Dynamic analysis on hydrocarbon migration of accumulation periods in low permeability-tight sandstone reservoir

Key words:  low permeability-tight sandstone  main accumulation period  reservoir t^ht history  hydrocarbon migration  hydrodynamic analysis  Ordos Basin  Kuqa depression

Abstract:

By restoring the overpressure of main accumulation period in the deep of Kelasu structural belt of Kuqa depression and Yanchang formation of Yishan slope of Ordos Basin, the possible dynamic conditions during the process of hydrocarbon migration in the low permeability-tight sandstone reservoir were estimated combined with the analysis on reservoir physical properties evolution. The results show that the main dynamics of hydrocarbon migration in the low permeability-tigbt sandstone reservoir is characterized by diversity. The reservoir becomes tight in the natural gas accumulation period in the deep of Kelasu structural belt. The main dynamic of natural gas migration is the overpressure formed by the multiple factors of high-rate deposition, hydrocarbon generation, and teclonie compression and so on. The reservoir does not become tight in the oil infill injection early and middle stage in Yanchang formation of Yishan slope of Ordos Basin. The oil migrates laterally due to buoyancy. The reservoir becomes tight in ihe oil infill injection late stage. It mainly migrates laterally along the residual pathways that are oil-wet due to long-lerm contact with oil. The main dynamic of oil migration is capillary force and the difference of excess pressure among the reservoirs also plays a role in the oil migration. So the oil migration of main accumulation periods in Yanchang formation of Yishan slope of Ordos Basin is ihe joint action of the multi-stage and mu!li-dynamic.