Characteristics and geological significance of high-yield shale oil from the Lucaogou Formation in the northern Jimsar Sag of Junggar Basin:A case study of Well Qitan 1
In view of the breakthrough of high-yield shale oil flow in the Lucaogou Formation of Well Qitan 1 in the northern Jimsar Sag,based on crude oil,sandstone extract and source rock sample collection and correlation analysis tests,this paper analyzes oil source and clarifies the hydrocarbon source conditions for shale oil enrich-ment in the Lucaogou Formation of Well Qitan 1.The physical properties,fraction composition and biomarkers molecular characteristics of crude oil are analyzed.It is concluded that the source rock of Lucaogou Formation is a good mature oil source rock with good oil-generating potential,among which the lower section source rock is better than the upper section.The density and viscosity of crude oil in the Lucaogou Formation of Jimsar Sag have the law of increasing first and then decreasing with the increase of depth,and the highest value corresponds to the peak of oil production.The shale oil in the lower section of the Lucaogou Formation in Well Qitan 1 is a medium viscous oil.Reducing conditions of the water body which the Lucaogou Formation source rocks was formed gradually weakened from early to late.The higher maturity parameters of crude oil than adjacent deep source rocks are the result of the combined action of hydrocarbon expulsion from source rock,transport and mat-uration,and the shale oil in the lower section of the Lucaogou Formation in Well Qitan 1 has a certain degree of migration and aggregation process.The key exploration areas for the depression are the vertically interbedded source reservoir,the horizontally adjacent source reservoir configuration relationship,and the areas with deep developed source rocks.This understanding has important guiding role for the exploration and development of saltwater lacustrine shale oil of Fengcheng Formation in the Mahu Sag,Junggar Basin and other areas.
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