The Kongqueting oil-bearing structure located in the north of the Pinghu slope belt in the Xihu Depression has  abundant oil and gas resources, but the process of hydrocarbon accumulation is complicated, and the oil and gas sources and  

charging processes are still unclear. The sources, charging periods and accumulation time of oil and gas in the Kongqueting  structure were investigated by means of oil—source correlation, petrography, homogenization temperature, salinity of fluid

inclusions and laser Raman measurement. The results show that source rocks are mainly distributed in the Eocene Pinghu and  Baoshi Formations. Source rocks include coal, carbonaceous mudstone and mudstone, and the organic matter type is Ⅱ 1 — Ⅱ 2 .   The total organic carbon content ( TOC ), hydrocarbon generation potential ( S 1 + S 2 ) and hydrogen index ( HI ) of source rocks of   Upper, Middle and Lower Pinghu Formations and Baoshi Formations are different. Source rocks of the Lower Pinghu Formations   have higher total organic carbon content. The sandbodies of the Pinghu and Huagang Formations are multi-layer oil-bearing   systems, and the geochemical properties of the oil and gas are different. The oil-source correlation shows that the oil and gas in  this area can be divided into two type: the oil and gas with lower maturity of type I are derived from source rocks of the lower  Pinghu Formation in the middle and lower belts in the Kongqueting area, while the oil and gas with higher maturity of type II   may be derived from the source rocks of the middle and lower belts of the Baoshi Formation. The fluid inclusions in the Pinghu  Formation develop two stages: In the first phase, the gas-liquid two-phase inclusions fluoresce in yellow, yellow-green and blue green. Due to the special geologic processes, the capture homogenization temperature was 130~140 °C, and the accumulation  period was 5~2 Ma, which was dominated by light oil and condensate oil charging. The natural gas inclusions of the second   stage were gray with no fluorescence display and had not experience the special geologic processes. Combined with the main  peak homogenization temperature of 140~150 °C, it was considered that the hydrocarbon accumulation period was 2 Ma till  now, featured as natural gas charging, showing the characteristics of late charging. Asphaltene in the inclusions was detected by  laser Raman and it is speculated that there may have been gas washing in the late stage. The study shows that the main time of  hydrocarbon accumulation in the Kongqueting structure is from the deposition of the Santan Formation up to the present day. It  has a good spatiotemporal arrangement of reservoir-cap assemblage and structural evolution, and has the charging characteristics  of “early oil, late gas and late accumulation”.