Study On Oil And Gas Accumulation Conditions In Mai Chen Sag,Xuwen Exploration Area

This project makes comprehensive use of seismic,drilling,logging,core and other data.In the light of the diversity of hydrocarbon accumulation types and the complexity of control factors in Mai Chen sag,Xuwen exploration area.In this paper,the Weizhou and Liushagang formation as the target layer,the comprehensive evaluation of hydrocarbon source rocks,reservoir capping layers,preservation conditions has been emphatically carried out.And the prediction of the accumulation model and it's main control factors have been explored.A new understanding of hydrocarbon accumulation conditions and models is achieved.Through the study,the following results have been achieved:(1)There are two kinds of hydrocarbon source rocks of the Weizhou and Liushagang formation in the study area,which lay an important material foundation for oil and gas resources.The abundance of dark mudstone in the Liu Sha Gang formation is high and type II,the mudstone in the inner slope and the deep sag zone is all mature.And they are comprehensively evaluated as the middle-good source rock,and are the main source rock of Maichen sag.The dark gray mudstone and carbonaceous mudstone of the Weizhou formation which have high abundance are type III with high mature and effective only appeared in the deep sag.And it is a middle-good hydrocarbon source rock,which is a secondary source rock in the region.(2)The tectonic style is characterized by faulted in the south but overlapped in north,which led to the two types of depositional systems.Two sets of different depositional systems are confirmed by exploration.The Southern Fault Zone is the steep submarine fan depositional system.The North Slope is the lake-delta-river facies depositional system.(3)The reservoir-seal assemblage of Liushagang and Weizhou formation is important in the study area,and the "three-dimensional exploration" has been transformed from geological conjecture to exploration reality.The 2nd section of Liu Shagang regional cap and the 2nd section of Wei Zhou local cap are the main capping layers of the two sets of reservoir cap combination in Liu Shagang and Wei Zhou formation.(4)Based on the typical oil and gas reservoir analysis of the Mai 10 and 8 block,research results of key elements of the accumulation in The Weixinan and Fushan sag,this paper holds that the range of mature source rocks controls the distribution of oil and gas reservoirs.And the cover layers controlled vertical accumulation and transversal migration of oil and gas.The relationship between fault and cap controls oil and gas enrichment and migration.The reservoir characteristics determined the abundance and productivity of the reservoirs.(5)Based on the study of the main control factors of the typical oil and gas reservoirs in Xuwen exploration area,two kinds of accumulation models are predicted in Mai Chen sag,forming a variety of trap types in different tectonic units,and the Mai 12 block and 13 block are favorable targets for further exploration.