature shunt is connected with the grouting pipe through the transmission branch pipe and the tee joint.
Further, a second check valve is arranged on a transmission pipe between the negative temperature shunt and the current limiter, and the inlet of the second check valve faces the negative temperature shunt; the first check valve is arranged on the transmission branch pipe, and the inlet of the first check valve faces the negative temperature flow divider. The additional check valve can make the fluid flow according to single direction, prevents the adverse current.
Furthermore, a safety valve is installed on the liquid carbon dioxide storage tank, a first pressure gauge is installed on the transmission branch pipe, and a second pressure gauge is installed on the fracturing pipe. Can prevent that too big emergence of pressure from being dangerous through setting up the relief valve, set up the manometer in addition and can carry out the real-time supervision of pressure to required position.
The working method of the coal bed gas reservoir permeability increasing device adopting the liquid carbon dioxide cyclic fracturing comprises the following specific steps:
step 1: drilling a plurality of drilling hole combinations in advance by using a drilling machine to a coal bed gas reservoir in frozen soil or frozen rock areas, wherein each drilling hole combination comprises 1 fracturing drilling hole and 2-4 monitoring drilling holes, and the monitoring drilling holes are uniformly distributed by taking the fracturing drilling holes as centers;
step 2: the installation and the layout of the permeability increasing device of the coal bed methane reservoir stratum fractured by the liquid carbon dioxide circulation are finished, so that the inner pressure-resistant hole packer and the outer pressure-resistant hole packer respectively plug the fracturing drill hole; in the initial state, the first one-way valve and the second one-way valve are both in a closed state;
and step 3: mixing porous aggregate with carbon dioxide adsorption characteristic with water to form slurry, putting the formed slurry into a slurry tank body, starting a grouting pump, injecting the slurry into a fracturing borehole between an inner pressure-resistant hole packer and an outer pressure-resistant hole packer through a grouting pipe, continuously injecting the slurry until the pressure value in the grouting pipe reaches a set value through a first pressure gauge, stopping grouting and maintaining the pressure for 30 min;
and 4, step 4: after pressure maintaining is completed, a grouting pump is closed and a first one-way valve is opened, a carbon dioxide gas supply pipeline is connected with an air compressor at the moment, the air compressor is started, the carbon dioxide gas is compressed by the air compressor, compressed air flows through a multistage condenser to be liquefied to form liquid carbon dioxide, the liquid carbon dioxide enters a liquid injection pump and is pressurized by a liquid injection pump, high-pressure liquid carbon dioxide passes through a negative temperature flow divider, the first one-way valve and a grouting pipe and is injected into a fracturing drill hole between an inner pressure-resistant hole packer and an outer pressure-resistant hole packer, heat exchange is carried out between the liquid carbon dioxide and water in slurry at the moment, the temperature of the water is rapidly reduced to form ice to increase the volume, the liquid carbon dioxide is gasified after heat exchange, the gasified carbon dioxide gas is absorbed by porous aggregates to further expand the volume of the porous aggregates, and under the dual effects of the volume expansion of the porous aggregates and the volume increase of water phase changed into ice, self-pressurization hole sealing is realized for a fracturing drill hole between the inner pressure-resistant hole sealing device and the outer pressure-resistant hole sealing device to form a hole sealing section;
and 5: after the completion, closing the first one-way valve, opening the second one-way valve, keeping the working state of the air compressor, the multistage condenser and the liquid injection pump, injecting liquid carbon dioxide into the fracturing drill hole plugged at the hole sealing section through the second one-way valve, the current limiter and the fracturing pipe in sequence, stopping injecting liquid after the liquid injection time is reached, closing the second one-way valve to maintain the pressure of the fracturing drill hole, performing heat exchange between the liquid carbon dioxide and surrounding coal rocks at the moment to suddenly reduce the temperature of the coal rocks, and forming an obvious temperature gradient in the coal rocks during the heat exchange process, thereby inducing the generation of temperature stress to degrade the coal rock mass, simultaneously gasifying the liquid carbon dioxide after heat exchange, continuously increasing the air pressure in the fracturing drill hole due to the plugging action of the hole sealing section of the gasified carbon dioxide gas, thereby completing the fracturing process of the coal rock mass once under the dual functions of temperature stress and high-pressure gas impact;
and 6: after the pressure is maintained for 30min, opening a second one-way valve, completing the fracturing process again according to the set liquid injection time, repeating the circulation in such a way, stopping the circulating liquid injection process until the concentration of the carbon dioxide gas monitored in each monitoring drill hole exceeds 15%, and completing the permeability increasing process of the coal bed gas reservoir;
and 7: and (3) sealing each monitoring drill hole, and then merging each monitoring drill hole and the fracturing pipe into a coal bed gas extraction network together to perform negative pressure extraction.
