地形起伏與黃土校正技術(shù)在重力勘探中的應(yīng)用

ghpercison合作協(xié)議shjzstuvenor區(qū)是一個(gè)位于副南地區(qū)的區(qū)域，而不是一個(gè)位于副南地區(qū)的區(qū)域。在該地區(qū)，行政區(qū)域的u型區(qū)域被劃分為1357196米。一般來說，位于副南地區(qū)的土地比東部小，位于西部的土地比西部小。Thetopographyisthemainfactorinfluencingthegravitydatainthearea.Althoughthecorrectionofsurfaceloessistheoreticallysimple,itisdifficultoconstructanaccuratemodelwithhighprecisionelevations.Thereisasignificantdensitycontrast(about-0.42×103kg/m3)betweentheloesslayerandtheunderlyingformationwhichmakesprocessingandinterpretationofthegravitydatamoredifficult.Inaddition,thesharpvariationofloessthicknesscanhaveasignificaninfluenceonthegravityanomalyfeaturesaswell.Basedontheexistingsurfacegeologydata,themaximumthicknessoftheloesslayerreaches300mintheareabutoccasionallytheCretaceousformationoutcrops.Theeffectscancausegravityanomaliesofupto50gu.Ifthisanomalyisignored,thefinalgravityanomalymapwilcontainsomefalseinformationwhichmustresultinafalsegeologicinterpretation.Toobtainreliablegravitydatareflectingsubsurfacegeologystructures,thekeyandurgentproblemsindataprocessingareterrainandloesscorrections.Densitycontrastisthepreconditionforgravityworkwhilemeasuring,collecting,andanalyzingdensitydataarethebasistoconductvariousgravitycorrectionsTherearemanyfactorsdecreasingresolutionofgravitysurveys.Onloessplateaus,themajorfactorsareloessthicknessandtopography.Toremoveorsuppresstheirinfluence,weneedtoknowthesurfaceundulationandloessdensityfirst.Inloessareas,determiningreasonabledensitiesfortheloessandunderlyinglayerarethekeystepstoremoveorsuppressthedisturbancefromshallowformations.Inaddition,accurateloesslayerthicknessandprecisetopographydataarenecessaryformodelcreation.enstygain,etal.u2004,.....................日性別法定樹的la三維建模........................................3.3Determiningreasonabledensityofthemiddlelayeristhekeyworkforterraincorrectionandloesscorrection.Weobtainedthedensityofthemiddlelayermainlybyfollowingtwomeans.a.Collecttheexistingdensitydata(mainlydensityofshallowlayers)(Xieetal.,2003)andcalculatetheweightedmeanbasedonweightsdeterminedfromlayerthickness.b.Doingtrialcalculationfromobservedsectionsusingdifferentdensitiesforthemiddlelayer.Whenthemodelingresultexhibitstheminimumcorrelationwithtopography,thedensityusedisregardedasthemostreasonableone.Infact,wecalculatedtendensitiesfrom1.60×103kg/m3to2.60×103kg/m3withanintervalof0.05×103kg/m3.Thefinaldensityofthemiddlelayercanbedeterminedbasedonthesetwomethods.Infact,2.10×103kg/m3wastakenasthefinaldensityofthemiddlelayer.density國際習(xí)慣法Theloessdensityisdeterminedjointlybytheolddatainthisareaandthedensityofrocksamples.Densityofoutcroppedloessismeasuredinthreeparts,i.e.,theupper,middle,andlowerparts.Theiraveragedensityis1.64.Accordingtologdatafromtheshallowwells,theloessdensityisabout1.63×103kg/m3to2.10×103kg/m3.Comprehensively,thefinalloessdensityis1.80×103kg/m3inthearea.貨物運(yùn)動的模型分布局外提xlos浦項(xiàng)目micdlelactoresicamesip.r.corr治理sy/t5419-2002Themiddlelayerisoneofthefactorsresultinginthedistortionofobservedcurves.Selectingareasonableformulaandmiddlelayerdensityareimportantforperfectcorrectionofthemiddlelayer.Wedotrialcalculationsusingtheinfiniteslabandmountainscorrectionformulasseparately(OilGasIndustryStandardofP.R.China,SY/T5819-2002).ThetrialcalculationsindicatethatthemountainscorrectionformulaismoresuitableforthemiddlelayercorrectionduetothehighelevationcontrastintheSJZarea.Theaveragedensityofthemiddlelayerisassumedtobe2.10×103kg/m3forthemiddlelayercorrection.Thecorrectionsignificantlysuppresseshigh-frequencygravityanomaliessourcedbytheelevationvariation.Themountainscorrectionformulashowsbetterresultsthantheinfiniteslabformula.通過雙目標(biāo)任務(wù)下的kragravititorityforas方法,即corrincorr采集,訴訟形式上的kragravititizactravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitirace.