Hydrocarbon Accumulation Characteristics Of The Cretaceous Reserviors In The Dixi Area,junggar Basin

The Dixi area is located in the western Dinan Uplift,Junggar Basin.It has favorable petroleum geological conditions with great exploration potential.The Cretaceous is one of the most important oil-gas accumulation layers in the study area.Through hydrocarbon-source correlation,typical reservoir analysis,migration pathway system analysis and so on,combined with previous achievements,the Cretaceous hydrocarbon accumulation characteristics in the study area were studied in detail.The Cretaceous hydrocarbon accumulation mode was built,and the favorable exploration region was predicted.The results show that there are 2 types of crude oils in the study area,one from the Permian lacustrine source rock and the other one from the Jurassic coal measured source rocks.The Cretaceous natural gases include the oil type gas generated by the Permian lacustrine source rock and the coal-formed gas generated by the Carboniferous coal measured source rock.The Dongdaohaizi Depression is the main source kitchen in the study area.The reservoir adjustment and the migration pathway system were the key factors for the Cretaceous hydrocarbon accumulation in the Dixi area.In the Middle Jurassic,oil and gas,generated by the Carboniferous source rock in the Dishuiquan Depression and the Dongdaohaizi Depression,migrated vertically through fault systems and then migrated laterally through sand body carrier beds to the Jurassic reservoirs for accumulation.In the Early Cretaceous,crude oil,generated by the Permian source rock in the Dongdaohaizi Depression,accumulated on the palaeostructure high part of the Dixi area through faults and sand bodies.From the end of the Early Cretaceous to the Middle-Late Cretaceous,oil and gas,generated by the Carboniferous,Permian and Jurassic source rocks,migrated into the Cretaceous of the Dixi area and accumulated through faults and sand bodies,and some previously-formed reservoirs were damaged and their oil-gas also migrated into the Cretaceous in the Dixi area.In the Dixi area,there are 2 most favorable exploration targets.The Target I is located in the palaeostructure high part to the east of the Dixi 9 well.The Target II area is near the faults connecting the source rocks to the southwest of the Dixi 2 well,which is in the boundary of the Dongdaohaizi Depression and the Dinan Uplift.