Application of Organic Inclusion in Oil-Gas Migration of Sichuan Reservoir of Southwest Sichuan Basin

Organic inclusion is of great importance to the study of development, migration and origin of oil and gas. In Southwest Sichuan basin there are many pores, holes and fractures in the Sinian Dengying reservoir. The pore spaces were filled by dolomites and quarters of different stages. This paper analyzes the characteristics, fluorescence, homogenization temperatures, and chemical and isotopic compositions of the organic inclusions in the filled minerals of different stages. The homogenization temperatures of the organic inclusions in different stages distribute between 120-150 ℃, 160-190 ℃ and 200-(210 ℃). The chief chemical composition of the organic inclusions is CH₄ and CO₂. CH₄ contents of different stages' inclusions are respectively 10.09%-22.08%, 27.06%-40.40%, 55.33%-74.01%, corresponding values of their CO₂/CH₄ content being 3.37-5.87, 1.20-2.20, 0.26-0.63. On this basis, the authors analyze the stages of the origin, development, migration and accumulation of oil and gas. Results show that the natural gas is oil-generating. CO₂ is of organic origin and there is a little inorganic CO₂. There are three stages of migration and accumulation of oil and gas in the Sinian Dengying reservoir, which are different in history of development.