Author's brief introduction: Ye Jianping, male, born in 1962, is a professor-level senior engineer, assistant to the general manager of Zhonglian CBM Co., Ltd., and secretary-general of CBM Professional Committee of China Coal Society, mainly engaged in CBM exploration, development and scientific research. Address: No.88, Anwai Street, Dongcheng District, Beijing (1001), Tel: (0 10) 642657 10, and E-mail: yejp01@/kloc.
(China United Coalbed Methane Co., Ltd. Beijing10001/China Coal Society Coalbed Methane Professional Committee)
This paper analyzes the present situation of coalbed methane exploration, development and utilization, combs the technical progress of coalbed methane exploration and development, and makes a basic evaluation on the development of coalbed methane industry in China. It is considered that the exploration of coalbed methane in China is progressing rapidly, and the proven reserves are greatly increased. The scale of coalbed methane production capacity has expanded, and the production and sales volume have increased simultaneously; Coal bed methane industry has taken shape initially, and coal bed methane has become the most realistic supplementary energy of natural gas; Coalbed methane technology strongly supports industrial development, and technical bottlenecks still exist.
Keywords: CBM exploration and development technology industry development
Report on the Development of Coalbed Methane Industry in China
ye jianping
(China United Coalbed Methane Co., Ltd., Beijing 1000 1 1, China)
(Professional Committee of Coalbed Methane of China Coal Society)
This report analyzes the present situation of exploration, development and utilization of coalbed methane, combs the technical progress of exploration and development of coalbed methane, and makes a basic assessment of the development of coalbed methane industry in China. The exploration of coalbed methane in China is progressing rapidly at present. Proved reserves have increased significantly. The scale of coalbed methane production capacity has expanded. Both output and sales have increased. Coalbed methane industry has initially taken shape. Coalbed methane has become the most realistic supplementary energy of natural gas. Coalbed methane technology provides a strong support for coalbed methane industry; However, technical bottlenecks still exist.
Keywords: coalbed methane; Exploration and development technology; Industry development
The development of coalbed methane in China has entered the initial stage of industrialization. The ground development output of coalbed methane reached 65.438+0.7 billion m3 in 2005, 65.438+0.0/kloc-0.0 billion m3 in 2009, and it is expected to reach 65.438+0.0 billion m3 in 2065.438+05. Therefore, the coalbed methane industry has entered a rapid development track and has become a supplementary resource of real natural gas. This paper briefly reports the development and technical progress of exploration, development and utilization of coalbed methane in China in recent years.
1 CBM exploration has advanced rapidly, and the proven reserves have increased greatly.
In the past two years, the exploration progress of coalbed methane in China has been obviously accelerated, and the proven reserves have increased significantly. According to incomplete statistics, by the end of June 20 1 1, there were 5942 coalbed methane wells in China. By the end of 20 10, China had accumulated proven coalbed methane reserves of 290.275 billion m3, and the newly proven reserves were nearly112155 million m3, accounting for 39% of the total. During the 11th Five-Year Plan period, hundreds of billions of cubic meters of gas fields were discovered. The proven reserves of coalbed methane in China 1 1 are mainly distributed in the south of Qinshui basin and the southeast of Ordos basin, such as panzhuang, Chengzhuang, Fan Zhuang, Zheng Zhuang, Zaoyuan, Zhangzi and Sanjiao, Liulin, Xiangning-Jixian and Hancheng in the south of Qinshui basin. As shown in Table 1, the proven reserves of Qinshui Basin are 200.769 billion m3, accounting for 695.438+07%. The proven reserves of coalbed methane in Ordos Basin are 865.438+776 million m3, accounting for 28. 17%. Other regions accounted for 2.66%. Proven reserves have become a solid foundation for the development of coalbed methane industry in these areas. However, compared with the national resources of 36.8 1 trillion m3, the proven rate of coalbed methane resources in China is very low, only 8‰. The exploration potential of coalbed methane in vast areas is still unclear.
