Current status and development prospects of coalbed methane exploration and development in China

Xu Fengyin, Liu Lin, Zeng Wenting, Dong Yushan, Li Yanxiang, Zhou Xiaohong

(PetroChina Coalbed Methane Co., Ltd., Beijing 100028)

Abstract: "Clean and low-carbon" is a global trend. Accelerating the pace of coalbed methane exploration and development is of important strategic significance for reducing coal mine gas accidents, protecting the atmospheric environment, improving the energy structure, and ensuring energy security. China has continued to increase its efforts in the development of coal bed methane, and has introduced a series of incentive policies such as price concessions, tax incentives, development subsidies, resource management, and mineral rights protection. It has formed three major coal bed methane enterprises, including PetroChina, Shanxi Coal Group, and China United Coal. At present, the overall scale of the industry is small. In response to the mineral rights issue, three cooperation models have been formed to promote the coordinated development of coal and gas mining. Namely: Qinnan model, Lu'an model and Sanjiao model. Technically, supporting technologies for coalbed methane exploration and development suitable for different coal ranks and different geological conditions have been initially formed, a high-level coalbed methane laboratory has been built, and there are substantial achievements in the development of areas deeper than 800m and low-rank coal reservoirs. sexual breakthrough.

By the end of 2010, 5,426 coalbed methane wells had been drilled nationwide, and the proven geological reserves of coalbed methane were more than 290 billion cubic meters. The cumulative production capacity exceeds 30×108m3/a, the annual output is 15×108m3, and the commercial gas volume is 11.8×108m3. The completed pipeline transmission, compression/liquefaction capacity is 56×108m3/a. As of June 2011, the daily output of coalbed methane nationwide exceeded 400×104m3. A relatively complete coalbed methane pipeline network has been built or is under construction. The four favorable areas of Qinnan, Hancheng, Daning-Jixian and Baode are all close to existing natural gas trunk pipelines.

China is rich in coalbed methane resources, with great potential and good prospects. It should increase research and development efforts and rely on technological progress. It is especially recommended to strengthen work in four aspects: First, research and adjust countermeasures based on resource distribution; second, national Policy implementation and mutual cooperation between enterprises must be further strengthened; the third is to strengthen technical research in improving single well production and overall benefits; the fourth is to establish a unified information platform to avoid disorderly competition and repetitive investment. This will greatly promote the rapid development of the coalbed methane industry.

Keywords: China; Coal Bed Methane; Development; Industry; Technology; Current Situation; Prospects

Exploration & Development Status and Prospects For China's Coal Bed Methane

Xu Fengyin, Liu Lin, Zeng Wenting, DongYushan, Li Yanxiang, Zhou Xiaohong

(PetroChina CBM Co., Ltd, Beijing 100028, China)

Abstract: A global trend of "Clean and low-carbon＂ has been formed.To speed up CBM exploration and development is of significant importance to reduce coal mine gas accidents, to protect atmospheric environment and to improve energy structure.Greater efforts have been exerted to CBM development, given a series of encouraging policies, i.e. favorite price, tax preferences, development subsidy, resource management and mineral right protection. Three major CBM enterprises emerged including PetroChina, JAMG, and CUCBM, while the current industrial scale is relatively small. Considering the exploration right issues, 3 cooperation modes are developed to promote the coordinated development of gas extraction and coal mining such as Qinnan mode, Lu'an mode and Sanjiao mode. Regarding technologies, a couple of exploration and development technologies are developed, tailored for various rank coal methane and for different geological conditions, and a high-profile CBM lab was built.Besides, some substantial breakthroughs have been made in exploring CBM buried deeper than 800m and in low-rank coal bed methane development.

By the end of year 2010 ,5,426 CBM well

s have been drilled, about 290 bcm of the geological reserves proved. An annual production capacity of over 3 bcm were accumulatively built for surface extraction, producing 1.5 bcm/a, with 1.18 bcm of commercial production and 5.6 bcm/a for pipeline transportation, CNG and LNG capacity. The nationwide CBM yield has exceeded 4 million cubic meters per day by June, 2011. Four favorable blocks, like Qinnan, Hancheng, Daning-jixian and Baode all get close to the major existing pipelines.

