十万山盆地烃源岩有机成熟度评价

Maturity evaluation for hydrocarbon source rock in Shiwanshan basin

十万山盆地勘探程度较低 ,盆地内只有 3口探井 ,有利用价值的仅有万参 1井。此前对该盆地烃源岩演化评价有两种截然相反的观点 :一种观点认为该盆地主要烃源岩 (P2 、T1)分别处于凝析油 湿气演化阶段、生烃高峰 凝析油 湿气演化阶段 ;而法国ELF公司却认为盆地内所有烃源岩均处于过成熟演化阶段。为正确评价该盆地烃源岩热演化 ,避免露头样品因遭受氧化对准确测试烃源岩氧化程度的影响 ,共采集十万山盆地 8套烃源岩 2 0个地表样品及 2 7个浅井样品进行镜质组 (沥青 )反射率测试 ,结果认为泥盆系、石炭系及绝大部分二叠系烃源岩镜质组反射率高达 2 .0 %以上 ,已处于过成熟演化阶段 ,仅有局部二叠系样品处于凝析油 湿气演化阶段晚期 ,而三叠系烃源岩正处于生烃高峰至凝析油 湿气演化阶段。

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.