Table 1 distribution of proven reserves of coalbed methane in China
Qinshui Basin, as a super-large coalbed methane field in China, has great exploration potential. No.3 coal seam of Shanxi Formation and No.5 coal seam of Taiyuan Formation 15 are thick, stable in distribution, high in gas content, the best in China, and good in coalbed methane recoverability. In addition to the proven southern blocks, blocks such as Shizhuangnan, Shizhuangbei, Mabi, Qinnan, Qinyuan, Shouyang, Heshun and Shanghuangya belong to coalbed methane enrichment areas and extremely favorable target areas. Shouyang block is different from Jincheng area. Take Taiyuan Formation 15 coal seam as the target layer. After years of exploration, the breakthrough of economic single well output has been realized. The output of several coalbed methane wells in Han Zhuang mine field has reached more than 1000m3/d, and the proven reserves will be submitted in the near future. Yangquan has drilled 46 1 well, with a daily output of 65,438+500,000 m3, and has commercial production capacity.
The eastern margin of Ordos basin has good coal-bearing property, gas-bearing property and recoverability. Hancheng-Heyang well area in Weibei block, Wucheng-Yaoqu well area in Linfen block, Liulin-Sanjiaojing well area in Lvliang block and Baode-Shenfujing well area in Lvliang block are four CBM enrichment areas, which are also favorable areas for CBM exploration and development in the eastern margin of Ordos Basin. The proven rate, resource conversion rate and exploration degree of resources in the eastern margin of Ordos basin are low, and the prospect of coalbed methane exploration and development is broad. With the ability of commercial gas production and the conditions of forming large-scale coalbed methane fields, it will surely become a "dessert" area for large-scale, industrialized and commercialized operation of coalbed methane in China.
In addition to the above areas, Yilan in Heilongjiang, Laochang in Yunnan, Zhijin in Guizhou, Qijiang in Sichuan, Huaibei in Anhui, southern Junggar Basin and Binxian in Shaanxi have also made exploration breakthroughs.
The buried depth of coal seam in Yilan block of Heilongjiang Province is about 700 meters, the thickness is 16 meters, the gas content is 8 ~ 103/t, and the thickness of long-flame coal and caprock oil shale is 80 meters. 20 1 1, Heilongjiang Provincial Bureau of Coalfield Geology drilled four wells in Yilan Block, and drilled two test wells YD-03 and YD-04 for coalbed methane production. After drainage, the daily gas production of the two wells is about 1500m3/t, which reaches the industrial gas flow standard, marking an effective breakthrough in the development of low-rank coalbed methane in Heilongjiang.
Chang Bin Coal Industry Group drilled a horizontal well 1 well in Mesozoic Chang Bin block of Ordos Basin, with a daily gas production of 5600m3.
The CBM Management Department of China Petroleum Inner Mongolia Huolinhe Area has constructed the Hoxhorn 1 well in Huolinhe Area of Erlian Basin in North China, with a daily gas production of about 1300m3. Exploration and research have been carried out and some progress has been made.
The successful exploration in Yilan, Changbin and Huolinhe blocks marks the initial success of coalbed methane exploration in low-rank coal and has far-reaching significance.
A historic breakthrough has been made in the surface drainage test of coalbed methane in Dacun section of Guxu mining area in southern Sichuan coalfield. The average production of DCMT 3 CBM test well is 1 160m3/d, and the cumulative gas production exceeds 500,000m3 for more than one year. The gas production of DC- 1 well and DC-2 well before reached 500 ~ 1000m3/d ... It is preliminarily considered that the coalbed methane in Dacun mining area has a good commercial development prospect. The successful drainage test of coalbed methane wells in this area is of great significance, which will provide technology and experience for coalbed methane exploration and development in low permeability, thin coal seam, large dip angle and high stress areas in southern Sichuan coalfield.
A pilot test well group of 5 wells was built in Yunnan Laochang. Self-flow occurs after fracturing. After initial oil drainage, the output gradually increased, showing good exploration potential.
