| The resources of oil sands in northwest china are rich.But the level of exploration and development is not balanced.Until now,the exploration degree of oil sands is high in where northwestern margin of Junggar Basin,Qiketai area in Turpan Hami Basin and Yuka area,Youshashan area,Ganchaigou area in Qaidam Basin.Wuerhe area in Northwestern margin of Junggar,Shiyougou area in Jiuxi Basin and Qiketai area in Turpan Hami Basin have entered the development stage.The degree of exploration and developement in Southern Margin of Junggar Basin is relatively low.This paper relies on "Oil sands resources in Northwest China basic geological survey" from China Geological Survey Bureau of Oil and Gas resource survey Center.On the base of the survey of field geological and oil sands outcrops,combine additional data from Ka oil sand well No.1 and observation under the microscope,we can clear the geological characteristics and distribution of oil sands in study area.Collect previous studies' data and observation of cast thin section and SEM,we can study the characteristics of oil sand reservoirs in the study area,it includes the reservoir space,characteristics of petrology,physical property and sedimentary characteristics.On the base of oil content of oil sand reservoir and geochemical data of oil sands in the study area,we can study the degradation and degradation of oil sands in study area.In the end,combine the geological characteristics,structural characteristics,geochemical characteristics and reservoir characteristics,we can study the formation process of oil sand deposits,spatial and temporal distribution of oil sands and the main controlling factors of mineralization,establish the reservoirforming pattern of Jurassic oil sand deposits,calculate the reserves of oil sands in the study area,evaluate the resource potential of oil sands in the study area.The oil sand reservoirs in study area mainly distributes in the Jurassic Sangonghe formation and Toutunhe formation,exposed both in the core,the north and south wings of anticlinal.The oil sand reservoirs in Sangonghe formation mainly exposed in the core of anticlinal,the lithology is mainly gray fine siltstone.The oil sand reservoirs in Toutunhe formation mainly exposed in the north and south wings of anticlinal,the lithology is mainly yellow brown sandstone.The reservoir space of oil sand reservoirs in the study area is dominated by the secondary porosity,and the degree of reservoir physical properties are from low porosity to high porosity,and low permeability to high permeability.The reservoir property of the Toutunhe formation is slightly better than the Sangonghe formation's.The Sangonghe formation is mainly shallow lacustrine subfacies in lacustrine facies,the Toutunhe formation is mainly meandering river sedimentary system in the fluvial facies,oil sand reservoirs is mainly the oxbow lake subfacies and river bed retention and marginal deposit in riverbed subfacies.We analysised the geochemical test of oil sand in the study area and proved the source of Jurassic oil sands mainly comes from higher plants.The types and configurations of terpenes and steroids are the only ones with the strongest antioxidant capacity,indicates that the Jurassic oil sands in the study area were severely degraded.Controlling factors of Jurassic oil sand accumulation in the study area includes:1.Favorable source rock types;2.Good reservoir space;3.Tectonic activities conducive to the formation of oil sands deposits.The type of reservoir formation is Tectonic uplift type which is closely related to the tectonic evolution of the study area.Base on the oil sand formation revealed in Ka oil sand well No.1,we predicted the total oil sand resources in Toutun River area,the result is 5053.23 × 104 t.Base on the area of the study area,we think the resource potential of oil sands in the study area is large,which needs further research and study. |
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