CN114016984B - Heat injection yield increasing coalbed methane method based on hydraulic fracturing multi-branch horizontal well - Google Patents
Heat injection yield increasing coalbed methane method based on hydraulic fracturing multi-branch horizontal well Download PDFInfo
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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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2405—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection in association with fracturing or crevice forming processes
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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
- E21B43/006—Production of coal-bed methane
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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
- 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 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
- E21B43/2607—Surface equipment specially adapted for fracturing operations
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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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/10—Geothermal energy
Abstract
The invention discloses a heat injection yield increase coalbed methane method based on a hydraulic fracturing multi-branch horizontal well, which adopts a pulse injection mode to inject mixed liquor into a coalbed so that surfactant and nano metal particles in the mixed liquor fully contact with the inside of a crack, and the nano metal particles are adsorbed on the inner surface of the crack, and the surfactant fully reacts with the surface of the coal body to change the surface property of the coal body; thereby greatly improving the heat conduction capacity of the coal seam; then high-temperature high-pressure steam is injected into the branch well, the high-temperature high-pressure steam continuously impacts and presses and heats the cracks after entering the branch well, and the cracks of the coal bed are further expanded and developed after being subjected to the action of high temperature and high pressure; after the surfactant is used for preprocessing the coal bed, the liquid drops condensed in advance can not greatly influence the heat exchange efficiency of the subsequent steam, so that the subsequent steam can be ensured to be in direct contact with the nano metal particles, and finally, the heat transfer efficiency between the steam and the coal bed is continuously increased, and the yield of the coal bed gas is greatly increased.
Description
Technical Field
The invention relates to a method for increasing yield of coalbed methane, in particular to a method for increasing yield of coalbed methane by heat injection based on a hydraulic fracturing multi-branch horizontal well.
Background
Coalbed methane is unconventional natural gas and is also clean energy, the main component of the coalbed methane is methane, and the coalbed methane exists in the coalbed mainly in an adsorption state (more than 90%). However, coal bed gas generally has the characteristics of deep burial, low permeability, high density, high pressure, strong adsorptivity and the like at present, so that the coal bed gas exploitation efficiency is very low. In order to more effectively mine coalbed methane, reservoirs need to be modified so as to improve the permeability of the coalbed. The conventional reservoir reconstruction methods comprise hydraulic fracturing, gas driving technology, blasting technology and the like, however, due to the strong adsorption capacity of the coal bed gas, a large amount of coal bed gas still cannot be extracted in the coal in the later period of coal bed gas extraction, so that the single well yield of the coal bed gas well is reduced, and the single well yield of the coal bed gas well is difficult to effectively improve. At this time, the coal seam heat injection is a feasible method, because the adsorption capacity of the coal seam gas and the temperature of the reservoir are in an inverse relation, and the adsorption capacity of the coal seam gas is reduced by about 8 percent when the temperature of the coal seam is increased by 1 ℃. In addition, after the temperature of the coal is increased, the coal is subjected to thermal expansion, coal substrates are mutually extruded, new cracks are generated, and accordingly the permeability of the coal bed is increased.
Based on the above principles, injection of steam into coal seams is considered to be an economical and efficient method: the molecular energy of the water vapor is very high, and the water vapor can enter into the internal hole cracks of the coal; the steam is condensed after contacting with the coal, and the condensation heat exchange coefficient is far greater than that of other heat exchange modes such as heat conduction, etc., so that the temperature of the coal bed can be increased after the steam is injected into the coal bed, and the adsorption capacity of the coal bed gas can be reduced; in addition, since the adsorptivity of coal to water molecules is much greater than that of methane molecules, water vapor also has the effect of displacing methane. However, because of the poor thermal conductivity of the coal itself, for some coal seams with fewer cracks and compactness, if steam is directly injected, the steam is difficult to enter the deep part of the coal body, and finally effective heat exchange cannot be performed inside the coal body. Therefore, how to provide a method can pre-treat the coal bed, increase the crack and heat conduction capability of the coal, and further improve the heat exchange efficiency between the coal bed and the steam when the steam is injected subsequently, so as to realize rapid and large-scale improvement of the temperature of the coal bed, effectively promote desorption of the coal bed gas, and finally improve the yield of the coal bed gas, which is a research direction of the industry.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the heat injection yield increasing coalbed methane method based on the hydraulic fracturing multi-branch horizontal well, which can be used for pre-treating the coalbed, increasing the crack and heat conduction capacity of the coal, and further improving the heat exchange efficiency between the coalbed and the water vapor during the subsequent injection of the water vapor, thereby realizing the rapid and large-scale increase of the coalbed temperature, effectively promoting the desorption of the coalbed methane and finally improving the yield of the coalbed methane.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a heat injection yield increasing coalbed methane method based on hydraulic fracturing multi-branch horizontal well comprises the following specific steps:
