Controlling effect of saline sedimentary environment on enrichment and exploitation of shale gas and oil in lacustrine basin

Abstract

The salinity of continental lacustrine basin has a great influence on the properties of shale. The main objective of this paper is to present the characteristics of shale in different saline stages. In this study, we restored the saline process by the Kauchi method and evaluated the hydrocarbon generation capacity, reservoir property, oiliness and exploitability of shale in different saline stages. The sources of organic matter and paleoproductivity may vary among saline stages. Organic matter mainly originates from coccolithophyta and dinoflagellate in the saltwater stage, demonstrating the highest paleoproductivity. Meanwhile, paleosalinity has an important effect on the lithologic assemblage and mineral composition of shale, which controls its reservoir properties, oiliness and compressibility. The lithology in the saltwater stage is dominated by lamellar argillaceous limestone/calcareous mudstone and lamellar limestone, with good original physical properties. The carbonate content in such stage is the highest, making it easy to dissolve into dissolution pores and thus increasing the porosity and saturation of movable fluid. The high hardness of carbonate gives optimum compressibility to shale.