Further, the minimum ultimate strength of the plugged section formed within the fracture borehole is:
wherein λ is the friction coefficient of the wall surface of the fracturing bore hole, L General hole sealing section Total length of hole sealing for fracturing CO2 Is CO 2 Injection pressure of (2), S End section For fracturing the cross-sectional area of the borehole, P Hole packer Is the pressure in the hole packer, S Surface area Is the cross-sectional area of the hole packer, L Grouting section Distance, P, of hole sealing and grouting section for fracturing Aggregate slurry Is the grouting pressure in the grouting section.
Compared with the prior art, the method adopts a mode of combining the sealing effect of the reinforced hole sealing section, the temperature stress of the liquid carbon dioxide and the air pressure impact of the carbon dioxide gas, wherein the low-temperature phase change characteristic of the liquid carbon dioxide can cause coal rock deterioration to a greater extent, and the permeability of the coal rock is greatly improved. On one hand, carbon dioxide is injected into the porous aggregate slurry rich in carbon dioxide adsorption, so that the porous aggregate can be stimulated to absorb the carbon dioxide to the maximum extent, the volume of the porous aggregate is expanded to realize secondary self-pressurization hole sealing of the fracturing drill hole, and the high sealing performance of the drill hole is greatly improved. On the other hand, the low-temperature liquid carbon dioxide can exchange heat with the coal rocks, so that the temperature of the coal rocks suddenly drops and the coal rocks are vaporized and pressurized by the low-temperature liquid carbon dioxide. An obvious temperature gradient is easily formed in the coal rock body in the heat exchange process, so that the generation of temperature stress is induced, and high-pressure gas formed by gasification can also cause high-pressure impact on the coal rock body. The circulating injection mode overcomes the defects of insufficient pressure and the like of the traditional single injection mode, and the circulating freezing-thawing process of frozen soil or a frozen rock area per se and the multi-time temperature reduction process during low-temperature carbon dioxide circulating injection are utilized to enable the coal rock matrix to circularly contract and expand, so that fatigue damage is continuously accumulated in the coal rock, the strength of the coal rock is weakened, when the damage is accumulated to a certain degree, the yield strength of a degraded coal sample is reduced to the gas pressure after liquid carbon dioxide gasification, a large number of cracks are derived in the coal rock, the problems of gas pressure attenuated due to crack expansion and poor sealing performance of the frozen soil or the frozen rock area per se can be continuously compensated through the high sealing performance of a hole sealing section and the circulating injection mode, and the crack extension degree and the communication complexity are increased. And finally, the acidizing environment formed by the carbon dioxide and the water after fracturing is finished can realize blockage removal, the connectivity of a coal bed gas flow channel is promoted, the circularly injected carbon dioxide gas can displace the coal bed gas to the maximum extent, and adsorption saturation is realized. The method is simple to operate, can realize the efficient extraction of the coal bed gas in the frozen soil or rock area, can effectively seal and store the carbon dioxide gas, and realizes the dual effects of fracturing and sealing.
Drawings
FIG. 1 is a schematic view of the overall layout structure of the present invention;
FIG. 2 is a schematic structural view of a sealing section according to the present invention;
FIG. 3 is a schematic view of the position of the drilling assembly of the present invention;
fig. 4 is a sectional view taken along line a-a of fig. 3.
