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Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, East Africa
By Michael E. Brownfield
Digital Data Series 69–GG
U.S. Department of the InteriorU.S. Geological Survey
Chapter 11 ofGeologic Assessment of Undiscovered Hydrocarbon Resources of Sub-Saharan AfricaCompiled by Michael E. Brownfield
ATLANTIC OCEAN
SOUTHATLANTIC
OCEAN
INDIAN OCEAN
INDIAN OCEAN
MEDITERRANEAN SEA
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Morondava
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U.S. Department of the InteriorSALLY JEWELL, Secretary
U.S. Geological SurveySuzette M. Kimball, Director
U.S. Geological Survey, Reston, Virginia: 2016
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Suggested citation:Brownfield, M.E., 2016, Assessment of undiscovered oil and gas resources of the Morondava Province, East Africa, in Brownfield, M.E., compiler, Geologic assessment of undiscovered hydrocarbon resources of Sub-Saharan Africa: U.S. Geological Survey Digital Data Series 69–GG, chap.11, 14 p., http://dx.doi.org/10.3133/ds69GG.
ISSN 2327-638X (online)
iii
Contents
Abstract ...........................................................................................................................................................1Introduction.....................................................................................................................................................1Tectonic History and Geology of the Morondava Province, Madagascar, East Africa .....................4Petroleum Occurrence in the Morondava Province, Madagascar, East Africa .................................4
Source Rocks.........................................................................................................................................4Reservoirs, Traps, and Seals ...............................................................................................................8
Exploration ....................................................................................................................................................10Geologic Model ............................................................................................................................................11Resource Summary .....................................................................................................................................11For Additional Information ..........................................................................................................................12Acknowledgments .......................................................................................................................................12References ....................................................................................................................................................12
Figures 1. Map showing Morondava Province and the Mesozoic-Cenozoic Reservoirs
Assessment Unit along the central coast of East Africa .......................................................2 2. Map showing generalized geology of East Africa ..................................................................3 3. Reconstruction of the early breakup of Gondwana during the Early Jurassic ..................5 4. Map showing generalized plate-tectonic development of the Madagascar
Province .........................................................................................................................................6 5. Stratigraphic columns for Coastal Mozambique, the Mozambique Channel
and Coastal Tanzania, Coastal Morondava Basin, and Seychelles, East Africa ...............7 6. Cross section across the Mozambique Channel and the Morondava Basin,
East Africa, showing top of oil and gas windows ...................................................................8 7. Stratigraphic column of the Morondava Basin, western Madagascar ...............................9 8. Cross section across the Majunga Basin, northwest Madagascar ..................................10 9. Events chart for the Mesozoic Composite Petroleum System and the Mesozoic-
Cenozoic Reservoirs Assessment Unit, Madagascar ..........................................................11
Table 1. Morondava Province assessment results for undiscovered, technically
recoverable oil, gas, and natural gas liquids .........................................................................12
Abbreviations Used in This Reportkm2 square kilometer
AU assessment unit
TOC total organic carbon
TPS total petroleum system
USGS U.S. Geological Survey
Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, East Africa
By Michael E. Brownfield
most likely began in the latest Jurassic or earliest Cretaceous, and it continues today in the offshore parts of the assessment unit. Most generated hydrocarbons migrated into Cretaceous and Paleogene reservoirs and traps. Traps are mostly structural within the syn-rift rock units and both structural and stratigraphic in the post-rift rock units. The primary reservoir seals are Mesozoic and Cenozoic mudstone and shale. Rifted passive margin analog was used for assessment sizes and numbers because of similar source, reservoirs, and traps.
The U.S. Geological Survey estimated mean volumes of undiscovered, technically recoverable conventional oil and gas resources for the Mesozoic-Cenozoic Reservoirs Assessment Unit in the Morondava Province. The mean volumes are estimated at 10,750 million barrels of oil, 167,219 billion cubic feet of gas, and 5,176 million barrels of natural gas liquids. The estimated mean size of the largest oil field that is expected to be discovered is 1,016 million barrels of oil, and the estimated mean size of the expected largest gas field is 7,837 billion cubic feet of gas. For this assessment, a minimum undiscovered field size of 5 million barrels of oil equivalent was used.
Introduction
The main objective of the U.S. Geological Survey’s (USGS) National and Global Petroleum Assessment Project is to assess the potential for undiscovered, technically recover-able oil and natural gas resources of the United States and the world (U.S. Geological Survey World Conventional Resources Assessment Team, 2012). As part of this project, the USGS recently completed an assessment of the Morondava Province (fig. 1) (Klett and others, 1996), an area of approximately 460,690 square kilometers (km2). The Morondava Province is characterized by rift, rift-sag, passive margin, and drift rocks of Paleozoic to Holocene age. This assessment was based on data from oil and gas exploration wells (IHS Energy, 2009) and published geologic reports. A map showing generalized geology of east Africa, Madagascar, and the Morondava Basin is shown in figure 2.
