At 1920 and 193 1, the United States drilled three artesian wells of coalbed methane in Wyodek coal seam in the middle of Fenhe basin and Pittsburgh coal seam in Bigelang gas field in northern Appalachia. Since 1950s, Philip Oil Company has participated in the development of coalbed methane in San Juan Basin, and has drilled a large number of gas wells in Fruit Formation coal seam, most of which have been successful. During this period, conventional oil and gas theory is used to guide drilling. In 1970s, under the influence of the global energy crisis, the US Department of Energy made a decision to carry out research on unconventional natural gas exploitation, including coalbed methane. From 1978, the coalbed methane in American 16 coal-bearing basin has been studied for 8 years. In the course of research, the migration mechanism, production mode and mining technology of coalbed methane have been further understood, and the resources of 14 basin have been calculated successively.
In the early 1980s, the United States made great breakthroughs in the development and utilization of coalbed methane, especially in the San Juan Basin and the Darth Vader Basin (Yang Xilu et al., 1995). After 1986, based on the experience of CBM development in shallow coal-bearing basins in the east, the United States carried out research on deep coal-bearing basins in the west, and achieved obvious development results (Zhang Wu et al., 2000).
In recent years, the key to the great progress of coalbed methane industry in the United States is a systematic and comprehensive geological evaluation of coal-bearing basins, especially large-scale research and development experiments in Darth Vader Basin, Pischens Basin and San Juan Basin. According to the experience of various places, it is proposed that a series of geological factors should be considered when selecting favorable blocks for coal seam exploration and development for comprehensive geological evaluation, namely, gas content, permeability, coal rank, coal seam physical properties, coal seam thickness and buried depth. Among them, coal seam thickness, coal rank, gas content, permeability, buried depth and structural conditions are the factors that must be given priority when selecting favorable blocks for coalbed methane development.
The exploration and development of coalbed methane in the United States represents the development of coalbed methane industry in the world. In recent years, coalbed methane exploration in Australia is also very active, mainly concentrated in several Permian-Triassic coal-bearing basins in the east, including Sydney, Goneda, Bowen and other basins. Some wells in Bowen Basin have been converted into production wells after testing. From 2000 to 20001year, the exploration cost of coalbed methane in Bonn basin alone reached $44.4 million, accounting for 37% of the total exploration cost in the basin ($654.38+0.2 billion). Queensland Natural Gas Company successfully exploited coalbed methane in Argyle- 1 well near Chianchill, with a daily output of over 2.823× 104m3. The exploration and development of coalbed methane has become the basic part of Queensland oil and gas industry. But so far, the production of coalbed methane in Australia is mainly based on mine coalbed methane extraction, and the produced coalbed methane is mainly supplied to coalbed methane power stations built at the wellhead. There are three main reasons for the rapid development of coalbed methane exploration in Australia: first, Australia is rich in coal and coalbed methane resources; Second, several coal-bearing basins are close to the densely populated areas on the east coast, and there are potential sales markets for coalbed methane; Thirdly, the successful experience of the United States is used for reference in the exploration process, and it is combined with the objective geological situation in China.
In addition to the United States and Australia, more than 30 countries and regions in the world have begun to explore and develop coalbed methane, but only a few countries have successfully developed coalbed methane on a large scale. There are three main reasons: first, coalbed methane, as an unconventional natural gas, often needs a lot of capital investment in its preliminary work, and it is difficult to attract funds without preferential tax policies; Second, except the United States, no country can completely solve its own specific technical problems; Thirdly, the particularity of coalbed methane itself, that is, it usually takes a long time from geological evaluation to industrial mining.
1.2.2 history and present situation of development and utilization of coalbed methane in China.
The exploration and development of coalbed methane in China started late. From the late 1970s to the early 1990s, coal mine safety was still the main purpose of gas drainage, and coal bed methane mining experiments were carried out in some mines. 1980, the gas drainage capacity in China has reached 2.934× 108m3, among which there are five mines with the height of 1000× 104m3. 1985 The State Economic Commission revised the Catalogue of Comprehensive Utilization of Resources to include gas as waste energy, and 1996 included coalbed methane development and coalbed methane power generation in the catalogue. 1992, the coal sector signed an agreement with the United Nations Development Programme (UNDP) to invest100000 USD for the experiment. The project includes four subprojects, namely Songzao Mining Bureau, Kailuan Mining Bureau, Tiefa Mining Bureau and Xi 'an Branch of Coal Research Institute. Its main purpose is to introduce technology and equipment for the development of coalbed methane industry in China. At present, it mainly draws lessons from American technology and experience, but it is not suitable for China coal-bearing area with complex geological conditions, so there is no breakthrough. However, through experiments, we have some knowledge about the exploration and development of coalbed methane in China, which laid the foundation for the exploration and development of coalbed methane in the later period.