China is rich in CBM resources, with great potentials and promising prospects. Thus, the following four suggestions are proposed: to work out proposals based on resource distribution; to further coordinate governmental policies and entrepreneurial performance; to strive to make technological breakthroughs in increasing single well yield and in promoting integrated economic efficiency; to establish a unified information platform to avoid disorderly competition and repeated investment. All these four proposals are likely to stimulate the progress of CBM industry.

Key words: China ;CBM;development;industry;technology;status;prospects

Introduction

Coalbed methane is commonly known as gas. The main component is methane. It is formed during the coalification process and is mainly adsorbed on the surface of coal pores. There are three forms of occurrence: , distributed in coal pores and fissures, and dissolved in coal seam water, mainly in the adsorption state. When the amount of hydrocarbon generation in the coal seam increases or the external temperature and pressure conditions change, the three occurrence forms can transform into each other. "Cleaning and low-carbonization" is a global trend, and energy transition and low-carbon economy have become important strategies for the economic and social development of countries around the world.

The development and utilization of coalbed methane has the advantage of “killing three birds with one stone”.

First of all, it is a clean, efficient and safe new energy. Its combustion produces almost no waste gas, which is conducive to optimizing the energy structure and making up for energy shortages. Furthermore, gas is the "number one killer" of coal mine safety, and its development is beneficial to coal mines. Safe production and reduce coal mine gas accidents; at the same time, it is also a strong greenhouse effect gas. The greenhouse effect is 20 times that of CO2. The development of coalbed methane can effectively reduce the greenhouse effect. Overall, it reflects the three major benefits of economy, safety and environmental protection. Accelerating the pace of coalbed methane exploration and development is of important strategic significance for reducing coal mine gas accidents, protecting the atmospheric environment, improving the energy structure, and ensuring energy security. The mining methods of coalbed methane are divided into two methods: underground drainage and surface drainage. Surface drainage is basically the same as conventional oil and gas production technology in terms of drilling and completion, well logging, fracturing, drainage, and gathering and transportation processes.

1 Current status of world coalbed methane resources and industry

1.1 Resource distribution

The amount of coalbed methane resources in the world with a burial depth of less than 2000m is approximately 260×1012m3, mainly Distributed in Russia, Canada, China, the United States, Australia and other countries (Figure 1).

Figure 1 Distribution of coalbed methane resources around the world

1.2 Industry status

At present, the coalbed methane industry development in the United States, Canada, Australia and other countries is becoming mature. Since the 1980s, 14 coal-bearing basins in the United States have been engaged in coalbed methane exploration and development, with proven recoverable reserves of 3×1012m3. In 2009, there were more than 50,000 coalbed methane production wells, with a production of 542×108m3. Coalbed methane production accounts for an increasing proportion of total natural gas production, and in 2009 the proportion of coalbed methane production reached 9%. Canada's coal bed methane industry is developing rapidly. Exploration began in 1987 and large-scale development began in 2002. In 2009, there were 7,700 production wells with a production of 60×108m3. Australia has also formed an industrial scale. Mainly distributed in the three coal-bearing basins of Sydney, Surat and Bowen in the east, there were 1,300 production wells in 2005 and a production of 12×108m3. In 2009, the production reached 48×108m3.

1.3 Current status of technology

Through long-term theoretical and technological research and development, four main technologies and four engineering technologies have been formed internationally. The four main technologies include: geological selection theory and high-yield enrichment area prediction technology, coalbed methane reservoir evaluation technology, air drilling, open hole cave completion technology, and multi-branch horizontal well drilling technology.

The four engineering technologies include: coiled tubing drilling, small nitrogen reservoir stimulation technology, short radius drilling and U-shaped horizontal well technology, nitrogen injection and carbon dioxide replacement coalbed methane production stimulation technology, and integrated coal and gas mining technology.

2 Current status of China's coalbed methane industry

2.1 Current status of exploration and development

Affected by the rapid development of coalbed methane in the United States, Canada, Australia and other countries, coupled with the introduction of a national A series of preferential policies, China's coalbed methane development scale and enterprises have grown rapidly, and three major coalbed methane production enterprises have been formed: PetroChina, Shanxi Coal Group, and China United Coal.

