The Special Lithologic Characteristics of Sha-1 Member Source Rocks and Hydrocarbon Generation Models in the Bohai Sea Area

The special lithology of Sha-1 Member source rocks in Bohai Sea can be divided into two categories,calcareous shale combination and calcareous mudstone combination,by core or cuttings observation and analysis of electrical characteristics.Combined with analysis of palaeo-geomorphology and sedimentary facies,two kinds of development pattern for the special lithologic combination have been established.The thermal simulation experiments on hydrocarbon generation indicated that the hydrocarbon generated from these two kinds of lithology association was higher,with hydrocarbon yield of calcareous shale combination up to 500 mg/gTOC,and calcareous mudstone combination was about 300 mg/gTOC.Those two kinds were both high quality source rock,with TOC over 1.0%.The hydrocarbon generation models for these two kinds of special lithologic combination have been established through geochemical study.The oil generation threshold depth of calcareous shale combination was shallow,and the hydrocarbon generation model is immature-mature strong double peak model.The oil generation threshold depth of calcareous mudstone combination was very deep,the hydrocarbon generation model is small double peaks model.