Recent advances in geophysical technology: introduction and review

Abstract

Inm any basins ande specially thosei nNW Europe, 3Dseismic datah aveb ecomeanecessary prerequisiteto development,appraisaland, almost routinely,exploration drilling, but equally theyarerarely seen asbeingsufficient.Whyist his,whent he majority ofi ndustry analysts recognizethe valueof3Dseismic data to ano ilcompany's exploration portfolio:a reg eophysicistst oo successful atm arketing?Arewevictims of promisingtoo much, or shouldwesee thishungerfor everm oresubsurface information asencouragement to refineexistingtechnologiesfurtherandto develop newones? InSeptember2 002,the GeologicalSociety meetingon exploration inv olcanic margins hearda bout a successful strategyof'drillingthe bumps',which led to the discovery ofthe Marjun hydrocarbon accumulation, the first inFaroesewaters. Petex2002 wastoldthatthe biggest UK NorthSea discovery for adecade had not used 'geophysicalm alarkey'. Iss eismic technologyinadequate, or hasitr eached its limits ast he targets getever tougher? Evidently,a st he remainingb asins becomec overed bys eismic surveys,the easy findsareb ecomingf ewer. Havingc onsumed roughly halfthe world's provenr eserves,newr eservesm ust be foundusinge verm ore imaginativeg eologicalhypotheses,a ndremotesensingtechnologiesw ill need to givea ccess to everm ore information andprovide discrimination to test the hypothesesandreduce the risk. The quest for resolution isu nrelentinga ndfi ners patials amplingi sp rovidingsignificant improvementsin imaging.Honouringwell information requiresm orerealistic, anisotropic velocity models for pre-stack depth migration which furnishimagesthatarebetterrepresentations ofthe drillablegeology. The need to qualifythe datainaseismic surveyhasresulted insomany auxiliary measurementsofthe acquisition systemitselfthatthe subsurface dataa rea lmost inaminority,b ut thisbringsimproved, quantified repeatability,withthe potential to drived own time-lapseseismic noisea ndreveals ubtle, production-related reservoirchanges. Qualified amplitudesandcareful control duringprocessingallow inversion for elastic parameters ofthe subsurface.With goodpetrophysicalandgeomechanicalmodels,elastic inversionscanbenefitboththe reservoirengineerandthe drillerandofferfurtherp otentialfor multi-component acquisition inr eservoircharacterization.Salt,b asalt or complextectonic overburdens posetheirown challengestoimagingandencourage potentialfieldmeasurements to complement seismic datainvelocity modelbuildingandthe prediction ofreservoirrocksorfluids. Very long offsets andvery low seismic frequenciesmayalso havearôleto playintheseenvironments. Breakthroughsin datah andlingandvisualization technologyallow us to take full benefitoftheseimprovements. The stimulus for innovation isasstrongaseverand, evenif the immediateeconomic context isuncertain,the industry isresponding.Thispaperwill reviewseveralofthe current technologytrendsandoffersomespeculation on the road ahead.