Restoration of the palaeo-fluid pressures from the Suowa Formation in the Esima area, Qiangtang Basin

The restoration of the palaeo-fluid pressures is explored on the basis of the examination of the fluid inclusions samples from the Suowa Formation reservoirs, Esima area, Qiangtang Basin. There occurred three phases of hydrocarbon charging, of which the second phase of hydrocarbon charging is believed to be the main period for the accumulation in the study area. The timing of the three phases of hydrocarbon generation and accumulation is based on the burial history of the hydrocarbon reservoirs. The palaeo-fluid pressure data are obtained by using the PVT thermodynamic simulation of the fluid inclusions. The results of research for the stratigraphic evolution in the Suowa Formation show that the regional structures and geothermal evolution may be the main controlling factors for the palaeo-fluid pressures. The palaeo-fluid pressures have gone through three stages of evolution:the overpressure systems during the early stage of the hydrocarbon generation, normal hydrostatic pressure systems during the culmination, and low pressure systems during the decline of hydrocarbon generation.