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The CentralGrabenarea wasfilled withathick pileofsediments duringthe MiddleM ioceneQuaternary,correspondingto aperiodof15Ma.Ashydrocarbon expulsion from the most prolific source rock, the UpperJurassic BoMember,wasinitiated only 20 Ma BP andstill occurs today,the MiddleM ioceneQuaternary evolution isimportant.Int he MiddleMiocene, the CentralGrabenarea wascovered byasea with waterdepthof500 -700 m. Duringthe LateMiocene(Tortonian),the basinwassuccessively filled byprograding slopeanddeltaic sedimentsfrom the northeast. The progradationalinfill resulted inlocaltiltingofthe substratum dueto the loadinge ffecto fthe deposits. Int he latest LateM iocene(Messinian),the maininput ofsediments occurred from the south, asillustrated byathick onlappingsuccession ofupperMessiniansediments. Pliocene sedimentation wascharacterized byr egularinfill from the east withinashelfto shallow marined epositional environment.Followingthe Miocenea ndP liocene, the NorthS ea Basint ilted dueto stronguplifto fthe Fennoscandians hielda ndi ncreased subsidence andsedimentation ratesw ithint he CentralGrabenarea.This furthercomplicated the maturation ofthe source rock, migration pathways anda ccumulation ofh ydrocarbons. The consequence ofthiscomplexburialhistory isexemplified bythe Kraka andHalfdanfields. The Kraka Field hasalarge down-flankoilaccumulation,which ist he result ofaporosity anomaly resultingf rom anearly invasion ofoilint hisp osition beforethe latetiltingofthe NorthS ea Basin. The history ofthe non-structural accumulation ofthe HalfdanFieldcanbe readily modelled;itconstituted asimplefour-waydipclosureduring the LateMiocenewhenpeak oilmigration occurred.The Quaternary tiltingofthe NorthSea Basindueto upliftof the FennoscandianShielda ndstrongsubsidence ofthe CentralGrabenarea resulted inad istinctgradient favouringlong-distance migration ofhydrocarbons. The occurrence ofviablemigration routes,especially within Paleocenesandlayers,hasresulted inlong-distance migration ofoilinto the Sirisubmarinevalleysystem. The most northern indication ofh ydrocarbons hasbeenr ecognized asfaras7 5kmfrom the source area.Longdistance migration ofh ydrocarbons isalso indicated bydirecthydrocarbon indications( DHIs) throughoutt he Cenozoic succession int he DanishN orthS ea.DHIsareparticularly prominent abovek nown hydrocarbon accumulationsint he CentralGraben. Thisindicatesp ronounced verticalm igration,f or instance alonga ctive faults,abovethesestructures.

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