北美典型克拉通盆地页岩气成藏特征、模式及启示

Characteristics and patterns of shale gas accumulation in typical North American cratonic basins and their enlightenments

北美含页岩气克拉通盆地主要以密执安盆地、伊利诺斯盆地和德拉华盆地为代表。对上述盆地的岩性特征、有机质类型、生气方式、埋深、热成熟度、吸附气含量、裂缝对页岩气成藏的作用进行了探讨,梳理了北美克拉通盆地页岩气的两种成藏模式,分别以密执安盆地Antrim页岩气成藏模式(A型模式)和德拉华盆地Barnett页岩气成藏模式(B型模式)为代表。A型模式主要特征为:从盆地周缘较浅至较深部位赋存着具有生物成因和热成因的"二元"成因结构的天然气,依次从生物气过渡到混合气,最后为热成因气。B型模式主要特征为:页岩气生气方式为热成因天然气"原地"生成聚集,在不同成熟度的区域,产出不同热成因类型的天然气。结合我国克拉通盆地油气地质特征认为,德拉华盆地Barnett页岩气成藏模式(B型模式)对我国页岩气勘探更有意义,密执安盆地Antrim页岩气成藏模式(A型模式)对我国页岩气勘探的意义不能忽视。

Michigan Basin, Delaware Basin and Illinois Basin are the typical cratonic basins with shale gas plays in North America. This paper analyzed shale gas reservoir lithology, organic matter type, hydrocarbon generation, burial depth, ther- mal maturity, adsorbed gas content and the role of fracture in shale gas accumulation. We summarized two shale gas accu- mulation patterns：the Antrim shale gas accumulation pattern in Michigan Basin （A-pattern） and the Barnett shale gas accumulation pattern in Delaware Basin （B-pattern）. The primary features of A-pattern is that, from the shallow periphery to the deep basin,biogenie gas,mixed gas and thermogenic gas oeccur in sequence. The main characteristics of B-pattern are that the shale gas is of thermogenic origin and is indigenously generated and accumulated, Shale gas of different ge- netic types occur in areas with different thermal maturities. We suggested that the Barnett shale gas accumulation pattern （B-pattern） of Delaware Basin is of greater significance for shale gas exploration in China, and Antrim shale gas accumu- lation pattern in Michigan Basin （A-pattern） also cannot be ignored for shale gas exploration.