Since the early 1990s, China has carried out coalbed methane exploration experiments and made substantial breakthroughs and progress. Since 1990, CBM exploration and drilling have been carried out in more than 30 coal-bearing basins in China, and many reservoir test parameters and production parameters have been obtained, and even industrial gas flow has been obtained in some areas. In order to speed up the development of coalbed methane in China, the State Council approved the establishment of Zhonglian CBM Co., Ltd. at the beginning of 1996. Both the Ninth Five-Year Plan and the Tenth Five-Year Plan have established coalbed methane research and experimental projects. At the same time, the State Planning Commission has set up a national first-class geological exploration project "Evaluation of coalbed methane resources in China". In order to promote the process of coalbed methane industrialization, in 2002, the national "973" plan set up the project "Basic research on coalbed methane accumulation mechanism and economic exploitation in China", systematically studied the key scientific problems restricting coalbed methane development in China from the level of basic and applied basic theory, and applied the results to coalbed methane exploration and development. Up to now, more than 270 coalbed methane wells have been built in China, and 3 1 block has been tested in different degrees, mainly distributed in natural gas gathering areas such as North China, Northeast China and South China, and 2 coalbed methane wells have been built. The proven geological reserves of coalbed methane are10.23×1012m3. A new round of national CBM resources forecast by China United CBM Company and Xi Branch of China Coal Research Institute shows that the total CBM resources in China is 31.46×1012m3.
From 1999 to 2002, Dongmei 107 team drilled 8 CBM surface development wells in Fuxin Basin, Liaoning Province, providing residents with a daily gas production of more than 2× 104m3, marking a zero breakthrough in the commercial development of CBM surface drilling in China. In 2005, the first demonstration project of comprehensive development and utilization of coalbed methane in China, with an investment of US$ 237 million, was started, and it is expected to be completed and put into operation in 2008. In this project, about 1.66× 108m3 coalbed methane is extracted every year by drilling holes into underground coal seams from the surface, which will be used as fuel for local industrial and commercial users and residents, and a 12× 104kW coalbed methane power plant will be built.
1.2.3 progress and trend of coalbed methane exploration and development in China
From 2004 to 2006, under the joint organization of the National Development and Reform Commission, the Ministry of Land and Resources and the Ministry of Finance, a new round of coalbed methane resource evaluation was carried out nationwide, and Zhonglian Company, PetroChina, Sinopec and China University of Mining and Technology undertook specific evaluation tasks. The coalbed methane resources in lignite are considered for the first time in the evaluation, and the coalbed methane resources in key mining areas in China are evaluated for the first time.
Up to now, the proven geological reserves of coalbed methane in China are 1023.08× 108m3. Among them, the proven reserves mainly based on surface development are 754.44× 108m3, and those mainly based on mine drainage are 268.64× 108m3.
1.2.3. 1 A historic breakthrough was made in the commercial development of coalbed methane on the ground.
Since the small-scale commercial development of coalbed methane was realized in Fuxin mining area in 2000, China has made breakthroughs in the commercial development of coalbed methane in several blocks in Jinnan anthracite area, showing the unique geological characteristics and commercial development prospects of coalbed methane in China.
1) coalbed methane development project of liujiajing formation in Fuxin city, Liaoning province: 1999 ~ 2002, a total of 8 coalbed methane wells were drilled in liujiajing mine field in Fuxin mining area, forming a small-scale development well pattern, with an average gas production of about 0.3× 104m3/d and a maximum gas production of 0.6×1d.
2) Coal-bed methane development test project of Zaoyuan Well Group in Qinshui, Shanxi Province: This project has 15 production test well and a small coal-bed methane power station with a daily power generation of 400 kW, which began to supply gas to the outside world in April 2003.
3) Ground development project of coalbed methane in panzhuang, Jincheng, Shanxi Province: In 2003, 30 development wells were built and commercial production began. At present, the development scale of well 2 10 has been formed, of which well 1 10 has been put into production. The daily gas production is 30× 104m3, and the maximum output of a single well is1.3x104m3, forming an annual production scale of1.5x108m3. At present, the produced coalbed methane is not only used for local power generation, gas supply for residents and automobile fuel, but also sold as a civil or industrial gas source to Zhengzhou, Changzhi, Anyang and other places.
