Research On Characteristics Of Heavy-oil Reservoir In Es₃ In Sanhecun Sub-sag Of Zhanhua Sag

Sanhecun sub-sag is one of the important oil and gas regions of Zhanhua sag with huge potential in exploration.But the deep zone's exploration was restricted because of the superficial degree of understanding.By the theory of reservoir geology,combined with different data and experimental technique,the results show that fan delta and nearshore subaqueous fan sediment systems developed in Es₃ formation.Exist a variety of graded type of rock in the study area,including siltstone,sandstone and conglomeratic sandstone,conglomerate,etc.Separation is mainly medium to low,Shape is subrounded and few subangular-subrounded.Composition maturity is medium and texture maturity of clastic reservoir is low.The main diagenesis types of researched area include compaction,cementation,metasomatism and dissolution.Diagenetic stage of the Es₃ formation is from the early B and the medium A.Diagenetic facies can be concluded as three types:matrix filling-compaction diagenetic facies,dissolution diagenetic facies,carbonate cementation diagenetic facies,then established the distribution mode of diagenetic facies.Storage spaces were divided into three kinds : primary pore,secondary pore-cleavage and mixed pore.According to the capillary pressure curve,the pore structure was divided into four types.Study on the reservoir physical property show that Low porosity characteristics,extra low permeability to ultra-low permeability.In vertical,variation tendency of porosity and permeability are similar,in the 2300,porosity and permeability are very high,Beside sedimental micro-facies and diagenesis,the influence of tectonization and overpressure on deep reservoir are also obvious.Based on reservoir characteristics of heavy oil in the study area,the use of log response,the intersection graph method and geochemical data to identify oil layer,oil-water layer,water layer and dry layer.analysis of its vertical and horizontal distribution characteristics,lithology,physical properties and faults control the heavy oil reservoir distribution.Based on the above research,combined with regional sedimentary facies and physical property values of sandstone,reservoirs are evaluated,and the results are as below:the main type of reservoirs in the upper part of Es₃ belong to ?^?;the main type of reservoirs in the lower part of Es₃ belong to ?^?,as for the vertical,the second overlap belt of sand body is the most favorable reservoir,besides,the third overlap,a nearshore subaqueous fan,is also favourable;As for the plane,the southeast of 322 and the southeast of 71 are the favorable reservoir zones.