Improved matchingofreservoirs imulation modelr esults to production datai ngasfieldsallows improved reservoirm anagement andoptimization ofh ydrocarbon production. Inhigh net:gross aeolian sandstonesthisrequiresthe full range ofscalesofpermeability heterogeneity to be represented inamodel. This necessitatest he modellinga nda ppropriateupscalingofrock properties,i ncludingthe millimetre-scalelamina effects withinthe aeolianduneslipface facies,the contrast betweenduneapron andslipface faciesandthe impact offi rst-a ndsecond-orderboundingsurfacesw ithint he dunec omplexesandthe super-boundingsurfacest hat separatethem.The NeptuneGasFieldliesonthe northwest marginofthe Southern NorthSea gasbasinandinBlock 47/4b andextendsinto Blocks47/5a and42/29. Gasisreservoired inthe LowerLemanFormation which inthe Neptune Field, comprisesasuccession ofstacked dry aeolians andstonesandthin,wetinterduned eposits. Permeability variessignificantly atthe laminaandbedform scaleandthesevariations impactthe performance ofproduction wells int he field.Adeterministic reservoirsimulation modelwasconstructed prior to development drilling, withpermeability determined from porosity-permeability transforms based on corea nalysisdata.The collection ofc ontinuous bottom-holepressure(BHP)dataf rom three ofthe development wells showed thatt hism odelfailed to match accurately the rateofpressured eclinewhilst flowing, andover-predicted the build-up pressurewhent he wells wereshut in. Reviewo fthe sedimentologicalinformation revealed thatheterogeneity int he aeolians andsw as beinglost inthe modellingofpermeability andthe coarseupscaling.Totest whetherthe poor dynamic history match wasdueto the deterministic modeln ot incorporatingthe permeability heterogeneity,afine-scale geocellularm odelw asbuilt to characterizethe expected geologicalheterogeneity andthenu pscaled for flow simulation. Toaccommodatethe range inscalesofheterogeneity present,the modellingwasundertakenintwo principalsteps. First,the lamina-scaleeffects weremodelled to determineaverage flow propertiesperpendicular andparallelt odunemigration directions. The results ofthe lamina-scaleh eterogeneity modellingwerethen incorporated into petrophysicalmodels ofdunebodiesthatwerecharacterized bylow permeability duneapron faciesandhigh permeability baseofduneslipface faciesthatgrade upwardsinto moderatepermeability slipface facies.Upscalingofthe stochastic permeability grid captured the impacto fthe fine-scaleh eterogenetity andg ave BHP responsesatt he development wells inbetteragreement withthe production datathanany deterministic permeability distribution modelled.The stochastic rock property distributionshave, thus,b eenadopted ast he basecasei nall futurehistory match andreservoirperformance prediction studies.