4) Pilot test project for development and utilization of coalbed methane in Panhe, Jincheng, Shanxi Province: The project plans to build 900 coalbed methane wells, which will be completed in three phases. In the first phase of 2006, 50 coalbed methane production test wells/kloc-0 were completed, and it is planned to build a production demonstration base with an annual output of about 1× 108m3. On June 5438+065438+1 October1day, the base officially began to supply compressed coalbed methane to the outside world, with a daily gas production of about 7× 104m3.
1.2.3.2 CBM exploration and development test activities are active.
By the end of August 2006, there were about 650 coalbed methane wells in China (Figure 1. 1), of which more than 80% were distributed in Shanxi and Shaanxi provinces. Since 1980s, China has invested 21~ 2.2 billion yuan in the exploration and development of coalbed methane, and introduced about1.80 billion US dollars of foreign capital. On the basis of more than 30 exploration or development experimental areas before 2000, new blocks have been further expanded in recent years. At present, more than 20 blocks have been put into operation, the scale and technical level of development experiments have been greatly improved, and new progress has been made in foreign cooperation. At present, China has registered 64 coalbed methane blocks, and the enthusiasm of all parties to participate in coalbed methane exploration and development activities is unprecedented.
Figure 1. 1 CBM drilling number in different periods in China.
(According to Ye Jianping, 2006)
In addition to the above four commercial development projects, there are currently more than 20 blocks such as Duanshi, Hancheng, Hegang and Shenbei in exploration, development and testing, which are operated or cooperated by Zhonglian Company. Huainan Pan Xiedong, Baode, Qinyuan, Shouyang, Fengcheng, Urumqi Baiyang River, Panxian Qingshan, Yunnan Old Factory and other blocks that cooperate with foreign companies; Daning-Jixian, Ningwu, Zheng Zhuang, Fan Zhuang and Urumqi blocks operated by China Petroleum and Natural Gas Group; Jincheng Lan Yan Company operates its own blocks in Tunliu, Zheng Zhuang, Chengzhuang, Zhaozhuang and Hudi. In addition, some large coal enterprises in China are also actively carrying out surface drainage of coalbed methane, such as Tiefa, Fushun, Huainan, Pingdingshan, Jiaozuo, Lu 'an and Songzao. The above work has achieved remarkable results, such as drilling coalbed methane gushing wells in Hancheng, panzhuang in Jincheng and Qingshan in Panxian, revealing the great prospect of coalbed methane resources development in these areas.
In the above-mentioned blocks, five major projects are about to be put into development test: ① Hancheng project has 1 1 vertical wells, plus the previous six coalbed methane wells (average gas production is 0. 1× 104m3/d), forming Hancheng development test area; ② Two multi-branch horizontal wells were constructed in Duan's block of Jincheng, and the gas production of a single well was about1×1.04m3/d after drainage test; ③ Five multi-stage multilateral wells were constructed in Daning block of Jincheng, among which the daily gas production of DNP02 well, which was put into trial production at the end of 2000, was stable at about 2× 104m3/d; ④ It is planned to build 200 vertical wells in Jincheng Fan Zhuang Block to form a coalbed methane development zone, and dozens of wells have started to enter the drainage test; ⑤ Daning-Jixian has formed a development test well pattern consisting of 34 vertical wells and 1 multi-lateral horizontal wells, and drainage tests are being carried out, and the test results of single well (0.1~ 0.28) ×1.04m3/d have been obtained.
Since 1998, China signed the first domestic CBM product sharing contract (Huaibei Project) with Texaco of the United States, 27 CBM product sharing contracts have been signed with 16 foreign companies, with a total area of more than 3.5× 104km2. By the end of 2005, 254 CBM wells, 204 CBM wells with fracturing drainage and 2,065km of 2D earthquake have been built in the foreign cooperation block, and pilot development and test well groups such as panzhuang, Shizhuang, Baode, Sanjiao, Shouyang, Huaibei, Fengcheng and Hong En have been established, and the CBM production with commercial value has been obtained, and the international cooperation has achieved remarkable results.
1.2.3.3 technical progress of coalbed methane exploration and development
After more than 20 years of research and practice, China has formed a complete technical method system from coalbed methane resource evaluation, geological selection, exploration to surface development. In recent years, some key technologies have made new breakthroughs.