A. assembling a heat injection yield increasing system: the heat injection yield increasing system comprises a steam generating station, a superheater, a first booster pump, a second booster pump, a negative pressure pump, a gas separator, a pulsation pressure controller, a mixing chamber, a nanoparticle storage tank, a surfactant storage tank, a packer, a water injection pipe and a steam injection pipe, wherein an outlet of the steam generating station is connected with an inlet of the superheater through a pipeline, an outlet of the superheater is connected with an inlet of the first booster pump through a pipeline, and an outlet of the first booster pump is connected with one end of the water injection pipe through a pipeline; the nano particle storage tank and the surfactant storage tank are respectively connected with an inlet of the mixing chamber through a pipeline, an outlet of the mixing chamber is connected with an inlet of the second booster pump through a pipeline, an outlet of the second booster pump is connected with one end of the steam injection pipe through a pipeline, and the pulsation pressure controller is used for controlling the pulsation pressure frequency and the pressure variation range of the second booster pump; the other end of the water injection pipe and the other end of the steam injection pipe extend into the main well to reach the inlet of the branch well, a packer is arranged on the other end of the water injection pipe and the other end of the steam injection pipe and used for sealing the inlet of the branch well, and a controllable pressure relief valve is arranged on the packer; then sealing the wellhead of the main well, wherein an inlet of the gas separator is connected with an outlet of the negative pressure pump through a pipeline, the inlet of the negative pressure pump is connected with the inside of the main well through a pipeline, a first one-way valve is arranged on the pipeline between the steam generating station and the superheater, and the inlet of the first one-way valve faces the steam generating station; a second one-way valve is arranged on a pipeline between the first booster pump and the superheater, and an inlet of the second one-way valve faces the superheater; a pipeline between the first booster pump and the water injection pipe is provided with a third one-way valve, and the inlet of the third one-way valve faces the first booster pump; a pipeline between the negative pressure pump and the main well is provided with a fourth one-way valve, and an inlet of the fourth one-way valve faces the main well; a fifth one-way valve is arranged on a pipeline between the second booster pump and the steam injection pipe, and the inlet of the fifth one-way valve faces the second booster pump; a sixth one-way valve is arranged on a pipeline between the second booster pump and the mixing chamber, and the inlet of the sixth one-way valve faces the mixing chamber; a seventh one-way valve is arranged on a pipeline between the nanoparticle storage tank and the mixing chamber, and the inlet of the seventh one-way valve faces the nanoparticle storage tank; an eighth one-way valve is arranged on a pipeline between the surfactant storage tank and the mixing chamber, and the inlet of the eighth one-way valve faces the surfactant storage tank; completing the assembly of the heat injection yield increasing system, and initially, closing all the one-way valves;
B. and the primary crack expansion and heat conduction capacity of the coal bed are improved: firstly opening an eighth one-way valve, injecting surfactant and water into a mixing chamber, wherein the water temperature is 25-30 ℃, opening a seventh one-way valve after the surfactant and the water are uniformly mixed, injecting nano metal particles, and then uniformly mixing the nano metal particles, the surfactant and the water to form a mixed solution; then opening a fifth one-way valve and a sixth one-way valve, and controlling the second booster pump to generate periodically-changing pulsating pressure through a pulsating pressure controller, wherein the frequency of the pulsating pressure is 20Hz, and the pressure change range is 0.5-3 MPa; injecting the mixed solution into a branch well through a water injection pipe, and then impacting primary cracks and secondary cracks originally existing in a coal bed after the mixed solution enters the branch well, so that the cracks are further expanded to generate new fine cracks, wherein nano metal particles in the mixed solution are adsorbed in the cracks of the coal bed after impacting and contacting the cracks, and meanwhile, a surfactant is attached to the surface of the coal bed to hydrophobically modify the surface of the coal bed; after the continuous process is carried out for 15-20 minutes, closing the fifth one-way valve to the eighth one-way valve, stopping the second booster pump, disconnecting the second booster pump from the water injection pipe, and discharging the residual mixed liquid in the branch well through the water suction pump and the water injection pipe, thereby completing the primary crack expansion of the coal seam and the improvement of the heat conduction capacity;
C. secondary crack extension and coalbed methane analysis are carried out on the coal bed: opening the first one-way valve to the third one-way valve, enabling the steam generation station, the superheater and the first booster pump to start working, enabling water to enter the steam generation station through the water filling port, enabling the steam generation station to generate steam with the temperature of 100-130 ℃, enabling the steam to enter the superheater, and heating the steam to be superheated steam with the temperature of 200-300 ℃; the superheated steam enters a first booster pump, the pressure of the superheated steam is increased to 5-8 Mpa to form high-temperature high-pressure steam, the high-temperature high-pressure steam is injected into a branch well through a steam injection pipe, the main cracks and the secondary cracks originally existing in the coal bed are impacted and pressurized and heated after the high-temperature high-pressure steam enters the branch well, and the coal bed cracks are further expanded and developed after being subjected to the action of high temperature and high pressure; because the nano metal particles in the cracks have better heat conduction capability, when high-temperature high-pressure steam enters the cracks, the heat exchange efficiency between the coal bed and the high-temperature high-pressure steam can be greatly improved, so that the high-temperature high-pressure steam can heat a larger range of coal beds, the high-temperature high-pressure steam can condense into water after heat exchange with the coal beds, the water wettability of coal is changed due to the action of a surfactant, the contact angle between the coal and the water is increased, and at the moment, condensed water forms liquid drops on the surfaces of the coal in a beaded mode, so that the heat exchange efficiency between the subsequent high-temperature high-pressure steam and the coal beds is further ensured;