In the figure: 1-a coal bed methane reservoir; 2-fracturing the borehole; 3-monitoring the borehole; 4-fracturing the tube; 5-inner pressure-resistant hole packer; 6-outer pressure-resistant hole packer; 7-porous aggregate slurry; 8-grouting pipe; 9-a three-way joint; 10-a first pressure gauge; 11-a pipe clamp; 12-a flow restrictor; 13-a second one-way valve; 14-a first one-way valve; 15-negative temperature shunt; 16-grouting pump; 17-slurry tank; 18-a priming pump; 19-liquid carbon dioxide line; 20-return line; 21-safety valve; 22-a liquid carbon dioxide storage tank; 23-a multi-stage condenser; 24-a return tee; 25-air compressor.
Detailed Description
The present invention will be further explained below.
As shown in fig. 1, the permeability increasing device for the liquid carbon dioxide circulation fracturing coal bed methane reservoir comprises an inner pressure-resistant hole packer 5, an outer pressure-resistant hole packer 6, a grouting pipe 8, a fracturing pipe 4, a current limiter 12, a negative temperature current divider 15, a grouting pump 16, a slurry tank body 17, a liquid injection pump 18, a return pipeline 20, a liquid carbon dioxide storage tank 22, a multistage condenser 23 and an air compressor 25;
the inner pressure-resistant hole packer 5 and the outer pressure-resistant hole packer 6 are both arranged in the fracturing borehole 2, one end of a grouting pipe 8 penetrates through the outer pressure-resistant hole packer 6 and is positioned between the inner pressure-resistant hole packer 5 and the outer pressure-resistant hole packer 6, the other end of the grouting pipe 8 is connected with an outlet of a grouting pump 16, and an inlet of the grouting pump 16 is connected with a slurry tank body 17 through a pipeline;
the outlet of the air compressor 25 is connected with the inlet of the multistage condenser 23 through a pipeline, the outlet of the multistage condenser 23 is connected with the inlet of the liquid carbon dioxide storage tank 22 through a pipeline, the outlet of the liquid carbon dioxide storage tank 22 is connected with the inlet of the liquid carbon dioxide injection pump 18 through a liquid carbon dioxide pipeline 19, the outlet of the liquid injection pump 18 is connected with one end of a transmission pipe, the other end of the transmission pipe is connected with one end of the fracturing pipe 4 through a pipe hoop 11, the other end of the fracturing pipe 4 sequentially penetrates through the outer pressure-resistant hole packer 6 and the inner pressure-resistant hole packer 5 to extend into the fracturing drill hole 2, the negative temperature shunt 15 and the flow restrictor 12 are arranged on the transmission pipe, and one port of the flow restrictor 12 is connected with a pipeline between the air compressor 25 and the multistage condenser 23 through a return pipeline 20 and a return tee 24; one port of the negative temperature shunt 15 is connected with the grouting pipe 8 through the transmission branch pipe and the three-way joint 9; a second one-way valve 13 is arranged on a transmission pipe between the negative temperature shunt 15 and the flow restrictor 12, and the inlet of the second one-way valve 13 faces the negative temperature shunt 15; a first one-way valve 14 is arranged on the transmission branch pipe, and the inlet of the first one-way valve 14 faces the negative temperature flow divider. The additional check valve can make the fluid flow according to single direction, prevents the adverse current. A safety valve 21 is arranged on the liquid carbon dioxide storage tank 22, a first pressure gauge 10 is arranged on the transmission branch pipe, and a second pressure gauge is arranged on the fracturing pipe 4. The safety valve 21 can prevent danger caused by overlarge pressure, and the pressure gauge is additionally arranged to monitor the pressure at a required position in real time.
The inner pressure-resistant hole packer 5, the outer pressure-resistant hole packer 6, the three-way joint 9, the current limiter 12, the first one-way valve 14, the second one-way valve, the negative temperature current divider 15, the liquid injection pump 18, the safety valve 21, the multistage condenser 23 and the air compressor 25 are all existing equipment or parts and can be purchased in the market. The inner structure of the three-way joint 9 has a stepped aperture, only liquid carbon dioxide fluid is allowed to enter the grouting pipe 8, and the grout cannot flow back; the liquid injection pump 18 is an explosion-proof and reciprocating pump body for mining, and the pumping flow and pressure can be adjusted as required; the grouting pump 16 is a diaphragm pneumatic type grouting pump, and high-pressure air flow is used as a power source. The grouting pipe 8 and the liquid carbon dioxide pipeline 19 both use a mining high-pressure rubber pipe, and the outside of the liquid carbon dioxide pipeline 19 is wrapped with a heat-insulating material; the pressure limiting threshold of the negative temperature shunt 15 is 15MPa, and when the actual pressure in the liquid injection process exceeds the threshold, the shunt valve can be automatically adjusted.
