Hydrocarbon migration and accumulation process of Hetaoyuan Formation in the northern gentle slope zone of Biyang Depression

In order to understand the distribution of oil and gas, this paper studies the oil migration and accumulation process of Hetaoyuan Formation in the northern gentle slope zone of Biyang Depression using the micro-fluorescence spectrum and fluid inclusion and the burial-thermal history of one-dimensional basin simulation, combined with the analysis of seismic structural attributes and sedimentary facies. The results show that three kinds of fluorescent color oil inclusions, orange, yellow-green and blue-green, are detected in the third member of Hetaoyuan Formation in the northern gentle slope zone, reflecting three episodes of oil with different maturities. The abundance of oil inclusions and the homogenization temperature and burial history curve of associated aqueous inclusions indicate that there are two stages (three episodes) of filling events in the northern reservoir. The first stage was small in scale, and occurred in the relatively low maturity orange yellow fluorescent oil at the end of fault depression and the second stage appeared in the yellow green and blue green fluorescent oil with higher maturity at the end of Miocene tectonic uplift. The fluid overpressure in the second stage filling shown by the paleopressure simulation of fluid inclusions suggests its relation to the tectonic compaction. The continuous overpressure caused by compression and the fluid potential difference increasing with the source rocks in the deep depression caused by the uplift of the northern strata provide a strong driving force for the second stage of oil and gas. The frequent fault activities, especially strike slip faults, caused the transformation of a single sand body transport along the stratain to a composite transport system of sand body transport along the strata+fault vertical transport, leading to the quick migration of crude oil to the Northern gentle slope zone. It is important to understand the tectonic uplift control of oil and gas migration.