AbstractThe main objective of the U.S. Geological Survey’s
National and Global Petroleum Assessment Project is to assess the potential for undiscovered, technically recover-able oil and natural gas resources of the United States and the world. As part of this project, the U.S. Geological Survey completed an assessment of the Morondava Province, located along the western part of Madagascar, an area of approxi-mately 460,690 square kilometers. The Morondava Province is characterized by rift, marginal-sag, passive-margin, and drift rocks of Paleozoic to Holocene age. This assessment was based on data from oil and gas exploration wells, producing fields, and published geologic reports.
The Morondava Province and associated assessment unit was assessed for the first time because of increased exploratory activity and increased interest in its future oil and gas potential. The assessment was geology based and used the total petroleum system concept. The geologic elements of a total petroleum system include hydrocarbon source rocks (source-rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and distribution), and traps for hydrocarbon accumulation. Using these geologic criteria, the U.S. Geological Survey defined the Mesozoic-Cenozoic Composite Total Petroleum System with one assessment unit, the Mesozoic-Cenozoic Reservoirs Assessment Unit, an area of approximately 440,410 square kilometers. The total petroleum system was defined to include Mesozoic to Paleogene lacustrine and marine source rocks and conventional reservoirs. At the time of the assessment, the Morondava Province contained two gas accumula-tions exceeding the minimum size of 5 million barrels of oil equivalent; the province is considered to be underexplored on the basis of its exploration effort.
Oil and gas were generated from Permian to Jurassic Karoo-age lacustrine and continental source rocks (rift stage) averaging 4.0 to 5.0 weight percent total organic carbon, from Early to Middle Jurassic restricted-marine rocks containing as much as 9 weight percent total organic carbon, and from Cretaceous Type II source rocks containing as much as 12 weight percent total organic carbon. Hydrocarbon generation
2 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
Figure 1. Morondava Province and the Mesozoic-Cenozoic Reservoirs Assessment Unit along the central coast of East Africa.
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Morondova7373
AFRICA
INDEX MAP
Base from U.S. Geological Survey digital data, 2002World Geodetic System 1984 (WGS 84)Prime Meridian, Greenwich, 0°
0 150 300 KILOMETERS
0 300 MILES150
Réunion
MAURITIUS
COMOROS
Mayotte
ZAMBIA
MALAWI
ZIMBABWE
LESOTHO
SWAZILAND
SOUTHAFRICA
KENYA
BURUNDI
RWANDA
70°E66°E62°E58°E54°E50°E46°E42°E38°E34°E30°E
2°S
6°S
10°S
14°S
18°S
22°S
26°S
30°S
34°S
TANZANIA
MADAGASCARMOZAMBIQUE
SEYCHELLES
INDIAN OCEAN
Mesozoic-Cenozoic Reservoirs Assessment Unit boundary
EXPLANATIONMorondava Province boundary
Gas fieldOil field
Morondava7373
Introduction 3
Figure 2. Generalized geology of East Africa showing Madagascar, Majunga, and Morondava Basins, and the Tsimiroro heavy-oil field. Modified from Ophir Energy (2007).
CongoBasin
TANZANIA
KalahariBasin
Beira
MAPUTO
Dar es Salaam
MOGADISHU
Somali OceanicBasin
Continent-oceanicboundary
(COB)
OgadenBasin
RovumaDeltaDavie Fracture Zone
Moz
ambiq
ue C
hann
el
Aswa Shear Zone
Cupa Fault Zone1,0
00
KarrooBasin
Continent-oceanicboundary
(COB)
MandawaBasin
MajungaBasin
MorondavaBasin
MozambiqueBasin
INDIAN OCEAN
MA
DA
GA
SCA
R
Mombasa
0 200 400 600 KILOMETERS
0 600 MILES200 400
EXPLANATION
Bathymetric contour, 1,000 meter line—Location approximate
Continental crust—Palo fill
Permian-Triassic–Early Jurassic—Karoo-age rock
Phanerozoic—Intracratonic basin
ContactFault or fault zone—Dashed where approximate. Arrows show relative motion
Post Early Jurassic—Passive margin basin
Tertiary—Volcanic province
Undifferentiated—Precambrian basement
Graben—Teeth on downthrown side
MOZAMBIQUE
Tsimiro
roFie
ld
4 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
The Morondava Province and its associated assessment unit were assessed because of increased energy explora-tion activity and increased interest in its future oil and gas potential. The assessment was geology based and used the total petroleum system concept. The geologic elements of a total petroleum system consist of hydrocarbon source rocks (source-rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and distribu-tion), and traps for hydrocarbon accumulation. Using these geologic criteria, the USGS defined the Mesozoic-Cenozoic Composite Total Petroleum System (TPS) with one assessment unit, the Mesozoic-Cenozoic Reservoirs Assessment Unit (AU) (fig. 1), an area of approximately 440,410 km2. The total petroleum system was defined to include Mesozoic to Paleogene lacustrine and marine source rocks and conventional reservoirs.
