Production characteristics and the key factors in high-rank coalbed methane fields: A case study on the Fanzhuang Block, Southern Qinshui Basin, China
Highlights
► CBM wells production performance in the Southern Qinshui Basin was introduced. ► GS theory and statistics were used to study the factors affecting gas production. ► Hydraulic fracturing determines the initial production performance of CBM wells. ► Gas content and permeability determine the long-run performance of CBM fields.
Introduction
At present, China is both the largest consumer and producer of coal in the world (Dai et al., 2012) and much attention has been focused on the origin, distribution, and production of coalbed methane (CBM). As China has gradually expanded its investment in the development of coalbed methane fields in recent years, the number of drilling and producing wells has increased markedly. From 1980 to 2004, only 287 CBM wells had been drilled (Sun, 2005). However, the number of drilled CBM wells by August 2010 had grown to 4657, among of which more than 3700 were producing wells (Sun et al., 2010). Due to the increase in the number of producing wells, China has gained a significant breakthrough in CBM production. In 2005, the annual CBM production from wells drilled from surface reached 1.5 × 108 m3 (Cai, 2008). By 2010, the annual production had grown to more than 15 × 108–20 × 108 m3 (Gao et al., 2010). Nonetheless, the goal that China's annual CBM production was expected to be 100 × 108–110 × 108 m3 by 2015 (Lin and Fu, 2004) will not be achieved without a substantial increase in CBM production in the Qinshui Basin, the largest CBM producing basin in China (Meng et al., 2011, Qian et al., 2009). The problems causing the lag in the development of CBM in the Qinshui Basin need to be analyzed and overcome for CBM reservoir to reach its true potential in production.
The gas and water production performance of the CBM wells in the Southern Qinshui Basin varies significantly from one well to another. However, the CBM production has been affected by a lack of knowledge about the temporal and spatial variations of well productivity and its various factors (depth, thickness, gas content, porosity/permeability, effect of fracturing, structural setting and hydrogeological conditions), which limits reservoir engineers to make practical decisions for the aim of increasing gas production. Therefore, understanding the temporal and spatial variations of production patterns in areas where gas and water production are influenced by structural features will further facilitate the effective management of CBM fields (Pashin and Groshong, 1998).
The goal of this study is to evaluate the impact of various factors on the temporal and spatial variations of productivity and to determine which factor has the greatest effect. The temporal and spatial production characteristics of numerous wells in the Southern Qinshui Basin, as well as the key factors regarding the characteristics of the temporal and spatial variations in CBM well production, are discussed based on correlation scatter diagrams, bivariate correlation analysis, and the gray correlation theory (Cao and Hu, 1993, Deng, 1985, Huang, 2007, Lian et al., 2007, Liu and Xiao, 2010).
Section snippets
Overview of the Qinshui Basin
The Qinshui Basin covers an area of 23.5 × 103 km2 and is bounded to the south by the Zhongtiaoshan Uplift, to the east by the Taihangshan Uplift, to the north by the Wutaishan Uplift, and to the west, the basin is separated from the Linfen Basin and the Lvliangshan Uplift by the Huoshan Uplift (Fig. 1; Cai et al., 2011, Liu et al., 2010, Ye, 2009, Zhang, 2004). The long axis of the basin is more than 330 km long and is generally aligned northeast-southwest and (Zhang, 2004). The basin is a large
Productivity characteristics of CBM wells in the Southern Qinshui Basin
The Fanzhuang Block, operated by PetroChina, is one of the major commercial CBM producing blocks in the Southern Qinshui Basin. By the end of 2010, more than 500 CBM wells had been drilled in this block, over 90% of which were vertical producing wells.
Gas and water rates as well as their production trends in CBM wells differ significantly in the different production stages. The productivity characteristics of CBM wells that initially produced at different times are also markedly varied (
Effects of factors on gas production in the Southern Qinshui Basin
Coalbed methane productivity is dominated by the complex interplay among six key controls: coal distribution, coal rank, gas content, permeability, ground-water flow, and depositional and structural setting (Kaiser et al., 1994). In this study, seven factors including burial depth and thickness of the coal, gas content, porosity and permeability, fracturing effect, structure and hydrogeological conditions, were analyzed to reveal which factor has the greatest effect on gas production in the
Gray correlation analysis and the effect of key factors on CBM well productivity
As mentioned above, the relationships between CBM well productivity and depth, thickness, gas content, porosity, and the effect of hydraulic fracturing have been analyzed. However, the predominant factors affecting CBM well productivity are yet to be determined. To determine the primary factors, gray correlation analysis was introduced to quantify them and to evaluate the influence of the magnitude of various factors on CBM well productivity.
