Identify re-development concepts to enhance Abu Roash “C― oil reservoir productivity Sitra

33 Pages·2016·19.71 MB·English

by  H. Salama

EgyptianJournalofPetroleum(2016)xxx,xxx–xxx
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FULL LENGTH ARTICLE
Identify re-development concepts to enhance Abu
”
Roash ‘‘C oil reservoir productivity Sitra Area,
Abu Gharadig Basin, Western Desert, Egypt
H. Salamaa,*, M. Darwishb, M. Wahdana, A. El-Batalc
aBadr El-DinPetroleum Company (BAPETCO),Egypt
bGeologyDepartment, Faculty ofScience, CairoUniversity, Egypt
cQarun Petroleum Company,Egypt
Received 28January 2016; revised17March2016; accepted 13April2016
KEYWORDS Abstract ThisstudyincludesanewunderstandingofthedepositionalmodelofAbuRoash‘‘C”
MemberdepositedinSitraFieldinAbuGharadigBasinduringTuroniantime,andillustratesthe
Faciesmodeling;
Depositionalmodel; major affecting factors that control the behavior of this reservoir and consequently offer a great
Reservoircharacterization; opportunityforSitrafield’sfuturedevelopmentactivitiesthroughanewmethodologytomaximize
Redevelopmentconcepts; thefield’sultimaterecovery.
Enhanceoilproductivity TheSitradevelopmentleaseislocatedinnorthWesternDesertandoccupiesthecentralwestern
partofAbuGharadigBasinandcoversthesouthernextensionofBadrEl-dinPetroleumCompany
(BAPETCO)leaseswithanareaof322.4km2.SitraAreaisdividedintoseveralstructuralclosures;
themainproducingoneistheSitra8blockinwhich39wellsweredrilledsince1993.Variousdata
fromthesewellswereevaluatedtoconstructthedepositionalfaciesmodelsfortheAbuRoash‘‘C”
reservoir.Theloganalyseshavebeenintegratedwiththecoredescriptions,andditchcuttingdatato
interpretthedepositionalfaciesmodelthatcontrolledthereservoircharacteristics.
In Sitra Area the Abu Roash ‘‘C” Member exhibits all of the characteristics of the Shallow
Marine-Tidaldominatedestuarieswhicharelinkedtothesouthwithafluvio-marineenvironment,
thetide-dominatedestuariesarerepresentedintidalchannelsandtidalflatfacies,marchdeposits,
anddistributarymouthbars.ThebestreservoirrockintheAbuRoash‘‘C”Memberwasdeposited
asdistributarychannelfill/Mouthbarsthatcutthroughtheunderlyingstrata.
Twomajorparasequenceswereidentified,thefirstloweronewasdevelopedduringashallowing
upward sequence represented by shale/sand intercalations into which the main Abu Roash ‘‘C”
reservoir sandbodiesareincluded,andreached itsendbytheappearance ofalaterally extended
coal marker nearly one meter thick. This parasequence was deposited subsequently to a falling
sealevelphasewhichoccurredafterthedepositionofAbuRoash‘‘D”limestone.Thesucceeding
parasequence(deepeningupward)reacheditsmaximumfloodingsurface(MFS)bythedeposition
ofthewidelyextensiveshalemarkerbeingrichinpelagicPelecypodshells.
* Correspondingauthor.
E-mailaddress:[email protected](HananSalama).
PeerreviewunderresponsibilityofEgyptianPetroleumResearchInstitute.
http://dx.doi.org/10.1016/j.ejpe.2016.04.003
1110-0621(cid:1)2016EgyptianPetroleumResearchInstitute.ProductionandhostingbyElsevierB.V.
ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Pleasecitethisarticleinpressas:H.Salamaetal.,Identifyre-developmentconceptstoenhanceAbuRoash‘‘C”oilreservoirproductivitySitraArea,AbuGharadig
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2 H. Salamaetal.