D. pumping coal bed gas: after high-temperature high-pressure steam is continuously injected for 10-15 hours, stopping injection, closing all the one-way valves, stopping the operation of the steam generating station, the superheater and the first booster pump, and fully heating the coal bed when the high-temperature high-pressure steam further presses and expands and develops the cracks, wherein the adsorption of the coal bed on the coal bed gas can be reduced after the temperature of the coal bed is increased, so that the desorption of the coal bed gas is realized under the dual actions of the further expansion and development of the cracks of the coal bed and the temperature rise of the coal bed; simultaneously continuously monitoring the pressure in the branch well through a controllable pressure relief valve, discharging condensed water out of the branch well through a water injection pipe after the pressure is reduced to below 0.5MPa, finally opening the controllable pressure relief valve and a fourth one-way valve, starting a negative pressure pump to pump the mixed gas of redundant steam and coalbed methane, enabling the mixed gas to enter a gas separator through the negative pressure pump, separating in the gas separator, recycling the redundant steam after condensing and purifying, and storing the separated coalbed methane in a gas storage tank;
E. circularly treating and continuously pumping coal bed gas: and (3) continuously extracting the coalbed methane until the pressure in the branch well monitored by the controllable pressure relief valve is reduced to below 0.08MPa and is continued for 10 hours, stopping extracting, repeating the steps (B) to (D) again, continuously extracting the coalbed methane, detecting the content of the coalbed methane in the mixed gas, repeating the steps for a plurality of times until the content of the coalbed methane in the mixed gas is not increased after one-time coalbed methane desorption treatment is completed, and stopping the coalbed methane extraction work of the well.
Further, the mass ratio of nano-metal particles to water in the mixing chamber was 1:10. The surfactant is nonionic surfactant OP-10 or is formed by compounding cationic surfactant YS-1, fluorocarbon surfactant FS-2 and nonionic surfactant FS-1.
Further, the controllable pressure relief valve is an electric pressure relief valve with a gas pressure sensor.
Further, the nano metal particles are Fe 3 O 4 Nanoparticles or CuO nanoparticles. The nano metal particles have better heat conduction performance, stronger adsorptivity and higher impact performance than water molecules, so that the nano metal particles can improve the impact effect of the mixed liquid on cracks when the mixed liquid impacts the cracks of the coal seam, and can be adsorbed in the cracks after impact, thereby greatly improving the heat conduction capability of the coal seam.
Compared with the prior art, the mixed liquid is injected into the coal seam in a pulse injection mode, so that the surfactant and the nano metal particles in the mixed liquid can fully contact with the inside of the crack, so that the nano metal particles are adsorbed on the inner surface of the crack, and the surfactant fully reacts with the surface of the coal body to change the surface property of the coal body; the nano metal particles have better heat conduction performance, stronger adsorptivity and higher impact performance than water molecules, so that when mixed liquid is used for carrying out pulsation impact on the coal seam cracks, the nano metal particles carry out better pulsation impact on the existing cracks in the coal seam, so that fatigue damage is generated, the cracks are easier to expand and extend, a large-range crack network is formed, when steam is injected in the follow-up process, the steam can heat the coal seam in a larger range through the cracks, and meanwhile, the steam can be adsorbed in the cracks after impact, so that the heat conduction capability of the coal seam is greatly improved; then injecting high-temperature high-pressure steam into the branch well, continuously impacting and pressurizing and heating main cracks and secondary cracks originally existing in the coal seam after the high-temperature high-pressure steam enters the branch well, and further expanding and developing the coal seam cracks after the coal seam cracks are subjected to the action of high temperature and high pressure; the nano metal particles in the cracks have better heat conduction capability, when high-temperature and high-pressure steam enters the cracks, the heat exchange efficiency between the coal bed and the high-temperature and high-pressure steam can be greatly improved, the high-temperature and high-pressure steam can heat a larger range of coal beds, water can be condensed after the high-temperature and high-pressure steam exchanges heat with the coal beds, the wettability of the coal water is changed due to the action of the surfactant, the contact angle between the coal and the water is increased, at the moment, the condensed water forms liquid drops on the surface of the coal in a beaded mode, and the heat transfer coefficient of the beaded condensation is 5-10 times greater than that of the membranous condensation, so that the heat exchange efficiency of the follow-up steam cannot be greatly influenced by the liquid drops after the coal beds are pretreated by the surfactant, the condensate water cannot cover the nano metal particles on the surface, the follow-up steam can be guaranteed to be in direct contact with the nano metal particles, the heat transfer efficiency between the steam and the coal beds is finally continuously increased, and the part of the stronger coalbed gas can be finally desorbed, so that the adsorptivity of coalbed gas is greatly increased.
