THE SEDIMENTARYBASINS OFWESTERNAUSTRALIA THESEDIMENTARY BASINS OF WESTERN AUSTRALIA BASEDON THE PROCEEDINGSOF THE WEST AUSTRALIAN BASINSSYMPOSIUM SPONSOREDBY THE WESTERN AUSTRALIANBRANCH OF THE PETROLEUM EXPLORATION SOCIETY OF AUSTRALIA LIMITED ANDHELDINPERTH, WESTERN AUSTRALIA, AUGUST14-17,1994 THE SEDIMENTARY BASINS OF WESTERN AUSTRALIA Edited by P.G.and R.R.PURCELL Copyright1994byPetroleum Exploration Societyof Australia Limited unlessotherwisestated herein. The Crown retains copyright on material in papers byauthors from the Australian Geological Survey Organisation,and the Bureauof ResourceSciences. ISBN0646196073 This book is copyright. Apart from any fair dealing for the purpose of private study, research, criticism or review, as permitted under the Copyright Act, no part may be reproduced by any process without written permission.Enquiries should be made tothePetroleumExplorationSociety of Australia(WABranch). Copiesof thisvolumemaybeobtainedonlyfrom: Thisvolumeshouldbeidentifiedasfollows: PESALimited WABranch GPOBoxTl786 Perth,WA6001 Purcell,P.G.&R.R.(Eds),1994,TheSedimentaryBasinsof WesternAustralia:Proceedingsof PetroleumExploration Societyof Australia Symposium,Perth,1994. Individualpapersshouldbecitedas,forexample: Labutis, V.,1994, Sequence Stratigraphy and the North West Shelf, in: Purcell, P.G.and R.R. (Eds), The Sedimentary Basins of WesternAustralia:Proceedingsof PetroleumExplorationSocietyof Australia Symposium,Perth,1994. TypesettingbyAikenTypeProductions. Printed byFrank DanielsPtyLtd. FRONT COVER:Aerialview,SharkBay,Western Australia. (PhotograpybyR.Woldendorp,PhotoIndex,Perth). Preface ThisisthethirdsymposiumsponsoredbytheWestern Australian Branch of the Petroleum Exploration Society of Australia. The first, in1984,wasfocussedontheCanning Basin; thesecond, in1988,ontheNorth WestShelf. Both wereheldatcriticalmomentsinthehistoryof petroleum exploration and production in this State. This symposium is nodifferent;itdealswiththegeologyandpetroleum resourcesof allthebasinsinWesternAustralia,andthe moment isnolesscritical. Australia's oil self-sufficiency peaked at 96% in1986 and, at that time, looked likely todecline rapidlyandbeas low as55%by1995.Tomaintaina50%self-sufficiencyinto thenextcentury, Australianeededtodiscoverabout150 MMBBL of recoverableoilreserveseveryyear.The1988 symposium was underwritten by the conviction that the best hopeforthosediscoverieswasinthebasinsof theNorth WestShelf. That visionandcommitment hasbeen rewarded.Since 1988, there have been over 20 oil and gas discoveries on the North West Shelf. The most significant have been Wanaea, Cossack, Griffin, Roller, Skate and Wandoo, involving a total of about 450 MMBBL andrepresentinga35%increase in Australia'sreserves.WanaeaandGriffinarethemost significant discoveries in Australia since the Gippsland Basin. Griffin,Roller,andSkatewillcomeonstreamin 1994; Wandoo,inmid-1995,Wanaea-Cossack,in1996. Western Australian oil production will exceed 350 000 BOPD by1996andtheNorthWestShelfwillreplacethe GippslandBasinasAustralia'smainoilproducingregion. Atthesametime,gasandLPGproductionwillsoarto newlevelsandcondensatewillbeamajorexport-income earner. That isthe good news; the bad news is that oil production willdeclinerapidlybeyondthatpeak.Australiamust continue tofindoil.Self-sufficiencyis nowexpectedtobe about 76% in1995and,on current reserves,willdecline to about 60% by the year 2000. Tomaintain that level of selfsufficiency into the next century, Australia needs to discover about twobillion barrels of oil inthenext decade.The best hopeforthatliesstillinWesternAustralia'ssedimentary basins,especially ontheNorthWestShelf. PESA WA1993 President, Jim Durrant saw that thiswas anopportunetimetoreviewthesedimentarygeologyand petroleum potential of all the State's basins and set the basis forrenewedexplorationinthe1990sandbeyond.The Symposium has enjoyed the support of many companies and organisations, by way of contribution to the organisation or v the technical content. Mr Robert Young, Managing Director of West Australian Petroleum Pty Ltd, was Chairman of the SymposiumCommittee,withJimDurrantof Durrant and AssociatesasViceChariman.PhillipsAustralianOil CompanythroughBrendanO'ReillyandNoelGuppie, provided theSecretariat; Western Mining Corporation Ltd, throughDonPoyntonandGrahamPitt,providedthe RegistrationSecretariat.PhilLawry,atMinoraResources NL,actedasTreasurer. Wehavebeen mindful in recent monthsof theill health of Dr Elwood Horstman. Elwood was Chairman of the first symposium,mentorof thesecondand,untilhisillness,a guidingcommitteemember forthissymposium.Wewish himwell.Wehopetoseehislikeagainintheyounger generationtowhom hisbatonisnowpassed. Thisvolume,thepre-publishedproceedingsfromthe