Abstract: Solid bitumen and oil seepage are widely distributed in the Mesoproterozoic strata in the Jibei Depression, North China, suggesting large scales of hydrocarbon accumulation. In this study, microscopic petrographic observations and fluid inclusion analyses were used to reconstruct the hydrocarbon accumulation history in the Lujiazhuang and Shuangdong paleo-oil-reservoirs within the Jibei Depression. Results show that there was a large scale of hydrocarbon accumulation during the Mesoproterozoic. One more stage of hydrocarbon accumulation occurred during the Yanshanian in the Lujiazhaung paleo-oil reservoirs, while two more stages in the Shuangdong paleo-oil reservoirs. The homogenization temperatures of fluid inclusion indicate that the time of hydrocarbon accumulation of the two paleo-oil reservoirs during the Yanshanian was concentrated during 185-150 Ma. Our study shows that the critical time of hydrocarbon accumulation in the Jibei Depression was related to the high paleo-geotemperature caused by regional active volcanic activity during the Yanshanian.

Key words: hydrocarbon accumulation stage, fluid geochemistry, Lujiazhuang paleo-oil reservoir, Shuangdong paleo-oil reservoir;
Jibei Depression