Numerical Simulation of Petroleum Generation, Migration and Accumulation of the Es₃ Formation in Banqiao Depression

The mudstones of the Es₃ formation in Banqiao depression are the dominant source rocks for the major hydrocarbon accumulations and the sandstones of Es₃ formation are major reservoir rocks. Petroleum generation, migration and accumulation history of the Es₃ formation in Banqiao depression are modelled based on reconstruction of the burial, thermal and maturity history in this paper. The Modelling results are calibrated with measured vitrinite reflectance (R_o), borehole temperatures and drilling results of 63 wells. The modelling results indicate that: (1) the present-day heat flow in Banqiao depression varies from 59.8 to 61.7mW/m² and that the paleoheat flow increased from 65 to 50.4Ma, reaching peak heat flow values at 50.4Ma then decreased with from 50.4 to 0Ma; (2) the source rocks maturity of Es₃ formation ranges from 0.75% to 1.8% R_o at present day and from 0.5% to 1.25% R_o at the end of the Ed formation deposition (26Ma). Oil generation (0.5% R_o) in Es₃ formation began from around 35Ma and peak hydrocarbon generation (1.0% R_o) occured from 30Ma; (3) the timing of hydrocarbon expulsion from Es₃ formation source rocks began from 31Ma, the predominant phase of hydrocarbon expulsion is from 31 to 26Ma and the phase of less hydrocarbon expulsion is from 26 to 0Ma; (4) secondary petroleum migration pathways of Es₃ formation of Banqiao depression at present and 26Ma are controlled by the paleo-structure surface and the spreading flowing, confluence flowing and the planar flowing occur in depression zone, the gentle slope zone and the steep slope zone respectively. Six favorable zones of oil accumulations in the Es₃ formation of Banqiao depression are identified, especially the oil accumulations zone Ⅰ and Ⅱ, due to their location being close to the generative kitchens, short oil migration distance and powerful drive force.