On the scientific exploitation of high-rank CBM resources

Zhu, Qingzhong; Yang, Yanhui; Zuo, Yinqing; Song, Yang; Guo, Wei; Tang, Feng Ling; Ren, Jie; Wang, Gang

doi:10.1016/j.ngib.2020.01.008

Cited by 14 publications

(11 citation statements)

References 2 publications

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“…Because of its huge resource potential and cleanability, CBM is considered an important source for meeting China’s growing energy demand. Unlike Australian and American countries that extract CBM from low-rank CBM reservoirs, high-rank coal is the major contributor to CBM production in China, accounting for more than 90% of total production. − However, after decades of development as China’s first commercially exploited CBM field, production in the southern Qinshui Basin has yet to meet expectations. Therefore, increasing production is the current priority for CBM extraction in China.…”

Section: Introductionmentioning

confidence: 99%

Experimental Evaluation of Working Fluid Damage to Gas Transport in a High-Rank Coalbed Methane Reservoir in the Qinshui Basin, China

Liu

Lin²,

Guo

et al. 2023

ACS Omega

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Formation damage induced by the injected working fluid runs through the whole life cycle of coalbed methane (CBM) extraction and ultimately reduces the production of CBM wells. The conventional method uses permeability as a parameter to evaluate the formation damage severity to coal by working fluids containing solids. However, less attention has been attracted to the formation damage of the pure liquid phase of the working fluid on the multiscale gas transport process of CBM. Therefore, we present a multiscale working fluid filtrate damage evaluation method considering the desorption, diffusion, and seepage and use it to evaluate high-rank coal in the Qinshui Basin of China. The results show that pure liquids with different pH values and salinities significantly damage the desorption–diffusion and seepage ability of CBM. The damage rates of alkaline fluid, hydrochloric acid fluid, and clear water on the methane desorption capacity of coal are 63.64, 17.63, and 24.34%, respectively, while those on the permeability of coal are 29.88, 42.38, and 46.66%, respectively. The formation damage severity in the seepage process is higher than that in the desorption–diffusion process, which proves the necessity of multiscale working fluid damage evaluation on CBM. Effective channel reduction and resistance increase in gas transport are the mechanisms of working fluid filtrate-induced formation damage, which are caused by water blocking, sensitive mineral swelling and clogging, and strengthened stress sensitivity. In addition to controlling the solid damage of the working fluid, reducing the invasion of the working fluid filtrate and maintaining its compatibility with the coal and formation fluids are even more important to protect the coal reservoir.

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Section: Introductionmentioning

confidence: 99%

Experimental Evaluation of Working Fluid Damage to Gas Transport in a High-Rank Coalbed Methane Reservoir in the Qinshui Basin, China

Liu

Lin²,

Guo

et al. 2023

ACS Omega

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“…Other coal-bed methane enrichment blocks have made positive progress in exploration and development in recent years. According to the research report of Zhu et al, the production of high coal rank coal-bed methane (CBM) has accounted for more than 90% of the total production of CBM in China. , However, due to the complex occurrence conditions of CBM − and the high metamorphic degree and generally low permeability of high-rank coal, it is difficult for its exploration and development to achieve the expected results. With the rapid growth of CBM mining technology, the current mining technologies such as hydraulic fracturing and multibranch horizontal well drainage have become the focus of CBM development. − …”

Section: Introductionmentioning

confidence: 99%

“…According to the research report of Zhu et al, the production of high coal rank coal-bed methane (CBM) has accounted for more than 90% of the total production of CBM in China. 1,2 However, due to the complex occurrence conditions of CBM 3−5 and the high metamorphic degree and generally low permeability of high-rank coal, it is difficult for its exploration According to the evaluation of unconventional oil and gas by the Ministry of Land and Resources in 2015, it is predicted that the geological resources of CBM in the East Yunnan and West Guizhou gas-bearing basin group are 3.12 trillion m 3 . The recoverable resources of CBM are 1.38 trillion m 3 , and the average recoverable coefficient of CBM resources reaches 44.29%.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Porosity and Permeability Change of High-Rank Coal under Cyclic Loading and Unloading

