WO2024087979A1 - Method for enhancing coalbed methane exploitation and co2 storage in unworkable seam - Google Patents

Method for enhancing coalbed methane exploitation and co2 storage in unworkable seam Download PDF

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Publication number
WO2024087979A1
WO2024087979A1 PCT/CN2023/121008 CN2023121008W WO2024087979A1 WO 2024087979 A1 WO2024087979 A1 WO 2024087979A1 CN 2023121008 W CN2023121008 W CN 2023121008W WO 2024087979 A1 WO2024087979 A1 WO 2024087979A1
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Prior art keywords
methane
extraction
injection
valve
pipe
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PCT/CN2023/121008
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French (fr)
Chinese (zh)
Inventor
王传兵
丰安祥
童校长
周言安
杨洋
周韬
叶春辉
陈本良
曹腾飞
余旭
陈爱坤
翟成
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平安煤炭开采工程技术研究院有限责任公司
平安煤矿瓦斯治理国家工程研究中心有限责任公司
中国矿业大学
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Publication of WO2024087979A1 publication Critical patent/WO2024087979A1/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
    • E21F17/16—Modification of mine passages or chambers for storage purposes, especially for liquids or gases
    • 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
    • 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
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells

Definitions

  • the present invention relates to the field of coalbed methane development and CO2 geological storage, and in particular to a method for enhanced coalbed methane mining and CO2 storage in unmineable coal seams.
  • the present invention provides a method for enhanced coalbed methane extraction and CO2 storage in unmineable coal seams, which can inject a large amount of CO2 gas into deep unmineable coal seams and effectively improve the gas extraction rate of the coal seam.
  • the coal seam can have a good sealing effect after CO2 is stored, effectively reducing the CO2 storage cost.
  • the technical solution adopted by the present invention is: a method for enhancing coalbed methane mining and CO2 storage in unmineable coal seams, the specific steps are:
  • Drilling construction First determine the location of the unmineable coal seam, then drill from the ground through the rock layer and aquifer to the unmineable coal seam. The injection well and the drainage well are constructed separately. After the injection well is formed, the horizontal fracturing section is drilled from the deepest part of the injection well along the unmineable coal seam. After completion, the drilling work is stopped;
  • the pulsating CO2 foam passes through the injection pipe to reach the horizontal fracturing section to perform pulsating fracturing on the unmineable coal seam, thereby forming a fracture network around the horizontal fracturing section, and connecting with the drainage well through the fracture network, so that part of the CO2 gas enters the fracture.
  • the change of the methane concentration sensor value is observed in real time.
  • the foam generator and the high-pressure pulsating pump are turned off, and the CO2 is turned off at the same time. 2 valves, foaming agent valves, and injection valves complete the fracturing process of unmineable coal seams;
  • the coalbed methane in the drainage well also enters the CO2 -methane separator after passing through the extraction pipe and extraction pump. After the coalbed methane is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again.
  • the methane concentration sensor When the methane concentration drops below 0.5%, close the extraction. Extract valve 2 to complete the first stage of extraction;
  • CO2 injection to displace coalbed methane for enhanced extraction Open the CO2 valve and start the high-pressure pulsating pump again. CO2 gas is continuously injected into the horizontal fracturing section through the foam generator and the high-pressure pulsating pump. CO2 gas enters the fracture network and competes with coalbed methane for adsorption, thereby displacing coalbed methane from the coal seam to the drainage well. At the same time, the extraction pump is kept in continuous working state, forming injection-extraction simultaneous operation. At this time, the coalbed methane and CO2 gas mixture in the drainage well passes through the extraction pipe and the extraction pump and enters the CO2 -methane separator.
  • the methane After the mixed gas is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again.
  • the CO2 gas circulates continuously, causing the coal seam to absorb a large amount of CO2. 2 gas, and then continuously displace the desorbed coalbed methane to be extracted.
  • the pulsation frequency of the high-pressure pulsating pump is adjusted according to the pressure peak of the pressure gauge to maintain the pressure peak displayed on the pressure gauge within the range of 35-45MPa. Then, the concentration changes detected by the methane concentration sensor are observed.
  • CO2 storage The injection pipe and extraction pipe are taken out from the injection well and the drainage well respectively, and the injection well and the drainage well are sealed to seal the large amount of CO2 adsorbed in the unmineable coal seam.
  • the unmineable coal seam is a thin coal seam with a depth of more than 1000m, and there is an aquifer on the upper part of the coal seam that can serve as a natural barrier for CO2 geological storage, and the roof of the coal seam is mudstone or dense sandstone or sandy mudstone as a cap rock.
  • Using the above coal seam for CO2 geological storage can further ensure its storage effect and greatly reduce the possibility of CO2 escaping from the coal seam in the later stage.
  • the diameters of the injection well and the drainage well are both 100 mm, the distance between the two vertical wells is 150 m, the length of the injection pipe entering the horizontal fracturing section is 100 m, and the horizontal distance between the horizontal fracturing section and the drainage well is 15 m.
  • first packer and the second packer are both compression type Y441 packers with a sealing length of 5 to 8 meters. This type and length can meet the requirements of sealing injection wells and drainage wells.
  • the present invention has the following advantages:
  • the present invention uses CO2 foam as a fracturing fluid to expand the CO2 adsorption space, and through the pulsating fracturing method, it can solve the shortcomings of traditional hydraulic fracturing, such as large water consumption, difficulty in fracturing fluid backflow, and "water lock” damage, effectively reducing the inhibitory effect of water on CO2 geological storage, and pulse fracturing can reduce the coal body fracture pressure and expand reservoir transformation. range, improving the cracking effect of the coal body and providing a broad adsorption space for the storage of CO2 .
  • the CO2 gas in the CO2 foam can enter the fracture and compete with the adsorbed methane for adsorption, driving the adsorbed methane to desorb and discharge, thereby achieving the effect of driving the desorption of methane while forming a fracture network by fracturing, so that the coalbed methane is discharged and the CO2 gas is adsorbed in the coal seam.
  • the present invention starts the CO2 injection to displace the coalbed methane intensified extraction process when the methane concentration decreases.
  • the CO2 injection and coalbed methane extraction are carried out simultaneously, and the CO2 gas forms a closed cycle between the extraction system, the injection well, the unmineable coal seam and the drainage well, so that the CO2 gas is continuously injected into the various cracks in the coal seam, continuously displacing the adsorbed methane for desorption and discharge, and adsorbing the CO2 gas in the coal seam until the coalbed methane is extracted in large quantities, and a large amount of CO2 gas is also adsorbed in the coal seam.
  • a large amount of CO2 gas is injected into the unmineable coal seam for adsorption and retention, and the effect of displacing the coalbed methane to enhance the extraction efficiency is achieved.
  • the present invention seals the injection well and the drainage well. Due to the existence of the aquifer above the unmineable coal seam for storing CO2 and the rock layer with strong sealing properties as the cap layer, it is equivalent to adding two closed defense lines to the CO2 storage site, effectively preventing the escape of CO2 during the storage process, and providing a more stable storage environment for the geological storage of CO2 .
  • FIG1 is a schematic diagram of the overall layout of the present invention.
  • 1-foaming agent storage tank 2- CO2 storage tank; 3-foaming agent valve; 4- CO2 valve; 5-foam generator; 6-high-pressure pulsating pump; 7-pressure gauge; 8-injection valve; 9-first packer; 10-injection pipe; 11-injection well; 12-unmineable coal seam; 13-drainage well; 14-second packer; 15-extraction pipe; 16-first extraction valve; 17-extraction pump; 18-methane concentration sensor; 19- CO2 -methane separator; 20-methane storage tank; 21-methane valve; 22-second extraction valve; 23-connecting pipe; 24-horizontal fracturing section; 25-rock formation; 26-aquifer; P1-vertical drilling cut-off position of injection well; P2-end position of injection pipe; P3-construction cut-off position of horizontal fracturing section; P4-drilling cut-off position of drainage well; P5-initial position of packer; P6-end position of packer.
  • Drilling construction First determine the location of the unmineable coal seam 12, then drill from the ground through the rock layer 25 and the aquifer 26 In the unmineable coal seam 12, injection well 11 and drainage well 13 are constructed respectively, so that the injection well 11 and the drainage well 13 reach the P1 and P4 positions respectively.
