Maturity evaluation for hydrocarbon source rock in Shiwanshan basin

Shiwanshan basin is very less explored that only 3 test wells have been drilled, and only Well Wancan 1 can be exploited. There have been two completely different viewpoints on maturity evolution stage of the main source rocks (P 2, T 1) in Shiwanshan basin. One point, put forward by Nanning Institute, is that maturity of the source rock (P 2) and (T 1) is in the stage of condensate wet gas evolution and the peak hydrocarbon generation to condensate wet gas evolution, respectively; but the other one, held by ELF Company of France, is that maturity of all source rocks of Shiwanshan basin is at over maturity evolution stage. In order to assess maturity evolution stage of several hydrocarbon source rocks of the Shiwanshan basin correctly, and to avoid being affected by Oxidation, we tried to get 47 samples (27 from shallower wells and 20 from the Earth surface) subordinate to 8 groups of source rocks and measured reflectance of vitrinite (or bitumen). This paper draws a conclusion that the vitrinite reflectance of source rocks from Devonian, Carboniferous and most of Permian systems is larger than 2.0%, which means that the three source rocks mentioned above are all at over maturity evolution stage. Only the maturity of a few source rock samples (P 2) is at the higher stage of condensate wet gas. Maturity of source rock (T 1) is in the high stage of peak hydrocarbon generation up to the stage of condensate to wet gas evolution.