Drawings
FIG. 1 is a schematic diagram of the overall layout of the heat injection stimulation system of the present invention;
FIG. 2 is a schematic illustration of the positional relationship of a controllable pressure relief valve, a packer, a water injection pipe and a steam injection pipe in the present invention;
FIG. 3 is a schematic diagram showing the adsorption of nanoparticles in a coal seam in a partially enlarged manner at A in FIG. 1;
FIG. 4 is a comparative schematic diagram of the different condensing modes of steam in a seam of coal according to the present invention;
fig. 5 is a schematic diagram of the pulsating pressure generated in the pulsating pressure controller of the present invention.
In the figure: 1-water filling port, 2-steam generating station, 3-1-first check valve, 3-2-second check valve, 3-3-third check valve, 3-4-fourth check valve, 3-5-fifth check valve, 3-6-sixth check valve, 3-7-seventh check valve, 3-8-eighth check valve, 4-superheater, 5-1-first booster pump, 5-2-second booster pump, 6-negative pressure pump, 7-gas separator, 8-pulsation pressure controller, 9-mixing chamber, 10-nanoparticle storage tank, 11-surfactant storage tank, 12-casing, 13-main well, 14-water injection pipe, 15-steam injection pipe, 16-branch well, 17-main slit, 18-secondary slit, 19-controllable pressure relief valve, 20-packer, 21-coal bed, 22-nano metal particles, 23-slit surface, 24-liquid film, 25-liquid droplet.
Detailed Description
The present invention will be further described below.
The invention is applied in the later period of exploitation of the conventional coal bed gas horizontal branch well under the condition that the hydraulic fracturing and drainage depressurization can not meet the production requirement and the yield of the coal bed gas can not be improved.
As shown in fig. 1, the specific steps of this embodiment are:
A. assembling a heat injection yield increasing system: the heat injection yield increasing system comprises a steam generating station 2, a superheater 4, a first booster pump 5-1, a second booster pump 5-2, a negative pressure pump 6, a gas separator 7, a pulsation pressure controller 8, a mixing chamber 9, a nanoparticle storage tank 10, a surfactant storage tank 11, a packer 20, a water injection pipe 14 and a steam injection pipe 15, wherein an outlet of the steam generating station 2 is connected with an inlet of the superheater 4 through a pipeline, an outlet of the superheater 4 is connected with an inlet of the first booster pump 5-1 through a pipeline, and an outlet of the first booster pump 5-1 is connected with one end of the water injection pipe 14 through a pipeline; the nanoparticle storage tank 10 and the surfactant storage tank 11 are respectively connected with an inlet of the mixing chamber 9 through pipelines, an outlet of the mixing chamber 9 is connected with an inlet of the second booster pump 5-2 through a pipeline, an outlet of the second booster pump 5-2 is connected with one end of the steam injection pipe 15 through a pipeline, and the pulsation pressure controller 8 is used for controlling the pulsation pressure frequency and the pressure variation range of the second booster pump 5-2; the other end of the water injection pipe 14 and the other end of the steam injection pipe 15 extend into the main well 13 to reach the inlet of the branch well 16, as shown in fig. 2, a packer 20 is arranged on the other end of the water injection pipe 14 and the other end of the steam injection pipe 15 and is used for sealing the inlet of the branch well 16, a controllable pressure relief valve 19 is arranged on the packer 20, and the controllable pressure relief valve 19 is an electric pressure relief valve with a gas pressure sensor; then sealing the wellhead of the main well 13, connecting the inlet of the gas separator 7 with the outlet of the negative pressure pump 6 through a pipeline, connecting the inlet of the negative pressure pump 6 with the inside of the main well 13 through a pipeline, arranging a first one-way valve 3-1 on the pipeline between the steam generating station 2 and the superheater 4, and leading the inlet of the first one-way valve 3-1 to face the steam generating station 2; a second one-way valve 3-2 is arranged on a pipeline between the first booster pump 5-1 and the superheater 4, and the inlet of the second one-way valve 3-2 faces the superheater 4; a third one-way valve 3-3 is arranged on a pipeline between the first booster pump 5-1 and the water injection pipe 14, and the inlet of the third one-way valve 3-3 faces the first booster pump 5-1; a fourth one-way valve 3-4 is arranged on a pipeline between the negative pressure pump 6 and the main well 13, and the inlet of the fourth one-way valve 3-4 faces the main well 13; a fifth one-way valve 3-5 is arranged on a pipeline between the second booster pump 5-2 and the steam injection pipe 15, and the inlet of the fifth one-way valve 3-5 faces the second booster pump 5-2; a sixth one-way valve 3-6 is arranged on a pipeline between the second booster pump 5-2 and the mixing chamber 9, and the inlet of the sixth one-way valve 3-6 faces the mixing chamber 9; a seventh one-way valve 3-7 is arranged on a pipeline between the nanoparticle storage tank 10 and the mixing chamber 9, and the inlet of the seventh one-way valve 3-7 faces the nanoparticle storage tank 10; an eighth one-way valve 3-8 is arranged on a pipeline between the surfactant storage tank 11 and the mixing chamber 9, and the inlet of the eighth one-way valve 3-8 faces the surfactant storage tank 11; completing the assembly of the heat injection yield increasing system, and initially, closing all the one-way valves;