The working method of the coal bed gas reservoir permeability increasing device adopting the liquid carbon dioxide circulation fracturing comprises the following specific steps:
step 1: drilling a plurality of drilling hole combinations in advance by using a drilling machine to a coal bed gas reservoir 1 in a frozen soil or frozen rock area, wherein each drilling hole combination comprises 1 fracturing drilling hole 2 and 4 monitoring drilling holes 3, and the monitoring drilling holes 3 are uniformly distributed by taking the fracturing drilling holes 2 as centers; the distance between each drilling hole combination is 3-5 m; the distance between the fracturing drill hole 2 and the monitoring drill hole 3 in the drill hole combination is 5-10 m;
step 2: the installation and the arrangement of the permeability increasing device of the coal bed gas reservoir fractured by the circulation of the liquid carbon dioxide are completed, so that the inner pressure-resistant hole packer 5 and the outer pressure-resistant hole packer 6 are used for plugging the fractured borehole 2 respectively; and the initial state first check valve 14 and the second check valve are both in a closed state;
and step 3: mixing porous aggregate with carbon dioxide adsorption characteristic with water to form slurry (wherein the porous aggregate is the existing material, the mixing proportion of the porous aggregate and the water is determined according to the expansion condition of the porous aggregate and the water), putting the formed slurry into a slurry tank body 17, then starting a grouting pump 16, injecting the slurry into a fracturing borehole 2 between an inner pressure-resistant hole packer 5 and an outer pressure-resistant hole packer 6 through a grouting pipe 8, and continuously injecting the slurry until the pressure value in the grouting pipe 8 reaches a set value through a first pressure gauge 10, stopping grouting and maintaining the pressure for 30 min;
and 4, step 4: after pressure maintaining is completed, the grouting pump 16 is closed and the first one-way valve 14 is opened, at the moment, a carbon dioxide gas supply pipeline is connected with the air compressor 25, the air compressor 25 is started, the carbon dioxide gas is compressed by the air compressor 25, the compressed air flows through the multistage condenser 23 to be liquefied to form liquid carbon dioxide, the liquid carbon dioxide enters the liquid injection pump 18 and is pressurized by the liquid injection pump 18, high-pressure liquid carbon dioxide passes through the negative temperature current divider 15, the first one-way valve 14 and the grouting pipe 8 and then is injected into the fracturing drill hole 2 between the inner pressure-resistant hole packer 5 and the outer pressure-resistant hole packer 6, at the moment, the liquid carbon dioxide and water in the slurry are subjected to heat exchange, the temperature of the water is rapidly reduced to form ice to increase the volume, the liquid carbon dioxide is gasified after the heat exchange, and the gasified carbon dioxide gas is absorbed by porous aggregate to further expand the volume of the porous aggregate, under the dual actions of volume expansion of porous aggregate and volume increase of water phase changed into ice, self-pressurization hole sealing of a fracturing drill hole between the inner pressure-resistant hole packer 5 and the outer pressure-resistant hole packer 6 is realized, and a hole sealing section is formed as shown in fig. 2; the minimum ultimate strength of the hole sealing section is as follows:
wherein λ is the friction coefficient of the wall surface of the fracturing drill hole, L General hole sealing section Total length of hole sealing for fracturing borehole, P CO2 Is CO 2 Injection pressure of S End section For fracturing the cross-sectional area of the borehole, P Hole packer Is the pressure in the hole packer, S Surface area Is the cross-sectional area of the hole packer, L Grouting section Distance, P, of hole sealing and grouting section for fracturing Aggregate slurry Is the grouting pressure in the grouting section. When the hole sealing section meets the condition, the plugging effect can be ensured, and the subsequent circulating fracturing effect is further improved.