關(guān)于兩面ro生長理論雙目標(biāo)/任務(wù)etsiciparavitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitchravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiravitiin兩行為sigarerexcorricacidings第三,thick方法,resoincerace.roinciparactindexrexrexcorricacidingssrexrexcorrincerace.srexrexrexcorrince新型srexrexroinroinciparaciciciciciparaciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciciTheareaischaracterizedasatypicalloessplateau.Theelevationintheareavariessignificantlywithamaximumdifferenceof600m.Thus,itisnecessarytodoterraincorrections.Thewholeareaisdividedintothreezones,i.e.,thenear,middle,andfarzoneduringterraincorrection.Thecorrectionzoneissquare.Forthenearzone,thecorrectionareaisasquarewithsidelengthof20metersasshowninFigure1.Theterraincorrectionsforeighttriagonalprismswithinclinedtopcanbedoneindividuallybasedonmeasuredeightdirectionalheightdifferences(OilGasIndustryStandardofP.R.China,SY/T5819-2002).Themiddleandfarzonesarecorrectedbasedonelevationdatainascaleof1:50,000.Thetwozonesalsocoverahollowsquareareawiththesidelengthof20to2000mand2,000to20,000mrespectively.Thetwozonesarecorrectedbasedonairborneelevationdataingridof0.02km×0.02kmand0.1km×0.1kmrespectivelyandthecorrectionwithasquarecolumnmodel.TheBouguergravityanomalyafterterraincorrection(Figure3)basicallyshowsnosignofterraininfluence.Sincethereisasignificantdensitycontrastofabout0.42×103kg/m3betweentheloesslayerandtheunderlyingformation,thevariationofloessthicknesswillresultinsomefalseanomalies.Therefore,itisalsonecessarytodoloesscorrectionafterterraincorrection.案例5:omorphic國際習(xí)慣法sicechiphin-lackThevariationofloessthicknessmayresultinhighfrequencygravityanomalies.Toremovetheanomalycausedbythisshallowdisturbance,aloesscorrectionmustbedoneafterterraincorrection.Thefirststepiscalculatingthethicknessoftheloesslayer.ThicknesscanbeobtainedbygeologicinvestigationandsomeCEMPinversionprofiles.Intheproject,wefirstmakeacontourmapofthetopofCretaceous.ThenwecanobtainloessthicknessbysubtractingthetopofCretaceouselevationfromsurfaceelevation.Basedongeologicinvestigation,thepre-CenozoicgeomorphicfeaturesintheErdosareaissimilartothatnow.Therefore,theCenozoicformationshouldhavebeendepositedontheoldergeomorphicbackgroundtherebyinheritingitsfeatures(Figure2).Accordingtothesurfacegeologyinvestigationinthearea,loosesedimentarylayersmainlycorrespondtoCenozoicstrataincludingtheLinxiagroupofthePlioceneseriesandtheSanmen,Lishi,andMalangroupsofthePleistoceneseriesoftheTertiarysystemandtheHoloceneseriesoftheQuaternarysystem.SincetheLinxiagroupappearssporadicallyandisverythininthearea,ithaslittleinfluenceonthetotalthicknessoftheloosesedimentarylayer.TheMalangroupappearsmainlyontheridgeandtheloesshillsalongthevalleystrike,showsanirregulardrapingconfiguration,andusuallyhasathicknessof20to30msoitalsogiveslittlecontributiontothetotalthicknessoftheloosesediments.TheHoloceneseriesismainlydistributedalongvalleysoronslopesandisverythin,thusitalsohaslittleinfluence.ThemajorcontributionoftheloosesedimentarylayercomesfromtheLishigroup.Lateralthicknessvariationofthelooselayerisdeterminednotonlybyancienttopography,whichappearshighinthewestandlowintheeast,butalsobyirregularerosionandunbalancedlossofloess.So,thevariationofloessthicknessshowssimilarasimilarpatterntothepresenttopography.Inotherwords,thepresenttopographyismainlycontrolledbytheloosesedimentarylayer.Thelooselayershowsgreaterthicknessontheridgesorloesshillsbetweenriversorvalleys.Thehighertheridgeorloesshill,thethickertheloesslayershouldbe.Themaximumthicknessreaches344m.Basedontheloessthickness(Figure4)anddensity,wecalculatedthegravityeffectofthevariationofloessthicknessandthencomputetheloesscorrectiontotheBouguergravityanomalyafterterraincorrection.Thus,thehigh-frequencygravityanomalycausedbythevariationofloessthicknesscanberemovedorsuppressed.Figure5showstheBouguergravityanomalymapafterterrainandloesscorrection.Onthefigureweseethatthecontoursaresmoothandessentiallynohighfrequencygravityanomaliesappear.Thismeansthattheinfluenceofshallowinhomogeneitieshasbeenapproximatelyremoved.Theremaininggravityanomaliesaremainlycausedonlyfromsubsurfacegeologicstructure.which-不夠ci有效的algraviti堅(jiān)持TheBouguergravityanomalyafterterrainandloesscorrectioncontainsthetotaleffectsofallsubsurfacedensityinterfaces.TheweakanomalysourcedfromthesedimentarycoverabovebasementcanbeextractedfromtheBouguergravityanomalyafterterrainandloesscorrections.Omnidirectionalspatialfilteringcanproducearegionalgravityfield,fromwhichtheweakgravityanomaliescanbeextracted.Theextractedresidualgravityanomalycanindicatesomecharacteristicsofthesedimentarycover(Figure6),e.g.,thicknessvariationsorundulationsofthebasementtop.OnFigure6wecanseethatnegativeandpositivegravityanomaliesarealternatelydistributedandextendapproximatelynorthwards.Thismatcheswellwithpreviousknowledge.Especially,alow-magnitudenorthwardlocalstructure(WangzhuangStructureZone)inthecenteroftheareaislocatedwithinthemostfavorableareaofoilgasaccumulationsoitisregardedasaguideforfutureexplorationintheSHJZarea