The influence of high-yield-water characteristics on productivity of CBM wells and expulsion and production method carried out in Yanchuannan block of the Ordos basin, China

• Published in: Journal of coal science & engineering, China Vol. 19; no. 4; pp. 514 - 521
• Main Authors: Zhao, Xing-Long, Xu, Zu-Wei, Tang, Da-Zhen, Xu, Hao, Tao, Shu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2013
• Subjects: Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Mechanical Engineering; 中国; 产品特性; 产水; 气井产能; 煤层气井; 生产方法; 鄂尔多斯盆地; 采矿设备; Ordos basin; high water yield; expulsion and production method; installation lectotype; Yanchuannan block; influence on productivity; CBM
• ISSN: 1006-9097; 1866-6566
• DOI: 10.1007/s12404-013-0412-0

In order to further study the influence of high-yield-water on the productivity of CBM （coalbed methane） wells and the expulsion and production method carried out in CBM wells, by means of analyzing and researching production characteris- tics and geologic condition of the CBM wells with high water yield in Yanchuannan block located at the eastern margin of Or- dos basin, the mechanism of high water yield decreasing the productivity of CBM well was discussed, and the expulsion and production method for this type of CBM well was proposed. The results show that high water yield would decrease the produc- tivity of CBM wells, and the mechanism is： first, in some circumstances, high water yield could reflect that there was dissipa- tion during the process of coalbed methane reservoir forming, which would lower the gas saturation of coal gas reservoir and reduce the productivity of CBM well; second, a large quantity of coalbed methane dissipated in the form of solution gas, caus- ing the practical reservoir pressure when gas appeared in casing to be lower than critical desorption pressure of the coal bed; finally, the CBM well with high water yield would have higher requirements of discharge and mining installation, system and continuity, and any link with problems would have a great impact on the well＇s productivity and would increase the difficulty of discharge and mining. In the case of wells with high water yield, the key is to select applicable discharge and mining installa- tion, which should be able to make the bottom hole flowing pressure decline smoothly and fast, and make the wells produce gas as quickly as possible but able to slow down the rate of discharge and mining properly when gas has appeared. In addition, in view of the CBM wells with high water yield, an installation lectotype method based on Darcy＇s law was proposed, which was found with good accuracy and practicability through field application.