Western Australian Basins Symposium, contains 60 papers and representsthework of over100 authors.On behalf of PESA WAanddelegatestothisSymposium,wethankall authors for their efforts. As editors, we thank them personally, aswellasallwhohelped withtheediting.For most, there is little reward in this, other than the contributing- but that is what isneeded.The challenge of the futureloomslarge. WesternAustralia'sgassupplieswillunderwritethe growthof thisStateovercomingdecadesandcontribute more than anyother source tothe wealth and well-being of all people here, and elsewhere in Australia. The gas pipeline from the North West Shelf to theKalgoorlie goldfields will traversemuchof theState'srichmineralfieldsandmay finally allow victory over what the historian Geoffrey Blainey called'thetyrannyof distance' .Thereserves-to-annual production ratio for known natural gas resources in Western Australian basins iscloseto150 years. That is a sustaining asset forthe21st century. The discovery of new oil fields is anGas export willhelpoffsetthecostof oilimportbillsbutthatisno substituteforthehighest possibleoilself-sufficiency. The petroleum resouces of Western Australia are a gift of nature. The discoveryanddevelopment of thoseresources isa prize our industry has won, and shared with the nation. Wehopethatthenewgenerationof explorers,whomust winthe prize anew in the century ahead, find thisvolume a usefulbeginningandguideintheir quest. Peter and Robyn Purcell Perth, Western Australia July,1994. PETROLEUM EXPLORATIONSOCIETY OF AUSTRALIALIMITED WESTERN AUSTRALIAN BRANCH West Australian Basins SymposiumCommittee Chairman... .... .. ... .... ............................. .... ...... ..... . ViceChairman ........ .. ... .. ..... .. .... .................... .. .. .. . Secretary ........ ...................................... .. ............. . RegistrationSecretary....................................... .. Treasurer .. .... .. ..... ............ ..... .......... ....... .... ... .... ... . Editors ... .......... ...... ..... ..... .. ... .... ........ .... .... .. ...... ... . Members .. .. .E.Horstman Geocon Australia PtyLtd. E.Howell Hadson EnergyLimited. A. Williams Hadson EnergyLimited. AndrewSvalbe GeologicalSurveyof Western Australia J.Gorter HardyPetroleumLimited. Robert Young West AustralianPetroleum PtyLtd. Jim Durrant Durrant and Associates. BrendanO'Reilly NoelGuppy PhillipsOilCompany Australia. DonPoynton GrahamPitt WesternMiningCorporation. PhilLawry Minora ResourcesNL. Peter &RobynPurcell P&RGeologicalConsultantsPtyLtd. J.Warren CurtinUniversity. R. Malcolm AmpolexLimited. N. Milne,J. Winterholder WoodsideOffshore Petroleum Ltd. D.Burt David Burt andAssociates. H.Moors West AustralianPetroleum Pty Ltd. B.Logan Universityof Western Australia. SPONSORS ProceedingsSponsors AmpolexLimited AustralianGeologicalSurveyOrganisation BHP Petroleum PtyLtd EnterpriseOilExploration Ltd Kufpec Australia PtyLtd PhillipsOilCompany Australia SagascoResourcesLtd West Australia PetroleumPty Ltd WesternMiningCorporationLimited vi SessionSponsors BP PetroleumDevelopment Australia PtyLtd Command Petroleum HoldingsNL HadsonEnergyLimited MinoraResourcesNL PetrozNL PhillipsOilCompany Australia ShellDevelopment(Australia)PtyLtd WestemMiningCorporationLimited Table of Contents INTRODUCTION The Sedimentary Basinsof Western Australia: AnIntroduction. PG.and R. R. Purcell.. .. .... .... ....... ... ....... ....... ........... .... .. .... .. .................. .. .... .. .... ... .... .... ......... ....... ...... .. ... ...... .. .....3 BASINFRAMEWORK ANDEVOLUTION AnAtlasof NeoproterozoicandPhanerozoicBasins of WesternAustralia. R.Hocking, A.J.Moryand I.R.Williams. ....... ......... .................... ... ........ ........ ................. ... .......... ........... ........... .21 TectonicFramework of WesternAustralia'sNeoproterozoictoRecentSedimentary Basins. PWBaillie,C.MeA.Powell, Z.X.Liand A.M.Ryall. ... ..... ..... .... ... ....... ..... .......... ... ..... ..... ......... .. ...... ........ ..... .45 DeepReflectionsontheNorthWestShelf: ChangingPerceptionsof BasinFormation. AGSONorthWestShelf StudyGroup . .. ... .. . .... .. ... .. ... . .. ... .. ..... .. ... .. ... .. ..... .. ..... ....... .. .... ... .. ... . .. .. .. ..... .. .. .... .. .. .. .. .. .. .. .63 Lineament Tectonics: An ApproachtoBasin AnalysisandExploration. C. Elliott . ... .. .... ..... .. ... ... ... .. .... .... .. ... .. .. ... .. ..... .. .. ... .. .. .. .. ... .. ...... .... ... .. ..... .. ........... . .. .......... ...... .. .... ... .. . .. .. .. ... ... .. ..... ... .77 PETROLEUM SYSTEMS ANDRESOURCES PetroleumSystemsinWest AustralianBasins. M.TBradshaw, J.Bradshaw,A.PMurray,D. J. Needham,L.Spencer,R.E.Summons,J.Wilmot and S. Winn . . .. . . . . .. . . . . . . . .. . .. . . . . .. .. . .. . . . . . . . . . .. . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 Petroleum Resourcesof theWestern AustralianBasins. S. R.lePoidevinand R.D.Lowden.... ..... ............ ........ ..... ..... ....... ....... .. ..... ....................... ... ......... ....... .. ..... ........ ...119 NorthernCarnarvonBasinHydrocarbon DistributionandFuturePetroleumPotential. E. Kopsen.. ...... ..... ....... .......... ..... ...... ....... ..... ..... ............. .. ....... ........... ........................... ....... ....... ... ............ ...... ........127 SourceRocksof West Australian Basins - Distribution,Character andModels. J.Scott........ ....... ....... ..... .. ...... ... ......... .. ............... ..... .......... ... ....... ....... ... ...... ........ ...... ......... .... .. ........ .. ........ ...... .. .....141 NORTH WEST SHELF Sequence StratigraphyandtheNorth West Shelf of Australia. VR.Labutis. .. ..... .. .. ... .. ............ . ..... .. .. .. . ..... ..... ... .. .... .... .. ... ..... .... ..... .. .. ... .. ..... .. .... . .. .... .... ...... ......... ... ...... .. .... .. .. .. . .. ..159 The Mesozoic and Cainozoic Sequences of theNorthwest Australian Margin,asrevealed by ODP Core Drilling andRelated Studies. N.FExonandU.vonRad ........................ .. .... .......... .. .......... .. .... ............ .. .... .. .......................................... .......... ...181 vii TowardsanEarlytoMiddleJurassicPalaeogeography fortheNorth WestShelf:AMarinePerspective. M. Apthorpe ......... ... ... ... ... ... ...... ............. .. .... ............ ...... ..... .... ... .. .. .......... ..... ... ...... ...... .. ......... ......... ..... ....... ... ... ... ...201 TheRoleof RegionalSeismicSurveysintheExplorationof theNmth WestShelf. J.Ostbyand C.Johnston..... ............ ..... .. .. .. ... .... ..... ... ... ... .. .... ... .. ....... ........... .. ... ..... ... ..... .. .... .. .... .. .... .. ... ... .... ... .. .... .211 BONAPARTEBASIN MeanderstoFans:ASequence Stratigraphic Approach toUpper Jurassic- LowerCretaceous Sedimentation intheSahulSyncline, NorthBonaparte Basin. PH.Robinson,H.S.Stead,J.B.O'Reillyand N.K.Guppy.. .. .. .. ................ .... .. .. .......... .... .... .. .. .. ...... .. ...... .. .......223 Sequencestratigraphyof theFlamingoGroup, SouthernBonaparteBasin. B.E.J.Messent,A.K.Goody,E.Collinsand S.Tobias.... .......... ............ .............. .. .... .. .. .. .............................. ....243 ASalt-related Detachment Model fortheDevelopment of theVulcanSub-basin. E.PWoods .. .................. .... .. ................ ............ ..... .. ............... ... .... .... ....... .. ........... ..... ..... ......... .... ....... .. ... .... ....... .....259 TheGood andBad of Diagenesis- AReviewof SandstoneReservoirsintheNorthBonaparte Basin. M.F.Killick and PH.Robinson ........................ .. .................... .. ........................................ .... ............................ .. ..275 ContemporaryStressesintheTimorSea:ImplicationsforFault-trapIntegrity. S.D.Mildren,R.R.Hillis,T.Fettand PH.Robinson .... ......................................................................................291 OilMigrationintheCartier Trough,VulcanSub-basin. M.Lisk and PEadington ..... .. ..................... .. ...... .. ................ .... ...... ............ .. .. ... .. .... ... .... .... .. ..... ..... .. .. .. .... ... ...........301 BROWSE BASIN DeepStructureof theBrowseBasin:ImplicationsforBasinDevelopment andPetroleum Exploration. PA.Symonds,C.D.N.Collinsand J.Bradshaw .... ...... .. ...... ........ .. ............ .. .... .. .... .. .. .. ........ ............ .... .. .. .... .. .. ...315 AReviewof thePetroleumPotentialof theBrowse Basin. T.U Maung,S.Cadmanand B.West... ............ .... .................. .. .............. .. .. .. .. .. .... .... ............ .. .... .. .......... .. ..............333 CARNARVON BASIN TheStructuralFoundationsof theNmthernCarnarvonBasin. M.J.Staggand J.B.Colwell .. .. .... .. .. .... ...... .. ............ .. .. .. .. .......... .. .... .... .. .. .... .. .. .... .. .. .......... .. .. .. .. .. .... .... .. .. .... .. .......349 The HydrocarbonPotentialof theOnshoreCarnarvonBasin. B.J.Warris .. .. . .. .... . .. .. .. .. . ... . ...... ..... ......... ... .. .... ...... ... .. ... .... ..... .. .... .... ..... .. ..... ..... .. .. .. .. . . . .. .. .. ...... . ..... .. .. .... .. ... .. .. .. ......365 Lower PalaeozoicFaciesintheCarnarvonBasin, WesternAustralia: StratigraphyandHydrocarbon Prospectivity. J.D.Gorter,R.S.Nicolland C.B.Foster.......................................................... .. ...... ...... .. ...... .. ...... .......... .. ........373 TriassicSequence Stratigraphy of theCarnarvonBasin,Western Australia. J.D.Gorter ... ... ... .. .. .. ... ..... . .. .... ..... ... .. .. ..... ...... .... . . .. . .. ... .. .. ... .. ... ... .... .. ... ..... ..... .. ...... .... ............ ..... .. ..... .. .. .. .. ........ .. ..397 Flourescence AlterationandThermalMaturationModellingof CarnarvonBasin Wells. R.WT.Wilkins,N.J.Russell and M.VEllacott ...... .... ...... ................ .. .... ................................ .. .... .. .. .. ........ .... ....415 BARROW AND EXMOUTH SUB-BASINS SequenceStratigraphyof theLower Neocomian BarrowDelta,ExmouthPlateau,Northwestern Australia. M.I.Ross and PR.Vail...... .... ........ .... .................... .. .... ........ .. ...... .. .. ........ .. .. .. .... .. ........................ .................. .. .... .435 OilandGas Accumulationsof theOffshoreBarrow- Exmouth Sub-basins - TrendsinHydrocarbonHabitat. L.Zaunbrecher .. .. ... ...... ....... ..... .... .... .... ..... ... . .. .. .. .. ... .. ....... ... .. ... .. . .. ..... .. ... .. .. ... .. .... .. .. .. ........ .. .. ... .. ... .. .. .. .. .. .......... .. ..449 Mid-CretaceousConcretionary CarbonateReservoirsatBarrowIsland,Western Australia. G.Ellis,A. M.Taitand PJ.Gibson.. .... .. ...... .. .... ...... .. .... ........ .. .. ...... .............. .... ...... .... .. ........ .. .. .... .. .. .. .... .. .. .. .. ....459 viii DAMPIER AND BEAGLE SUB-BASINS MesozoicStructural Development of theBeagle Sub-basin - ImplicationsforthePetroleumPotential of theNorthernCarnarvonBasin. J.E.Blevin,A.E. Stephensonand B.G. West.. ... .. .. ........... .... .... .. .... .... ... .. .... ......... ... ... ....... .. .... ... ... .......... ............479 CluestotheStructuralHistoryof theRankin Trendfrom3-DSeismic Data. S.Newman .. .... ..... ....... ........... ..... ......... ....... ........... ..... .. ...... ........... ............... ............ ..... ..... ...... ... .... ..... ...................497 RankinPlatform, WesternAustralia: StructuralDevelopment andExplorationPotential. A.Stein..... .. .. .. .... . ..... ... .. .. ....... .. ..... .. ..... .. ......... .. ... .... .... .... .. ... .... .. ... .. . .. ... .... ..... .... .. .. .. .. .... .... .. . ..... .. . .. ....... .... .. ..........509 SequenceStratigraphyandPetroleum Potentialof Upper Jurassic- Lower CretaceousDepositional SystemsintheDampier Sub-basin, NorthWestShelf, Australia. PBarber. ........................ .... ..... ........... ..... ...... .. ..... ..... ... ........... .... ...................... ........... ... ...... .. .... ... ........ .. .... ..... .... ..525 HighResolutionPalynostratigraphyof theTithonian Angel Formationinthe Wanaea and Cossack OilFields, Dampier Sub-basin. A. N.Bintand N.G.Marshall.. .... ..... ... .......... .. .... .... .. .. .... ....... ..... ...... ......... .... ... ... .. ..... .... ....... .......... ....... ... ..... .. ... .543 NORTH WEST SHELF FIELDS ANDDISCOVERIES The ReservoirGeologyof the WanaeaandCossackOilFields. G.A.E.diToro. ........ ..... .... ... .. ... .. .. ..... .. .. ....... ....... .. ... ... .. ..... .... ... .. .. .. .. .. ..... .. ....... ........ ........ .. ..... .. .. ........... .... .. .... ....557 The Leatherback Discovery, CarnarvonBasin. J.A.Bauer,E.C.D.Hooper and J.Crowley .. ... ........ .. .. ... .. ... ... ...... .. ... .. ... .. .......... .... ... ...... .... .... ...... ..... .. .. ......... ....573 WestMuironDiscovery,WA-155-P- NewLifeforanOld Prospect. L.Mitchelmoreand N.Smith....... .. ................ .. ... .. .. .......... ... .... ... .. .... .. ....... .... ..................... .... ... ...... .. .. .. ..... ........... .583 MaitlandGasDiscovery - AGeological/Geophysical CaseHistory. K.H.Sit,PM.Hillockand N.WD.Miller...... ........ ...... .. ... .. .. ... .... .. ..... .. .... .. .. ...... ... .. .. .. .... ..... .... .... ..... ... .. .. ........ .597 WandooOilField:AFormation EvaluationCaseHistory. E.Delfos ..... ....... .. .................. ..... .. ... ....................... .................................... .. ... .. ....... .. ... ... ....... .. ..............................615 Recent Gas DiscoveriesontheRankin Trend, North WestShelf, Australia: The Echo/YodelandNorthRankin WestFields. L.Tilbury....... .... .... ... .. ..... ...... .... ....... ......... ....... .. ..... .... . ...... . .. .. .. .. ... .... .. ... .. ....... .. .. .. .. .. ... . .. .... .. ......... .. .. .. ...... .. .. ... . .. ..633 Recent WAPETDiscoveriesnear Thevenard Island,Southeast BarrowSub-basin. G.J.Beacher,M.K.McLerie and N.W.Miller ............................ .. .................................................... ............ .. .... .639 The Tanami,SinbadandUlidia FieldsandtheStagDiscovery, BarrowandDampier Sub-basins, WA. M. Ballesteros ................. ... ........ ... ....... ........ ...... ... ...... ..... ... ......... .... ....... ....... ................ ... ............................... ........643 TheRivoliGasField, ExmouthSub-basin. PJ.LawryandPA.Carter... .. ... .... ..... .. .. .. .. .. ... .. ..... ... ....... .. ....... ...... ... .. .. .. .. ... .. ...... .. ............ .. ...... ................. .. ......649 NeboOil Discovery, BeagleSub-basin. D.G.Osborne ... ... .... .... .. ... .. .. .. . .. ... .. .. ... .. ..... ..... ..... ........ ... .. .. ... ..... .......... .. ...... . .. ... ..... .. ... .. ......... ... ...... .. .. .... .. ......... ..653 CANNING BASIN DepositionalSequencesand AssociatedPetroleumSystems of theCanningBasin, WA. J.M.Kennard,M.J.Jackson,K.K.Romine,R.D.ShawandPN.Southgate........ ............ .... .. .. ... ... ............ ....657 TheOrdoviciantoSilurianPhaseof theCanningBasin, WA: StructureandSequence Evolution. K. K.Romine,PN.Southgate,J.M.Kennardand M.J. Jackson.... .. .... .............. .. .... .. ................ .......... .. ............677 AProposed Third-orderSequenceFramework fortheUpperDevonianOutcropsof theNorthern CanningBasin. D.B. Whittam,J.M.Kennard,R.B.Kirk,J.PSargand PN.Southgate ........ .. ...... .. .. .. .... .. ... ...... .. .... .. .. ... .. ...... .697 A CarbonateDilaform, BrookingSprings, CanningBasin, WA. B. W.Logan,D. J.Francesand M.Economo...... .. .. .. ...... .... ........ .. .. .. ...... .. ........ .. ...... .. .. .. ...... .. ........ .. ...... .. ........ .. ..703 ix Carbonate BrecciasandQuartzo-feldspathicSandstonesof theMarginalSlope,DevonianReef Complex, CanningBasin,Western Australia. A.D.George,PE.Playford and C.MeA.Powell ........... ....... ... ..... ... .... ..... ..... ..... ..... ....... ....... ... ........... ... .. .. ... ..... .727 Timingof Hydrocarbon MigrationintotheAdmiralBayFault Zone, Canning Basin. S.MCCracken.. ... .... ..... ...... ....... ..... .. ... .. ... ..... .. ............. ......... ..... .... ........ ..... ..... ...... .... .......... ..... ....... .... .. ...... ............739 AReviewof theSedimentologyandStratigraphy of thePermo-CarboniferousGrantGroup, CanningBasin, Western Australia. 1.Redfernand E.Millward .. ........... .. ......... .. ... ... ... .... ...... .... ..... ..... .. ..... ..... ....... .... ...... .... ... ...... ....... .... ...... ....... ... ... ..753 Structure oftheOffshoreCanning Basin: First Impressionsfroma NewRegionalDeep-seismicData Set. 1.B.Colwelland H.M.1.Stagg .. ..... ... ... ....... ........ .. .... .... ........ .. ... ........ ... .. .. ..... ....... ....... ........ .... ............. ...... .......757 StructuralFrameworkandDepositionalHistoryof theBedout andRowleySub-basins. P Lipski.... ....... ....... ... ..... .. ... ..... .... ........ ..... .. ....... ... ....... ......... ............. ........ .... ........ ............... .... ........... .... ... .... .........769 PERTH BASIN Structural Evolutionof theOnshoreNorthernPerth Basin, Western Australia. A.1.Maryand R.PIasky..... ... ..... ... ..... .... .......... .. .......... ....... ....... .... ........ ...... ... ..... ..... ........................... ....... ..... ...781 TheInfluenceof Basement onFaultingwithinthePerthBasin,WesternAustralia. M.C.Dentith, A.Long,1.Scott,L.B.Harrisand S.A.Wilde.. .. .... .... ..... ..... ..... ............ ..... ... ... ... .......... .... .... .... ...791 Transtensional AnalogueModellingappliedtothePerthBasin, Western Australia. L.B.Harris,R. I.Higgins,M.C.Dentithand M.FMiddleton ..... ....... ..... ..... .... ... .. ..... ............ ........... ... ... .... ..... .801 TheStructural ArchitectureandStratigraphyof theOffshoreNorthernPerthBasin,Western Australia. PQuaife,J. Rosser and S.Pagnozzi . .. .. ..... ... ........ . .. .... .. ... .. .. .. ..... .. ... .... ... .. .. ... .. ..... . .. ... .. ....... .... ........ .... .. .. .. .... .. .. ...811 Advancesintheunderstandingof Upper Permian Reservoir DistributionandQuality,NorthPerthBasin. N.PTupper,S. E.Phillips and B.P1.Williams ..... ... ...... .. ........ ...... ......... ...... .. .... ......... .................. .....................823 PROTEROZOICBASINS The NeoproterozoicSavory Basin, Western Australia. I.R.Williams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .841 TheNeoproterozoicCentralianSuperbasin in Western Australia: theSavoryandOfficer Basins. M.R.Walter and 1.D.Gorter. .... .......... ...... .... .. ... ...... ............ ......... ....... ......... .... ......... ..... .............. ..... .. .... .. ...... ..... ...851 X Wandoo Oil Field: AFormation Evaluation Case History. Abstract TheWandoooildiscoveryinhighporosity, unconsolidated,glauconiticsandstoneschallengedall forms of formation evaluation.The effects of glauconite on wireline logs,both electric and nuclear are difficult to determine because of itscomplex elemental makeup andthevaryingweightpercentof eachelement.The over35percentporosityandtensofdarciesof permeabilitymeantthatconventionalanalytical measurements weremade at the edgeof thereliability envelope. The presence of glauconite in most North West Shelf reservoirshasresultedindegradationof reservoirsto 'thief zones'.However,theglauconiteintheWandoo areaisofamicrocrystallinepelletalform,packed randomly and not as a matrix and, therefore, forms part of therockframeworkandhelpsmaintainexcellent reservoir properties. The appraisal of the unique Wandoo Oil Field has been achievedbytheutilisationofnewcoringandcore analysestechniquesandmanipulationof wirelinelog data.Thishasshownthatglauconitehassignificant microporosity that can contain saline formation waters. The combination of iron and saline water in glauconite provides sufficient resistivity suppression in oil columns thatconventionalloganalysesimplyhighwater saturations.HoweverNMRtechniqueshaverevealed that macroporositywithinhighpercentage,glauconite reservoirs can contain moveable hydrocarbons with no water production. The integration of all formation evaluation techniques hasenabledaclearunderstandingof theM.australis Sandstonereservoir.Whereasinisolation,each techniquewouldhaveprovidedcounter-productive information to be utilised in a reservoir simulation model. 1AmpolexLimited. Acknowledgements: TheauthorthankstheAmpolexmanagementfor permissiontopublishthispaper, andappreciates thesignificant efforts of the Ampolex staff who have contributed to the acquiring and supervising of formationevaluationdata inthefield, aidedwiththeinterpretation of these data,thedraftingoffigures, andthetypingofnumerousdrafts. Some of the evaluation techniques discussed in this paper were achieved throughgenerouscontributionsandinnovativeideasofthirdparty services, including Australian Core Services and SchlumbergerWireline andresearchcentres. Lastlytheauthorthankstheproceedingseditors,whohavemadea significantcontributiontomaintainingconsistencyandcoherency throughout thispaper. E.Delfos1 Introduction The Wandoo Oil Field is situated 65 km north of Dampier inthenorthwest of Western Australia.The discoverywell, Wandoo-1,wasdrilled inJune1991and islocated2.5km northeastofEnderby-!drilledalmost20yearsearlier (Fig.1). Wandoo-1identifiedanexitingnewhydrocarbontrend intheDampierSub-basinandanewreservoirobjective withinapoorlydefinedstratigraphicunit.Theshallow reservoirunithadbeenencounteredpreviouslybutits potentialwasoverlookedinthepursuitof deepertargets. Relative failureof the early explorationwells compared to the major oil and gas discoveries elsewhere in the Dampier ANGEL NORTHRANKIN 0 ,,fo'

WANAEA [)TALISMAN (JLEGENDRE AUSTRALIA Figure 1:Location map, Wandoo Oil Field and other nearby hydrocarbon accumulations. 616WandooOilField WA-209-P I I 1------f-$- ELIASSEN1 L I I I I I I I I I ENDERBY-1 - SIZE um VOLUME: MEAN: MEDIAN: 10.00 302.3 MEAN I MEDIANRATIO: MODE: 0.20.4 100.0 132.8 196.1 0.677 200.3 25.00 242.7 % um um um 2345710 50.00 196.1 2030 PARTICLE DIAMETER( um) 75.00 153.5 50100200400700 Figure 7:Grainsize distribution for Unit B in Wandoo-3.The excellent reservoir characteristics for theM. australis Sandstone Member are a function ofthe unimodal distribution.In areas of increased glauconite concentration the peak is broadened slightly downwards. 620WandooOilField GMMA RAYDEEP LATEAOLOG oGAPI150i0.20HM2000240 SHALLOW LATEAOLOG 0.20- - OHMM- - -20clo COMP.SONIC US/F 40 Figure 8:Wandoo-1sonicloghighlightingtheslowerthan fluid velocity transit time at the base of Unit A and top of Unit B.Production test and RFT data confirm the GOC is at 599 m. Wandoo-1penetrateda22.1moilcolumnandan interpreted (at the time) five metre gas cap.Core recoveries were poor;theholewaswashedout becauseof lowmud wei_ghts;and sonic velocities were difficult to interpret due totheunconsolidated nature of thereservoir.The lack of significant grain-to-grain contacts resulted intransit times in excessof fluidvelocities.