Theresultantstratigraphicunitsconsistof:geneticallyrelateddepositionalcycles(3cycles)and
theircomponentsoffaciessequences(5faciestypes),eachcyclehasitsowndistribution,faciesclas-
sificationandreservoircharacteristics.
(cid:1)2016EgyptianPetroleumResearchInstitute.ProductionandhostingbyElsevierB.V.Thisisanopen
accessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction The Badr El Din Petroleum Company (Bapetco) operates
the SITRA concession (50% Shell Egypt and 50% EGPC)
Recently, the most potentially exciting news of Oil and Gas onbehalfof Sitrapetroleum Company(SiPetCo).
discoveriesinEgyptiscomingfromtheWesternDesertregion,
whereseveraloutstandingdiscoverieshavebeenachievedsince 1.1. Locationofthe study area
onlyeighties [39].
Abu Gharadig Basin comprises many of the most produc- The Sitra development lease is located in the Western Desert
tive oil and gas fields in the northern part of the Western and occupies the central western part of Abu El-Gharadig
Desert [2]. In Badr El-Din Concession, oil and gas have been basin and the southern extent of Badr EL-Din concession
produced until now from the Late Cretaceous (Cenomanian (Fig.1).Sitrafieldhasintotalsixstackedhydrocarbonreser-
-Turonian)AbuRoashC,D,E,FandGMembersandfrom voirs;fourreservoirsarelocatedintheAbuRoashFormations
the underlying Cenomanian Bahariya and Albian Kharita in which three of them AR‘‘C”, AR‘‘E”& AR‘‘G” Upper are
formations. oil bearing and one is gas bearing AR‘‘G” Lower. The last
tworeservoirsarelocatedinBahariyaFormations,theUpper
Figure1 LocationmapsforSitradevelopmentleaseandourstudyarea).
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Re-development concepts toenhance AbuRoash‘‘C” oil reservoir productivity 3
Bahariya is oil bearing while the Lower Bahariya is gas bear- sequences were studied by [26,27,51,49,86,87,28,78,44,29,35,36],
ing. Kharitareservoir iswaterbearing. amongothers.
Thetectonicframeworkandstructuralsettingofthenorth
1.2.The mainobjectives ofthis study WesternDesertwerestudiedandanalyzedbymanyauthorsof
mention: [94,86,107,14,83,80,81,70,71], and [72,38,73,3,15,31],
➣ IntegrationbetweencoredataandWirelineloggingdataof and[32,45,66,105].
AbuRoash‘‘C”toidentifypotentiallybypassedHCinter- Previous studies on the Northern Western Desert relevant
vals thatmight bea wayfor additionalreserves. to the regional integration of the present work include the
➣ FaciesanalysesanddepositionalmodelofAbuRoash‘‘C” works of[11,3,104,4,23,43,46,56,42,106,77,6,50,37,30,76].
member. Cretaceousdepositsarewidelydistributedinthesubsurface
➣ Identify and evaluate alternative re-development concepts ofthenorthernWesternDesertofEgypt.Sincethesedeposits
for AR”C” oil reservoir through the redistribution of its aremajorexplorationtargetsforpetroleumresources,alotof
depositional Modeland Faciesanalyses. palynologicalworkhasbeendoneontheme.g.[84,85,97–100,
103,101,102,82,8],and paperscited in [88,89,58].