By the end of 2010, 5,426 coalbed methane wells had been drilled nationwide, and the proven geological reserves of coalbed methane were more than 290 billion cubic meters. The cumulative production capacity exceeds 30×108m3/year, the annual surface extraction output is 15×108m3, and the commercial gas volume is 11.8×108m3. The completed pipeline transmission, compression/liquefaction capacity is 56×108m3/a. As of June 2011, the daily output of coalbed methane in the country exceeded 400×104m3.

PetroChina: In December 2010, the Ministry of Commerce and other four ministries and commissions announced that in order to further expand foreign cooperation in coalbed methane mining, three new companies, PetroChina, Sinopec and Henan Coalbed Methane Company, were added as the first batch of pilot projects. unit. At present, PetroChina’s registered coalbed methane resources exceed 3×1012m3, and its proven geological reserves account for 64% of the country’s total, mainly distributed in the two major coalbed methane basins of Qinshui and Eastern Hubei.

In recent years, we have actively carried out preliminary evaluation, exploration selection and development pilot tests of coal bed methane, and the investment has increased significantly. Two large coal bed methane fields with a scale of more than 100 billion cubic meters have been discovered in Qinshui and eastern Hubei, and gradually formed Qinnan, Weibei and Linfen. and the development pattern of the four blocks in Luliang. By the end of 2010, the commercial gas volume was nearly 4×108m3.

After several years of exploration and cooperation with coal enterprises and local governments, three cooperation models have been formed to promote the coordinated development of coal and gas mining. Namely: Qinnan model: Mining rights overlapping areas are divided by agreement and developed separately, and both parties carry out downstream cooperation; Lu'an model: overall planning, step-by-step implementation, and simultaneous maintenance of mining order to avoid repeated investments; Sanjiao model: first Gas extraction, coal mining, and simultaneous development. These models have been affirmed by Vice Premier Zhang Dejiang and relevant national ministries and commissions.

A relatively complete coalbed methane pipeline network has been built or is under construction. The four favorable areas of Qinnan, Hancheng, Daning-Jixian and Baode are all close to existing natural gas main pipelines (Figure 2).

A high-level coalbed methane laboratory has been built, with test samples covering most of the country’s coalbed methane exploration and development zones. The workload accounts for 80% of the country’s work, and its technical level ranks among the best in the country.

The main experimental technologies include: gas content testing technology, isothermal adsorption testing technology, coal reservoir physical property analysis technology, coal seam fracturing damage testing technology, etc.

Jinmei Coal Group: By the end of 2010, 2,510 wells had been drilled, and surface extraction production reached 9×108m3. The Sihe-Jincheng 10×108m3/a gas transmission pipeline was built; the Jincheng-Boai gas pipeline was built as a shareholding. Together with Hong Kong and China, we jointly invested in a coalbed methane liquefaction project with a daily liquefaction capacity of 25×104m3; a 120-megawatt coalbed methane power plant was put into operation. The development areas include Qinshui, Yangquan, Shouyang and Xishan in Shanxi, Ningxian in Gansu, Jiaozuo in Henan, etc.

China United Coal merges with CNOOC: China United Coal currently has a mining rights area of ??2×104km2, of which the foreign cooperation block area reaches 1.6×104km2. By the end of 2010, the National Qinnan High-Tech Industrialization Demonstration Project and the Duanshi National Oil and Gas Strategic Selection Demonstration Project had been completed in Panhe, Qinshui Basin.

Currently, 672 wells have been drilled and 230 have been put into production, with a daily gas production of 50×104m3. In 2010, CNOOC successfully intervened in the exploration and development of coalbed methane by acquiring 50% of China United Coal, laying the foundation for the development of the coalbed methane industry. Base.

Figure 2 Schematic diagram of China's oil and gas trunk pipeline network

Fuxin Coal Industry: Fuxin Coal Mining Group and Liaohe Petroleum Exploration Bureau cooperated to carry out three cooperative coalbed methane mining models, significantly improving improve the overall development efficiency. The three development models include: short-radius hydraulic jet drilling in non-mined areas has achieved practical results; surface negative pressure drainage technology has been applied in active mining areas to achieve coordinated gas mining; and drilling through goafs has been successful. In 2010, 52 wells were drilled, with a daily gas production of 10×104m3 and a commercial gas volume of 3226×104m3. Three CNG stations were built, mainly supplying CNG filling stations in Panjin and Fuxin.

