Discussion on the Applicability of Mercury Content in Natural Gases as an Identification Index of Coal-Type Gas and Oil-Type Gas
详细信息
- 责任者：Han Zhongxi (Langfang Branch ; Research Institute of Petroleum Exploration & Development ; PetroChina ; Langfang 065007 ; China) ; Li Jian
- 刊名：Acta Petrolei Sinica
- 出版年：2013
- 卷期：34(2)
- 关键词：天然气成因 ; natural gas origin ; 汞 ; mercury
- 页码：p.323-327
- 图表：illus., 5 tables, 20 refs.
- 分类号：1003
- issnNo：ISSN0253-2697
- isbnNo：CN11-2128/TE
摘要
Although the mercury content in natural gases used as an identification index of coal-type gas and oil-type gas has been accepted by many gas geochemists,it is not used so much in practical exploration.The reason is probably that the index is not clearly understood.In order to clarify the applicability of this index,firstly,we discussed the genetic mechanism of mercury in natural gases.Through examining the mercury content in coal and the gas production ratio of coal,and conducting a thermal releasing mercury experiment on crumble coal,we concluded that mercury in natural gases comes mainly from source rocks,especially coal,only the formation temperature reaches to a certain value,can mercury in source rocks begin to be released enormously by the force of heat,and migrate into a gas pool with generated gas and accumulate there.Therefore,the mercury content in gases is determined both by the source rock type and formation temperature.Secondly,we measured the mercury content of gas samples collected from more than 500 gas wells in 8 giant basins of China,and performed the carbon isotopic measurement of alkane-gas from some wells.The statistical analysis of these data showed that the gas can be generally judged as a coal-type gas when the mercury content in the gas is more than 30 μg/m3;it is more likely to be a coal-type gas when its mercury content ranges between 10~30 μg/m3;and it should be pointed out that an reasonable conclusion can be drawn only by combining this measurement value with other geological data.However,the mercury content in natural gases can be used only as an auxiliary identification parameter when it varies between 5~10 μg/m3 or even much lower.