the steam generating station 2, the superheater 4, the first booster pump 5-1, the second booster pump 5-2, the negative pressure pump 6, the gas separator 7, the pulsation pressure controller 8, the mixing chamber 9, the nanoparticle storage tank 10, the surfactant storage tank 11, the packer 20, the controllable pressure relief valve 19 and each one-way valve are all existing equipment or components; and each one-way valve is a one-way valve with a valve. Each one-way valve is used for ensuring that the gas or liquid flowing through the one-way valve can only flow in one direction after the valve is opened, and stopping the flow of the gas or liquid after the valve is closed.
B. And the primary crack expansion and heat conduction capacity of the coal bed are improved: firstly opening an eighth one-way valve 3-8, injecting surfactant and water into a mixing chamber 9, wherein the water temperature is 25-30 ℃, opening a seventh one-way valve 3-7 after the surfactant and the water are uniformly mixed, injecting nano metal particles, and then uniformly mixing the nano metal particles, the surfactant and the water to form a mixed solution; wherein, the mass ratio of the nano metal particles to the water is 1:10, and the surfactant can be a surfactant with an emulsifying effect such as a nonionic surfactant OP-10 or a compound of a plurality of surfactants such as a cationic surfactant YS-1, a fluorocarbon surfactant FS-2 and a nonionic surfactant FS-1, thereby achieving the effect of modifying the coal hydrophobicity; because the surface properties of different types of coals are greatly different, in order to determine the proportions (namely concentration values) of various surfactants and water, before practical use, a field coal sample is firstly taken, after the contact angle between the coals and the water is measured in a laboratory, a group of proportions which enable the contact angle between the coals and the water to be relatively large in amplitude are selected as the proportions of the surfactants and the water in the mixed solution. The nano metal particles 22 are Fe 3 O 4 Nanoparticles or CuO nanoparticles; as shown in fig. 3, the nano metal particles 22 have better heat conduction performance, stronger adsorptivity and higher impact performance than water molecules, so that when the mixed liquid impacts the coal seam cracks, the nano metal particles 22 can improve the impact effect of the mixed liquid on the cracks, and can be adsorbed in the cracks after impact, thereby greatly improving the heat conduction capability of the coal seam.
Then the fifth check valve 3-5 and the sixth check valve 3-6 are opened, and the second booster pump 5-2 is controlled by the pulsation pressure controller 8 to generate a periodically varying pulsation pressure, whereinThe pulsation pressure variation is schematically shown in fig. 5, and other pulsation pressure parameters have the following meanings: t-time, P-instantaneous pressure (pressure at each moment), T-period (here 0.05 s), P min Minimum pressure (minimum value of instantaneous pressure in one cycle, here 0.5 MPa), P max Maximum pressure (maximum instantaneous pressure in one cycle, here 3 MPa), P ave Average pressure (average value of pressure over time), P A Pressure amplitude (the difference between the maximum and minimum values of the pulsating pressure in one cycle, here 2.5 MPa);
injecting the mixed liquid into the branch well 16 through the water injection pipe 14, and then impacting the primary cracks 17 and the secondary cracks 18 originally existing in the coal seam 21 after the mixed liquid enters the branch well 16, so that the cracks are further expanded to generate new fine cracks, wherein nano metal particles 22 in the mixed liquid are adsorbed in the coal seam cracks after impacting and contacting the cracks, and meanwhile, a surfactant is attached to the surface of the coal seam to hydrophobically modify the surface of the coal seam; after the continuous process is carried out for 15-20 minutes, the fifth one-way valve 3-5 to the eighth one-way valve 3-8 are closed, the second booster pump 5-2 is stopped, the connection between the second booster pump 5-2 and the water injection pipe 14 is disconnected, and the residual mixed liquid in the branch well 16 is discharged through the water suction pump and the water injection pipe 14, so that the primary crack expansion of the coal seam and the improvement of the heat conduction capacity are completed;
