Relation between palaeohydrodynamic field and hydrocarbon migration and accumulation in Gaoyou sag

Key words:  Gaoyou sag  formation water  palaeohydrodynamic field  hydrocarbon system  hydrocarbon migration and accumulation

Abstract:

There are close relationships among the hydrodynamic field and the hydrocarbon migration, accumulation and dis-iribution in petroliferous basin. Based on the study of hydrochemical characteristics of formation water, the distribution of palaeohydrodynamic field in main oil-gas migration period and its influence on hydrocarbon migration and accumulation in Gaoyou sag were discussed. The results show that during the main oil-gas migration period,Gaoyou sag was a typical asymmetrical compaction-gravity driven flow basin and it is comprised palaeohydrodynamic subfield of upper petroleum system and palaeohydrodynamic subfield of lower petroleum system. On longitudinal and flat, each subfield is composed of several types of local groundwater hydrodynamic units, which include centrifugal flow caused by mudstone compaction, discharge area by cross-formational flow, or cross-formationai and evaporation, and gravity-induced centripetal flow recharged by meteoric water. The oil-gas migration and accumulation are related closely to compaction driven flow and discharge area by cross-formationai flow. It is indicated that the potential exploration areas of upper petroleum system include the inner slope and the outer region of north slope, and those of lower petroleum system include Zheduo, area to the north of Shanian and area to the west of Matouzhuang, where the exploration and research on deep oil-gas reservoirs should be strengthened.