And 5: after the completion, the first one-way valve 14 is closed, the second one-way valve is opened, the working states of the air compressor 25, the multistage condenser 23 and the liquid injection pump 18 are kept, liquid carbon dioxide is injected into the fracturing drill hole 2 plugged in the hole sealing section through the second one-way valve, the current limiter 12 and the fracturing pipe 4 in sequence, the liquid injection is stopped after the liquid injection time is reached, the second one-way valve is closed to maintain the pressure of the fracturing drill hole 2, at the moment, the liquid carbon dioxide and surrounding coal rocks exchange heat to suddenly reduce the temperature of the coal rocks, and an obvious temperature gradient can be formed in the coal rocks in the heat exchange process, thereby inducing the generation of temperature stress to degrade the coal rock mass, simultaneously gasifying the liquid carbon dioxide after heat exchange, leading the air pressure in the fracturing drill hole 2 to be continuously increased due to the plugging action of the hole sealing section of the gasified carbon dioxide gas, thereby completing the fracturing process of the coal rock mass once under the dual functions of temperature stress and high-pressure gas impact;
and 6: after the pressure is maintained for 30min, opening a second one-way valve, completing the fracturing process again according to the set liquid injection time, repeating the circulation in such a way, stopping the circulating liquid injection process until the concentration of the carbon dioxide gas monitored in each monitoring drill hole 3 exceeds 15%, and completing the anti-reflection process of the coal bed methane reservoir 1;
and 7: and (3) sealing each monitoring borehole 3, and then merging each monitoring borehole and the fracturing pipe 4 into a coal bed gas extraction network together for negative pressure extraction.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (2)
1. The working method of the permeability increasing device for the liquid carbon dioxide circulation fracturing coal bed gas reservoir is characterized in that the permeability increasing device for the liquid carbon dioxide circulation fracturing coal bed gas reservoir comprises an inner pressure-resistant hole packer, an outer pressure-resistant hole packer, a grouting pipe, a fracturing pipe, a current limiter, a negative temperature current divider, a grouting pump, a slurry tank body, a liquid injection pump, a backflow pipeline, a liquid carbon dioxide storage tank, a multi-stage condenser and an air compressor; the inner pressure-resistant hole packer and the outer pressure-resistant hole packer are both arranged in the fracturing drill hole, one end of the grouting pipe penetrates through the outer pressure-resistant hole packer and is positioned between the inner pressure-resistant hole packer and the outer pressure-resistant hole packer, the other end of the grouting pipe is connected with an outlet of a grouting pump, and an inlet of the grouting pump is connected with the slurry tank body through a pipeline; the outlet of the air compressor is connected with the inlet of the multistage condenser through a pipeline, the outlet of the multistage condenser is connected with the inlet of a liquid carbon dioxide storage tank through a pipeline, the outlet of the liquid carbon dioxide storage tank is connected with the inlet of a liquid injection pump through a liquid carbon dioxide pipeline, the outlet of the liquid injection pump is connected with one end of a transmission pipe, the other end of the transmission pipe is connected with one end of a fracturing pipe through a pipe hoop, the other end of the fracturing pipe sequentially penetrates through an outer pressure-resistant hole packer and an inner pressure-resistant hole packer to extend into a fracturing drill hole, a negative temperature shunt and a current limiter are arranged on the transmission pipe, and one port of the current limiter is connected with the pipeline between the air compressor and the multistage condenser through a return pipeline and a return tee joint; one port of the negative temperature shunt is connected with the grouting pipe through the transmission branch pipe and the tee joint; a second check valve is arranged on a transmission pipe between the negative temperature shunt and the current limiter, and the inlet of the second check valve faces the negative temperature shunt; the transmission branch pipe is provided with a first one-way valve, and the inlet of the first one-way valve faces the negative temperature shunt; the liquid carbon dioxide storage tank is provided with a safety valve, the transmission branch pipe is provided with a first pressure gauge, the fracturing pipe is provided with a second pressure gauge, and the method comprises the following specific steps:
step 1: drilling a plurality of drilling hole combinations in advance by using a drilling machine to a coal bed gas reservoir in frozen soil or frozen rock areas, wherein each drilling hole combination comprises 1 fracturing drilling hole and 2-4 monitoring drilling holes, and the monitoring drilling holes are uniformly distributed by taking the fracturing drilling holes as centers;