  • the horizontal fracturing section 24 is drilled from the P1 position of the injection well 11 along the unmineable coal seam 12 to the P3 position, and the drilling work is stopped after completion; wherein the diameter of the injection well 11 and the drainage well 13 are both 100mm, the distance between the two vertical wells is 150m, the length of the injection pipe 11 entering the horizontal fracturing section 24 is 100m, and the horizontal distance between the horizontal fracturing section 24 and the drainage well 13 is 15m.
  • the use of such parameters for construction can ensure that after the subsequent fracturing forms a fracture network, the fracture network can connect the horizontal fracturing section 24 and the drainage well 13, thereby facilitating the subsequent CO2 injection to displace the enhanced extraction of coalbed methane.
  • one end of the injection pipe 10 is extended from the ground into the injection well 11 and reaches the P2 position of the horizontal fracturing section 24, the other end of the injection pipe 10 is outside the injection well 11, one end of the extraction pipe 15 is extended from the ground into the drainage well 13, and the other end is outside the drainage well 13;
  • the first packer 9 and the second packer 14 are respectively installed between the P5 and P6 positions at the same horizontal height in the injection well 11 and the drainage well 13 to seal the injection well 11 and the drainage well 13, wherein the first packer 9 and the second packer 14 are both compression type Y441 packers with a sealing length of 5 to 8 meters.
  • the outlet of the high-pressure pulsating pump 6 is connected to the other end of the injection pipe 10, the inlet of the high-pressure pulsating pump 6 is connected to the outlet of the foam generator 5, the two inlets of the foam generator 5 are respectively connected to the foaming agent storage tank 1 and the CO2 storage tank 2 through pipelines, the air suction port of the extraction pump 17 is connected to the other end of the extraction pipe 15, the exhaust port of the extraction pump 17 is connected to the air inlet of the CO2 -methane separator 19 through a pipeline, the two separation outlets of the CO2 -methane separator 19 are respectively connected to the CO2 storage tank 2 and the methane storage tank 20 through pipelines, the injection pipe 10 and the extraction pipe 15 are connected by a connecting pipe 23, the pipeline between the foaming agent storage tank 1 and the foam generator 5 is equipped with a foaming agent valve 3, and the pipeline between the CO2 storage tank 2 and the foam generator 5 is equipped with a CO2 2 valve
  • the pulsating CO2 foam passes through the injection pipe 10 to reach the horizontal fracturing section 24 to perform pulsating fracturing on the unmineable coal seam 12, thereby forming a fracture network around the horizontal fracturing section 24, and connecting with the drainage well 13 through the fracture network, so that part of the CO2 gas enters the fracture.
  • the methane concentration sensor 18 is used to observe in real time.
  • the coalbed methane in the drainage well 13 also enters the CO2 -methane separator 19 after passing through the extraction pipe 15 and the extraction pump 17.
  • the methane After the coalbed methane is separated in the CO2 -methane separator 19, the methane enters the methane storage tank 20 for storage, and the remaining CO2 gas enters the CO2-methane separator 19 again.
  • 2 Storage tank 2 during the continuous extraction process, observe the value of the methane concentration sensor 18, and when the methane concentration drops below 0.5%, close the extraction valve 22 to complete the first stage of extraction;
  • the methane After the mixed gas is separated in the CO2 -methane separator 19, the methane enters the methane storage tank 20 for storage, and the remaining CO2 gas enters the CO2 storage tank 2 again.
  • the CO2 gas circulates continuously, so that the coal seam absorbs a large amount of CO 2 gas, and then continuously displace the desorbed coalbed methane to be extracted.
  • the value changes of the pressure gauge 7 and the methane sensor 18 are observed.
  • the pulsation frequency of the high-pressure pulsating pump 6 is adjusted according to the pressure peak of the pressure gauge 7, so that the pressure peak displayed by the pressure gauge 7 is maintained within the range of 35-45MPa. Then, the concentration change detected by the methane concentration sensor 18 is observed.
  • CO2 storage The injection pipe 10 and the extraction pipe 15 are taken out from the injection well 11 and the drainage well 13 respectively, and the injection well 11 and the drainage well 13 are sealed, so as to seal a large amount of CO2 adsorbed in the unmineable coal seam.
  • the above-mentioned unmineable coal seam 12 is a thin coal seam with a depth of more than 1000m, and there is an aquifer 26 on the upper part of the coal seam which can serve as a natural barrier for CO2 geological storage.
  • the roof of the coal seam is mudstone or dense sandstone or sandy mudstone as a capping layer.

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Abstract

Disclosed in the present invention is a method for enhancing coalbed methane exploitation and CO2 storage in an unworkable seam. Firstly, an unworkable seam is fractured in a CO2 foam pulsation fracturing mode, thereby expanding the range of reservoir transformation, improving a coal body cracking effect, and providing a wide adsorption space for storage of CO2; then, a process of injecting CO2 for displacement of coalbed methane and extraction enhancement is started, and by performing CO2 injection and coalbed methane extraction simultaneously, CO2 gas forms a closed circulation among an extraction system, an injection well, the unworkable seam, and a drainage well, so that the CO2 gas is continuously injected into fractures in the seam, and adsorbed-state methane is continuously displaced, desorbed and discharged; and the CO2 gas is adsorbed in the seam until a large amount of coalbed methane is extracted, and then well sealing is performed on the unworkable seam to achieve storage of CO2. The methane gas extraction rate of the seam can be effectively improved, and a good sealing effect is achieved after CO2 is stored.

Description

一种不可采煤层强化煤层气开采及CO2封存的方法A method for enhancing coalbed methane mining and CO2 storage in unmineable coal seams 技术领域Technical Field
本发明涉及煤层气开发和CO2地质封存领域，特别是涉及一种不可采煤层强化煤层气开采及CO2封存的方法。The present invention relates to the field of coalbed methane development and CO2 geological storage, and in particular to a method for enhanced coalbed methane mining and CO2 storage in unmineable coal seams.
背景技术Background technique
CO2的地质封存作为一条具有巨大潜力的碳减排技术路径而受到人们的广泛关注。深部不可采含气煤层是封存CO2的理想目标地层，其上部一般具有天然密封盖层，能够有效防止CO2的逸散从而保证CO2地质封存的稳定性与持久性。同时，利用煤体对CO2优先吸附的特点，注入CO2能够更有效的驱替和置换煤层中的CH4。但是目前现有将CO2注入不可采煤层进行封存技术，其由于无法对深部煤层具有较好的压裂，进而无法在煤层内形成复杂的裂隙网络，导致CO2注入量较少，因此封存效果较差，如需进行大规模压裂则需要增加较大的设备，导致成本较高，另外现有的方式无法对煤层内的瓦斯气体进行有效抽采，故目前很少采用深部不可采煤层进行CO2封存，另外其他的CO2封存方式还存在封存时密封效果较差，导致后期CO2逸出，从而可能造成安全性的影响。因此如何提供一种方法，能将CO2气体大量注入深部不可采煤层内，同时能有效提高该煤层的瓦斯抽采率，另外煤层对CO2封存后能具有较好的密封效果，有效降低CO2封存成本，是本行业的研究方向之一。As a technical path for carbon emission reduction with great potential, geological storage of CO 2 has attracted widespread attention. Deep unmineable gas-bearing coal seams are ideal target strata for storing CO 2. They generally have natural sealing caprocks on top, which can effectively prevent the escape of CO 2 and thus ensure the stability and durability of CO 2 geological storage. At the same time, by taking advantage of the preferential adsorption of CO 2 by coal bodies, injecting CO 2 can more effectively displace and replace CH 4 in coal seams. However, the existing technology of injecting CO 2 into unmineable coal seams for storage is unable to achieve good fracturing of deep coal seams, and thus unable to form a complex fracture network in the coal seams, resulting in a small amount of CO 2 injection, so the storage effect is poor. If large-scale fracturing is required, larger equipment needs to be added, resulting in high costs. In addition, the existing methods cannot effectively extract gas in coal seams, so deep unmineable coal seams are rarely used for CO 2 storage. In addition, other CO 2 storage methods also have poor sealing effects during storage, resulting in the escape of CO 2 in the later stage, which may affect safety. Therefore, how to provide a method to inject a large amount of CO2 gas into deep unmineable coal seams, while effectively improving the gas extraction rate of the coal seams, and also to ensure that the coal seams have a better sealing effect after CO2 is sealed, thereby effectively reducing the CO2 storage cost, is one of the research directions of this industry.
