The Characteristics Of Fluid Dynamics And Their Effect On Hydrocarbon Accumulation In Western Qaidam Basin

The distribution of hydrocarbon is controlled by many factors in western Qaidam Basin,such as fluid dynamic system,source rock,reservoir,passage system,pathway system.The research on the hydrodynamic will help to deepen our understanding of hydrocarbon accumulation in this area.This paper analyzes the hydrochemical characteristics of each layer and studies the correspondence between water chemistry parameters with oil-bearing property and reservoir distribution with the the comprehensive utilization of hydrochemical test data and oil test data.Then,with the use of actual formation temperature and pressure data,this paper has a research on the plane and profile distribution characteristics of formation pressure.Integrate the tectonic,sedimentary characteristics and variation feature of hydrochemistry and hydrod ynamic,this paper divides western Qaidam Basin into hydrodynamic zones in vertical direction and hydrodynamic systems in horizontal direction.Moreover,the ancient hydrodynamic of typical profile is restored with the usage of numerical simulation.Then,this paper analyzes the excess pressure in the critical periods and its relationship with formation and distribution of reservoir.Get the recognition from the above research:(1)The formation water in western Qaidam Basin belongs to the brine,and its salinityis much higher than the eastern basin.There is no significant dependences of the total salinity and the formation depth.The ratio of the ion reflects the seal of formation is good.Abnormal pressure is developed commonly in western Qaidam Basin,and normal pressure and abnormal low pressure is distributed along the Altun Mountains in horizontal direction.O verpressure has a good corresponding with depositional center at that time.Reservoirs are mainly distributed in places where salinity is relatively high and sealing is good ion ratio refleced and water head is low.The direction from high to low of water head indicates the direction of hydrocarbon migration.(2)The simulation results show that in early period,hydrocarbon is stored in source rocks,mainly forming lithologic reservoirs;In late period,due to the frequent tectonic activity,the original reservoirs are destroyed,and this period is mainly formed of the secondary reservoirs.