1) favorable zone optimization technology based on dynamic conditions: this technology includes two aspects: one is the ternary identification index of elastic energy accumulation and dispersion degree of coalbed methane reservoir, which is used to predict the accumulation effect of coalbed methane; The second is the elastic energy accumulation and dispersion model of coal reservoir, and a dynamic quantitative prediction method of coalbed methane favorable area is formed based on this model. Using ternary identification marks, the accumulation effect of coalbed methane is divided into three levels and 27 types. The related methods have been verified in the prediction of coalbed methane enrichment and high permeability dynamic condition development zone in Qinshui basin, and an advanced prediction technology of coalbed methane favorable area suitable for China's geological conditions has been formed.
2) CBM seismic exploration technology: Based on the traditional 2D and 3D seismic exploration technology, 3D longitudinal wave CBM seismic exploration technology is developed, and "two theories and six technologies" are put forward to guide CBM exploration. Six technologies include seismic attribute technology, seismic inversion technology, azimuth AVO technology, azimuth anisotropy technology, nonlinear inversion technology of coal seam thickness and multi-source information prediction technology based on MAPGIS. Taking lithologic seismic exploration as the core, a series of advanced coalbed methane seismic exploration technologies have been formed, which have achieved good application results in detecting the geometric shape of coal seam and the development degree of cracks.
3) Air/atomizing drilling technology for coalbed methane wells: Based on the geological characteristics of coalbed methane in China and the introduction of relevant technologies from the United States, air drilling design software was further developed, and a series of air drilling technologies were formed. At present, this technology has been widely used in Panhe national coalbed methane development demonstration project in the south of Qinshui basin, shortening the drilling cycle from 15 d to less than 5 d, reducing the construction cost and avoiding the damage of drilling fluid to the reservoir.
4) Multi-branch horizontal well drilling and production technology: In June 2004, the first multi-branch horizontal well of coalbed methane in China was put into production. The total footage of horizontal wells in coal seam is 8000m, and the daily output of a single well is stable at more than 2× 104m3, thus achieving a double breakthrough in CBM development technology and productivity. Up to now, China has built 14 multi-lateral horizontal wells. Daning mine field has completed three multi-branch horizontal wells and is currently draining water; Two multi-branch horizontal wells were implemented in Duan block, and the single well productivity was predicted to be above 2× 104m3, which was the first time to realize the drilling record of double main multi-branch horizontal wells. Wu M 1- 1 multi-branch horizontal well, coal seam footage of 6088m；; The PSC project in Daning realized the horizontal directional drilling record for the first time, with a total footage of 9000 m; There are three multi-branch horizontal wells in Shouyang block, and drainage tests are being carried out. The successful application of this technology in China provides a new technical way for the efficient development of coalbed methane in low permeability coal seams in China.
5) Technology of increasing production by injecting carbon dioxide: During the Tenth Five-Year Plan period, China carried out the pilot test of enhancing coalbed methane recovery by injecting carbon dioxide, studied the technological parameters suitable for China's geological characteristics, and achieved remarkable results in increasing production. In April, 2004, the field experiment of injecting carbon dioxide into well TL-003 in the south of Shanxi Province was completed, which provided advanced technical reserves for the sustainable development of China's coalbed methane industry and underground storage of carbon dioxide.
6) Nitrogen foam fracturing technology: Nitrogen foam fracturing technology is mainly suitable for coal seams with low pressure, low permeability and strong water sensitivity. The Panhe project completed the nitrogen foam fracturing construction of two wells, and successfully increased the daily output of coalbed methane single well by about 3 times. The contrast test of nitrogen foam fracturing was carried out in panzhuang project, and the daily production of coalbed methane in the test well was increased by about 1 time compared with that in the control well. In Hancheng development test project, through the actual implementation of nitrogen foam fracturing technology, the adaptability of this technology to specific coalbed methane geological conditions is analyzed, which has accumulated valuable experience for the application of this technology in China.
1.2.4 China coalbed methane research and exploration stage
The exploration and development of coalbed methane in China started late. Since 1950s, it can be divided into three stages.
1.2.4. 1 coal mine gas extraction and utilization stage
From 1950s to the end of 1970s, the main purpose of coalbed methane exploration and development in China was to extract and utilize underground gas in order to reduce gas disasters in coal mines. China's coal mine underground drainage of coalbed methane has a long history. 1980 coalbed methane drainage amount reached 2.934× 108m3, among which there were 5 mines with the volume above 0. 1× 108m3. 1996 pumping capacity reached 6.338× 108m3, and there were 16 mining areas with pumping capacity above 0. 1× 108m3. This is of great significance to reduce underground gas accidents, protect the environment and improve the energy structure. Gas drainage is also an effective technology for coalbed methane development.
