The Distribution of Gas Components within a Shale System and Its Implication for Migration

Abstract

Experimental studies on the desorption and adsorption of shale are conducted extensively and used for in-depth research on shale gas components and isotopic components. However, there is little systematic research aimed at a given shale stratum. This study takes the Chang-7 shale of the YC23 Well in the Ordos Basin as the research object, and attempts to obtain a full understanding of the distribution characteristics of different gas components, and to explore the migration ability of different gas components. In this study, Chang-7 shale gas in Well YC23 can be sorted into three categories: generated gas, retained gas and accumulated gas. Geochemical parameters including TOC, S1 and S2 are used to evaluate the generated gas, and the fractionation of hydrocarbon components is used to distinguish retained gas and migrated gas. The fractionation of non-hydrocarbon components as well as carbon isotopes is also analyzed and discussed. This study confirms that shale gas in different locations has unique gas components due to gas migration.