发明内容Summary of the invention
针对上述现有技术存在的问题，本发明提供一种不可采煤层强化煤层气开采及CO2封存的方法，能将CO2气体大量注入深部不可采煤层内，同时能有效提高该煤层的瓦斯抽采率，另外煤层对CO2封存后能具有较好的密封效果，有效降低CO2封存成本。In response to the problems existing in the above-mentioned prior art, the present invention provides a method for enhanced coalbed methane extraction and CO2 storage in unmineable coal seams, which can inject a large amount of CO2 gas into deep unmineable coal seams and effectively improve the gas extraction rate of the coal seam. In addition, the coal seam can have a good sealing effect after CO2 is stored, effectively reducing the CO2 storage cost.
为了实现上述目的，本发明采用的技术方案是：一种不可采煤层强化煤层气开采及CO2封存的方法，具体步骤为：In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for enhancing coalbed methane mining and CO2 storage in unmineable coal seams, the specific steps are:
A、钻井施工：先确定不可采煤层的位置，然后从地面穿过岩层与含水层向不可采煤层 分别施工注入井和排采井，在注入井形成后，从注入井最深处沿不可采煤层走向钻取水平压裂段，完成后停止钻井工作；A. Drilling construction: First determine the location of the unmineable coal seam, then drill from the ground through the rock layer and aquifer to the unmineable coal seam. The injection well and the drainage well are constructed separately. After the injection well is formed, the horizontal fracturing section is drilled from the deepest part of the injection well along the unmineable coal seam. After completion, the drilling work is stopped;
B、布设CO2注入及煤层气抽采***：将注入管一端从地面伸入注入井并到达水平压裂段，注入管另一端处于注入井外部，抽采管一端从地面伸入排采井内、另一端处于排采井外部；注入井和排采井内分别装有第一封隔器和第二封隔器，分别对注入井和排采井进行密封；高压脉动泵的出口与注入管另一端连接，高压脉动泵的进口与泡沫发生器的出口连接，泡沫发生器的两个进口分别通过管路与发泡剂储存罐和CO2储存罐连接，抽采泵的抽气口与抽采管另一端连接，抽采泵的排气口通过管路与CO2-甲烷分离器的进气口连接，CO2-甲烷分离器的两个分离排出口分别通过管路与CO2储存罐和甲烷储存罐连接，注入管和抽采管之间通过连通管连接，所述发泡剂储存罐和泡沫发生器之间的管路上装有发泡剂阀门，CO2储存罐和泡沫发生器之间的管路上装有CO2阀门，注入管上装有压力表和注入阀门，抽采管上装有第一抽采阀门，连通管上装有第二抽采阀门，抽采泵和CO2-甲烷分离器之间的管路上装有甲烷浓度传感器，CO2-甲烷分离器和甲烷储存罐之间的管路上装有甲烷阀门，完成CO2注入及煤层气抽采***的布设；B. Laying out CO2 injection and coalbed methane extraction system: extending one end of the injection pipe from the ground into the injection well and reaching the horizontal fracturing section, the other end of the injection pipe is outside the injection well, one end of the extraction pipe is extended from the ground into the drainage well, and the other end is outside the drainage well; the injection well and the drainage well are respectively equipped with a first packer and a second packer to seal the injection well and the drainage well respectively; the outlet of the high-pressure pulsating pump is connected to the other end of the injection pipe, the inlet of the high-pressure pulsating pump is connected to the outlet of the foam generator, the two inlets of the foam generator are respectively connected to the foaming agent storage tank and the CO2 storage tank through pipelines, the air suction port of the extraction pump is connected to the other end of the extraction pipe, the exhaust port of the extraction pump is connected to the air inlet of the CO2 -methane separator through a pipeline, the two separation exhaust ports of the CO2 -methane separator are respectively connected to the CO2 storage tank and the methane storage tank through pipelines, the injection pipe and the extraction pipe are connected by a connecting pipe, a foaming agent valve is installed on the pipeline between the foaming agent storage tank and the foam generator, CO A CO2 valve is installed on the pipeline between the storage tank and the foam generator, a pressure gauge and an injection valve are installed on the injection pipe, a first extraction valve is installed on the extraction pipe, a second extraction valve is installed on the connecting pipe, a methane concentration sensor is installed on the pipeline between the extraction pump and the CO2 -methane separator, and a methane valve is installed on the pipeline between the CO2 -methane separator and the methane storage tank, completing the layout of the CO2 injection and coalbed methane extraction system;
C、对不可采煤层进行压裂：初始状态各个阀门均为关闭状态，打开第一抽采阀门、甲烷阀门、注入阀门、CO2阀门和发泡剂阀门，开启泡沫发生器、高压脉动泵、抽采泵和CO2-甲烷分离器，此时发泡剂储存罐中的发泡剂与CO2储存罐中的CO2进入泡沫发生器内进行混合发泡后形成CO2泡沫，接着CO2泡沫经过高压脉动泵施加脉动力后形成脉动CO2泡沫，然后脉动CO2泡沫经过注入管到达水平压裂段对不可采煤层进行脉动压裂，从而在水平压裂段周围形成裂隙网络，并通过裂隙网络与排采井连通，进而部分CO2气体进入裂隙内，在压裂过程中实时观测甲烷浓度传感器数值的变化情况；待甲烷浓度传感器数值出现明显变化且检测的甲烷浓度在10％以上时停止压裂工作，此时关闭泡沫发生器与高压脉动泵，同时关闭CO2阀门、发泡剂阀门、注入阀门，完成不可采煤层的压裂过程；C. Fracturing the unmineable coal seam: In the initial state, all valves are closed. Open the first extraction valve, methane valve, injection valve, CO2 valve and foaming agent valve, turn on the foam generator, high-pressure pulsating pump, extraction pump and CO2 -methane separator. At this time, the foaming agent in the foaming agent storage tank and the CO2 in the CO2 storage tank enter the foam generator for mixing and foaming to form CO2 foam. Then, the CO2 foam is subjected to pulsating force by the high-pressure pulsating pump to form pulsating CO2 foam. Then, the pulsating CO2 foam passes through the injection pipe to reach the horizontal fracturing section to perform pulsating fracturing on the unmineable coal seam, thereby forming a fracture network around the horizontal fracturing section, and connecting with the drainage well through the fracture network, so that part of the CO2 gas enters the fracture. During the fracturing process, the change of the methane concentration sensor value is observed in real time. When the methane concentration sensor value changes significantly and the detected methane concentration is above 10%, the fracturing work is stopped. At this time, the foam generator and the high-pressure pulsating pump are turned off, and the CO2 is turned off at the same time. 2 valves, foaming agent valves, and injection valves complete the fracturing process of unmineable coal seams;
D、对不可采煤层内的煤层气进行第一阶段抽采：打开甲烷阀门和第二抽采阀门，并持续保持抽采泵和CO2-甲烷分离器的工作状态开始进行煤层气抽采，此时裂隙网络内的煤层气部分从裂隙中析出至水平压裂段，还有部分煤层气从裂隙中析出至排采井内，接着水平压裂段内的煤层气依次经过注入管、连通管、抽采管和抽采泵后进入CO2-甲烷分离器内，同时排采井内的煤层气经过抽采管和抽采泵后也进入CO2-甲烷分离器，煤层气在CO2-甲烷分离器内经过分离后，甲烷进入甲烷储存罐内进行储存，其余CO2气体再次进入CO2储存罐，在持续抽采过程中观测甲烷浓度传感器的数值，待甲烷浓度降至0.5％以下时，关闭抽 采阀门二，完成第一阶段抽采；D. Carry out the first stage of extraction of coalbed methane in the unexcavable coal seam: open the methane valve and the second extraction valve, and keep the extraction pump and CO2 -methane separator in working state to start coalbed methane extraction. At this time, part of the coalbed methane in the fracture network is precipitated from the fracture to the horizontal fracturing section, and part of the coalbed methane is precipitated from the fracture to the drainage well. Then the coalbed methane in the horizontal fracturing section passes through the injection pipe, connecting pipe, extraction pipe and extraction pump in turn and enters the CO2 -methane separator. At the same time, the coalbed methane in the drainage well also enters the CO2 -methane separator after passing through the extraction pipe and extraction pump. After the coalbed methane is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again. During the continuous extraction process, observe the value of the methane concentration sensor. When the methane concentration drops below 0.5%, close the extraction. Extract valve 2 to complete the first stage of extraction;