1.2.4.2 initial stage of coalbed methane exploration and development test
From the end of 1970s to the beginning of 1990s, with coal mine safety as the main purpose, some mines in China simultaneously carried out coalbed methane mining experiments and conducted hydraulic fracturing experiments. At present, we mainly learn from American technology and experience, but the research on the complexity of geological conditions in China is not deep enough and there is no breakthrough. However, we have gained some knowledge, accumulated some experience and learned some advanced technologies in the exploration and development of coalbed methane.
1.2.4.3 CBM exploration and production test is in full swing.
From the early 1990s to the present, China has carried out coalbed methane exploration experiments from the perspective of high-quality energy utilization, and made substantial breakthroughs and progress. Petroleum, coal, geological and mineral systems and some local governments actively participated in this work, and set up special research institutions for coalbed methane in the early 1990s. Many foreign companies are also actively investing in CBM exploration and testing in China. Since 1990, there have been more than 30 coal-bearing areas in China, 1 19 exploratory and production test wells have been drilled, and many reservoir test parameters and production parameters have been obtained, and industrial gas flow has been obtained in Liulin, Jincheng, Dacheng, Tiefa and other coal-bearing areas. At present, China's coalbed methane exploration has made great progress and made substantial breakthroughs in both geological selection evaluation and technology. However, China's understanding of the law of coalbed methane enrichment and high yield under complex geological conditions is not deep enough, and the technology has not completely passed the standard. The evaluation of coalbed methane geological selection is still the primary research topic at this stage.
1.2.5 brief introduction to geological research and development of coal-formed gas
Coal-formed gas is also a very important natural gas, and many countries in the world are mining coal to form gas. Some large coal-producing areas in China are also coal-formed gas fields, such as Ordos area and coal-bearing areas in North China, which contain a large number of coal-formed gas reservoirs. For example, the exploration of coal-formed gas in Zhongyuan Oilfield is mainly concentrated in Dongpu sag, and ancient and new coal-formed gas fields and mixed gas fields such as Wen 23, Baimiao and Hubuzhai have been discovered. The proven geological reserves of Zhong 23 coal-formed gas field are 149.4× 108m3, which is the main gas field in Zhongyuan Oilfield. Well Wen Gu 2 in Dongpu Depression was fractured in the 38/kloc-0 /3.5 ~ 3,834.3m interval (16.8m/3 layer) of the Upper Paleozoic Shiqianfeng Formation in 2003, with a daily production of natural gas1.1×104m3. Coal-formed gas in Su Qiao of North China is concentrated in Ordovician, and "Wen 23" coal-formed gas reservoir and Baimiao mixed gas reservoir in Central China are concentrated in Shahejie Formation of Tertiary. The gas reservoirs in wells 155 and Gubei 1 in Jiyang area are mainly concentrated in Carboniferous and Permian reservoirs, and the coalbed methane in well Qugu 1 is mainly concentrated in the second member of Shahejie Formation in Tertiary.
There have been many research practices in the exploration and development of coal-formed gas, and researchers at home and abroad have achieved many research results (M.Teichmuller,1983; B. Walter et al., 2002; Yang Junjie et al.,1987; Dai Jinxing et al., 20065438+0; Zhang Xinmin et al., 2002).
Generally speaking, the research on coal-formed gas geology at home and abroad has the following development trends: ① Great attention is paid to the source and microstructure of coal-series organic matter closely related to hydrocarbon generation potential and gas production; (2) High and new technologies are constantly used in analysis and testing, such as enrichment analysis of trace biomarkers in natural gas, isotope analysis of monomer hydrocarbons, analysis of nitrogen-containing compounds, etc. (3) From the viewpoint of system dynamics, the generation, migration, accumulation and diffusion of natural gas are regarded as a dynamic evolution system, and the research on this system has developed from qualitative and semi-quantitative to quantitative; ④ The simulation experiment is more practical, which not only simulates the evolution law of hydrocarbon generation of different macerals, but also explores the process of hydrocarbon expulsion, secondary migration and accumulation in coal measures strata, and obtains many parameters. ⑤ Have a further understanding of the storage performance and sealing ability of coal seam itself.