1.3.Previouswork
2. Geologic settings
ThenorthWesternDesert ofEgyptattractedthe attention of
severalworkersfromthegeologicalandhydrocarbonpotential 2.1. Stratigraphic framework ofAbu GharadigBasin
viewpoints. Petroleum potentiality and petroleum systems of
the Western Desert have been studied by many investigators, The stratigraphic column in the northern part of the Western
among them are [13,1,10,11,48,59,79,74,83,106,25,64,109,12,9 Desertisthickandincludesmostofthesedimentarysuccession
3,9,40,41,60,95,33,55,5,2,57,7,54,75,61,62,108], and [63,67,65]. fromrecentto Pre-Cambrianbasementcomplex(Fig.2).The
TheUpperCretaceoussequenceswerethesubjectofnumerous Sedimentary cover(i.e. the sequence ofdeposits overlyingthe
studies since [90]. The surface outcrops at the Bahariya basement rocks) regionally thickens northwards, reaching
Depression and Abu Roash District were considered the type more than 35,000 ft. in the Abu Gharadig Basin, thinning to
sectionsoftheCenomanian-Maastrichtiansequences.Thedif- some10,000feet overthe RasQattara ridgewhich marksthe
ferent stratigraphic units of these surface and subsurface northern edgeof the basin, [42].
The 3rd Cycle Abu Roash Fm.
Figure2 StratigraphicframeworkoftheAbuGharadigbasin(ModifiedfromWECEgypt,Schlumberger,1984;EGPCWesternDesert,
OilandGasFields,1992;andO.Shaarawy,GUPCOinM.AbdelHalim,EGPC,1994).
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4 H. Salamaetal.
Figure3 MajorGeotectoniccycles,(EGPC,1992).
The stratigraphic section consists of alternating deposi- ThereisevidenceovermuchoftheWesternDesertthatthe
tionalcycles ofclastics andcarbonates. upperboundaryoftheAbuRoashFormationisanunconfor-
Fivecycles havebeen recognized asfollows: mity. Abu Roash Formation thickens to the north and
becomes dominated by carbonates in the Mediterranean
1. The first cycle of clastic facies dominates the oldest sedi- coastalarea.
mentaryrocksandincludestheentirePaleozoicandLower IthasCenomaniantoTuronianage,locallyextendinginto
Jurassic formations. Coniacian and Santonian in the upper most units (‘‘A” and
2. A carbonate section of Middle and Upper Jurassic ‘‘B”). The Abu Roash Formation was deposited on a wide
formations. shallow marine shelf during several sedimentary cycles, in
3. The Third Cycle (second cycle of clastics) comprises the response to oscillation of the sea level. Transgressive phases
Lower Cretaceous up to Upper Cretaceous Early aremarkedbylimestoneandshalesequences,whileregressive
Cenomanian. phasesare clasticdominated.
4. From Upper Cenomanian and up to the Middle Eocene, FullyMarineconditionspersistedthroughouttheLateCre-
dominantcarbonatedepositsareagaindistributedthrough- taceousandthePaleogene.TheUpperCretaceousAbuRoash
outnorthernWestern Desert. andKhomanformationsarecharacterizedbyacyclicalterna-
5. The upper most clastic depositional cycle includes the tion of shallow water sandstones, neritic to deep-water Lime-
UpperEocene–Oligocene, Miocene and younger section. stones, and deep-water Shale. The transgressive/regressive
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Re-development concepts toenhance AbuRoash‘‘C” oil reservoir productivity 5
sedimentarycyclesoftheAbuRoashFormationareregionally ‘‘C”,‘‘E”and‘‘G”containvariableamountsofdetritalmate-
importantandhavebeenlabeledthe‘‘A”Member,atthetop, rial. The Lower boundary is at the base of Abu Roash ‘‘G”
throughtothe‘‘G”Memberatthebase.The‘‘A”,‘‘B”,‘‘D”, which rests on the Bahariya Formation. The upper boundary
and ‘‘F” Members are mainly composed of carbonates and of the Abu Roash is the base of the Khoman Formation or
shale,depositedinaneriticenvironment,whiletheAbuRoash of the Apollonia Formation, whenever the Khoman Forma-
‘‘C”,‘‘E”,and‘‘G”Memberscontaincoastalplain,lagoonal, tion ismissing.
