Dynamic evolution of the hydrocarbon kitchen in the Lower Cambrian, Sichuan Basin

The Lower Paleozoic marine source rocks in the Sichuan Basin became mature during the early stage and are over mature now. The hydrocarbon kitchen changed from a kerogen pyrolysis type to an ancient oil reservoir cracking type, resulting in successive hydrocarbon supply, which controlled hydrocarbon accumulation in the Lower Paleozoic highly mature and over mature strata. As a result, the analysis and accurate identification of the dynamic evolution of hydrocarbon kitchen is fundamental for exploration. We studied the tectonic, sedimentary evolution and thermal systems in the Sichuan Basin, and described the distribution of the kerogen type hydrocarbon kitchen in the Lower Cambrian Niutitang Formation using a TSM basin modelling system, based on the burial, thermal evolution and hydrocarbon generation histories of source rocks. We also identified the location of the ancient oil kitchen and dynamically traced the hydrocarbon kitchen using an accumulation probability method, combined with the analyses of ancient structure, fluid potential and effective reservoir. The Niutitang source rocks generated and discharged hydrocarbon during the Caledonian and Hercynian periods, and the kitchen center was found in Ziyang, Yibin, and Chishui in the southwest, Xiushan and Lichuan in the east, and in the northeastern margin of the Sichuan Basin. At the end of Late Indosinian, most source rocks were over mature and had expelled a large amount of hydrocarbon. Ancient oil kitchens took the role of hydrocarbon supply instead of kerogen pyrolysis kitchens, and were found mainly in Ziyang, Chongqing, Yibin and the southern, northern, and northeastern margins of the basin.