Coalbed Methane Development In China Research Articles

Main controlling factor of coalbed methane enrichment area in southern Qinshui Basin, China

Despite the significant progress made in coalbed methane (CBM) exploration and development in recent years, understanding of CBM enrichment mechanisms remains limited. This study aims to elucidate the CBM enrichment mechanism in the southern Qinshui Basin, China, by analyzing characteristics of global CBM basins and building a geological model of the study area. Field analyses are conducted to predict sweet spots of high CBM abundance and production potential. The findings reveal a high-yield model of CBM accumulation at relatively elevated structural positions within enriched areas. Compared to other global basins, low permeability poses the primary challenge for CBM development in China. Coal seam thickness shows minimal variation in southern Qinshui Basin, exerting negligible impact on CBM productivity. The shallow burial depth of coal seams in this region results in low stress, conferring high permeability conducive to high CBM yields. In situ stress conditions exert a primary control on the development of microfracture systems, which in turn govern reservoir permeability. This work provides new insights into CBM enrichment patterns in the southern Qinshui Basin. The proposed high-yield model enables better understanding of favorable conditions for CBM accumulation. Overall, this study represents a valuable contribution toward unlocking China’s CBM potential through improved geological characterization.

Current status, challenges, and policy suggestions for coalbed methane industry development in China: A review

AbstractChina is vigorously promoting the development of coalbed methane (CBM) resources because CBM is cleaner than coal and a hazardous gas in coal mining. However, the CBM production in China is significantly lower than that in other coal‐rich countries, such as Australia and the United States. In this paper, the main problems hindering CBM development in China are discussed to provide management suggestions for the government. These key problems include exploration and development techniques, the overlap of mining rights, management, financial supporting policy, investment environment, regulations, and market conditions. The results of this study indicate that to improve the development of the CBM industry in China, national and local governments must enact specific and exercisable regulations to increase financial support, improve technology, increase investment in CBM exploration, strengthen public project establishment, and improve the reform of CBM exploration and development policies.

Hydrogeochemistry characteristics of produced waters from CBM wells in Southern Qinshui Basin and implications for CBM commingled development

The hydrogeochemistry characteristics of water co-produced with coalbed methane (CBM) can act as effective indicators for exploration and development of CBM. This study investigated the geochemical compositions of the water co-produced with CBM extracted from the Pennsylvanian–Permian Taiyuan Formation and Shanxi Formation in Southern Qinshui Basin (SQB), which is the most active area of CBM development in China. Water samples were collected from 27 CBM producing wells involving twenty “single-layer drainage” wells and seven “commingled drainage” wells distributed in six CBM blocks of SQB. The samples were conducted for concentration measurements of major ions and trace elements, and determinations of hydrogen (H) and oxygen (O) isotope ratios. The results show that more than 95% water samples produced from CBM wells in SQB are of Na-HCO3 type, and the remaining approximately 5% are of Na-SO4 type. The stable isotope analyses indicate that the waters co-produced with CBM predominantly have a meteoric origin; the H and O isotopic compositions of most of the produced waters are characterised by “18O drift”, in addition, some individual produced waters exhibit “D drift”. δD and δ18O values of produced waters in the study area are relatively more negative at shallower depths and have a rising trend with the increase of burial depth of the coal seams. It shows that CBM wells with lighter H and O isotopes in the produced waters tend to produce more water during the same producing time; accordingly, the pressure drop funnels of these wells are relatively hard to form. The produced waters from different target coal seams have unique trace elements signatures, and approximately 65% trace elements in the produced waters from the lower main coal seam (No.15 coal seam) have a higher concentration than that in the produced waters from the upper main coal seam (No.3 coal seam). To identify the main source of the produced waters from commingled drainage wells, five indicative trace elements (Li, Ga, Rb, Sr and Ba) were extracted firstly and then the standard templates of indicative trace elements of produced waters from “single-layer drainage” wells were established. Based on the standard templates, the produced water source and the degree of interlayer interference process of commingled drainage wells sampled in this study were analyzed qualitatively. Finally, a case study was dissected to verify the applicability of water chemistry indicators (indicative trace elements) in evaluating the feasibility of CBM commingled drainage.

Research on Hydraulic Technology for Seam Permeability Enhancement in Underground Coal Mines in China

Coalbed methane (gas) is a high quality and clean resource, but it also causes disasters in coal mines in China. The low permeability of coal seams is the main reason that developing coalbed methane (CBM) as an energy resource is difficult, so increasing coal seam permeability is the key to CBM development in China. In this paper, the principal techniques for seam permeability enhancement are presented. The paper focuses on hydraulic technology for seam permeability enhancement (HTSPE), which is considered an economic and highly efficient technology for seam permeability enhancement. The process of HTSPE development is reviewed and the current status of the theories behind HTSPE and the technology and equipment for its use are summarized. The goal is to identify the gaps in HTSPE research and the problems in its implementation. In the future, integration and diversification of the technologies along with on-board intelligence and miniaturization may be the trends for the equipment. Finally, it is shown that tree-shaped borehole fracturing can be used to develop CBM in underground coal mines. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.