C. secondary crack extension and coalbed methane analysis are carried out on the coal bed: opening the first to third check valves 3-1 to 3-3, and starting the operation of the steam generation station 2, the superheater 4 and the first booster pump 5-1, allowing water to enter the steam generation station 2 through the water filling port 1, generating steam with a temperature of 100-130 ℃ by the steam generation station 2, allowing the steam to enter the superheater 4, and heating the steam to 200-300 ℃ superheated steam; the superheated steam enters the first booster pump 5-1, so that the pressure of the superheated steam is increased to 5-8 Mpa to form high-temperature high-pressure steam, the high-temperature high-pressure steam is injected into the branch well 16 through the steam injection pipe 15, and the main cracks 17 and the secondary cracks 18 which are originally existing in the coal bed are impacted and pressurized and heated after entering the branch well 15, so that the coal bed cracks are further expanded and developed after being subjected to the action of high temperature and high pressure; because the nano metal particles 22 in the cracks have better heat conduction capability, when high-temperature and high-pressure steam enters the cracks, the heat exchange efficiency between the coal seam 21 and the high-temperature and high-pressure steam can be greatly improved, so that the high-temperature and high-pressure steam can heat the coal seam 21 in a larger range, the high-temperature and high-pressure steam can condense into water after exchanging heat with the coal seam 21, the water wettability of the coal is changed due to the action of the surfactant, the contact angle between the coal and the water is increased, and at the moment, the condensed water forms liquid drops 25 on the surface of the coal in a beaded mode, so that the heat exchange efficiency of the subsequent high-temperature and high-pressure steam and the coal seam is further ensured;
as shown in fig. 4, if the coal body is not pretreated, after the water vapor condenses in the coal, the steam forms a liquid film 24 on the crack surface 23 in a film-like condensation manner due to the small contact angle between the coal and water, which hinders the heat transfer efficiency of the subsequent steam to the coal. After the coal body is treated with the surfactant, the water wettability of the coal is changed and the contact angle between the coal and water is increased, at which time the steam condenses in the form of beads on the coal surface, i.e. droplets 25 form on the coal surface. The heat transfer coefficient of bead condensation is 5-10 times greater than that of film condensation, so that after the coal layer 21 is pretreated by the surfactant, the liquid drops of the pre-condensation do not greatly affect the heat exchange efficiency of the subsequent steam, and the condensed water does not cover the nano metal particles 22 on the surface due to the liquid drop form, so that the subsequent steam can be ensured to be in direct contact with the nano metal particles 22, and finally, the heat transfer efficiency between the steam and the coal layer 21 is continuously increased. In addition, the steam condensate is in the form of liquid drops 25 and is not easy to be adsorbed on the surface of the crack, so that the crack is not blocked, and the liquid is easier to flow back.
D. Pumping coal bed gas: after high-temperature high-pressure steam is continuously injected for 10-15 hours, stopping injection, closing all check valves, stopping the steam generating station 2, the superheater 4 and the first booster pump 5-1, and fully heating the coal bed 21 while the high-temperature high-pressure steam further presses, expands and develops cracks, and the adsorption of the coal bed 21 to coal bed gas can be reduced after the temperature of the coal bed 21 is increased, so that desorption of the coal bed gas is realized under the dual effects of further expanding and developing the cracks of the coal bed and heating the coal bed; simultaneously, the pressure in the branch well 16 is continuously monitored through a controllable pressure relief valve 19, after the pressure is reduced to below 0.5MPa, condensed water is discharged out of the branch well 16 through a water suction pump, finally, the controllable pressure relief valve 19 and a fourth one-way valve 3-4 are opened, the negative pressure pump 6 is started to extract the mixed gas of redundant steam and coal bed gas, the mixed gas enters the gas separator 7 through the negative pressure pump 6, the gas separator 7 is used for separation, the redundant steam can be recycled after being condensed and purified, and the separated coal bed gas is stored in the gas storage tank;
E. circularly treating and continuously pumping coal bed gas: and (3) continuing to perform coal bed gas extraction until the pressure in the branch well 16 monitored by the controllable pressure relief valve 19 is reduced to below 0.08MPa for 10 hours, stopping extraction, repeating the steps B to D again, continuing to perform the coal bed gas extraction, detecting the content of the coal bed gas in the mixed gas, repeating the steps for a plurality of times until the content of the coal bed gas in the mixed gas is not increased after one-time coal bed gas desorption treatment is completed, and stopping the coal bed gas extraction work of the well.
The scheme of this embodiment only illustrates the treatment method of a single branch well 16, and for other branch wells 16, the same method is adopted for treatment, and multiple steam injection pipes 15 and water injection pipes 14 can be selected to be respectively placed in each branch well 16, then all the steam injection pipes and the water injection pipes are used for analysis and production increase of coalbed methane through the same heat injection production increase system, and several branch wells can be treated simultaneously, or after one branch well is treated, other branch wells can be treated.
