Oil & Gas Geology ›› 2017, Vol. 38 ›› Issue (6): 1098-1104,1216.doi: 10.11743/ogg20170610

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A discussion on the influence factors of dryness coefficient of coal-derived gas: A case from the Upper Paleozoic reservoir in northern Ordos Basin

Ni Chunhua1,2, Bao Jianping1, Liu Guangxiang2, Zhu Jianhui2, Wu Xiaoqi2, Zhai Changbo2   

  1. 1. School of Earth Environment and Water Resources, Yangtze University, Wuhan, Hubei 430100, China;
    2. Wuxi Research Institute of Petroleum Geology, Petroleum Exploration and Production Research Institute, SINOPEC, Wuxi, Jiangsu 214126, China
  • Received:2017-05-25 Revised:2017-09-16 Online:2017-12-28 Published:2018-01-08

Abstract: The dryness coefficient is widely used in the studies on the geochemical characteristics,genetic types and accumulation of coal-derived gas,but only a few of them have addressed the factors affecting the dryness coefficient of coal-derived gas.The major coal-derived gas fields of the Upper Paleozoic reservoir in northern Ordos Basin,such as Dongsheng (Hangjinqi),Daniudi and Sulige,are chosen.Based on the measured and collected data of chemical components,lateral and vertical distribution characteristics of dryness coefficient of coal-derived gas are analyzed,and a two-stage vertical distribution pattern is established.The main controlling geological factors are discussed within the context of regional geological background.The results indicate that ① the dryness coefficient of the Upper Paleozoic coal-derived gas decreases from the center to the margin of the basin,and it displays a two-stage vertical distribution pattern in which the dryness coefficient firstly increases and then decreases from bottom to top.② The dryness coefficient of coal-derived gas is influenced by maturity,geochromatograph effect and leakage effect.③ The maturity of the Upper Paleozoic source rocks determines the regional distribution characteristics of the dryness coefficient.The main controlling factors affecting the "two-stage" vertical distribution of the dryness coefficient are different in the different depth.The source layer and geochromatograph effect the lower and upper reservoirs,respectively.The dryness coefficient is also affected by leakage effect in the areas with poor preservation conditions.

Key words: dryness coefficient, maturity, geochromatograph effect, leakage effect, coal-derived gas, Upper Paleozoic, Ordos Basin

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