andshallowmarinesandsandshales,togetherwithsomethin
limestones.Allofthesesandshavepotentialreservoirquality, 2.2. Tectonicframework
and are Oil-bearing in several fields in Abu Gharadig Basin
[24]. ThetectonicevolutionofnortheastAfricahasbeenextensively
The Abu Roash Formation has been divided into seven
described by numerous authors (including [86,72]). Several
units ‘‘A” to ‘‘G”, ‘‘A” was being the highest. Units ‘‘B”,
continentalplatecollisionphasesarerecordedbetweenPangea
‘‘D” and ‘‘F” are relatively clean carbonates, units ‘‘A”,
mega segments of Laurasia and Gondwana throughout the
Figure4 (A)MapofEgyptandsoutheastMediterraneanSeashowingmainstructuralelementsandsedimentarybasins(modifiedafter
[Sestini,1995]).(B)BasementtectonicmapofNorthWesternDesert(afterMeshreif,1988).
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6 H. Salamaetal.
Fig.4(continued)
Phanerozoic[92].LateCarboniferoustoearlyPermianrifting Ontheotherhand,Egyptcanbesubdividedintofivemajor
and crustal separation was the first step in the break-up of morpho-structural units (Fig. 4(A)). (1) the Mediterranean
Pangaea with the opening of the Permo-Tethyan seaway and Fault Zone, (2) a belt of linear uplifts and half-grabens, (3)
the EastMediterranean Basins. the North Sinai Fold Belt ‘‘Syrian Arc”, (4) the Suez and
Thesewereinterruptedbyextensionalriftphasesassociated RedSeaGraben,and(5)theintra-cratonicbasinsofsouthern
withoceaniccrustformationandfloodingofcontinentalplate Egypt.
margins.Afurtherimportantfactorwasthesinistralordextral TheCentralportionoftheWesternDesertcoversthetran-
rotation of the Sahara/North African plate relative to Laura- sition zone between the Stable and the Unstable Shelves. Six
sia, which had a strong modifying effect on the local basinal major geotectonic cycles or phases can be recognized in the
tectonicstylesencounteredinthenortheastAfricaandinpar- Phanerozoicin the Western Deserttheseare (Fig. 3):
ticularthe Western Desert.
Egypt lies at the northeastern corner of the African plate 1. CaledonianCycle (Cambrian-Devonian)
and can be broadly divided into four structural divisions. 2. Variscan-Hercynian (Late Paleozoic)
These are the Hinge Zone and Unstable Shelf in the north, 3. Cimmerian/Tethyian (Triassic- EarlyCretaceous)
and the Stable Shelf and the Nubian/Arabian Cratons in the 4. Sub-Hercynian-Early SyrianArc (Turonian Santonian)
south[86]. TheStableShelfisabelt extendingfromsouthern 5. SyrianArc mainphase(Paleogene)
Egypttoa northernlimitarrivingasfarascentral Sinai.Itis 6. RedSeaPhase (Oligocene–Miocene)
characterized by low structural relief and with thin sedimen-
tary cover of fluvio-continental deposits mainly of Mesozoic Structurally, Abu Gharadig Basin is primarily extensional
age,deformedbyseveralsetsofregionalfolds[86].TheUnsta- in nature and is affected mainly by faulting. Folding is rela-
ble Shelf occupies almost all of the northern parts of Egypt, tivelysubordinateandisoftenrelatedtomovementsonnearby
characterized by a northward thickening sedimentary section faults. Abu Gharadig anticline appears to be related to the
underlainbyhighbasementreliefduetoblockfaulting.More- Syrian arc system, which is comprised of a series of NE–SW
over, it is characterized by surface tectonic features of lateral trending folds that cross the entire unstable shelf of northern
stressesduetodifferentcompressionalepisodessuchasSyrian Egypt. This system has been attributed to Late Cretaceous-
Arcfolds in northern Sinai. Early Tertiary NW–SE compression (normal to the folding
On the other hand, the Hinge Zone coincides nearly with axis).ThestructuralstyleoftheAbuGharadiganticlineispro-
thepresentMediterraneancoastalareaseparatingtheunstable posedtobetheresultofaregionaleast–westrightlateralshear
shelffromtheMiogeosynclinalbasinalarea.Itcausesarapid, couple.Thestructureisanortheastplungingasymmetricanticline
basin wards thickening of Oligocene to Pliocene sediments. which has been cut by a series of northwest trending exten-
Presently it is submerged and partially buried under thick sionalfaults.Thesefaultshavedissectedthefieldintoanum-
Plio- Pleistocene depositsin relationto the Nile Delta. berofseparatereservoirblocks.[42,70–73]studiedthetectonic
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Re-development concepts toenhance AbuRoash‘‘C” oil reservoir productivity 7
Figure5 N–SSeismic(Trace4618)passingthroughSitra8-29(Z)totheleft,E–WSeismic(Line1839)passingthroughSitra8-29(Z)to
theright(AfterBAPETCOGeophysicsteam,2012).
