Quantitative Characterization of Pore Space for the Occurrence of Continental Shale Oil in Lithofacies of Different Types: Middle Jurassic Lianggaoshan Formation in Southeastern Sichuan Basin of the Upper Yangtze Area

In addition to marine and marine-continental transitional strata, the continental ones are also widely distributed in various oil and gas-bearing basins in China. The continental shale generally provides favorable material bases for hydrocarbon generation, such as wide distribution, large thickness, multiple series of strata, high TOC content, nice organic matter type, and moderate thermal evolution. Part of such shale contains shale oil, but the pore space characteristics for the occurrence of this oil are not thoroughly studied. In order to accurately and quantitatively characterize the pore space where the continental shale oil in different types of lithofacies occurs, we sampled the rock cores from the Middle Jurassic Lianggaoshan Formation in the southeastern Sichuan Basin of the Upper Yangtze Area. The TOC content and mineral composition were analyzed, and we also carried out experiments on CO2 and N2 adsorptions, high-pressure mercury injection, and wash oil. Results show significant differences in pore space characteristics for the occurrence of shale oil in different types of lithofacies. In organic-rich mixed and clayey mudstones with the highest TOC content, the free shale oil, occupying the largest reservoir space, mainly occurs in macropores and mesopores, and the adsorbed shale oil, occupying the largest reservoir space, mainly occurs in mesopores. In the organic-bearing clayey mudstone, which has a higher TOC content, the free shale oil takes a larger reservoir space and mainly occurs in macropores, followed by mesopores, and the absorbed one, occupying a larger reservoir space, mostly occurs in micropores and then the mesopores. The organic-bearing mixed mudstone has a moderate TOC content, in which the free shale oil occupies a smaller reservoir space and primarily occurs in mesopores, followed by macropores, and the absorbed one, which takes a larger reservoir space, all occurs in mesopores. In the fine sandstone, the free shale oil occupies a smaller reservoir space and primarily occurs in mesopores, while the absorbed one occupies a smaller reservoir space and all occurs in mesopores.

Structural deformation characteristics of the Lower Yangtze area in South China and its structural physical simulation experiments

The analysis of structural deformation characteristics in the Lower Yangtze area of South China is of great significance to petroleum exploration and development in this area. Based on the geological and geophysical data, the structural deformation characteristics of the Lower Yangtze area are systematically discussed. Structural physical simulation experiments are further conducted to model the typical structural deformation systems and to discuss their dynamic mechanism. The results show that the hedging system is characterized by “asymmetric opposite hedging in the south and north” of the study area. The structural deformation on the northwest of the hedging system mainly occurred in the Middle-Late Triassic and was controlled by southeaster compression in the Indo-Chinese Period. The deformation of southeastern side of the hedging system mainly occurred in Middle-Late Jurassic and was controlled by northwester strong compression in the early period of the Yanshanian Movement. According to the development and evolution sequence of the hedging structure system in the Lower Yangtze area, Wuxi area has weak structural deformation and has not undergone intensive transformation in later periods. Also, the other factors of petroleum accumulation, including the source rock, reservoir, and sealing conditions, are superior, which make a potential area for exploration.