Sinopec: The coalbed methane mineral rights areas are mainly the Heshun block in the northern Qinshui Basin and the southern Yanchuan block in eastern Hubei. In 2010, 34 wells were drilled, with a gas production of 84×104m3. The current daily gas production is nearly 3000m3. In 2010, the East China Bureau and Huainan Mining signed a "Letter of Intent for Cooperation in Coalbed Methane Research and Development" and selected a 100km2 favorable block in the Huainan Panxie mining area. ***Together with the development of coalbed methane resources. In 2011, a framework agreement was signed with Australia Pacific in Beijing, and both parties established non-binding key commercial terms.

Others: Joint ventures such as Longmen, Greco, Far East Energy and Asia-American Continent, as well as other private enterprises, have been involved in coalbed methane exploration and development and increased the scale of production capacity construction. Among them, Asia-American Continent currently produces 19.7×104m3 of gas per day. .

Generally speaking, the southern part of the Qinshui Basin has become a hot spot for coalbed methane development in my country. The first built production capacity is nearly 25×108m3/a. The current daily gas production is nearly 380×104m3, realizing large-scale pipeline network external transmission. and large-scale commercial operations, initially forming an industrial pattern integrating upstream and downstream production, transportation and marketing.

2.2 Government preferential policies and technical support

In order to encourage the development of the coal bed methane industry, the Chinese government has introduced a series of preferential policies, including price concessions, tax incentives, development subsidies, resource management and Mining rights protection, etc. (Table 1), have achieved obvious results.

Table 1 The Chinese government’s preferential policies to encourage the development of the coal bed methane industry

At the same time, it also provides strong support at the technical level. Since 2007, the National Development and Reform Commission has specially established two national engineering research centers for coal bed methane development and utilization and coal mine gas control. The Ministry of Science and Technology has established a major national science and technology project for “Large Oil and Gas Fields and Coalbed Methane Development”. PetroChina has established a professional coalbed methane company and established a major science and technology project called "Key Technologies and Demonstration Projects for Coalbed Methane Exploration and Development". These have created conditions for the development and technological progress of the coalbed methane industry.

2.3 Technical status

The geological conditions in my country are somewhat different from those in the United States. At present, coalbed methane development all originates from the earliest theories in the United States. With the in-depth development on a large scale, many different types of coal ranks and coal bed structure, structural conditions, and hydrogeological conditions have been tested on site for coalbed methane storage characteristics. It has been proven that whether this theory is fully suitable for China's coalbed methane geological conditions remains to be further confirmed. Some of the different exploration and development technologies developed for the geological conditions of different basins in China have made breakthrough progress.

2.3.1 There is a new understanding of geology

There is a new breakthrough in the evaluation method of favorable areas: through comprehensive geological research on coal and rock characteristics, gas content, permeability, gas production, etc., a The evaluation criteria for high-yield areas are enriched, and the criteria and methods for dividing development units in production capacity construction areas are proposed.

There is a breakthrough in the production of coalbed methane wells deeper than 800m: It is generally believed that as the depth of the coal seam increases, the pressure increases, the permeability decreases sharply, and the gas production also decreases. At present, domestic commercial development depths are all in areas shallower than 800m. With the further advancement of exploration and development, industrial gas flow has also been obtained from wells deeper than 800m (the maximum gas production is 2885m3/d) (Figure 3). However, the law of coal seam gas production is still unclear, and is being confirmed through strengthened research and large well group drainage tests. .

Figure 3 Drainage curve of wells deeper than 800m

The permeability of coal reservoirs is generally low, and reservoir protection is the key: the study of coal storage conditions is a key restricting factor in the development of coalbed methane . The permeability of #3 coal in Qinshui Basin is (0.013~0.43)×10-3μm2, with an average of 0.112×10-3μm2; and in eastern Hubei (0.22~12)×10-3μm2, with an average of 1×10-3μm2. Overall, coal seams have poor physical properties and strong heterogeneity. Therefore, strengthening reservoir protection during drilling is key. During the drilling and fracturing process, underbalanced drilling and low-damage fracturing fluids that are less harmful to the coal reservoirs around the wellbore should be used as much as possible.

