Implication of Shale Gas in Hydrocarbon-Related Zones in the Southern Song Hong Basin, Vietnam: A Case Study

This study focuses on the assessment of hydrocarbon generation potential of source rocks, types of organic matter, thermal maturity and mineral compositions for defining multiple hydrocarbon-related zones in SH-1X well that are integrated from the results of Rock-Eval pyrolysis, vitrinite reflectance and X-Ray Diffraction analyses in the Upper Miocene to Oligocene. Organic matters in the Upper Miocene to Middle Miocene shales show low to moderate potential of hydrocarbon generation with low contents of TOC and pyrolysis yields, mainly deriving from type III kerogen and in immature to early mature stages. Shale zones in the Lower Miocene and Oligocene are fairly good-quality source rocks with TOC values of 1.04-1.65 wt.% and S2 pyrolysis yields of 1.40-3.21 mg/g, giving moderate potential of hydrocarbon generation of type III kerogen. The organic matters preserved within the mature stage and reached peak of hydrocarbon generation phase with Ro=0.60-0.83%, Tmax=443-456^oC and PI=0.20-0.44. Mineral compositions of the Lower Miocene and Oligocene shales mainly comprise brittle minerals of over 40% such as quartz, feldspar, plagioclase, carbonate minerals that are favorable conditions for fracturing shale beddings to release gas. High pressure recorded in the Middle Miocene is early a good indicator of seal capacity around and within the shales and also providing reservoir energy needed for driving gas flow. Several hydrocarbon-related zones were defined in the whole well with an implication of weak to effective shale gas-bearing found in the Upper Miocene-Middle Miocene, and significant gas-bearing with a little oil-bearing in Lower Miocene-Oligocene.