E、CO2注入驱替煤层气强化抽采：打开CO2阀门，再次开启高压脉动泵，CO2气体经过泡沫发生器和高压脉动泵向水平压裂段持续注入CO2气体，CO2气体进入裂隙网络内与煤层气形成竞争吸附，从而驱替煤层气从煤层内解吸至排采井内，同时保持抽采泵的持续工作状态，形成注入-抽采同时作业，此时排采井内的煤层气和CO2气体混合气体经过抽采管和抽采泵后进入CO2-甲烷分离器，混合气体在CO2-甲烷分离器内经过分离后，甲烷进入甲烷储存罐内进行储存，其余CO2气体再次进入CO2储存罐，CO2气体持续循环，使煤层大量吸附CO2气体，进而持续驱替煤层气解吸被抽采，在该过程中观测压力表与甲烷传感器的数值变化，根据压力表的压力峰值调节高压脉动泵的脉动频率，使压力表显示的压力峰值维持在35～45MPa范围内，接着观察甲烷浓度传感器检测的浓度变化，待甲烷浓度降至0.1％停止注入和抽采，此时关闭CO2阀门、高压脉动泵、甲烷阀门、抽采泵和CO2-甲烷分离器，完成CO2注入驱替煤层气强化抽采过程；E. CO2 injection to displace coalbed methane for enhanced extraction: Open the CO2 valve and start the high-pressure pulsating pump again. CO2 gas is continuously injected into the horizontal fracturing section through the foam generator and the high-pressure pulsating pump. CO2 gas enters the fracture network and competes with coalbed methane for adsorption, thereby displacing coalbed methane from the coal seam to the drainage well. At the same time, the extraction pump is kept in continuous working state, forming injection-extraction simultaneous operation. At this time, the coalbed methane and CO2 gas mixture in the drainage well passes through the extraction pipe and the extraction pump and enters the CO2 -methane separator. After the mixed gas is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again. The CO2 gas circulates continuously, causing the coal seam to absorb a large amount of CO2. 2 gas, and then continuously displace the desorbed coalbed methane to be extracted. During this process, the value changes of the pressure gauge and the methane sensor are observed. The pulsation frequency of the high-pressure pulsating pump is adjusted according to the pressure peak of the pressure gauge to maintain the pressure peak displayed on the pressure gauge within the range of 35-45MPa. Then, the concentration changes detected by the methane concentration sensor are observed. When the methane concentration drops to 0.1%, the injection and extraction are stopped. At this time, the CO2 valve, the high-pressure pulsating pump, the methane valve, the extraction pump and the CO2 -methane separator are closed to complete the CO2 injection to displace the coalbed methane enhanced extraction process;
F、CO2封存：将注入管和抽采管分别从注入井和排采井中取出并对注入井和排采井进行密封，从而将不可采煤层内吸附的大量CO2进行封存。F. CO2 storage: The injection pipe and extraction pipe are taken out from the injection well and the drainage well respectively, and the injection well and the drainage well are sealed to seal the large amount of CO2 adsorbed in the unmineable coal seam.
进一步，所述不可采煤层为深度超过1000m的薄煤层，且煤层上部存在含水层能作为CO2地质封存的天然屏障，同时该煤层的顶板为泥岩或致密砂岩或砂质泥岩作为盖层。采用上述煤层进行CO2地质封存，能进一步保证其封存效果，大大降低后期CO2从煤层内逸出的可能性。Furthermore, the unmineable coal seam is a thin coal seam with a depth of more than 1000m, and there is an aquifer on the upper part of the coal seam that can serve as a natural barrier for CO2 geological storage, and the roof of the coal seam is mudstone or dense sandstone or sandy mudstone as a cap rock. Using the above coal seam for CO2 geological storage can further ensure its storage effect and greatly reduce the possibility of CO2 escaping from the coal seam in the later stage.
进一步，所述注入井与排采井的直径均为100mm，两竖直井间距为150m，注入管进入水平压裂段的长度为100m，水平压裂段与排采井的水平距离为15m。采用这种参数进行施工，能在后续压裂形成裂隙网络后，保证裂隙网络能将水平压裂段和排采井连通，从而便于后续CO2注入驱替煤层气强化抽采的工作。Furthermore, the diameters of the injection well and the drainage well are both 100 mm, the distance between the two vertical wells is 150 m, the length of the injection pipe entering the horizontal fracturing section is 100 m, and the horizontal distance between the horizontal fracturing section and the drainage well is 15 m. With such parameters for construction, after the subsequent fracturing forms a fracture network, it can be ensured that the fracture network can connect the horizontal fracturing section and the drainage well, thereby facilitating the subsequent CO2 injection to displace the enhanced extraction of coalbed methane.
进一步，所述第一封隔器与第二封隔器均为压缩式Y441型封隔器，密封长度为5～8m。采用这种型号及长度能满足对注入井和排采井的密封。Furthermore, the first packer and the second packer are both compression type Y441 packers with a sealing length of 5 to 8 meters. This type and length can meet the requirements of sealing injection wells and drainage wells.
与现有技术相比，本发明具有如下优点：Compared with the prior art, the present invention has the following advantages:
1、本发明采用CO2泡沫作为压裂流体拓展CO2吸附空间，并通过脉动压裂的方式可解决传统水力压裂的耗水量大、压裂液反排困难、产生“水锁”伤害等缺点，有效降低水的存在对于CO2地质封存的抑制作用，并且脉冲式压裂可降低煤体起裂压力，扩大储层改造 范围，提升煤体裂化效果，为CO2的封存提供广阔的吸附空间，同时形成裂隙网络后CO2泡沫中的CO2气体能进入裂隙内与吸附态的甲烷形成竞争吸附，驱替吸附态甲烷解吸排出，从而实现在压裂形成裂隙网络的同时还能驱替甲烷解吸的作用，使煤层气排出同时CO2气体吸附在煤层内。1. The present invention uses CO2 foam as a fracturing fluid to expand the CO2 adsorption space, and through the pulsating fracturing method, it can solve the shortcomings of traditional hydraulic fracturing, such as large water consumption, difficulty in fracturing fluid backflow, and "water lock" damage, effectively reducing the inhibitory effect of water on CO2 geological storage, and pulse fracturing can reduce the coal body fracture pressure and expand reservoir transformation. range, improving the cracking effect of the coal body and providing a broad adsorption space for the storage of CO2 . At the same time, after the formation of the fracture network, the CO2 gas in the CO2 foam can enter the fracture and compete with the adsorbed methane for adsorption, driving the adsorbed methane to desorb and discharge, thereby achieving the effect of driving the desorption of methane while forming a fracture network by fracturing, so that the coalbed methane is discharged and the CO2 gas is adsorbed in the coal seam.
2、本发明在进行第一阶段抽采后，当甲烷浓度降低后开始进行CO2注入驱替煤层气强化抽采过程，通过CO2注入与煤层气抽采同时进行，CO2气体在抽采***、注入井、不可采煤层和排采井之间形成封闭的循环，从而使CO2气体持续注入煤层内的各个裂隙内，持续驱替吸附态甲烷解吸排出，并将CO2气体吸附在煤层内，直至煤层气被大量抽采完毕后，煤层内也吸附了大量的CO2气体，如此实现了不可采煤层内大量注入CO2气体进行吸附留存，同时驱替煤层气强化抽采效率的效果。2. After the first stage of extraction, the present invention starts the CO2 injection to displace the coalbed methane intensified extraction process when the methane concentration decreases. The CO2 injection and coalbed methane extraction are carried out simultaneously, and the CO2 gas forms a closed cycle between the extraction system, the injection well, the unmineable coal seam and the drainage well, so that the CO2 gas is continuously injected into the various cracks in the coal seam, continuously displacing the adsorbed methane for desorption and discharge, and adsorbing the CO2 gas in the coal seam until the coalbed methane is extracted in large quantities, and a large amount of CO2 gas is also adsorbed in the coal seam. In this way, a large amount of CO2 gas is injected into the unmineable coal seam for adsorption and retention, and the effect of displacing the coalbed methane to enhance the extraction efficiency is achieved.