Challenges and Opportunities of Coalbed Methane Development in China

Coalbed methane (CBM) resources in China have been estimated to exceed 36 Tcm. As of 2014, there were ∼9300 producing CBM wells in China with an annual production of ∼4.4 Bcm. To satisfy its need for energy and to transition to a low-carbon economy, China has a big need to accelerate CBM development. This paper gives an overview of the status of CBM development in China, identifies key technical challenges, and proposes solutions to overcome them. Our review of the literature has revealed that current CBM development in China faces several technical challenges. Current projects are focused on high-rank coals in the Qinshui and Ordos basins, which have major geological and engineering challenges. The former includes low permeability, subhydrostatic reservoir pressure, and a lack of understanding of the connectivity of coal seams, which leads to difficulty in sweet spot indication. The latter includes difficulty in hydraulic fracturing in vertical wells, because of the ductile nature of the coal seams in th...

A new attempt of a CBM tree-like horizontal well: A pilot case of Well ZS 1P-5H in the Qinshui Basin

A multi-lateral horizontal well is one of the main well types employed in the coal bed methane (CBM) development. In a traditional CBM multi-lateral horizontal well, either a major hole or laterals will go crossing through coal beds to the largest extent, which may eventually result in bed collapse, footage failing to meet the design requirement, and the major hole unable to be monitored, re-entered and flushed. Therefore, this paper puts forward a design idea of a tree-like horizontal well composed of a major hole (for dredging passage), laterals (for controlling drainage area) and sub-laterals (for enhancing production). The major hole is usually drilled on the stable roof or floor of a coal bed, laterals are drilled from the major hole into coal beds, and several sub-laterals are drilled from laterals. The major hole, laterals and sub-laterals constitute a tree-like drainage and recovery system, whose major hole remains stable for a long period and can be monitored and maintained. The technique has been successfully applied in Well ZS 1P-5H in the Qinshui Basin, Shanxi. The well included one major hole, 13 laterals, and 26 sub-laterals, with a total drilling footage of 12288 m, a total coal bed footage of 9512 m, and a total pure coal footage of 9408 m. Its major hole was fully placed in the mudstone of the coal bed roof. This well records a successful case of incident-free single well drilling with a footage of more than 10,000 m and serves as a new well type for efficient CBM development in China.

Geologic and hydrological controls on coal reservoir water production in marine coal-bearing strata: A case study of the Carboniferous Taiyuan Formation in the Liulin area, eastern Ordos Basin, China

Coalbed methane (CBM) is commercially explored and produced in the continental Permian Shanxi Formation of the southern Qinshui and eastern Ordos Basins of China. However, CBM production in marine Carboniferous Taiyuan Formation is hindered by a lack of knowledge about the controlling factors on water production. The Liulin area of the eastern Ordos Basin is one of the trail areas for CBM development in China. In this study, water yield characteristics and their influencing factors during CBM production in the Liulin area were investigated by fluid inclusion studies, core slice observations, and stable isotope analyses of groundwater. The results demonstrated that the recharge area for this limestone aquifer of the Taiyuan Formation is the exposed carbonate in the northeastern Liulin area. The thickness along with the dissolved pores and fractures of the limestone aquifer were closely related to the water production of the CBM well. From an engineering point of view, hydraulic fracturing allows the direct movement of water from coal seams to the roof limestone aquifers, which was a key factor in the high water yield of CBM wells in the Liulin area. Finally, based on the structure and distribution of roof limestone as well as water production data, the geologic scenarios for water production in the Taiyuan Formation was divided into four types. These divisions indicated that the best prospective target areas for CBM production should have low numbers of faults, small limestone thicknesses, relatively large burial depths and normal reservoir pressures and temperatures. The results of this study are helpful for CBM exploration and production in the marine coal-bearing strata of China.

New progress and future prospects of CBM exploration and development in China

Efforts to speed up China’s coal bed methane (CBM) exploration developments related to production safety, optimization of energy structures, prevention of energy waste and reduction of greenhouse gas emissions are all of great significance. In order to strengthen CBM exploration and development in China and to encourage increased growth in the CBM industry, we firstly give a general overview of the recent technological innovations and other developments in CBM exploration in the U.S., Canada and other countries. Using this background information as the starting point, we further present observations and analyses of CBM exploration and development, preferential policies, technical support and implications of R&D for CBM development in China. The results show that the problems related to CBM exploration technology development and lack of a complete set of management policies are still the major issues slowing down the growth of domestic CBM industry. Development of resource exploration and technology, R&D and establishment of favorable government policy to support the industry and the creation of a relevant information platform, etc. are finally recommended.

97/00348 Microbial origin of Australian coal-bed methane

Coalbed methane (CBM) drilling technology is critical in achieving efficient CBM development. The geological conditions for CBM development in China are complex, including special terrain, high-rank coal areas, deep coal seams, multiple superposed coal seams and coal measure gas symbiosis areas, steeply inclined coal seam areas, and tectonic coal seam areas. Therefore, it is critical to apply the optimum drilling technology in each different area. This paper first reviews the current CBM drilling technologies and gas production behaviors in China. It is found that although vertical wells and cluster well groups are common well types for CBM development in China, U-, V- and L- shaped horizontal wells and multilateral horizontal wells have been favored for CBM development in recent years. The paper then discusses the applicability of different well types to geological conditions and proposes a modification method for well design in various geologic conditions. This method uses the coal structure, Ro, in situ stress, and ratio of critical desorption pressure to the reservoir pressure as the main inputs.