(Fig.8). The initial analysis of the Wandoo hydrocarbon column wascarriedoutbasedonRepeat Formation Tester(RFT) information and resistivity data.The RFT data confirmed theoil-water contact andidentified the gascomponent of the reservoir; asthis wasnot possible from logs due tothe effectsof glauconite.Ampolex'sinvolvementwiththe majority of low relief Cretaceous oil fields in the North West Shelf provided confidence in defining the oil-water contact at the base of a small resistivity ramp (rather than midway alongthe ramp). ThreeRFf probetypes,standard,longand martineux, were used for the collection of pressure data.The martineux, althoughitisdesignedforunconsolidatedreservoirs continually plugged in theM. australis Sandstone. The best results were achieved with the' long nose probe'.Pressure pointselectionoftenrequiredreferencetocoreanalyses resultsintheupperportionof thereservoir,aspoorlog resolutionof sideritecouldimplyathickerthanactual non-net reservoir.The tool Wasfrequently moved at 0.1m intervals toobtain pressure readings. GAMMA RAY GAPIosoi0.20 CALIPER - - -w- - -16 RFT 10.75m3 GAS NOH ,0 RFT 3 53L OIL NO H ,0 INVASION INDUCED RESISTIVITY RAMP Figure 9:Wandoo-2 resistivity log highlighting the resistivity rampat thebaseof theoilcolumn,inducedby conductive mud filtrate invasion. Coring InWandoo-2,emphasiswasplacedonenhanced core-recoveries and improved hole stability to compensate for low core-recoveries in Wandoo-1.Wandoo-1 was drilled slightly overbalanced at theM.australis level.Wandoo-2 was drilled with10 ppg (1.20 SG) mud weight and the hole was in perfect condition at the time of logging; however,a stronginvasionprofilecanbeseenontheWandoo-2 resistivitylog(Fig.9). Corerecoverieswereimprovedsignificantlyinwells post-Wandoo-1byusingalowinvasioncore-bitwhich deflectedall circulatingmudawayfromthe core facevia venting ports located midway between the core entry point and the outer edge of the core head (Fig.10).This prevented mud fromcirculating around thecore, reducingsandstone to rubble and washing it away.A large diameter core barrel wasused toensure thegreatest surface area wasavailable for the core-catcher to grip.The advantage of larger diameter coreneedstobeoffsetagainsttheextraweightinthe recoveredcorecausingexcessivepressureonthe core-catcher.Trial and error has shown that four and a half metrecoresprovidetheoptimumlengthinthemost unconsolidated section of the reservoir.Fibreglass sleeves .LOWER SHOE INNER ANNULUS COREHEAD SHANK Figure 10: Cross-section of anon-invasivecore-headusedto acquire the unconsolidated core at Wandoo.Note only halfthe cross-section shown, and the circulating mud does not come in contact with the core edge. are usedtoensure minimal frictioninsidethecore bane! while cuttingcore and to provide an optimum capsule for transportationfromthewellsite.These fibreglasssleeves are cut intoonemetrelengths,sealedwith end caps,and transported to the laboratory. The unconsolidated nature of the cores made sea or road transportation unsuitable, so cores were airfreightedfromtherigtoPerth. Therefinedcoreacquisitiontechniquesimproved recoveriesfromunder50percenttoover80percent.A significant factorinthisimprovement wastheexperience of the core hands at the rigsite and their increasing familiarity withthereservoir.Forexamplethelengthof corecut depended strongly on the rate of penetration (ROP).If coring was slow and then rapidly increased, then it was likely that thezoneoffastROP(uptol 00m/ h)represented unconsolidated material which had insufficient rock strength topushthealready-cutcorefurtherintothebarrel. Conversely,if the ROP washigh and asideritestreak was then intersected,resulting inareduced ROP,oftenaslow as lm/h, then coring was telTllinated; this siderite plug would holdthecoreinthebarrel,andsubsequentcorewould probably be washed away.Currently, consideration is being given to cutting 18m cores and hoping that siderite streaks will be encountered and act as plugs in the base of the barrel; the risk isthat asideritestreak will not be encountered in the length of the18mbarrel,and the core weight exceeds the frictional strength of the core catcher and be lost on the way to the surface.Coring is time-consuming and, therefore, expensive.However,coreinformationisvitaltoseveral disciplines, including drilling and production, making it an almost mandatoryacquisition in fieldappraisal. Alternative core sleeves, such as rubber, were considered toimproverecovery;however,therockstrengthof the M.australis Sandstone is believed to be insufficient to force E.Delfos621 the rubber over the core.To prevent core destruction during transportation, resinating the core at the rigsite is becoming common practice for unconsolidated core.However for this to work, an annulus is required between the fibreglass sleeve and the core.Unfortunately theM.australis Sandstone is sounconsolidated that itslumpsintothe annulus. Oncethecore-acquisitionproblemwasovercome, unconsolidationprevented25mm core plugsbeing taken inthelaboratoryusingtheconventionaldrillingmanner. Consequently,thecoreswere