| Toolebuc shale is a set of marine limy shale with obvious stratification(section) characteristics in Australia. In this paper, geochemical analysis，scanning electron microscope，energy spectrum analysis，lithofacies division and correlation were used to study the differences of oil accumulation conditions of shale reservoir of Eromanga Basin. It is concluded as follows： (1)the TOC of Toolebuc shale is high in general, and has reached low-maturity stage, the dark gray carbonaceous shale of middle section with the highest TOC is the main hydrocarbon generation layer; (2)the upper limy shale has the most abundant types of micropores, with the development of intergranular pores in skeleton of fossils, calcareous dissolved pores, and organic acid dissolved pores with large pore size and good connectivity, which are the dominant reservoir of shale oil; (3)when the lithofacies of the middle section, the upper section and the upper overburden are combined as “mudstone-limy shale-shale”, it is the most favorable sealing cap for shale oil. Through the analysis of S1 and TOC of Toolebuc shale, the lowest limit of TOC of effective source rocks in upper mumber, middle mumber and lower mumber are 4%,7% and 5% respectively, and it is believed that the upper limy shale is more conducive to hydrocarbon retention, the TOC required for hydrocarbon retention is the highest, the proportion of effective source rocks exceeds 60%, and the hydrocarbon expulsion is the most significant in the middle stage. Toolebuc shale has the characteristics of oil accumulation with hydrocarbon supplying in multiple sections, dominant lithofacies reservoiring, differential sealing and retention in effective source rock. The distrubution and accumulation of shale oil are determined by the differences of reservoir forming conditions in shale strata and lithofacies is the main controlling factor of the difference between source, reservoir and cap. |