3、本发明在完成煤层气抽采及CO2注入过程后，将注入井和排采井进行密封，由于封存CO2的不可采煤层上方含水层的存在以及封闭性较强的岩层作为盖层，相当于给CO2的封存场所添加了两道密闭防线，有效防止CO2在封存过程中的逸出，给CO2的地质封存提供了更稳定的封存环境。3. After completing the coalbed methane extraction and CO2 injection process, the present invention seals the injection well and the drainage well. Due to the existence of the aquifer above the unmineable coal seam for storing CO2 and the rock layer with strong sealing properties as the cap layer, it is equivalent to adding two closed defense lines to the CO2 storage site, effectively preventing the escape of CO2 during the storage process, and providing a more stable storage environment for the geological storage of CO2 .
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1是本发明的整体布设示意图。FIG1 is a schematic diagram of the overall layout of the present invention.
图中：1-发泡剂储存罐；2-CO2储存罐；3-发泡剂阀门；4-CO2阀门；5-泡沫发生器；6-高压脉动泵；7-压力表；8-注入阀门；9-第一封隔器；10-注入管；11-注入井；12-不可采煤层；13-排采井；14-第二封隔器；15-抽采管；16-第一抽采阀门；17-抽采泵；18-甲烷浓度传感器；19-CO2-甲烷分离器；20-甲烷储存罐；21-甲烷阀门；22-第二抽采阀门；23-连通管；24-水平压裂段；25-岩层；26-含水层；P1-注入井竖直钻进截止位置；P2-注入管端部位置；P3-水平压裂段施工截止位置；P4-排采井钻进截止位置；P5-封隔器初始位置；P6-封隔器终点位置。In the figure: 1-foaming agent storage tank; 2- CO2 storage tank; 3-foaming agent valve; 4- CO2 valve; 5-foam generator; 6-high-pressure pulsating pump; 7-pressure gauge; 8-injection valve; 9-first packer; 10-injection pipe; 11-injection well; 12-unmineable coal seam; 13-drainage well; 14-second packer; 15-extraction pipe; 16-first extraction valve; 17-extraction pump; 18-methane concentration sensor; 19- CO2 -methane separator; 20-methane storage tank; 21-methane valve; 22-second extraction valve; 23-connecting pipe; 24-horizontal fracturing section; 25-rock formation; 26-aquifer; P1-vertical drilling cut-off position of injection well; P2-end position of injection pipe; P3-construction cut-off position of horizontal fracturing section; P4-drilling cut-off position of drainage well; P5-initial position of packer; P6-end position of packer.
具体实施方式Detailed ways
下面将对本发明作进一步说明。The present invention will be further described below.
如图1所示，本发明的具体步骤为：As shown in Figure 1, the specific steps of the present invention are:
A、钻井施工：先确定不可采煤层12的位置，然后从地面穿过岩层25与含水层26向 不可采煤层12分别施工注入井11和排采井13，使注入井11和排采井13分别达到P1和P4位置，在注入井11形成后，从注入井11的P1位置沿不可采煤层12走向钻取水平压裂段24达到P3位置，完成后停止钻井工作；其中注入井11与排采井13的直径均为100mm，两竖直井间距为150m，注入管11进入水平压裂段24的长度为100m，水平压裂段24与排采井13的水平距离为15m。采用这种参数进行施工，能在后续压裂形成裂隙网络后，保证裂隙网络能将水平压裂段24和排采井13连通，从而便于后续CO2注入驱替煤层气强化抽采的工作。A. Drilling construction: First determine the location of the unmineable coal seam 12, then drill from the ground through the rock layer 25 and the aquifer 26 In the unmineable coal seam 12, injection well 11 and drainage well 13 are constructed respectively, so that the injection well 11 and the drainage well 13 reach the P1 and P4 positions respectively. After the injection well 11 is formed, the horizontal fracturing section 24 is drilled from the P1 position of the injection well 11 along the unmineable coal seam 12 to the P3 position, and the drilling work is stopped after completion; wherein the diameter of the injection well 11 and the drainage well 13 are both 100mm, the distance between the two vertical wells is 150m, the length of the injection pipe 11 entering the horizontal fracturing section 24 is 100m, and the horizontal distance between the horizontal fracturing section 24 and the drainage well 13 is 15m. The use of such parameters for construction can ensure that after the subsequent fracturing forms a fracture network, the fracture network can connect the horizontal fracturing section 24 and the drainage well 13, thereby facilitating the subsequent CO2 injection to displace the enhanced extraction of coalbed methane.
B、布设CO2注入及煤层气抽采***：将注入管10一端从地面伸入注入井11并到达水平压裂段24的P2位置，注入管10另一端处于注入井11外部，抽采管15一端从地面伸入排采井13内、另一端处于排采井13外部；在注入井11和排采井13内同一水平高度的P5和P6位置之间分别装有第一封隔器9和第二封隔器14，分别对注入井11和排采井13进行密封，其中第一封隔器9与第二封隔器14均为压缩式Y441型封隔器，密封长度为5～8m。采用这种型号及长度能满足对注入井11和排采井13的密封。高压脉动泵6的出口与注入管10另一端连接，高压脉动泵6的进口与泡沫发生器5的出口连接，泡沫发生器5的两个进口分别通过管路与发泡剂储存罐1和CO2储存罐2连接，抽采泵17的抽气口与抽采管15另一端连接，抽采泵17的排气口通过管路与CO2-甲烷分离器19的进气口连接，CO2-甲烷分离器19的两个分离排出口分别通过管路与CO2储存罐2和甲烷储存罐20连接，注入管10和抽采管15之间通过连通管23连接，所述发泡剂储存罐1和泡沫发生器5之间的管路上装有发泡剂阀门3，CO2储存罐2和泡沫发生器5之间的管路上装有CO2阀门4，注入管10上装有压力表7和注入阀门8，抽采管15上装有第一抽采阀门16，连通管23上装有第二抽采阀门22，抽采泵17和CO2-甲烷分离器19之间的管路上装有甲烷浓度传感器18，CO2-甲烷分离器19和甲烷储存罐20之间的管路上装有甲烷阀门21，完成CO2注入及煤层气抽采***的布设；B. Arrangement of CO2 injection and coalbed methane extraction system: one end of the injection pipe 10 is extended from the ground into the injection well 11 and reaches the P2 position of the horizontal fracturing section 24, the other end of the injection pipe 10 is outside the injection well 11, one end of the extraction pipe 15 is extended from the ground into the drainage well 13, and the other end is outside the drainage well 13; the first packer 9 and the second packer 14 are respectively installed between the P5 and P6 positions at the same horizontal height in the injection well 11 and the drainage well 13 to seal the injection well 11 and the drainage well 13, wherein the first packer 9 and the second packer 14 are both compression type Y441 packers with a sealing length of 5 to 8 meters. This type and length can meet the sealing requirements of the injection well 11 and the drainage well 13. The outlet of the high-pressure pulsating pump 6 is connected to the other end of the injection pipe 10, the inlet of the high-pressure pulsating pump 6 is connected to the outlet of the foam generator 5, the two inlets of the foam generator 5 are respectively connected to the foaming agent storage tank 1 and the CO2 storage tank 2 through pipelines, the air suction port of the extraction pump 17 is connected to the other end of the extraction pipe 15, the exhaust port of the extraction pump 17 is connected to the air inlet of the CO2 -methane separator 19 through a pipeline, the two separation outlets of the CO2 -methane separator 19 are respectively connected to the CO2 storage tank 2 and the methane storage tank 20 through pipelines, the injection pipe 10 and the extraction pipe 15 are connected by a connecting pipe 23, the pipeline between the foaming agent storage tank 1 and the foam generator 5 is equipped with a foaming agent valve 3, and the pipeline between the CO2 storage tank 2 and the foam generator 5 is equipped with a CO2 2 valve 4, a pressure gauge 7 and an injection valve 8 are installed on the injection pipe 10, a first extraction valve 16 is installed on the extraction pipe 15, a second extraction valve 22 is installed on the connecting pipe 23, a methane concentration sensor 18 is installed on the pipeline between the extraction pump 17 and the CO2 -methane separator 19, and a methane valve 21 is installed on the pipeline between the CO2 -methane separator 19 and the methane storage tank 20, thus completing the layout of the CO2 injection and coalbed methane extraction system;