Since 2008, Anhui Huaibei Mining Group has built 12 "one well and three uses" wells in Huaibei Ⅲ1Ⅲ 2 mining areas of Luling. Most wells have reached about 800m3, and some high-yield wells, such as LG-6, have a maximum daily production of more than 3,000 m3 and a stable production of about 1200m3. The foreign cooperation project of Zhonglian Company and the pilot test of Xi 'an Research Institute of Coal Science and Technology Group in Sunan syncline of Huaibei have successively achieved commercial output, which shows that it has good exploration potential.
CBM exploration in other parts of China is also in full swing. Such as Zhijin-Nayong in Guizhou, Yanchuan South in Shaanxi, Heshun in Shanxi, Qinyuan in Shanxi and southern Junggar Basin in Xinjiang. The preliminary exploration practice shows that this area has good exploration potential for coalbed methane.
To sum up, after the successful development of high rank coalbed methane in the south of Qinshui Basin, the exploration of middle rank coalbed methane and low rank coalbed methane is gradually succeeding.
At the same time of coalbed methane exploration, a large number of scientific researchers have carried out a lot of research on coalbed methane enrichment law and geological control factors, extensively studied the porosity, permeability, adsorption, desorption and diffusion, mechanical characteristics and deformation characteristics of coal reservoirs, and conducted research on coalbed methane enrichment characteristics and selection evaluation of different coal ranks. These basic studies of geology and reservoir characteristics strongly support the formation and development of the basic theory of coalbed methane.
2 The scale of coalbed methane production capacity has expanded, and the production and sales volume have increased simultaneously.
During the "Eleventh Five-Year Plan" period, coalbed methane entered the stage of industrial development, the scale of coalbed methane production capacity expanded, and the production and sales volume increased simultaneously. With the completion and commissioning of the high-tech industrialization demonstration project of Qinnan CBM development and utilization of Zhonglian Company, the CBM development project of Qinnan CBM field of PetroChina North China CBM Company and the CBM mining project of Jincheng Coal Industry Group, China's CBM development has rapidly entered the initial stage of industrialization, and CBM development is in a rapid development stage. There are 3,200 production wells in China. By 2065,438+00, the national surface coalbed methane production capacity will reach 2.5 billion m3, the output will be 65.438+0.57 billion m3, the utilization amount will be 65.438+0.654 38+0.8 billion m3, and the utilization rate will be 78%. The underground coal-bed methane drainage amount is 6.96 billion m3, and the utilization amount is 265.438+0.90 billion m3, with a low utilization rate of 365.438+0.5%. 20 1 1 year ground development output will reach18 ~ 2.2 billion m3, as shown in table 2. In the past five years, the output of surface coalbed methane has increased by orders of magnitude, reaching 654.38+000 billion m3 in 2005, 654.38+006.5438+000 billion m3 in 2009, and is expected to reach 654.38+000 billion m3 in 2065.438+05. The output of coalbed methane mainly comes from the south of Qinshui basin, accounting for 96%, and a small amount comes from Hancheng, Fuxin, Liulin and Sanjiao areas.
At present, the commercial development areas are the south of Qinshui Basin in Shanxi, Hancheng in Shaanxi and Fuxin in Liaoning. Areas eligible for commercial development include Shanxi Sanjiao, Liulin, Daning-Jixian, Yangquan and Shouyang.
Table 2 CBM production of main CBM fields in China (incomplete statistics)
Note: The number of wells put into production includes produced gas wells and unexploited gas wells.
3 CBM technology strongly supports industrial development, and technical bottlenecks still exist.
Technical progress is the source power of coalbed methane development, which has been confirmed by exploration and development practices at home and abroad. During the Eleventh Five-Year Plan period, the experimental research on CBM stimulation and reconstruction technology made an effective breakthrough, and suitable fracturing fluids and fracturing technologies were developed for different reservoir parameters. Innovative achievements have been made in drilling and completion technology, surface gathering and transportation technology and coalbed methane extraction technology in coal mining areas. At present, the most remarkable technical progress is the development of drilling and completion technology of coalbed methane horizontal wells and staged fracturing technology of coalbed methane horizontal wells.
