Study On The Law Of Gas Accumulation In Nanpu Sag

In order to study the distribution law of natural gas and guide its exploration in Nanpu Sag,based on the existing drilling,seismic logging and analysis test data,the main controlling factors and models of gas accumulation in Nanpu Sag are studied by analyzing the types and distribution characteristics of natural gas,and combining with the source rock conditions,transporting pathway conditions,trap conditions,and on the basis of this,the favorable target of natural gas accumulation is predicted.The specific results obtained in the following 5 aspects:(1)Natural gas is mainly gas cap gas in Nanpu Sag,and they are mainly distributed in the Nanpu No.1 structure,Noble fort structure,Master temple structure and Nanpu No.5 structure,and a small number of them are distributed in the Nanpu No.2,No.3 and No.4 structure.The main horizons of them are Dongying formation and Guantao formation.(2)The natural gas in Nanpu Sag mainly comes from the source rocks of the third member of Shahejie Formation and the first member of Shahejie Formation,and among them,good source rocks of the three member of Shahejie Formation and the first member of Shahejie formation are mainly distributed in the middle part of the sag,and the distribution area of the source rock of the third member of Shahejie formation is larger than that of the first member of Shahejie Formation,and the main faults of natural gas migration are oil source faults,which are in middle late and early middle late faults,which are distributed in the whole depression.Natural gas traps are mainly fault traps,which are mainly distributed near the concentrated fault belts.(3)The gas accumulation in Nanpu Sag is mainly controlled by 5 factors:?The range of source rocks and oil source faults controlled the range of gas accumulation.?Broken cover configuration and reservoir with high ratio of sand strata ratio collectively control the horizon of natural gas accumulation.?The distribution of transporting faults controls the location of gas accumulation.?Antithetic faults barrier traps in the vicinity of the transporting faults provide places for gas accumulation.?Sealing gas ability of caprock and gas supply capacity of source rockcontrol the enrichment of natural gas.(4)There are 4 models of hydrocarbon accumulation in Nanpu Sag:?Natural gas pool forming model of reverse fault trap in middle and shallow layers of fault transportation within the source.?Natural gas pool forming model of reverse fault trap in middle and deep layers of fault transportation within the source.?Natural gas pool forming model of reverse fault trap in deep layers of source rock fracture transportation.?Natural gas pool forming model of reverse fault trap in deep and shallow layers of fracture transportation near source.(5)A total of 5 favorable targets for gas exploration in Nanpu Sag are predicted,and they are XM1-N-2 trap of Es2,NP3-3-N-1 trap of buried hill,XM1-N-1 trap of Esl,M160x1-N trap of Es2 and NP3-3-N-2 trap of buried hill.