Study On The Enrichment Regularity Of Yan-9Oil Reservoir In Southern Jingbian Oilfield

Based on Hydrocarbon Accumulation Geology,presentexploration and development ofthe reservoir of the Ninth Member of Yan’an Formation that is the north part of the Jingbian oilfield, the integrated use of a variety of analytical methods,such as core observation,conventional physical property, cast thin section identification, fluorescence thin sectionidentification, scanning electron microscopeidentification, cathodoluminescenceidentification,high-pressure mercury injection,whole rock and clay mineral fluorescent X-ray diffraction,fluid inclusions and temperature measurement, hydrocarbon source rock and crudeoilgeochemical characteristics, accurate stratigraphic division of the Yan’an Formation,thisarticle restores the pre-Jurassicpalaeogeomorphologycharacteristics of the study area, andcomprehensively studies the sedimentary facies and reservoir characteristics,oil accumulationmechanism and accumulation model,main controlling factors for oil and water distributionsystem.It is concluded that the following points:The Jurassic Tenth Member of Yan’an Formationin this area is mainly braided fluvialfacesdeposit, while the Ninth is mainly delta plain sub-facesdeposit.The Ninth Member ofYan’an Formationreservoir’s rocktypes are mainly feldspar sandstone and lithic feldsparsandstone, whichall have low mineralogical, mediumtexture maturity and strong diagenesis.The pore types are mainly intergranular pores, then dissolution pores. Based the pore size islarge, mainly for the micro pore-micro throat, the comprehensive evaluation of the NinthMember of Yan’an Formation reservoir is type Ι and Ι Ι.The Ninth Member of Yan’anFormation reservoir’s lithology, physical property, oil-bearing property and electricpropertyhave close relations, that is,middle-coarse sandstone and fine sandstoneare ofgoodreservoir physical property, good oil-bearing property, electric characteristics with lowvalue of natural potential and natural gamma ray, highvalue of resistivity.The Seventh Memberof Yanchang Formationsource rock, which is good oil source rock by geochemicalindicators,distributes in large area of this place, of which the average thickness is5.8m and thethicknessincreasesgradually to southwest and south.Geochemical characteristics of crude oilshow that oilmaturity of the Ninth Member of Yan’an Formation is lower than thatof theSeventh Member of Yanchang Formation source rock, suggesting that theyhave different source and the former is main of low aquatic organism.Comprehensive comparison of oilsource shows crude oil of the Ninth Member of Yan’an Formation in the study area are fromthe Seventh Member of Yanchang Formation source rock in the center of lake basin,in whichcrude oil first vertical and then long distanceslateral migrates.The Ninth Member of Yan’anFormationreservoir’s formation is that when oil in the Seventh Member of YanchangFormation source rockmigratesthrough networks of sand body superposed points,interconnected pores and various levels of the cracks to the Sixth Member, Fourth and FifthMember and Third Member of Yanchang Formation, driven byoverpressure of hydrocarbongeneration and pressure transmission, that is, it entersthe Jurassic paleochannel,its migrationdynamics turns into buoyancy, by which oil migrates to up-dip direction after to the top of thechannel(the bottom of the mudstone cap rock) and accumulates in small anticlines,high pointsof nose structures or lithological barriers.the Ninth Member of Yan’an Formation reservoir’stype in the study area is mainly structural-lithological composite reservoir. The formationand enrichment is controlled by sand body distribution, nose structures background (orpalaeogeomorphology) and migration pathways. The existence of the migration pathway whichconnects the underlying oil source is the key to its accumulation.