3. 1 drilling and completion technology of coalbed methane horizontal well
The understanding of geological and engineering influencing factors of coalbed methane horizontal wells has been significantly improved. The geological conditions of coalbed methane horizontal wells and multi-branch horizontal wells are limited, which require relatively simple structure, few faults and small formation fluctuation; The coal seam has stable development, high hardness and complete structure; The penetration rate of coal seam is high, so as to avoid the communication between borehole and aquifer; Horizontal borehole trajectory is arranged in the upward dip direction, which is beneficial to drainage, depressurization and gas production; The length of horizontal drilling hole should be as long as possible, and the spacing of branch horizontal wells should be moderate, which should match the permeability of coal seam.
There are many designs for coalbed methane horizontal wells. According to the topography, geological conditions and reservoir permeability, "U" type wells, "V" type wells, Sichuan type wells and cluster wells (horizontal wells with two coal seams and two steps) have been successfully designed in Shizhuangnan and Liulin.
Multi-branch horizontal well technology and key tools have been localized. Multi-branch horizontal well drilling realizes multi-wing branch drilling in one wellbore, which improves drilling efficiency and effective oil drainage area. With the support of the "863" project, the geo-steering device has been localized and achieved good application results.
Based on shale gas completion technology, the staged fracturing technology test of coalbed methane horizontal well was carried out, and it was successful in Sanjiao block. At present, the experimental application of this technology in the south block of Shizhuang is still continuing.
The workover of multi-branch horizontal wells in coalbed methane has always been a difficult problem, and now exploratory tests have been carried out, including borehole collapse diagnosis in multi-branch intervals, secondary drilling guidance and reservoir damage control.
The research results show that PEC screen completion can effectively protect wellbore stability and reduce wellbore collapse. Even if the borehole partially collapses during drainage and production, the sieve tube can still provide a good flow channel for coalbed methane and water. Gas-filled underbalanced drilling technology can effectively reduce the pollution and damage of coal reservoirs and protect them. Drilling horizontal wells along the roof and floor of coal seam can effectively avoid the stability problems of pulverized coal and structural coal, and directional perforation and staged fracturing can effectively communicate with coal reservoirs, release reservoir stress and realize the exploitation of coalbed methane. By optimizing borehole trajectory and drilling process parameters, the range of depressurization and desorption of coalbed methane can be increased, the desorption speed of coalbed methane can be accelerated, and the damage of coal reservoir can be reduced.
3.2 The research on new fracturing fluid is in the ascendant, with fruitful results.
The damage mechanism of fracturing fluid to reservoir is studied. According to the composition of chemical elements in coal, fracturing fluid and active water containing clay anti-swelling agent were developed to reduce the damage of desorption to coalbed methane.
It is considered that embedding damage and coal powder blocking cracks are the main factors affecting the long-term conductivity of coal reservoirs, and methods such as increasing sand concentration, increasing proppant particle size and adding dispersant to suspend coal powder can be adopted in construction.
A new clean fracturing fluid with low damage and high efficiency has been developed through major special research, which is characterized by low molecular weight, 300 ~ 400; High viscosity,15.0 MPa s; Less residue; The coal seam damage rate is low,11.5%; Low friction, clean water about 30%. A new type of coal powder dispersed active water fracturing fluid was developed. The damage rate of coal seam is low, 1 1.8%, which makes pulverized coal evenly distributed in fracturing fluid and avoids excessive construction pressure. When flowing back, the pulverized coal is discharged with the fluid to avoid blocking the crack channel. An efficient and applicable nitrogen foam fracturing fluid was developed.
3.3 Low density cementing fluid reduces the damage of cementing cement to the reservoir.
Aiming at the problems that the borehole wall of coal reservoir is easy to collapse and the drilling fluid is easy to pollute coal reservoir, a low-density drilling fluid system with hollow glass beads is developed. The drilling fluid has good rheology and filtration, and the mud cake is thin and dense. At the same time, it has good temperature resistance, pollution resistance, collapse prevention, settlement stability and reservoir protection performance. The ultra-low density cement slurry system was developed and the formula of the ultra-low density cement slurry system was determined. The compressive strength of the formula at 40℃ for 24 hours reached 8.04MPa (exceeding the expected 7MPa index). The field test was successfully carried out in the south block of Shizhuang, Qinnan, which effectively prevented the liquid from polluting the coal reservoir.
