| 煤层甲烷碳同位素在煤层气勘探中的地质意义--以沁水盆地为例 |
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| 引用本文： | 张建博,陶明信.煤层甲烷碳同位素在煤层气勘探中的地质意义--以沁水盆地为例[J].沉积学报,2000,18(4):611-614. |
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| 作者姓名： | 张建博 陶明信 |
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| 作者单位： | 1.中国地质大学,北京 100083; |
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| 摘 要： | 根据沁水煤层气甲烷碳同位素的组成与分布特征,从煤层甲烷碳同位素在煤层气解吸-扩散-运移中的分馏效应,结合水文地质条件和构造条件,讨论了煤层甲烷碳同位素在煤层气勘探中的地质意义,认为沁水煤层气δ13C1值不仅总体上较高,而且随埋深增大而增高,说明沁水煤层气存在因煤层抬升而卸压所导致的煤层气解吸-扩散-运移效应,从而形成了该区甲烷碳同位素在平面上的分带现象。
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| 关 键 词： | 煤层甲烷 碳同位素 |
| 文章编号： | 1000-0550(2000)04-0611-04 |
| 收稿时间： | 2000-06-09 |
| 修稿时间： | 2000年6月9日 |
Geological Significances of CoalBed Methane Carbon Isotope in Coal Bed Methane Exploration |
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| Abstract: | As an unconventional natural gas, the characteristics of carbonisotope in coal bed methane (CBM) is similar to conventional gas. This paper summarizes the character of China coal bed methane carbon isotope according to field desorption,thermo-modeling and carbon isotope testing. Taking Qinshui CBM field as a example , it points out the potential area and profitable target zone for CBM exploration and development from carbon isotope fractionation effect and desorption,diffusion and movement effect of CBM,combined with hydrology and structural condition. Geologic target area in China has complex tectonic and high maturation, lots of CBM was lost during evolution stage. The variation of carbon isotope value can directly reflect the CBM accumulation degree. Due to desorption, diffusion and movement effect of CBM, the thermo-modeling value of carbon isotope was much higher than carbon isotope value. Meanwhile,the carbon isotope,which also reflects the preservation condition of CBM trap, is important to evaluate the origin of CBM reservoir and exploration potential. Four different types are divided in terms of carbon isotope value distribution. According to this theory, Qinshui CBM basin in Jincheng area, Shanxi province was found. Rope coring technique was used and carbon isotope testing of field desorption gas was firstly conducted in Qinshui CBM basin. The desorption gas sample for carbon isotope analysis was collected at 4,24 and 96 hours by water displacement. Because of 12C having less electrical property than 13C, CBM molecule with 12C was prior to molecule with 13C in desorption procedure and lead to carbon isotope fractionation, the early adsorption gas had lighter carbon isotope than late adsorption gas. Qinshui CBM field is a large gas field and can be divided into 3 zones in terms of carbon isotope distribution feature. Carbon isotope in coal seam 15 is lighter than coal seam 3 because of being interfered by carbonate water. The best location lies in primary-secondary zone with carbon isotope at - 30‰～ - 40‰. |
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| Keywords: | coalbed methane carbon isotope |
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