Study On The Characteristics Of Oil And Gas Accumulation In The Second Step And Subsags Of The Baxian Depression

The amount of oil and gas, which the Souce rock of Es4to Ek in Baxian Subsags, isvery abundant and is the key exploration target of Huabei Oilfield. But the oil and naturalgas origin and the control factors are not clear, the better reservoir-forming patterns are notestablished in the resarch area. In this paper, through the integrated use of petroleumgeology, logging, seismic and geochemical data as well as former research results, weanalyse the oil and natural gas origin and the source of oil and gas in different structuralbelts in the north of Baxian Depression. Through the study of oil and gas accumulationperiod, the deep reservoir conditions, transportation systems and later preservationconditions on the control action of hydrocarbon accumulation in different structural belts,we sum up reservoir-forming patterns and predict the favorable exploration targets.The gas of the Second Step in Baxian, which the hydrocarbon gas content is high,C1/Cnranges from0.75-0.95,13C meets the feature of mature-high mature oil type gas,Ro%is around1.7%, belong to the product of source rocks in mature-high mature stage.We divide the oil into four categories in Baxian Depression, the oil in the north of Baxianis the third and fourth classes and sources from Es3z+xand Es4+Ek source rocks.By analyzing the reservoir characteristics, reservoir caprock conditions, hydrocarbonaccumulation period, oil and gas migration path and direction and later preservationconditions on the control action of hydrocarbon accumulation in different structural belts,we set up two reservoir-forming patterns, one is the early low mature-mature and laterhigh-mature reservoir-forming pattern in Baxian Second Step-Niu Tuozheng Raised, theother is the structure-lithological and formation-lithological reservoir-forming pattern inBaxian Subsags area.