C、对不可采煤层进行压裂：初始状态各个阀门均为关闭状态，打开第一抽采阀门16、甲烷阀门21、注入阀门8、CO2阀门4和发泡剂阀门3，开启泡沫发生器5、高压脉动泵6、抽采泵17和CO2-甲烷分离器19，此时发泡剂储存罐1中的发泡剂与CO2储存罐2中的CO2进入泡沫发生器5内进行混合发泡后形成CO2泡沫，接着CO2泡沫经过高压脉动泵6施加脉动力后形成脉动CO2泡沫，然后脉动CO2泡沫经过注入管10到达水平压裂段24对不可采煤层12进行脉动压裂，从而在水平压裂段24周围形成裂隙网络，并通过裂隙网络与排采井13连通，进而部分CO2气体进入裂隙内，在压裂过程中实时观测甲烷浓度传感器18 数值的变化情况；待甲烷浓度传感器18数值出现明显变化且检测的甲烷浓度在10％以上时停止压裂工作，此时关闭泡沫发生器5与高压脉动泵6，同时关闭CO2阀门4、发泡剂阀门3、注入阀门8，完成不可采煤层12的压裂过程；C. Fracturing the unmineable coal seam: In the initial state, all valves are closed. Open the first extraction valve 16, methane valve 21, injection valve 8, CO2 valve 4 and foaming agent valve 3, turn on the foam generator 5, high-pressure pulsating pump 6, extraction pump 17 and CO2 -methane separator 19. At this time, the foaming agent in the foaming agent storage tank 1 and the CO2 in the CO2 storage tank 2 enter the foam generator 5 for mixing and foaming to form CO2 foam. Then, the CO2 foam is subjected to pulsating force by the high-pressure pulsating pump 6 to form pulsating CO2 foam. Then, the pulsating CO2 foam passes through the injection pipe 10 to reach the horizontal fracturing section 24 to perform pulsating fracturing on the unmineable coal seam 12, thereby forming a fracture network around the horizontal fracturing section 24, and connecting with the drainage well 13 through the fracture network, so that part of the CO2 gas enters the fracture. During the fracturing process, the methane concentration sensor 18 is used to observe in real time. When the value of the methane concentration sensor 18 changes significantly and the detected methane concentration is above 10%, the fracturing work is stopped, and the foam generator 5 and the high-pressure pulsating pump 6 are turned off, and the CO2 valve 4, the foaming agent valve 3, and the injection valve 8 are closed at the same time, and the fracturing process of the unmineable coal seam 12 is completed;
D、对不可采煤层内的煤层气进行第一阶段抽采：打开甲烷阀门21和第二抽采阀门22，并持续保持抽采泵17和CO2-甲烷分离器19的工作状态开始进行煤层气抽采，此时裂隙网络内的煤层气部分从裂隙中析出至水平压裂段24，还有部分煤层气从裂隙中析出至排采井13内，接着水平压裂段24内的煤层气依次经过注入管10、连通管23、抽采管15和抽采泵17后进入CO2-甲烷分离器19内，同时排采井13内的煤层气经过抽采管15和抽采泵17后也进入CO2-甲烷分离器19，煤层气在CO2-甲烷分离器19内经过分离后，甲烷进入甲烷储存罐20内进行储存，其余CO2气体再次进入CO2储存罐2，在持续抽采过程中观测甲烷浓度传感器18的数值，待甲烷浓度降至0.5％以下时，关闭抽采阀门二22，完成第一阶段抽采；D. Carry out the first stage of extraction of coalbed methane in the unextractable coal seam: open the methane valve 21 and the second extraction valve 22, and keep the extraction pump 17 and the CO2 -methane separator 19 in working state to start coalbed methane extraction. At this time, part of the coalbed methane in the fracture network is precipitated from the fracture to the horizontal fracturing section 24, and part of the coalbed methane is precipitated from the fracture to the drainage well 13. Then the coalbed methane in the horizontal fracturing section 24 passes through the injection pipe 10, the connecting pipe 23, the extraction pipe 15 and the extraction pump 17 in sequence and enters the CO2 -methane separator 19. At the same time, the coalbed methane in the drainage well 13 also enters the CO2 -methane separator 19 after passing through the extraction pipe 15 and the extraction pump 17. After the coalbed methane is separated in the CO2 -methane separator 19, the methane enters the methane storage tank 20 for storage, and the remaining CO2 gas enters the CO2-methane separator 19 again. 2 Storage tank 2, during the continuous extraction process, observe the value of the methane concentration sensor 18, and when the methane concentration drops below 0.5%, close the extraction valve 22 to complete the first stage of extraction;
E、CO2注入驱替煤层气强化抽采：打开CO2阀门4，再次开启高压脉动泵6，CO2气体经过泡沫发生器5和高压脉动泵6向水平压裂段持续注入CO2气体，CO2气体进入裂隙网络内与煤层气形成竞争吸附，从而驱替煤层气从煤层内解吸至排采井13内，同时保持抽采泵17的持续工作状态，形成注入-抽采同时作业，此时排采井13内的煤层气和CO2气体混合气体经过抽采管15和抽采泵17后进入CO2-甲烷分离器19，混合气体在CO2-甲烷分离器19内经过分离后，甲烷进入甲烷储存罐20内进行储存，其余CO2气体再次进入CO2储存罐2，CO2气体持续循环，使煤层大量吸附CO2气体，进而持续驱替煤层气解吸被抽采，在该过程中观测压力表7与甲烷传感器18的数值变化，根据压力表7的压力峰值调节高压脉动泵6的脉动频率，使压力表7显示的压力峰值维持在35～45MPa范围内，接着观察甲烷浓度传感器18检测的浓度变化，待甲烷浓度降至0.1％停止注入和抽采，此时关闭CO2阀门4、高压脉动泵6、甲烷阀门21、抽采泵17和CO2-甲烷分离器19，完成CO2注入驱替煤层气强化抽采过程；E. CO2 injection to displace coalbed methane for enhanced extraction: open the CO2 valve 4, and start the high-pressure pulsating pump 6 again. The CO2 gas is continuously injected into the horizontal fracturing section through the foam generator 5 and the high-pressure pulsating pump 6. The CO2 gas enters the fracture network and forms competitive adsorption with the coalbed methane, thereby displacing the coalbed methane from the coal seam to be desorbed into the drainage well 13. At the same time, the extraction pump 17 is kept in a continuous working state, forming an injection-extraction simultaneous operation. At this time, the coalbed methane and CO2 gas mixture in the drainage well 13 passes through the extraction pipe 15 and the extraction pump 17 and enters the CO2 -methane separator 19. After the mixed gas is separated in the CO2 -methane separator 19, the methane enters the methane storage tank 20 for storage, and the remaining CO2 gas enters the CO2 storage tank 2 again. The CO2 gas circulates continuously, so that the coal seam absorbs a large amount of CO 2 gas, and then continuously displace the desorbed coalbed methane to be extracted. During this process, the value changes of the pressure gauge 7 and the methane sensor 18 are observed. The pulsation frequency of the high-pressure pulsating pump 6 is adjusted according to the pressure peak of the pressure gauge 7, so that the pressure peak displayed by the pressure gauge 7 is maintained within the range of 35-45MPa. Then, the concentration change detected by the methane concentration sensor 18 is observed. When the methane concentration drops to 0.1%, the injection and extraction are stopped. At this time, the CO2 valve 4, the high-pressure pulsating pump 6, the methane valve 21, the extraction pump 17 and the CO2 -methane separator 19 are closed to complete the CO2 injection to displace the coalbed methane enhanced extraction process;
F、CO2封存：将注入管10和抽采管15分别从注入井11和排采井13中取出并对注入井11和排采井13进行密封，从而将不可采煤层内吸附的大量CO2进行封存。F. CO2 storage: The injection pipe 10 and the extraction pipe 15 are taken out from the injection well 11 and the drainage well 13 respectively, and the injection well 11 and the drainage well 13 are sealed, so as to seal a large amount of CO2 adsorbed in the unmineable coal seam.