trends in northern Egypt using the potential data and sug- 3.2. Methodology
gested several uplifted structures separated by ENE trending
basins. He concluded that the E–W and N65(cid:3)E (Syrian 3.2.1. Geophysicaldata
Arc) trends are more developed in the northern Western
The evaluationwork was carriedoutwithintwo phases
Desert (Fig. 4(B)). The northern anticlinal structures are
extendedon-landattheextremewesternportionofthenorth-
i. Thefirstphase:Theevaluationworkwascarriedouton
ernWesternDesert.Southwardly,thistrendisfollowedbythe
thePSTM processed 3D 2008seismic data.
Qattara-northSinaiuplift,Bahariya–AtaqaupliftandNashfa-
ii. The second phase: The evaluation work (more fine-
WadiArabauplift.
tuned work) was carried out on the PSDM processed
3D(2010/2011) seismic data.
3.Materials andmethodology
IntheSitraArea(likemostareasintheWesternDesert)the
3.1.Data setanddata quality seismicattributesarenotaclearindicatorofsandorhydrocar-
bonpresence,thoughinvestigationshouldcontinueinsupport
U Theavailablewelldataofonlyfourwellsinthestudy of thesubsurface analysis.
area (Surface location coordinates (Red Belt system);
Deviation data; Log data (conventional logs and 3.2.2. Geologicaldata
calculatedcurves); and Formationtops). 3.2.2.1. Lithofaciesanalysis.
U The available Electric logs (Gamma Ray, Density, ➣ Detailed lithologic description of the individual lithofacies
-Neutron, andResistivity logs). units identified on the core slabs with emphasis on litho-
U 20seismic lines(2D and3D) as ahard copy. logic composition, bed thicknesses, color, grain-size
U Available Geologic reports (Core reports, Biostrati- arrangementpatternsanddegreeofcrystallinityfordetrital
graphicreports, finalwell reports...etc.). and authigenic components respectively, vertical grain size
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8 H. Salamaetal.
Figure6 ArbitrarylinepassingthroughSit8-29andSit9-20St.withmorefocusingonAR‘‘C”seismicmarker.
Figure7 (A)A/R‘‘C”seismicmarkerstructuremap(B)A/R‘‘C”semblancemap.(AfterthegeophysicsteaminBAPETCO,2014).
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Re-development concepts toenhance AbuRoash‘‘C” oil reservoir productivity 9
surfaces. These charts show the subdivision of the cored
Table1 Availablewelldata.
successions into their component lithofacies with a text
Wellname Mudlogs Electriclogs Coredata Image descriptionfor each.
data(BHI) ➣ The identified lithofacies suit is then used to diagnose the
p p p
Sitra8-1ST2 p p p (cid:2)p depositionalenvironmentofstudiedsuccessionandaccord-
Sitra8-17 p p ingly to predict the geometry of the significant lithofacies
Sitra8-20ST p p (cid:2) (cid:2) units.
