Hydrocarbon Accumulation Characteristics Of The Permian Reserviors In The Eastern Dongdaohaizi Sag,Junggar Basin

The Dongdaohaizi Sag of Jungar Baisn has big hydrocarbon generation potential and its Permian is the major source rocks and major oil and gas reservoirs.According to the results of oil and source rock correlation,determination of the major hydrocarbon sag,analyses and anatomy of the reservoir,the Permian reservoir-forming key factors of Dongdaohaizi Sag were studied in detail,and oil-gas formation model was established and finally forecasting of favorable area was completed.Carbon isotope and biological marker compound show that the oil and gas of the central area of Dongdaohaizi Sag came from Permian Pindiquan hydrocarbon source rocks forming in salty lake facies.The most important pathway system types of Dongdaohaizi Sag are faults and structural ridge(The palaeostructure sand ridges)and the key of oil reservoir forming study is recovering palaeostructure;while as for the slope areas of the Dongdaohaizi Sag,the key of pathway system is the faultes which develop in Permian and Jurassic and the key of reservoir forming study is the shape of fault surface.The present oil reservoirs are mainly distributed in the palaeostructural highs and areas developing sand body.Combining the distribution regularity of oil and gas and comprehensively considering the sourec of oil and gas,pathway system,palaeostructure high and dominant migrating pathway of sturctures,favorable areas were determined.The favorable area I is located in structure ridge of dominant migrating pathway with large thickness of sand body,which is pointing to the area of oil and gas migration;The favorable area II is located on fault convex with transport laye of sand ratio greater than 40%,which belongs to dominant migrating pathway.