A degradable drilling fluid for gas drainage in underground coal mine was developed. The double plugging removal measures of biological enzyme degradation and hydrochloric acid acidification can effectively relieve the damage of degradable drilling fluid to coalbed methane reservoir, and restore or even improve the gas permeability of coal and rock.
The wellbore stability mechanism of coalbed methane drilling and the determination of drilling fluid density window are studied.
3.4 Ground gathering and transportation engineering technology can effectively increase gathering and transportation radius and realize low-cost construction.
In the high-tech industrialization demonstration project of coalbed methane development and utilization in Qinnan, the surface gathering and transportation technology of coalbed methane, also known as "arrangement of branch valve group stations on branches", was studied and designed, which increased the gathering and transportation radius of coalbed methane to more than 13km. The application of new technology has cancelled countless manned stations that need to be built in traditional technology. The most important thing is to greatly improve the fluid flow environment, simplify the technological process and save the investment cost. The new device of gasoline and coalbed methane dual-purpose gas engine is used to replace the power system of pumping unit, and the new material of polyethylene pipe (pe pipe) is used for gas production pipeline, which saves the investment in engineering construction.
In Fanzhuang block of coalbed methane field in Qinshui Basin, the optimization technologies of surface gathering and transportation technology such as single well entry, pressurization technology and pressure system optimization are adopted. Gas gathering technologies such as prevention and control technology of coalbed methane hydrate, low-pressure transportation without alcohol injection, multi-well single-pipe series connection technology, determination of low-pressure gas gathering diameter, application of new material polyethylene pipe (pe pipe) and flexible composite pipe. The "standardized design and modular construction" of coal-bed gas field is put forward. The core of gas gathering station construction in coal-bed gas field is "four unifications and one harmony", that is, unified process flow, unified equipment selection, unified construction standard and unified single installation size, so as to maintain the harmonious development of plane layout and local environment and realize the unity of gas gathering station function and operation.
The construction of digital gas field realizes the integration of wireless, optical cable, cable and other communication modes in SCADA system, successfully reduces the investment of automatic control system in the process of informatization construction and maintenance of coalbed methane field, and is suitable for the characteristics of remote, multi-well, dense well, low pressure and low production of coalbed methane wells.
3.5 Production technology of coalbed methane drainage and production
Practice shows that reasonable drainage system and fine drainage control are the core of drainage technology for coalbed methane wells, constant pressure drainage system is suitable for drainage and depressurization stage at the initial stage of drainage, constant production drainage system is suitable for stable production stage, and graded stability and continuous depressurization are the core of fine drainage control.
Through the design of underground pipe string and surface flow of Liulin coalbed methane well, stepless numerical control pumping unit and permanent pressure monitoring are introduced, which well meets the requirements of drainage construction and data acquisition, laying the foundation for large-scale development in this area.
It is of great significance to study the reasonable interval and decline rate of dynamic liquid level height of coalbed methane for effectively maintaining the reasonable distribution of stress around the well and maintaining or improving reservoir permeability during mining.
The productivity equations of coalbed methane wells in different stages and the revised calculation formula of flowing pressure at the bottom of coalbed methane reservoir determine the production pressure difference of coalbed methane wells, which provides technical support for the determination of reasonable production pressure difference and normal drainage and production of coalbed methane wells.
3.6 CBM utilization technology
A large number of low-concentration coalbed methane will be discharged during coal mining. The purification and utilization of this part of coalbed methane is of great significance to energy development and utilization and environmental protection in China. The difficulty lies in how to separate CH4 and N2 economically and effectively.
Oxygen and nitrogen were separated from low concentration oxygen-bearing coalbed methane by cryogenic distillation. A liquefied (LNG) gas factory with an annual output of 20,000 tons will be built in Shigang Mine, Yangquan, and a low-concentration purified compressed (CNG) gas factory with an annual output of 20 million m3 will be built in Shentangzui Mine, Xinjing Mine, Yangquan, to provide urban low-cost compressed gas for buses and taxis, replacing oil with gas.
