也谈致密砂岩气藏的气源——与戴金星院士商榷

About origin of tight sandstone gas:To discuss with Academician Dai Jinxing

致密砂岩气属于非常规天然气,目前关于致密砂岩气气源的认识尚未统一。四川盆地元坝气田和通南巴气田须家河组气藏同为致密砂岩气,元坝气田须家河组9口井14个天然气样的碳、氦同位素等地球化学数据分析表明,元坝气田须家河组致密砂岩气主要由自源型的煤成气和他源型的油型气组成,同时伴有少量的无机成因气,为混合改造型;通南巴气田须家河组5口井5个天然气样的碳、氦同位素等地球化学数据分析表明,通南巴气田须家河组致密砂岩气主要由他源型的油型气组成,也伴有少量的无机成因气,为混合成因型。因此元坝气田和通南巴气田须家河组致密砂岩气并非单一的煤成气来源,故非常规致密砂岩气具有多种来源,而非"中国致密砂岩气藏的气源均为煤成气",主要为有机成因的煤成气或油型气,或二者的混合气。

Tight sandstone gas belongs to unconventional natural gas.There is no unanimous agreement about the source of tight sandstone gas source.Both the Yuanba and Tongnanba gas fields in the Sichuan Basin produce tight sandstone gas from Xujiahe Formation gas reservoirs.The geochemical data such as the carbon and helium isotopes of the 14 gas samples from the Xujiahe Formation of 9 wells in the Yuanba gas field show that the gas mainly consists of coal-derived gas from the self-source type,oil-type gas from other source,and a small amount of abiogenic gas,suggesting combination gas sources.The similar geochemical data of 5 gas samples from the Xujiahe Formation of 5 wells in the Tongnanba gas field indicate that the gas consists of oil-type gas from other source,accompanied by a small amount of abiogenic gas,also being of mixed origins.Therefore the Xujiahe Formation tight sandstone gases of the Yuanba and Tongnanba gas fields do not come from coal measure alone.They have a variety of sources,mainly the coal-derived gas or oil-type gas of organic origin or the mixture of them.