Yang

Liu

et al. 2022

ACS Omega

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It is of great significance to study the evolution law and change characteristics of the porosity and permeability of coal under cyclic disturbance to efficiently exploit coal-bed methane (CBM). In this paper, the GCTS rock mechanics experimental system is applied, the unsteady gas seepage test under cyclic loading and unloading is carried out with high-grade coal samples from Zhijin County, Guizhou Province, as the research object, and the mathematical formula of the dynamic change of porosity during loading and unloading is established. The results show that (1) the porosity and permeability parameters of coal are negatively correlated with confining pressure, and all decrease with the increase in confining pressure; (2) the change rate of the porosity and permeability of bedding coal decreases gradually with the increase in stress, and the porosity and permeability under high stress decrease gradually with the increase in cycle times; (3) during cyclic loading and unloading, the permeability loss ( D k ) of coal mainly occurs in the first loading (>90%), and D k gradually decreases with the increase in cyclic times; (4) under the same test conditions, the evolution law of the porosity and permeability of parallel bedding coal and vertical bedding coal is similar but the stress sensitivity of vertical bedding coal is higher; (5) the circumferential strain of parallel bedding coal is higher than that of vertical bedding coal, and the porosity change and permeability loss show a specific bedding effect; and (6) under the action of cyclic stress, the change of strain–permeability of coal is abnormal after it is destroyed. With the increase in strain before the sample is destroyed, the permeability drops sharply, and after the sample is destroyed, the strain decreases and the permeability never recovers. The research results can provide favorable theoretical guidance and technical support for pressure relief exploitation of coal-bed methane, such as multibranch horizontal wells.

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“…With soft coal seams widely distributed in eastern North China, Southern and Southwestern China, and the Ordos Basin, China has rich coalbed methane resources [1][2][3][4]. These coal seams with poor physical properties, low porosity, and permeability are difficult to develop [5][6][7][8] and need to be fractured to become economically viable.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation Investigation on Fracture Propagation of Fracturing for Crossing Coal Seam Roof

Xiao

Wang

2022

Processes

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The fracturing crossing coal seam roof is a technology that fulfills the fracturing of a coal seam through the vertical propagation of fractures. Geological conditions are the key factors determining the effect of this kind of fracturing, but there is hardly any research on this aspect. To determine the favorable geological conditions for through-roof fracturing, based on a 3D fracture propagation model, and considering the interlayer vertical fracture toughness and leak-off heterogeneity, a mathematical model of fracturing through a horizontal well in a coal seam roof was established, and the calculation method of fractures crossing layer propagation was determined. In this method, the effect of fracture communication with the coal seam is evaluated by taking the area and the area ratio of fractures in the coal seam as the objective functions. The effects of parameters such as in situ stress combination profile, coal seam fracture toughness, and fluid loss coefficient on fracturing results were evaluated. The reasonable distance from the horizontal well to the coal seam’s top surface was determined in this work. The study results show that: (i) the fracturing effect is better when the coal seam is lower in in situ stress; (ii) the distance between the horizontal well and the top surface of the coal seam is recommended to be less than 4 m to obtain the ideal fracturing effect; and (iii) the combination of the in situ stress profile is the key factor, and the fracture toughness and fluid loss coefficient of the coal seam, fluid viscosity, and the number of perforations in one cluster are the secondary factors affecting the fracturing effect.

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On the scientific exploitation of high-rank CBM resources

Cited by 14 publications

References 2 publications

Experimental Evaluation of Working Fluid Damage to Gas Transport in a High-Rank Coalbed Methane Reservoir in the Qinshui Basin, China

Experimental Evaluation of Working Fluid Damage to Gas Transport in a High-Rank Coalbed Methane Reservoir in the Qinshui Basin, China

Experimental Study on the Porosity and Permeability Change of High-Rank Coal under Cyclic Loading and Unloading

Numerical Simulation Investigation on Fracture Propagation of Fracturing for Crossing Coal Seam Roof

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