The foregoing is only a preferred embodiment of the invention, it being 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 present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (4)
1. A heat injection yield increase coalbed methane method based on hydraulic fracturing multi-branch horizontal well is characterized by comprising the following specific steps:
A. assembling a heat injection yield increasing system: the heat injection yield increasing system comprises a steam generating station, a superheater, a first booster pump, a second booster pump, a negative pressure pump, a gas separator, a pulsation pressure controller, a mixing chamber, a nanoparticle storage tank, a surfactant storage tank, a packer, a water injection pipe and a steam injection pipe, wherein an outlet of the steam generating station is connected with an inlet of the superheater through a pipeline, an outlet of the superheater is connected with an inlet of the first booster pump through a pipeline, and an outlet of the first booster pump is connected with one end of the water injection pipe through a pipeline; the nano particle storage tank and the surfactant storage tank are respectively connected with an inlet of the mixing chamber through a pipeline, an outlet of the mixing chamber is connected with an inlet of the second booster pump through a pipeline, an outlet of the second booster pump is connected with one end of the steam injection pipe through a pipeline, and the pulsation pressure controller is used for controlling the pulsation pressure frequency and the pressure variation range of the second booster pump; the other end of the water injection pipe and the other end of the steam injection pipe extend into the main well to reach the inlet of the branch well, a packer is arranged on the other end of the water injection pipe and the other end of the steam injection pipe and used for sealing the inlet of the branch well, and a controllable pressure relief valve is arranged on the packer; then sealing the wellhead of the main well, wherein an inlet of the gas separator is connected with an outlet of the negative pressure pump through a pipeline, the inlet of the negative pressure pump is connected with the inside of the main well through a pipeline, a first one-way valve is arranged on the pipeline between the steam generating station and the superheater, and the inlet of the first one-way valve faces the steam generating station; a second one-way valve is arranged on a pipeline between the first booster pump and the superheater, and an inlet of the second one-way valve faces the superheater; a pipeline between the first booster pump and the water injection pipe is provided with a third one-way valve, and the inlet of the third one-way valve faces the first booster pump; a pipeline between the negative pressure pump and the main well is provided with a fourth one-way valve, and an inlet of the fourth one-way valve faces the main well; a fifth one-way valve is arranged on a pipeline between the second booster pump and the steam injection pipe, and the inlet of the fifth one-way valve faces the second booster pump; a sixth one-way valve is arranged on a pipeline between the second booster pump and the mixing chamber, and the inlet of the sixth one-way valve faces the mixing chamber; a seventh one-way valve is arranged on a pipeline between the nanoparticle storage tank and the mixing chamber, and the inlet of the seventh one-way valve faces the nanoparticle storage tank; an eighth one-way valve is arranged on a pipeline between the surfactant storage tank and the mixing chamber, and the inlet of the eighth one-way valve faces the surfactant storage tank; completing the assembly of the heat injection yield increasing system, and initially, closing all the one-way valves;
B. and the primary crack expansion and heat conduction capacity of the coal bed are improved: opening a seventh one-way valve and an eighth one-way valve, putting nano metal particles in a nano particle storage tank and a surfactant in a surfactant storage tank into a mixing chamber, injecting a certain amount of water into the mixing chamber, wherein the water temperature is 25-30 ℃, and then uniformly mixing the nano metal particles, the surfactant and the water in the mixing chamber to form a mixed solution; then opening a fifth one-way valve and a sixth one-way valve, and controlling the second booster pump to generate periodically-changing pulsating pressure through a pulsating pressure controller, wherein the frequency of the pulsating pressure is 20Hz, and the pressure change range is 0.5-3 MPa; injecting the mixed solution into a branch well through a water injection pipe, and then impacting primary cracks and secondary cracks originally existing in a coal bed after the mixed solution enters the branch well, so that the cracks are further expanded to generate new fine cracks, wherein nano metal particles in the mixed solution are adsorbed in the cracks of the coal bed after impacting and contacting the cracks, and meanwhile, a surfactant is attached to the surface of the coal bed to hydrophobically modify the surface of the coal bed; after the continuous process is carried out for 15-20 minutes, closing the fifth one-way valve to the eighth one-way valve, stopping the second booster pump, disconnecting the second booster pump from the water injection pipe, and discharging the residual mixed liquid in the branch well through the water suction pump and the water injection pipe, thereby completing the primary crack expansion of the coal seam and the improvement of the heat conduction capacity;