Tectonic History and Geology of the Morondava Province, Madagascar, East Africa
The Morondava Province is directly related to the breakup of Gondwana (fig. 3) in the late Paleozoic and Mesozoic (Reeves and others, 2002). The province developed in four phases (Rusk, Bertagne & Associates, 2003; Stone and LeRoy, 2003a): (1) a pre-rift phase that started during the Carboniferous during which a mantle plume caused uplift, extension, microplate formation, rifting, and volcanism; (2) a syn-rift phase that started during the Permo-Triassic and continued into the Jurassic, resulting in the formation of grabens and half-grabens and the deposition of possible lacustrine and continental source rocks; (3) a syn-rift-drift phase that began in the Middle Jurassic and continued into the Paleogene, depositing marine clastic units and carbonate with periods of restricted-marine conditions during which marine source rocks were deposited; and (4) a passive-margin phase that began in the late Paleogene and continues to the present. The stratigraphic section present in the Morondava Province is generally the same as the section present in the coastal Mozambique and Tanzania provinces (figs. 2, 4; Rusk, Bertagne & Associates, 2003).
The opening of the Indian Ocean began in the Permian and continued into the Jurassic (Plummer and others, 1998). During the syn-rift stage, Madagascar, India, and the Morondava Province separated from Africa in Middle Jurassic, forming a passive margin and a carbonate platform, which was later covered by Upper Jurassic to Cretaceous marine clastic deposits (figs. 4, 5). From the Late Cretaceous to the Holocene, the Morondava Province has been the site of marine deposition in a drift-passive-margin basin.
Petroleum Occurrence in the Morondava Province, Madagascar, East Africa
Source Rocks
The Mesozoic-Cenozoic Composite TPS was defined to include Paleozoic to Paleocene source rocks and conventional reservoirs (figs. 4, 5). The Permian to Triassic section contains fluvial and lacustrine source rocks averaging 5 to 6 weight percent total organic carbon (TOC), and some samples have as much as 17.4 weight percent (Envoi—Energy Venture Opportunities International, 2011). Early to Middle Jurassic rock contains restricted-marine Type II kerogen source rocks, marginal marine and deltaic Types II and III kerogen source rocks, and Type I lacustrine source rock (Cope, 2000; Rusk, Bertagne & Associates, 2003). Early to Middle Jurassic restricted marine Type II source rocks contain as much as 12 weight percent TOC. Late Jurassic to Early Cretaceous marlstone contains Type II and Type III kerogen with as much as 5 weight percent TOC (Envoi—Energy Venture Opportunities International, 2011). Type II and III kerogen source rocks of Cretaceous age with TOC contents up to 7.4 weight percent, have been identified in the Ruvuma Delta of northern Mozambique and southern Tanzania (fig. 2) and should be found in the offshore part of the Morondava Province (Cope, 2000; Envoi—Energy Venture Opportunities International, 2011). Ophir Energy Company (2007) reported that Cretaceous shale had TOC contents ranging from 1 weight percent to 9.3 weight percent.
Oil and gas generation most likely began in the Early Cretaceous for the Upper Jurassic syn-rift source rocks in the province. Oil and gas generation began in the Late Cretaceous for the Barremian to Aptian post-rift sources and in the offshore parts of the province; the Late Cretaceous post-rift sources began oil and gas generation in the early Paleogene, and it is most likely continuing today. Oil and gas generation windows are shown in figure 6 for the Mozambique Channel and the Morondava Basin (Envoi—Energy Venture Opportunities International), 2011).
Reservoirs, Traps, and Seals
The Morondava Province and the Mesozoic-Cenozoic Reservoirs Assessment Units contains Mesozoic and Cenozoic sandstone reservoirs (Cope, 2000; Banks and others, 2008; Matchette-Downes, 2009; Tamannai and others, 2010; Envoi—Energy Venture Opportunities International, 2011).
