Variation of sediment provenance at the 09 - 1 Block, Cuu Long Basin: their significance in assessing the Oligocene - Miocene reservoir quality

Abstract

TheCuuLongBasinisoneoftheTertiarysedimentarybasinssituatedonthecontinentalshelfofVietnam,whichdemonstratesthehighpotentialofoilandgas.Apartfromfracturedgranitereservoirs,theOligocene-Miocenesandbodiesarethoughttohavesignificantpotentialforformingnon-structuraltraps.Theresultsofthestudyonthecompositionandphysicalpropertiesofthesedimentsderivedfromwells"X"and"Y",block09-1,CuuLongBasinshowthatthereisacleardifferencebetweentheLateOligoceneandEarlyMiocenesandstoneinthewell"X",namelytheMiocenesandstoneshowslargerparticlesize,higherroundnessandsortness(TB:434.2;Ro:0.69;So:2.22)thanthoseoftheLateOligocenesandstone(TB:104.28;Ro:0.64;So:1.46).ThisdifferenceislikelyattributedtothefactthattheMiocenesandstonewasinfluencedbythemarineenvironment,whichintensifiedtheroundnessandsortness.Meanwhile,thewell"Y"didnotshowmuchdifferenceinthephysicalparametersofthesedimentsbetweentheLateOligoceneandEarlyMioceneageranges.However,thegrainsizewasslightlyincreasedandtheroundnesswaslessduringtheEarlyMiocene.Itispossiblethatthe“Y”wellislocatedclosertothelocalsource.Thevariationinthephysicalparametersofthesediments,proportionofsandgrainsandclaymineralsshowsthatthequalityoflateOligocenereservoirisbetterthanthatofEarlyMiocenereservoir,andtheLateOligocenereservoirqualityinthe"X"wellisbetterthanthatintheborehole"Y