C. secondary crack extension and coalbed methane analysis are carried out on the coal bed: opening the first one-way valve to the third one-way valve, enabling the steam generation station, the superheater and the first booster pump to start working, enabling water to enter the steam generation station through the water filling port, enabling the steam generation station to generate steam with the temperature of 100-130 ℃, enabling the steam to enter the superheater, and heating the steam to be superheated steam with the temperature of 200-300 ℃; the superheated steam enters a first booster pump, the pressure of the superheated steam is increased to 5-8 Mpa to form high-temperature high-pressure steam, the high-temperature high-pressure steam is injected into a branch well through a steam injection pipe, the main cracks and the secondary cracks originally existing in the coal bed are impacted and pressurized and heated after the high-temperature high-pressure steam enters the branch well, and the coal bed cracks are further expanded and developed after being subjected to the action of high temperature and high pressure; because the nano metal particles in the cracks have better heat conduction capability, when high-temperature high-pressure steam enters the cracks, the heat exchange efficiency between the coal bed and the high-temperature high-pressure steam can be greatly improved, so that the high-temperature high-pressure steam can heat a larger range of coal beds, the high-temperature high-pressure steam can condense into water after heat exchange with the coal beds, the water wettability of coal is changed due to the action of a surfactant, the contact angle between the coal and the water is increased, and at the moment, condensed water forms liquid drops on the surfaces of the coal in a beaded mode, so that the heat exchange efficiency between the subsequent high-temperature high-pressure steam and the coal beds is further ensured;
D. pumping coal bed gas: after high-temperature high-pressure steam is continuously injected for 10-15 hours, stopping injection, closing all the one-way valves, stopping the operation of the steam generating station, the superheater and the first booster pump, and fully heating the coal bed when the high-temperature high-pressure steam further presses and expands and develops the cracks, wherein the adsorption of the coal bed on the coal bed gas can be reduced after the temperature of the coal bed is increased, so that the desorption of the coal bed gas is realized under the dual actions of the further expansion and development of the cracks of the coal bed and the temperature rise of the coal bed; simultaneously continuously monitoring the pressure in the branch well through a controllable pressure relief valve, discharging condensed water out of the branch well through a water injection pipe after the pressure is reduced to below 0.5MPa, finally opening the controllable pressure relief valve and a fourth one-way valve, starting a negative pressure pump to pump the mixed gas of redundant steam and coalbed methane, enabling the mixed gas to enter a gas separator through the negative pressure pump, separating in the gas separator, recycling the redundant steam after condensing and purifying, and storing the separated coalbed methane in a gas storage tank;
E. circularly treating and continuously pumping coal bed gas: and (3) continuously extracting the coalbed methane until the pressure in the branch well monitored by the controllable pressure relief valve is reduced to below 0.08MPa and is continued for 10 hours, stopping extracting, repeating the steps (B) to (D) again, continuously extracting the coalbed methane, detecting the content of the coalbed methane in the mixed gas, repeating the steps for a plurality of times until the content of the coalbed methane in the mixed gas is not increased after one-time coalbed methane desorption treatment is completed, and stopping the coalbed methane extraction work of the well.
2. The method for increasing the production of coal bed methane by injecting heat based on the hydraulic fracturing multi-branch horizontal well according to claim 1, wherein the mass ratio of nano metal particles to water in the mixing chamber is 1:10; the surfactant is nonionic surfactant OP-10 or is formed by compounding cationic surfactant YS-1, fluorocarbon surfactant FS-2 and nonionic surfactant FS-1.
3. The method for increasing the production of coal bed methane by injecting heat based on hydraulic fracturing a multi-branch horizontal well according to claim 1, wherein the controllable pressure relief valve is an electric pressure relief valve with a gas pressure sensor.
4. The method for increasing production of coalbed methane by injecting heat based on hydraulic fracturing multi-branch horizontal well as claimed in claim 1, wherein the nano metal particles are Fe 3 O 4 Nanoparticles or CuO nanoparticles.
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| CN102352747A (en) * | 2011-10-21 | 2012-02-15 | 中国石油天然气股份有限公司 | Pressure control injection yield increase method for coalbed methane well |
| CN104329055A (en) * | 2013-07-22 | 2015-02-04 | 郝占元 | Method for exploiting coal bed gas |
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| CN107387045A (en) * | 2017-07-20 | 2017-11-24 | 苏州大学 | A kind of coal bed gas heating exploitation system and recovery method |
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| CN104632270B (en) * | 2015-01-06 | 2016-11-16 | 中国矿业大学 | A kind of oscillating impulse formula high enegry gas fracturing and heat injection alternation mash gas extraction method |
| CN109025937B (en) * | 2018-06-22 | 2020-09-08 | 中国矿业大学 | Hydraulic slotting and multistage combustion shock wave combined fracturing coal body gas extraction method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102352747A (en) * | 2011-10-21 | 2012-02-15 | 中国石油天然气股份有限公司 | Pressure control injection yield increase method for coalbed methane well |
| CN104329055A (en) * | 2013-07-22 | 2015-02-04 | 郝占元 | Method for exploiting coal bed gas |
| CN105275443A (en) * | 2015-11-06 | 2016-01-27 | 中国矿业大学 | Coal mine underground high-power electric knock assisted hydraulic fracturing permeability enhancement method |
| CN107387045A (en) * | 2017-07-20 | 2017-11-24 | 苏州大学 | A kind of coal bed gas heating exploitation system and recovery method |
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