2.3.2 There are new measures for on-site management

There are new explorations in the well spacing of high coal rank development well patterns. Since the physical properties of high-rank coalbed methane reservoirs in my country are quite different from those in foreign countries, development has proven that the 300m×300m well spacing that has been used is not completely suitable. This is mainly reflected in the small number of high-yield wells, low production rate, and unreasonable production structure. To this end, through fine geological research, with the goal of increasing single well production, we numerically simulated the gas production effects of different well spacing and conducted pilot tests to explore a 200m×200m well pattern and well spacing for high-rank coalbed methane development. At the same time, the implementation of assisted drainage wells in the down-inclined parts of horizontal wells has also achieved initial results.

2.3.3 New progress in engineering technology support

Three-dimensional seismic exploration: 100km2 three-dimensional seismic survey was implemented in the Hancheng area. The data quality is significantly better than that of two-dimensional, and the description of small faults is clearer ( Figure 4), effectively guides well network deployment.

Figure 4 Comparison of three-dimensional and two-dimensional profiles in Hancheng area

Plume horizontal well drilling: Through market-oriented operation, the monopoly of foreign companies in the field of plume horizontal well construction has been broken , getting rid of the situation of completely relying on foreign companies for plume horizontal well drilling, and the cost has been greatly reduced.

Fracturing supporting technology: Based on the experimental analysis of coal seams, combined with a large number of fracturing practices, the principle of "variable displacement, low damage" is formed, and "high-pressure well processing technology, layered fracturing New technologies such as "fracturing technology" are adopted, using low-density proppant, sealing and pressing, and two-layer pressure-sharing in one trip.

Drainage technology: Form the eight-character principle of slow, stable, long-term and continuous; form three key links to cultivate high-yield wells: liquid level control, casing pressure control, and pulverized coal control; for the low-cost strategy, form There are two combinations of wellhead drainage equipment: electric motor + pumping unit, and pneumatic motor + pumping unit.

Ground gathering and transportation processing: standardized design, modular construction, and automated management basically achieve low-cost and efficient operations.

2.4 Utilization status

In 2009, 6 coalbed methane liquefaction plants were built across the country, with a liquefaction capacity of 260×104m3/d. In 2010, it was 300×104m3/d, and it can reach 700 in 2020. ×104m3/d. In addition, it is mainly used for low-concentration gas power generation, residential life, synthesis of ammonia, formaldehyde, methanol, carbon black and other chemical raw materials. An industrial system for the development and utilization of coalbed methane and coal mine gas has been gradually established.

2.5 Problems

Technically: Technology is the main problem restricting the current slow progress of the industry. The main existing problems include: gas control factors in high-permeability enrichment areas of coalbed methane, development theories that are in line with my country's coalbed methane geological conditions and used to guide production practice, key completion, fracturing, drainage and other key issues that are suitable for my country's geological conditions. Technology and corresponding equipment, etc.

Management: Mainly including: overlap of coalbed methane and coal mineral rights, difficulties in implementing policies such as gas extraction first, coal mining later, power generation and grid connection, high dependence on foreign cooperation, and restrictions on self-operated projects. The pipeline is small in scale, the market is fragmented, and uncertainty is high.

3 Coalbed methane development prospects and suggestions

With the development of the national economy, the rapid growth of natural gas demand provides opportunities for the development of coalbed methane. Since 2000, the average annual growth rate of natural gas has reached 16% (Figure 5). At the end of 2009, the total national natural gas consumption was 875×108m3. In 2010, the demand for natural gas exceeded 1400×108m3, and the supply capacity was about 1000×108m3. In 2015, The demand for natural gas is expected to be 2600×108m3, and the supply capacity is only 1600×108m3. By 2020, the natural gas gap will exceed 1000×108m3, which provides space for the development of unconventional gases such as coalbed methane.

