Sinian Dengying Formation Gas Reservior Geological Conditions In East Sichuan

In this paper,sedimentology,structural geology,petroleum geology,organic geochemistry is theoretical guide.Combined with synthetical analysis of regional outcrop and drilling geological data,geological conditions for reservoir forming of Sinian Dengying Formation in East Sichuan were studied by strata and sedimentation,reservoir distribution,hydrocarbon source rock,reservoir-cap,migration and accumulation condition,pool-forming elements,etc.The results show that dolomites of Sinian Dengying Formation in East Sichuan have big thickness and distribute widely;argillaceous source rocks like Doushantuo formation,Deng-? and Qiongzhusi formation of shelf environments develop,having well genetic potentiality and hydrocarbon-generating intensity;source rock matured in Late Caledonian-mainly generated oil in Hercynian period-mainly generated gas in Indosinian and entered highly matured stage;Deng-? developed grape-lace-algal-dolomite reservoir controled by intertidal algal-dolomite flat,Deng-? developed weathering crust karst and grain beach-type reservoir dominated by Tongwan ? episode and facies;mud and shale cap rock of Qiongzhusi formation deposited in shelf environments distribute widely,Deng-? developed local mud and shale cap;structural trap;structural trap has large numbers,areas and favourable gas reservoir formation geological conditions.Based on the comprehensive analysis of Sinian oil bearing geological conditions and combined the process of reservoir formation,using the technology of balanced section,two reservoir-forming patterns can be concluded in Sinian:the first pattern is that the horst formed during Caledonian-Hercynian period reversed during Indosinian where early gas reservoir model destroied varying degrees;the second pattern is anticline and faulted anticline formed during Indosinian-Yanshanian-Himalayan period where early gas pool adjusted with finality or late charging resovioir model.Three major explorative target exist in research area:the first is late-residue-low-amplitude anticline formed in the shaft of palaeohigh early which is favourable target;the second is gas pool of early anticline destroied,adjusted during later period and entered into late-forming faulted anticline,which is less favourable target;the third is late traps formed during Yanshanian-Himalayan period,which has poor effectiveness.Luzhou-Kaijiang palaeohigh near Middle Sichuan is long-term directional zone of oil-gas migration and adjustment,having excellent generating,reservoiring and capping conditions,which is the most favorable exploration area.