frozenindryiceand,after slabbing, plugs were cut using liquid nitrogen.This process reduced the core temperature to -210 degrees celcius.The plugs were then placed in lead and teflon sleeves and allowed to thaw out before analyses.Petrographic analysis confirmed thatthecoreslackedcementandclay,andthefreezing technique was considered to be appropriate to preserve core materialforanalyses. Initial measurements gave porositiesand permeabilities approachingaperfectgrain-packingporosity-model;the integrityof thedatasetwasquestionedandanalternative plug extraction process considered.The high porosity was confirmedby logcrossplot porosities(Fig.11). The current procedure for core plug extraction is not to freezethecoreinitially,buttocutawayawindowof fibre glass sleeve down the length of the core (Fig.12).This allowssufficient room for asteel core-plunge-bane! tobe pushed into the core through its fulldiameter.Once plugs are extracted on a30 em spacing, the fibreglasswindow is reattachedandthecorefrozen.Thecoreisthencut lengthways in a one-third: two-thirds ratio and prepared for description,core gamma rayloggingand photography. The correlation of core gamma raytowireline logshas enabled the confirmation of a residual oil column in Wandoo. The residual column is difficult to distinguish from the live column byfluorescence(Fig.13). 0.40 WANDOO - 2 J+ WANDOO -3 .. . . toW.. 0.38t-0c::f

ret0+... 0.36 t-0rM0 u; 0 0 a: 0 a. . .(.!) 0.34 0 t-...J 0

ltJ oD 0.32- 0 0 0 0 0 0.30 .l.1II 303234363840 CORE POROSITY Figure 11: Log-derived porosity ver suscore-derived porosity at net overburdenconditionsindicatestheclose relationshipof thedatasets.Notethescales representing only aten percent range. 622WandooOilField FIBREGLASS SLEEVE---.... 140mm Figure 12: The three procedures in laboratory preparation of Wandoo core. Top:cut awindow off the length of thefibreglasssleeve;left:insertcoreplungerat regular intervals throughthefulldiameterof the core;andright:tape on fibreglasswindow,freeze to -180Cand slabinto 1/3:2/3 ratios. To preserve the cores they are left in the fibre glass sleeves forsupportandstoredincommercialcoldstorageat0to -20degreescelcius. The coring of the reservoir in all the vertical and deviated wellsinthefieldhasresulted in asoundunderstandingof thereservoirrock.Hadcoresnotbeencutandanalysed, interpretation of logs alone would have resulted in the field beingconsideredtohavevaryingwater-saturationsand significant argillaceous material.Thiswould have resulted in a significantly different model being used in developing thereservoirsimulationmodel. Petrophysics Log analysis ofWandoo-1 highlighted the problem created bythepresenceofglauconiteintheupperandcentral portions of the reservoir.A direct relationship between the suppression of resistivity and the presence of glauconite was determined bycomparing core and log data (Fig.14).The wirelinedataindicatedthatwatersaturationsvaried throughout the reservoir with RTvalues ranging from10 to 200 ohmm, although porosities and permeabilities remained consistentlyhigh.Thepresenceof ironintheglauconite wasassumedtoberesponsibleforincreasedconductivity and consequent suppression of the resistivity measurements intheoilcolumn. Wandoo-3,aneasternflankwell,waschosenfora comprehensive evaluation of the reservoir.The oilcolumn wasfully cored, aswasan additional17.5minto the water column.Routine, special, and Nuclear Magnetic Resonance (NMR) core analyses were conducted to provide a range of methodsthat would measure porosity and permeability.In conjunctionwithconventionalwirelinetoolsin Figure 13: Natural light and ultra-violet light photographs of corefromWandoo-5highlighttheproblemof determining the liveoilcolumn(631.6- 632.6m) fromthe residual oilcolumn (636- 637m). high-resolution mode,theformationmicroscanner (FMS), geochemicallogging(GLT)andelectromagnetic propagationtools(EPT)wereruntoestablishadigital representationofthereservoirlithology.Quantifying lithologyfromlogswouldenableacorrectionforthe presenceof glauconite.Theconectionsweregoingtobe appliedbyvariableCEC(cationexchangecapacity)and variable m.Another objective was to determine if core data couldbereplacedbyinformationfromtheGLT.The following is a brief review on the experiences with the above methods. NuclearMagneticResonance(NMR)techniqueswere conductedbySchlumberger inRidgefieldConnecticut on five,15 em diameter, full -core samples. The aim ofthis work was to confirm the high porosities recorded by conventional EFFECTIVE GAMMA RAY -DEEPLA TEROLOGLOGPOROSITY GAP I 150:;;0.20 OHMM20000 PU 0.40 COREPOROSI TY 40 % TOPUNIT A l I' ' I,., ''' ,, I TOP 61 5 UNITB

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