上述不可采煤层12为深度超过1000m的薄煤层，且煤层上部存在含水层26能作为CO2地质封存的天然屏障，同时该煤层的顶板为泥岩或致密砂岩或砂质泥岩作为盖层。采用上述煤层进行CO2地质封存，能进一步保证其封存效果，大大降低后期CO2从煤层内逸出的 可能性。The above-mentioned unmineable coal seam 12 is a thin coal seam with a depth of more than 1000m, and there is an aquifer 26 on the upper part of the coal seam which can serve as a natural barrier for CO2 geological storage. At the same time, the roof of the coal seam is mudstone or dense sandstone or sandy mudstone as a capping layer. Using the above-mentioned coal seam for CO2 geological storage can further ensure its storage effect and greatly reduce the later escape of CO2 from the coal seam. possibility.
以上所述仅是本发明的优选实施方式，应当指出：对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。 The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (4)

  1. 一种不可采煤层强化煤层气开采及CO2封存的方法，其特征在于，具体步骤为：A method for enhanced coalbed methane mining and CO2 storage in unmineable coal seams, characterized in that the specific steps are:
    A、钻井施工：先确定不可采煤层的位置，然后从地面穿过岩层与含水层向不可采煤层分别施工注入井和排采井，在注入井形成后，从注入井最深处沿不可采煤层走向钻取水平压裂段，完成后停止钻井工作；A. Drilling construction: first determine the location of the unmineable coal seam, then construct injection wells and drainage wells from the ground through the rock layer and aquifer to the unmineable coal seam. After the injection well is formed, drill the horizontal fracturing section from the deepest part of the injection well along the unmineable coal seam. After completion, stop drilling;
    B、布设CO2注入及煤层气抽采***：将注入管一端从地面伸入注入井并到达水平压裂段，注入管另一端处于注入井外部，抽采管一端从地面伸入排采井内、另一端处于排采井外部；注入井和排采井内分别装有第一封隔器和第二封隔器，分别对注入井和排采井进行密封；高压脉动泵的出口与注入管另一端连接，高压脉动泵的进口与泡沫发生器的出口连接，泡沫发生器的两个进口分别通过管路与发泡剂储存罐和CO2储存罐连接，抽采泵的抽气口与抽采管另一端连接，抽采泵的排气口通过管路与CO2-甲烷分离器的进气口连接，CO2-甲烷分离器的两个分离排出口分别通过管路与CO2储存罐和甲烷储存罐连接，注入管和抽采管之间通过连通管连接，所述发泡剂储存罐和泡沫发生器之间的管路上装有发泡剂阀门，CO2储存罐和泡沫发生器之间的管路上装有CO2阀门，注入管上装有压力表和注入阀门，抽采管上装有第一抽采阀门，连通管上装有第二抽采阀门，抽采泵和CO2-甲烷分离器之间的管路上装有甲烷浓度传感器，CO2-甲烷分离器和甲烷储存罐之间的管路上装有甲烷阀门，完成CO2注入及煤层气抽采***的布设；B. Laying out CO2 injection and coalbed methane extraction system: extending one end of the injection pipe from the ground into the injection well and reaching the horizontal fracturing section, the other end of the injection pipe is outside the injection well, one end of the extraction pipe is extended from the ground into the drainage well, and the other end is outside the drainage well; the injection well and the drainage well are respectively equipped with a first packer and a second packer to seal the injection well and the drainage well respectively; the outlet of the high-pressure pulsating pump is connected to the other end of the injection pipe, the inlet of the high-pressure pulsating pump is connected to the outlet of the foam generator, the two inlets of the foam generator are respectively connected to the foaming agent storage tank and the CO2 storage tank through pipelines, the air suction port of the extraction pump is connected to the other end of the extraction pipe, the exhaust port of the extraction pump is connected to the air inlet of the CO2 -methane separator through a pipeline, the two separation exhaust ports of the CO2 -methane separator are respectively connected to the CO2 storage tank and the methane storage tank through pipelines, the injection pipe and the extraction pipe are connected by a connecting pipe, a foaming agent valve is installed on the pipeline between the foaming agent storage tank and the foam generator, CO A CO2 valve is installed on the pipeline between the storage tank and the foam generator, a pressure gauge and an injection valve are installed on the injection pipe, a first extraction valve is installed on the extraction pipe, a second extraction valve is installed on the connecting pipe, a methane concentration sensor is installed on the pipeline between the extraction pump and the CO2 -methane separator, and a methane valve is installed on the pipeline between the CO2 -methane separator and the methane storage tank, thus completing the layout of the CO2 injection and coalbed methane extraction system;
    C、对不可采煤层进行压裂：初始状态各个阀门均为关闭状态，打开第一抽采阀门、甲烷阀门、注入阀门、CO2阀门和发泡剂阀门，开启泡沫发生器、高压脉动泵、抽采泵和CO2-甲烷分离器，此时发泡剂储存罐中的发泡剂与CO2储存罐中的CO2进入泡沫发生器内进行混合发泡后形成CO2泡沫，接着CO2泡沫经过高压脉动泵施加脉动力后形成脉动CO2泡沫，然后脉动CO2泡沫经过注入管到达水平压裂段对不可采煤层进行脉动压裂，从而在水平压裂段周围形成裂隙网络，并通过裂隙网络与排采井连通，进而部分CO2气体进入裂隙内，在压裂过程中实时观测甲烷浓度传感器数值的变化情况；待甲烷浓度传感器数值出现明显变化且检测的甲烷浓度在10％以上时停止压裂工作，此时关闭泡沫发生器与高压脉动泵，同时关闭CO2阀门、发泡剂阀门、注入阀门，完成不可采煤层的压裂过程；C. Fracturing the unmineable coal seam: In the initial state, all valves are closed. Open the first extraction valve, methane valve, injection valve, CO2 valve and foaming agent valve, turn on the foam generator, high-pressure pulsating pump, extraction pump and CO2 -methane separator. At this time, the foaming agent in the foaming agent storage tank and the CO2 in the CO2 storage tank enter the foam generator for mixing and foaming to form CO2 foam. Then, the CO2 foam is subjected to pulsating force by the high-pressure pulsating pump to form pulsating CO2 foam. Then, the pulsating CO2 foam passes through the injection pipe to reach the horizontal fracturing section to perform pulsating fracturing on the unmineable coal seam, thereby forming a fracture network around the horizontal fracturing section, and connecting with the drainage well through the fracture network, so that part of the CO2 gas enters the fracture. During the fracturing process, the change of the methane concentration sensor value is observed in real time. When the methane concentration sensor value changes significantly and the detected methane concentration is above 10%, the fracturing work is stopped. At this time, the foam generator and the high-pressure pulsating pump are turned off, and the CO2 is turned off at the same time. 2 valves, foaming agent valves, and injection valves complete the fracturing process of unmineable coal seams;
    D、对不可采煤层内的煤层气进行第一阶段抽采：打开甲烷阀门和第二抽采阀门，并持续保持抽采泵和CO2-甲烷分离器的工作状态开始进行煤层气抽采，此时裂隙网络内的煤层气部分从裂隙中析出至水平压裂段，还有部分煤层气从裂隙中析出至排采井内，接着水平 压裂段内的煤层气依次经过注入管、连通管、抽采管和抽采泵后进入CO2-甲烷分离器内，同时排采井内的煤层气经过抽采管和抽采泵后也进入CO2-甲烷分离器，煤层气在CO2-甲烷分离器内经过分离后，甲烷进入甲烷储存罐内进行储存，其余CO2气体再次进入CO2储存罐，在持续抽采过程中观测甲烷浓度传感器的数值，待甲烷浓度降至0.5％以下时，关闭抽采阀门二，完成第一阶段抽采；D. Carry out the first stage of extraction of coalbed methane in the unextractable coal seam: open the methane valve and the second extraction valve, and keep the extraction pump and CO2 -methane separator in working state to start coalbed methane extraction. At this time, part of the coalbed methane in the fracture network is precipitated from the fracture to the horizontal fracturing section, and part of the coalbed methane is precipitated from the fracture to the drainage well. Then the horizontal The coalbed methane in the fracturing section passes through the injection pipe, connecting pipe, extraction pipe and extraction pump in sequence and enters the CO2 -methane separator. At the same time, the coalbed methane in the drainage well also enters the CO2 -methane separator after passing through the extraction pipe and extraction pump. After the coalbed methane is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again. During the continuous extraction process, the value of the methane concentration sensor is observed. When the methane concentration drops below 0.5%, the second extraction valve is closed to complete the first stage of extraction;