step 2: the installation and the layout of the permeability increasing device of the coal bed methane reservoir stratum fractured by the liquid carbon dioxide circulation are finished, so that the inner pressure-resistant hole packer and the outer pressure-resistant hole packer respectively plug the fracturing drill hole; in the initial state, the first one-way valve and the second one-way valve are both in a closed state;
and step 3: mixing porous aggregate with carbon dioxide adsorption property and water into slurry, placing the formed slurry into a slurry tank, starting a grouting pump, injecting the slurry into a fracturing drill hole between an inner pressure-resistant hole packer and an outer pressure-resistant hole packer through a grouting pipe, and continuously injecting the slurry until a pressure value in the grouting pipe reaches a set value through a first pressure gauge, stopping grouting and maintaining the pressure for 30 min;
and 4, step 4: after pressure maintaining is completed, a grouting pump is closed and a first one-way valve is opened, a carbon dioxide gas supply pipeline is connected with an air compressor at the moment, the air compressor is started, the carbon dioxide gas is compressed by the air compressor, compressed air flows through a multistage condenser to be liquefied to form liquid carbon dioxide, the liquid carbon dioxide enters a liquid injection pump and is pressurized by a liquid injection pump, high-pressure liquid carbon dioxide passes through a negative temperature flow divider, the first one-way valve and a grouting pipe and is injected into a fracturing drill hole between an inner pressure-resistant hole packer and an outer pressure-resistant hole packer, heat exchange is carried out between the liquid carbon dioxide and water in slurry at the moment, the temperature of the water is rapidly reduced to form ice to increase the volume, the liquid carbon dioxide is gasified after heat exchange, the gasified carbon dioxide gas is absorbed by porous aggregates to further expand the volume of the porous aggregates, and under the dual effects of the volume expansion of the porous aggregates and the volume increase of water phase changed into ice, self-pressurization hole sealing is realized for a fracturing drill hole between the inner pressure-resistant hole sealing device and the outer pressure-resistant hole sealing device to form a hole sealing section;
and 5: after the completion, closing the first one-way valve, opening the second one-way valve, keeping the working state of the air compressor, the multistage condenser and the liquid injection pump, injecting liquid carbon dioxide into the fracturing drill hole plugged at the hole sealing section through the second one-way valve, the current limiter and the fracturing pipe in sequence, stopping injecting liquid after the liquid injection time is reached, closing the second one-way valve to maintain the pressure of the fracturing drill hole, performing heat exchange between the liquid carbon dioxide and surrounding coal rocks at the moment to suddenly reduce the temperature of the coal rocks, and forming an obvious temperature gradient in the coal rocks during the heat exchange process, thereby inducing the generation of temperature stress to degrade the coal rock mass, simultaneously gasifying the liquid carbon dioxide after heat exchange, leading the air pressure in the fracturing drill hole to be continuously increased due to the plugging action of the hole sealing section of the gasified carbon dioxide gas, thereby completing the fracturing process of the coal rock mass under the dual actions of temperature stress and high-pressure gas impact;
step 6: after the pressure is maintained for 30min, opening a second one-way valve, completing the fracturing process again according to the set liquid injection time, repeating the circulation in such a way, stopping the circulating liquid injection process until the concentration of the carbon dioxide gas monitored in each monitoring drill hole exceeds 15%, and completing the permeability increasing process of the coal bed gas reservoir;
and 7: and (3) sealing the monitoring drill holes respectively, and then merging the monitoring drill holes and the fracturing pipe into the coal bed gas extraction network together to perform negative pressure extraction.
2. The working method of the liquid carbon dioxide circulation fracturing coal bed methane reservoir permeability increasing device of claim 1, wherein the minimum ultimate strength of the hole sealing section formed in the fracturing drill hole is as follows:
wherein λ is the friction coefficient of the wall surface of the fracturing bore hole, L General hole sealing section Total length of hole sealing for fracturing CO2 Is CO 2 Injection pressure of (2), S End section For fracturing the cross-sectional area of the borehole, P Hole packer Is the pressure in the hole packer, S Surface area Is the cross-sectional area of the hole packer, L Grouting section Distance, P, of hole sealing and grouting section for fracturing Aggregate slurry Is the grouting pressure in the grouting section.
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