The separation and purification of low concentration gas is realized by pressure swing adsorption. The technology was put into trial production in Yangquan in March of 20 1 1 year, and 50 million m3CNG industrial production lines will be put into production by the end of 201/year.
With the support of major national science and technology projects, the Institute of Physics and Chemistry of Chinese Academy of Sciences and Zhonglian CBM Company have successfully developed a skid-mounted liquefaction device with a capacity of 10000m3, which is suitable for the situation of low single well production of CBM, and will directly realize the liquefaction and utilization of CBM in the CBM well site.
3.7 Technology is still the bottleneck of CBM exploration and development.
The prediction of coalbed methane high permeability enrichment area lacks mature theoretical guidance, or the theory of coalbed methane exploration and development in China is not yet mature.
Except for Qinnan, the single well production of coalbed methane in most exploration areas in China is low, and the single well production in the same area is quite different. In addition to geological and reservoir conditions, it is also necessary to test and form drilling and completion technologies and stimulation and reconstruction technologies. According to the characteristics of complex multi-fracture coal seam, how to increase the sand spreading area, effectively improve the reservoir conductivity and increase the single well production is the key problem of increasing production and reconstruction.
How to control the drilling and completion technology of horizontal wells and multi-branch horizontal wells to keep wellbore stability and prevent well collapse needs further exploration and testing under the conditions of high geostress and soft reservoir.
The change of reservoir physical properties under the condition of high stress and low permeability in deep coal seam, and a series of changes in drilling, completion, stimulation and reconstruction technology and process parameters brought about by it, are the directions to be studied urgently.
Coalbed methane industry has begun to take shape and become the most realistic natural gas supplementary energy.
Coalbed methane is mainly transported to users through pipelines, accounting for about 85%~90%, and a small amount is transported in the form of liquefied natural gas and compressed natural gas. At present, coalbed methane pipelines include Duanshi-Aibo pipeline, Duanshi-Qinshui Bajiakou pipeline and Jincheng Coal Industry Group West-East Gas Pipeline, with an annual transportation capacity of 500,000 cubic meters. The transportation capacity of Hancheng-Weinan -Xi 'an pipeline and Xiyang-Taiyuan pipeline under construction is 300,000 cubic meters.
The users of coalbed methane are mainly users of west-to-east gas transmission, followed by supplying gas to Shanxi Province and neighboring provinces of Qinshui coalbed methane field, such as Henan and Hebei, and supplying gas to cities where coalbed methane is located, such as Hancheng and Fuxin. Widely used in city gas, industrial boiler gas, automobile refueling and other natural gas markets. By the end of 20 10, China's underground and surface coalbed methane production reached 8.53 billion m3, accounting for 9% of the natural gas production of 94.6 billion m3. Coalbed methane has become the most realistic supplementary energy for local natural gas.
5 CBM industry development prospects
According to the Twelfth Five-Year Plan for the development and utilization of coalbed methane (coal mine gas) in China, by the end of the Twelfth Five-Year Plan, the output of coalbed methane in China will reach 20 billion ~ 24 billion m3, including 65.438+054.38+065.438+00 billion m3 for surface mining and 65.438+00 billion m3 for underground gas extraction. The proven geological reserves of coalbed methane will enter a period of rapid growth, and will increase by15 years. Therefore, coalbed methane will enter a rapid development track in the "Twelfth Five-Year Plan". First, through the "Eleventh Five-Year Plan" development, it has accumulated a good technical foundation and reserve foundation; Second, with the active investment of large companies such as PetroChina, Sinopec and CNOOC, the exploration and development funds have been fundamentally guaranteed; Third, the continuous support of major national science and technology projects has laid a solid foundation for tackling scientific and technological problems in the exploration, development and utilization of coalbed methane and provided strong technical support for realizing industrial goals.
Thanks to Professor Zhao Qingbo for providing relevant statistics.
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