Conclusions
Since 2004, the CBM field in the Southern Qinshui Basin has been highly productive and has become the first commercially developed CBM area in China as well as the first commercial development of high-rank CBM fields in the world. The current production performance shows that the CBM well productivity in this field varies significantly and is controlled by various factors (burial depth, thickness, gas content, porosity/permeability, hydraulic fracturing, structural setting, and hydrogeological
Acknowledgments
This work was supported by the National Basic Research Program of China (“973” Project) (Grant No. 2009CB219600), the Major National Science and Technology Special Projects (Grant Nos. 2011ZX05034-001, 2011ZX05038-001), the Fundamental Research Funds for the Central Universities (2011PY0211). We appreciate the constructive comments and suggestions from the reviewers and the editors. We are also grateful to Yuanyuan Kang, Jinli Song and Jakob Johansson for improving the manuscript.
References (74)
- et al.
Geological controls on prediction of coalbed methane of No. 3 coal seam in Southern Qinshui Basin, North China
International Journal of Coal Geology
(2011) - et al.
Geochemistry of trace elements in Chinese coals: a review of abundances, genetic types, impacts on human health, and industrial utilization
International Journal of Coal Geology
(2012) - et al.
Coalbed methane liquefaction adopting a nitrogen expansion process with propane pre-cooling
Applied Energy
(2010) - et al.
A review on the gas hydrate research in China
Journal of Petroleum Science and Engineering
(2004) - et al.
Experimental study of gas and water transport processes in the inter-cleat (matrix) system of coal: anthracite from Qinshui Basin, China
International Journal of Coal Geology
(2010) - et al.
A numerical study on optimization of multilateral horizontal wellbore patterns for coalbed methane production in Southern Shanxi Province, China
International Journal of Coal Geology
(2011) - et al.
Constraining the hydrocarbon expulsion history of the coals in Qinshui Basin, North China, from the analysis of fluid inclusions
Journal of Geochemical Exploration
(2006) - et al.
In-situ stress, pore pressure and stress-dependent permeability in the Southern Qinshui Basin
International Journal of Rock Mechanics & Mining Sciences
(2011) Variable gas saturation in coalbed methane reservoirs of the Black Warrior Basin: implications for exploration and production
International Journal of Coal Geology
(2010)- et al.
Structural control of coalbed methane production in Alabama
International Journal of Coal Geology
(1998)
Geological controls over coal-bed methane well production in Southern Qinshui basin
Procedia Earth and Planetary Science
Geology of coalbed methane reservoirs in the Southeast Qinshui Basin of China
International Journal of Coal Geology
Dynamic variation effects of coal permeability during the coalbed methane development process in the Qinshui Basin, China
International Journal of Coal Geology
Simulation study on evolution of coalbed methane reservoir in Qinshui basin, China
International Journal of Coal Geology
Automated hydraulic correction technology for CBM horizontal wellbore
International Journal of Coal Geology
Coalbed gas systems, resources, and production and a review of contrasting cases from the San Juan and Powder River Basins
AAPG Bulletin
The relation between cleat frequency and coal rank
Journal of China Coal Society
The principle of effective stress
Teknisk Ukeblad
China national team has become the main force of coalbed methane research
Grey System Theory and Methods
Differences and origin of physical properties of low-rank and high-rank coal-bed methanes
Acta Petrolei Sinica
Hydraulic fracturing and wellbore completion of coalbed methane wells in the Powder River Basin, Wyoming: implications for water and gas production
AAPG Bulletin
Characterization and performance of coalbed methane wells in Drunkards Wash, Carbon County, Utah
Grey System
Geologic controls on coalbed methane production: an example from the Pottsville Formation (Pennsylvanian Age), Black Warrior Basin, Alabama, U.S.A.
Exploration and Development Technology Research of China Coalbed Methane
An analysis on the principal control factor of coal reservoir permeability in Central and Southern Qinshui Basin
Coal Geology & Exploration
Controls of hydrogeological conditions on gas content in Qinshui Basin
Gas content saturation features of seams and control factors analysis in southern part of Qinshui Basin
Coal Science and Technology
Reservoir engineering in coal seams: part I—the physical process of gas storage and movement in coal seams
SPE Reservoir Engineering
Hydrogeological characteristics of underpressure system, distribution of oil and gas in Shiwu fault subsidence, Southern Songliao Basin
Earth Science—Journal of China University of Geoscience
Classification and evaluation of heterogeneous reservoirs of uncompartmentalized oilfields in Shengli Oilfield
Petroleum Exploration and Development
Discussion of geological factor on gas content of coal seam in Qinshui Basin
West-China Exploration Engineering
Control of Late Carboniferous-Early Permian sea level fluctuation on coal reservoir heterogeneity, Taiyuan, Shanxi
Petroleum Exploration and Development
Improving results of coalbed methane development strategies by integrating geomechanics and hydraulic fracturing technologies
SPE
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