Assessment of Thermal Evolution Stages and Oil-Gas Migration of Carbonate Source Rocks of Early Tertiary in Eastern Sichuan, China, by Organic Inclusion Analysis: ABSTRACT

Abstract

The Jialinjiang Formation of early Tertiary in Sichuan, China, is a series of limestone and dolomite sediments deposited in a platform shoal environment. The diagenetic sequence and organic inclusions trapped in minerals of 95 samples from 20 drillings have been studied. At the late diagenetic stage, pale yellow organic inclusions consisted of liquid hydrocarbons disseminated in pore-infiltrating dolomite, and the homogeneous temperature of contemporaneous saline liquid inclusions possessing a low gas-liquid ratio was 86/degree/C. This indicates the evolution of the organic matter had gone over the oil generating threshold and oil formation had initiated. In the limestone formed at the late diagenetic stage, more brown-yellow organic inclusions were scattered and/or developed along with fissures, comprising 60-70% liquid hydrocarbons and 30-40% gaseous hydrocarbons. Contemporaneous saline liquid inclusions with gas-liquid ratios of 5-10% had homogeneous temperatures of 90/degree/-130/degree/C. These findings show that the organic material had entered a high evolution stage and oil migration had taken place on a large scale.