Sitra8-29 (cid:2) (cid:2)
3.2.2.2.Thin-sectionpetrographicanalysis.Petrographicinves-
tigationofbluedye-injectedthinsectionswerepreparedfrom
selectedcorechipsandexaminedunderaresearch-gradepolar-
izingmicroscope.Theinvestigationfocusesondeterminingthe
profiles, primary sedimentary structures, biogenic features mineral composition, matrix and/or cement material, fabrics
(body and/or traces), mineralogical aspects, bed contacts, and textures, porosity type(s) and degree of connectivity and
truncation events and/or erosional surfaces and hydrocar- syn- and post-depositional modifications. On determining the
bon indications. petrographic clans to which the analyzed samples belong, the
➣ Plottingoftheabove-mentioneddataonworkingsheetsat sandstone classifications and carbonate rock classification
ascaleof1:10.Thesesheetsarethenusedincompilingsed- schemeswere applied.
imentologiclogcharts(scale1:40)showingagraphicalrep-
resentation of the various depositional aspects and 3.2.2.3. Scanning-electron microscopy (SEM). Scanning elec-
pertinent data plotted against the gamma-ray log of the tron microscopy involves bombardment of gold-coated raw
cored succession, routine core analysis data and plain- surfacesoftherockspecimensbylowvelocityelectronbeams
light and ultraviolet-light photographs of the slabbed core which upon reflection yield detailed surface morphology at
Table2 Coredataoftheavailablewells.
Wellname CoreNo. Coredintervalwithoutshift Coreshift Recovery(%) LengthPerCore Coredintervalwithshift Formation
Top(mbdf) Bottom(mbdf) Top(mbdf) Bottom(mbdf)
Sitra8-1B Core#1 2940.50 2959.00 6.5+ 100% 18.50 2947.00 2965.50 A/R‘‘C”
Core#2 2959.00 2977.00 6.8+ 100% 18.00 2965.80 2983.80
Sitra8-17 Core#1 2837.17 2864.23 0.23+ 100% 27.06 2837.40 2864.46 A/R‘‘C”
Figure 8 The direct correlation between facies and a variety of other log shapes relative to the sedimentological relationship (Cant,
1992).
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10 H. Salamaetal.
nanometer scale. SEMs are capable of obtaining images at ➣ Fortheclay fraction examination, theclay fraction ispre-
magnifications over 100,000 times. These instruments can see paredthroughcrushingapartofthebulksample,plunging
and then analyze something that would not show up with a it with water, letting it settle down and pipetting a part of
polarized-light microscope. thesuspensionaftercertainperiodoftimeestimatedsothat
the suspended material is made up of less than 2lm size.
3.2.2.4. X-raydiffraction (XRD) analysis. Thisisthesizethatisrichestinclaymineralswiththepos-
➣ Thiswascarriedoutbothforthebulk-samplesandfortheir sibility ofco-existence of particlesof otherminerals.
clay fractions.
➣ Forthebulk-sampleexamination,thesampleswereprelim-
inarily investigated under the binocular microscope for 3.2.2.5.Biostratigraphicanalysis.Thehighresolutionbiostrati-
determination of their gross characteristics and texture, graphicanalysesarebasedonthefrequencyandabundanceof
and were then X-rayed for determination of their gross theidentifiedtaxasupportedthebiozonationandenvironmen-
mineralogy. talinterpretation for thestudied succession.
Sitra 8-29 : Sitra 8-20 ST: Sitra 8-b ST2: Sitra 8-17
the largest sand thickness a group of stacked channels a very clear fining upward pattern Two types of deposition , a clear
represent a blocky pattern of the represented by a fining upward in the stacked channels coarsening upward pattern
main tidal channel coming from and blocky patterns represented by the deposition of
the north the mouth bars at the lower part
and fining upward pattern for the
tidal channel above the coal
marker
Legend:
AR"C" Top
AR"C" Shale Marker
AR"C" Coal Marker
AR"D" Top
Figure9 WelllogsfromNtoSrespectively;reservoirintervalliesundertheAR‘‘C”shalemarkerinallwells.
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