New Perspectives – New Plays in the Douala Basin of Cameroonequatorialoil.com/PDFs for...
Transcript of New Perspectives – New Plays in the Douala Basin of Cameroonequatorialoil.com/PDFs for...
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New Perspectives – New Plays
in the Douala Basin
of CameroonRichard Bray & Steve Lawrence, ECL, UKSerge E Angoua Biouele, SNH, Cameroon
Exploration Consultants Limited, Highlands Farm, Greys Road,Henley-on-Thames, Oxfordshire, EnglandSNH
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EasternGulf of Guinea
Douala BasinLocation
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EasternGulf of Guinea
GeologicalSetting
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CameroonDouala Basin
Well and Oil Seep Locations
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Van Krevelen plot
Tissot & Welte 1978
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CameroonDouala Basin
HydrocarbonOccurrences
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Cameroon –Rio Muni
StratigraphySource Rocks
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Douala Basin
Stable Carbon IsotopeCharacteristics -Seep andReservoired Oils
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Douala Basin
OleananeCharacteristics -Seep andReservoired Oils
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SOURCE ROCK PROPERTIES FROM
OILS GEOCHEMISTRY 1
Two oil families are present:
Isotopically light with oleanane present – Tertiary source
Isotopically heavy with oleanane absent – Pre-Campanian
source (most likely Albian-Cenomanian)
Co-mingling of these two families occurs
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SOURCE ROCK PROPERTIES FROM
OILS GEOCHEMISTRY 2
All oils indicate:
Terrestrially derived oil-prone kerogen deposited in a marine
environment.
Dysoxic depositional conditions – organic preservation favoured
by high sedimentation rate rather than sea-bed anoxia.
Oil maturities indicate source rocks mostly in the early to mid
mature oil windows (some indications of late mature).
Other conclusions concern biodegradation, leakage from trapped
accumulations versus migration from source etc.
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Cameroon –Rio Muni
StratigraphySource Rocks
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Douala Basin - Souellaba & Matanda Formations - Geochemistry
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Douala Basin - Tertiary Petroleum System
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Douala Basin – Tertiary Sequence Architecture
Pliocene
Oligo-Miocene
Paleocene-Eocene
Deep waterchannel/fancomplexes
HST
TST
LST
HST - Deltaics showing well developed (basinward) progradationTST - Deep water muds showing local onlap, otherwise parallel reflectorsLST - Deep water sands, chaotic and concave-up reflectors, local progradation
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Douala Basin - Seismic Amplitude Map
RMS amplitude 100 msec above base Eo-Oligocene Unconformity
Courtesy of GESeis
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EasternGulf of Guinea -Burial HistoryPlots
Marginal Location
Basinal Location
40(C)
80(C)
120(C)80(C)
120(C)
80(C)
120(C)
Age (my)
020406080100120140
0
1000
2000
3000
4000
QPMOEPK
Pliocene
Miocene
SR 1
SR 2
Early Cretaceous
SR 3
Fm
t = 0
40(C)
80(C)
120(C)
160(C)
Age (my)
020406080100120
0
2000
4000
6000
8000
QPMOEPK
Pliocene
Miocene
Paleocene
LateCretaceous
Fm
SR 1
EarlyCretaceous
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Douala Basin
Tertiary PetroleumSystem Map
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PETROLEUM SYSTEM
In accordance with convention the petroleum system is
classified as hypothetical and described as follows:
N’Kapa/Souellaba – Northern oil seeps (.)
N’Kapa/Souellaba – N’Kapa/Souellaba (.)
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CONCLUSIONS 1
Tertiary-sourced petroleum system associated with the mid Tertiary
unconformity.
Source rocks in Souellaba Fm (Oligo-Miocene) or N’Kapa Fm (Paleocene-
Eocene). Source rocks also exist in the Cretaceous section.
Position of source above or below the unconformity is critical to its
maturation history.
Reservoirs are expected to be developed as lowstand channel/fan
complexes within a sediment wedge above the sequence boundary.
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CONCLUSIONS 2
More work is needed to positively identify a Tertiary source rock (oils /
well sample geochem).
The stratigraphic framework is poorly constrained. Work is needed to
resolve this (biostrat / seis-strat).
It is crucial to understand the thermal history and the history of uplift
and erosion of the basin (AFTA & high quality VR data).
The petroleum systems approach is a necessary step towards mapping
prospective play fairways.
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Thank you for your attentionSNH
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Additionalslides follow
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Slide 4
EasternGulf of Guinea -Study Wells &Outcrop SampleLocations
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Slide 14
Northern Equatorial Guinea - Northern CameroonCross-section
Shale diapir-associatedstructures
Benin
Moudi
Tsavorita
UPPER QUA IBOE
LOWERQUA IBOE
Zafiro
Amatista
AKATA
ISONGO
Alba
BONITO
AKATA
LATE CRETACEOUS
OCEANIC CRUST
SOUELLABA
LOGBABA
OCEANIC CRUST
Toe-thruststructures
Oil migrating fromCre taceoussource rocks
Deep water sands
Oil seeps associated withCretaceous exotics
Cameroon Volcanic Line
Isongo
Post-rift Marine(Albian-Turonian)
N i g e r D e l t a - R i o d e l R e y B a s i n Douala Basin
North-west South-east
MATANDA
LOGBADJECK
WOURI
Channel/fan sands
CONTINENTAL CRUST
Sanaga Delta
MUNDECK
Apt-AlbianSource RocksPost-rift SRs
Albian-Cen
N I G E R I A E Q U AT O R I A L G U I N E A C A M E R O O N
M’Via
Matanda
Souellaba
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Slide 16
Rio Muni -Cameroon
ThermalEpisodes &EustaticCurve
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Slide 9
S Cameroon - N Rio Muni - Schematic Thermal History
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CameroonLicence situationMay 2003