3.1 Development Prospects

According to relevant plans, by 2015, the output of coalbed methane from surface development nationwide will reach 100×108m3; in 2020, the natural gas output will be approximately 2020×108m3, of which unconventional The natural gas output will reach 620×108m3, and the coalbed methane developed on the ground will reach 200×108m3.

Figure 5 Change trend of natural gas consumption in China from 2000 to 2008

At the same time, relevant enterprises have also formulated development goals for the “Twelfth Five-Year Plan” (Table 2).

Table 2 Forecast of coalbed methane surface development in key areas and enterprises across the country

Whether the above goals can be successfully achieved, what the prospects are, and whether exploration and development and industrial scale can develop rapidly, mainly depend on The further implementation of national policies and the investment of several major enterprises. What is particularly important is the technological progress and breakthroughs made by these enterprises in response to the conditions for coalbed methane occurrence, rather than the funding issue, which must be paid great attention to. PetroChina will further increase investment and promote the rapid development of the coal bed methane industry. We will mainly increase the exploration and development efforts in the two key industrial bases in the southern Qinshui Basin and the eastern Ordos Basin, and actively explore supporting technologies for coalbed methane development in peripheral basins.

It is expected that in 2012, the newly discovered geological reserves of coalbed methane will be 2000×108m3, providing resource guarantee for the construction of production capacity; in 2013, the production capacity will be built at 45×108m3/year, and in 2015, the output will reach 45×108m3, and the commercial volume will be 40×108m3, becoming a domestic The first coalbed methane production enterprise. At the same time, it will become a leader in business technology, a setter of specifications and standards, and a leader in industry development. By 2020, the commercial volume of coalbed methane is expected to reach 100×108m3, becoming an important part of PetroChina’s main business and a strategic economic growth point.

3.2 Countermeasures and Suggestions

3.2.1 Research and adjust countermeasures according to resource distribution

The total amount of coalbed methane resources in the country with a burial depth of less than 2000m is 36.8×1012m3 , the amount of recoverable resources is about 10.8×1012m3. There are 8 basins with resources greater than 1×1012m3, with a total resource volume of 28×1012m3, accounting for 76% of the country, and are mainly distributed in the central and western regions. The amount of resources with a burial depth of less than 1000m is 14×1012m3, which is the main resource currently being developed. Low-rank coal bed methane resources account for 43%, but currently the main development areas are mid- and high-rank coal bed methane resources. Therefore, it is now necessary to strengthen the research and development tests on the development of medium-deep coalbed methane (burial depth greater than 800m) and medium-low rank coal in the western region, and strive for a larger-scale substantive breakthrough.

3.2.2 The implementation of national policies and mutual cooperation between enterprises must be further strengthened

Improve relevant policies and measures, formulate unified plans for coalbed methane and coal development, and achieve seamless and effective Implement "gas extraction first, coal extraction later" to achieve full utilization of resources. The three cooperation methods for coal mining and gas extraction need to be further expanded; the integrated cooperation between coal bed methane industry development and coal mine gas prevention and control should be actively promoted.

3.2.3 Strengthen technical research in improving single well production and overall benefits

Strengthen research on key technologies for coalbed methane exploration and development. Further research and development will be carried out to form suitable supporting facilities and equipment for drilling, fracturing, drainage and pipeline transportation based on the geological characteristics of coalbed methane, and efforts will be made to increase the development of key technologies for the development of plume horizontal wells.

3.2.4 Establish a unified information platform to avoid disorderly competition and repetitive investment

Strengthen information channels to achieve maximum sharing of resources and avoid disorderly competition and repetitive investment . Establishing a unified information management system for the coalbed methane industry is a very important basic task. It includes two aspects: the digital construction of coal bed methane fields should be strengthened within enterprises, and the statistics and exchange of industry technology and industrial information should be strengthened at the national level to provide unified information construction standards for the coal bed methane industry.

Conclusion

Low-carbon economy is the only way for the development of my country's energy economy. In order to reduce carbon emissions from the source and lead the energy structure and industrial diversification, the gap between natural gas supply and demand will exist for a long time, and the demand for coalbed methane will continue to increase. China is rich in coalbed methane resources. The overall scale of the industry is currently small, but it has great potential and good prospects. Increasing research and development efforts and relying on technological progress will greatly promote the rapid development of the coal bed methane industry.

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