Reservoir formation and modification controlled by thermal events in the Xihu Sag, East China Sea Basin

There have been many hydrocarbon explorations in the Xihu Sag of the East China Sea Basin recently, and these have shown that reservoir dissolution controlled by thermal events have impacted hydrocarbon accumulations in those formations over 3 000 m deep.We aimed to clarify these thermal events, and their control on reservoir dissolution, by using magnetic field, thermal field and 3D seismic datasets, and in particular to investigate the characteristics of ancient volcanos in the study area.Our study used core samples, thin sections, field emission spectroscopy environmental scanning electron microscopy (SEM) and physical properties.Thermal fluids carrying acids accelerated source rock evolution which released further organic acids.These acids led to the generation of secondary pores which modified the original sandstone reservoirs.In view of reservoir developments in different areas, we discuss the mechanism of reservoir reconstruction by thermal events, and predict the likely distribution of reservoirs influenced by thermal events.