Study on Reservoir Properties and Critical Depth in Deep Coal Seams in Qinshui Basin, China

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Coalbed methane (CBM) reservoir properties and relationship of properties with burial depth were studied based on the data derived from 204 deep CBM production wells in Qinshui Basin, China. Through the study, it is found that permeability and porosity decrease with the increase of burial depth and the decreasing trend shows step-change characteristics at a critical burial depth. They also show divisional characteristics at certain burial depth. Gas content, geostress, and geotemperature increase with the increase of burial depth, and the increasing trend shows step-change characteristics and also have divisional characteristics at certain burial depth. Based on the previous study on the reservoir property changes with burial depth, three series of critical depth using different parameters are obtained through simulating the critical depth using the BP neural network method. It is found that the critical depth is different when using different parameters. Combined the previous study with the normalization of three different parameter types, the critical depth in Qinshui Basin was defined as shallow coal seam is lower than 650 m and transition band is 650–1000 m, while deep coal seam is deeper than 1000 m. In deep coal seams, the geological conditions and recovery becomes poor, so it can be defined as unfavorable zones. Therefore, other development means, for example, CO ₂ injection, need to be used to accelerate the deep coal methane development.

Related collections

Most cited references 9

Record: found
Abstract: not found
Article: not found

Evaluation of coal structure and permeability with the aid of geophysical logging technology

Xuehai Fu, Yong Qin, Geoff G.X. Wang … (2009)

0 comments Cited 29 times – based on 0 reviews      Review now

Record: found
Abstract: found
Article: not found

Laboratory Study of Gas Permeability and Cleat Compressibility for CBM/ECBM in Chinese Coals

Guiqiang Zheng, Zhejun Pan, Zhongwei Chen … (2012)

Coal permeability is regarded as one of the most critical parameters for the success of coalbed methane recovery. It is also a key parameter for enhanced coalbed methane recovery via CO 2 and/or N 2 injection. Coal permeability is sensitive to stress and cleat compressibility is often used to describe how sensitive the permeability change to stress change for coal reservoirs. Coalbed methane exploration and production activities and interest of enhanced coalbed methane recovery increased dramatically in China in recent years, however, how permeability and cleat compressibility change with respect to gas species, effective stress and pore pressure have not been well understood for Chinese coals, despite that they are the key parameters for primary and enhanced coalbed methane production. In this work, two dry Chinese bituminous coal samples from Qinshui Basin and Junggar Basin are studied. Four gases, including H e , N 2 , CH 4 and CO 2 are used to study permeability behaviour with respect to different effective stresses, pore pressures, and temperatures. The effective stress is up to 5 MPa and pore pressure is up to 7 MPa. Permeability measurements are also carried out at highest pore pressures for each adsorbing gas, at three temperatures, 35, 40 and 45°C. The experimental results show that gas species, effective stress and pore pressure all have significant impact on permeability change for both coal samples. Moreover, the results demonstrate that cleat compressibility is strongly dependent on effective stress. More importantly, the results show that cleat compressibility is also strongly dependent on pore pressure. Cleat compressibility initially decreases with pore pressure increase then it increases slightly at higher pore pressures. However, temperature only has marginal impact on permeability and cleat compressibility change.