    E、CO2注入驱替煤层气强化抽采：打开CO2阀门，再次开启高压脉动泵，CO2气体经过泡沫发生器和高压脉动泵向水平压裂段持续注入CO2气体，CO2气体进入裂隙网络内与煤层气形成竞争吸附，从而驱替煤层气从煤层内解吸至排采井内，同时保持抽采泵的持续工作状态，形成注入-抽采同时作业，此时排采井内的煤层气和CO2气体混合气体经过抽采管和抽采泵后进入CO2-甲烷分离器，混合气体在CO2-甲烷分离器内经过分离后，甲烷进入甲烷储存罐内进行储存，其余CO2气体再次进入CO2储存罐，CO2气体持续循环，使煤层大量吸附CO2气体，进而持续驱替煤层气解吸被抽采，在该过程中观测压力表与甲烷传感器的数值变化，根据压力表的压力峰值调节高压脉动泵的脉动频率，使压力表显示的压力峰值维持在35～45MPa范围内，接着观察甲烷浓度传感器检测的浓度变化，待甲烷浓度降至0.1％停止注入和抽采，此时关闭CO2阀门、高压脉动泵、甲烷阀门、抽采泵和CO2-甲烷分离器，完成CO2注入驱替煤层气强化抽采过程；E. CO2 injection to displace coalbed methane for enhanced extraction: Open the CO2 valve and start the high-pressure pulsating pump again. CO2 gas is continuously injected into the horizontal fracturing section through the foam generator and the high-pressure pulsating pump. CO2 gas enters the fracture network and forms competitive adsorption with coalbed methane, thereby displacing coalbed methane from the coal seam to the drainage well. At the same time, the extraction pump is kept in continuous working state, forming injection-extraction simultaneous operation. At this time, the coalbed methane and CO2 gas mixture in the drainage well passes through the extraction pipe and the extraction pump and enters the CO2 -methane separator. After the mixed gas is separated in the CO2 -methane separator, the methane enters the methane storage tank for storage, and the remaining CO2 gas enters the CO2 storage tank again. The CO2 gas circulates continuously, causing the coal seam to absorb a large amount of CO2. 2 gas, and then continuously displace the desorbed coalbed methane to be extracted. During this process, the value changes of the pressure gauge and the methane sensor are observed. The pulsation frequency of the high-pressure pulsating pump is adjusted according to the pressure peak of the pressure gauge to maintain the pressure peak displayed by the pressure gauge within the range of 35-45MPa. Then, the concentration changes detected by the methane concentration sensor are observed. When the methane concentration drops to 0.1%, the injection and extraction are stopped. At this time, the CO2 valve, the high-pressure pulsating pump, the methane valve, the extraction pump and the CO2 -methane separator are closed to complete the CO2 injection to displace the coalbed methane enhanced extraction process;
    F、CO2封存：将注入管和抽采管分别从注入井和排采井中取出并对注入井和排采井进行密封，从而将不可采煤层内吸附的大量CO2进行封存。F. CO2 storage: The injection pipe and extraction pipe are taken out from the injection well and the drainage well respectively, and the injection well and the drainage well are sealed to seal the large amount of CO2 adsorbed in the unmineable coal seam.
  2. 根据权利要求1所述的不可采煤层强化煤层气开采及CO2封存的方法，其特征在于，所述不可采煤层为深度超过1000m的薄煤层，且煤层上部存在含水层能作为CO2地质封存的天然屏障，同时该煤层的顶板为泥岩或致密砂岩或砂质泥岩作为盖层。The method for enhanced coalbed methane extraction and CO2 storage in unmineable coal seams according to claim 1 is characterized in that the unmineable coal seam is a thin coal seam with a depth of more than 1000m, and there is an aquifer above the coal seam that can serve as a natural barrier for CO2 geological storage, and at the same time, the roof of the coal seam is mudstone or dense sandstone or sandy mudstone as a capping layer.
  3. 根据权利要求1所述的不可采煤层强化煤层气开采及CO2封存的方法，其特征在于，所述注入井与排采井的直径均为100mm，两竖直井间距为150m，注入管进入水平压裂段的长度为100m，水平压裂段与排采井的水平距离为15m。The method for enhanced coalbed methane extraction and CO2 storage in unmineable coal seams according to claim 1 is characterized in that the diameters of the injection well and the drainage well are both 100 mm, the distance between the two vertical wells is 150 m, the length of the injection pipe entering the horizontal fracturing section is 100 m, and the horizontal distance between the horizontal fracturing section and the drainage well is 15 m.
  4. 根据权利要求1所述的不可采煤层强化煤层气开采及CO2封存的方法，其特征在于，所述第一封隔器与第二封隔器均为压缩式Y441型封隔器，密封长度为5～8m。 The method for enhanced coalbed methane extraction and CO2 storage in unmineable coal seams according to claim 1 is characterized in that both the first packer and the second packer are compression type Y441 type packers with a sealing length of 5 to 8 m.
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CN115539130B (en) * 2022-10-28 2024-02-23 中国矿业大学 Coal seam gas exploitation and CO (carbon monoxide) enhancement of non-shearable layer 2 Sealing method
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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006045839A (en) * 2004-08-03 2006-02-16 Mitsubishi Materials Natural Resources Development Corp Well device having fluid injecting and recovering functions, and method of setting the well device
CN103061730A (en) * 2013-01-28 2013-04-24 中国石油大学(华东) Method for coal bed methane mining by multi-element thermal fluid foam displacement
CN112513419A (en) * 2018-07-30 2021-03-16 Ez-能源有限公司 Method and system for removing carbon dioxide
CN113027407A (en) * 2021-04-21 2021-06-25 太原理工大学 Foam-gas composite staged fracturing method for stratum
CN113530516A (en) * 2021-07-16 2021-10-22 中国矿业大学 Pulsating CO2Foam fracturing and evaluation simulation integrated test device and method
CN114412419A (en) * 2022-01-21 2022-04-29 中国矿业大学 Efficient closed-loop extraction method for superposed coal bed gas reservoir
CN114458271A (en) * 2020-10-22 2022-05-10 中国石油化工股份有限公司 Method for improving complexity of deep high-brittleness shale gas fracture and application
CN115539130A (en) * 2022-10-28 2022-12-30 中国矿业大学 Enhanced coal bed gas exploitation and CO of non-recoverable coal bed 2 Method for sealing

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102094610A (en) * 2010-12-24 2011-06-15 中国科学院广州能源研究所 Experiment simulation system for exploiting natural gas hydrate by using CO2
CN103244095A (en) * 2013-06-05 2013-08-14 重庆大学 Supercritical carbon dioxide fracturing method and supercritical carbon dioxide fracturing system

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006045839A (en) * 2004-08-03 2006-02-16 Mitsubishi Materials Natural Resources Development Corp Well device having fluid injecting and recovering functions, and method of setting the well device
CN103061730A (en) * 2013-01-28 2013-04-24 中国石油大学(华东) Method for coal bed methane mining by multi-element thermal fluid foam displacement
CN112513419A (en) * 2018-07-30 2021-03-16 Ez-能源有限公司 Method and system for removing carbon dioxide
CN114458271A (en) * 2020-10-22 2022-05-10 中国石油化工股份有限公司 Method for improving complexity of deep high-brittleness shale gas fracture and application
CN113027407A (en) * 2021-04-21 2021-06-25 太原理工大学 Foam-gas composite staged fracturing method for stratum
CN113530516A (en) * 2021-07-16 2021-10-22 中国矿业大学 Pulsating CO2Foam fracturing and evaluation simulation integrated test device and method
CN114412419A (en) * 2022-01-21 2022-04-29 中国矿业大学 Efficient closed-loop extraction method for superposed coal bed gas reservoir
CN115539130A (en) * 2022-10-28 2022-12-30 中国矿业大学 Enhanced coal bed gas exploitation and CO of non-recoverable coal bed 2 Method for sealing

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