Triassic to Middle Jurassic syn-rift rocks contain possible alluvial fans, fan deltas, fluvial deltas, and lacustrine sandstone reservoirs (Banks and others, 2008). Late Jurassic post-rift rocks contain reef and platform carbonates that are potential
Petroleum Occurrence in the Morondava Province, Madagascar, East Africa 5
Figure 3. Reconstruction of the early breakup of Gondwana during the Early Jurassic (200 Ma). Modified from Reeves and others (2002).
0 100 200 KILOMETERS
0 200 MILES100
HORN OF AFRICA
KENYA
TANZANIA
MADAGASCAR
INDIA
INDIA
SRI LANKA
EAST ANTARCTICA
SEYCHELLES
Mik
ume
Rift
Cambay Rift
Saurastra
Anza Rift
Narmada-Son
Basin
NORT
HM
OZA
MBI
QUE
Selous
Line of latitude or longitude— Oriented as on modern map
EXPLANATION
Precambrian crustal fragment
Rift-related rock
6 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
Figure 4. Generalized plate-tectonic development of the Madagascar Province: A, Early Cretaceous, following the separation of east and west Gondwana; B, early Late Cretaceous, during the separation of Seychelles-India from Madagascar; rotation of the plates shown in the Mascarene Basin; C, Paleocene, during the separation of India from the Seychelles. Black arrows show direction of movement and/or rotation. D, present day. Modified from Plummer and others (1998). Not to scale.
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EXPLANATIONNOT TO SCALE
Area of oceanic crust—Arrows show direction of crustal extension
Rift and passive margin rock
Shear zone—Arrows show direction of relative motion, dashed where uncertain
EASTAFRICA
EASTAFRICA
EASTAFRICA
INDIA
INDIA
INDIA
ANTARCTICA
MA
DA
GA
SCA
R
MA
DA
GA
SCA
R
MA
DA
GA
SCA
R
Mas
care
ne
Basin
Mascarene
Basin
Basin
Arabian
Som
ali
Arabian Basin
Mas
care
ne B
asin
Basin
Som
ali
Basin
Som
ali
Basin
Som
ali
Basin
SEYCHELLES
MADAGASCAR
SEYCHELLES
SEYCHELLES
A B
C D
SEYCHELLES
Petroleum Occurrence in the Morondava Province, Madagascar, East Africa 7
Figure 5. Generalized stratigraphy of coastal Mozambique, the Mozambique Channel and coastal Tanzania, coastal Morondava Basin, and Seychelles along the east coast of Africa (fig. 1). Carb., Carboniferous; cont., continental; Envir., environment; L, Lower; M, Middle; U, Upper; W, west; E, east. Modified from Rusk, Bertagne & Associates (2003) and PetroSeychelles (2013).
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EXPLANATION
Sandstone
Sandstone and conglomerate
Shale
Sandy shale
Calcareous shaley marlstone
Limestone Reservoir rock, East Africa
Salt
Igneous rock—Extrusive
Igneous rock—Oceanic crust
Basement
Unconformity
Contact—Dashed where location approximate
Extent uncertain
R
Source rock
Potential reservoirOil fieldGas field
CoastalMozambique
Tectonicevents
Tectonicevents
Mozambique Channeland Coastal Tanzania
CoastalMorondava Basin
Envir. Envir.W W
TERT
IARY
CRET
ACEO
USJU
RASS
ICTR
IASS
ICPE
RMIA
NCA
RBON
-IF
EROU
SPR
ECAM
-BR
IAN
Basement
Neo
gene
Pale
ogen
eUp
per
Low
erUp
per
Uppe
rM
ML
UL
Mid
dle-
Uppe
rLo
wer
FluvialDeltaic
Deltaic
Marine
?
?
?
Cont
inen
tal w
ith m
inor
mar
gina
l mar
ine
Zone
s o
f re
serv
oir
pote
ntia
l
Mar
ine
Mar
ine
Cont
inen
tal w
ith m
inor
mar
gina
l mar
ine
Shallowmarine
Deltaic tocont.
Shal
low
mar
ine
to c
ontin
enta
l
Shal
low
mar
ine
lago
onal
toco
ntin
enta
l
Mar
gina
l sag
and
pas
sive
mar
gin
Rift,
mar
gina
l sag
and
drift
Mar
gina
l sag
and
drif
t
Rift
and
mar
gina
l sag
Recu
rren
t rift
ing
and
uplif
t
Recu
rren
t rift
ing
and
uplif
t
Seyc
helle
s-In
dia
brea
kup
Mad
agas
car-
Seyc
helle
s-In
dia
brea
kup
from
Afri
ca
Mad
agas
car-
Seyc
helle
s-In
dia
brea
kup
from
Afri
ca
Rest
ricte
d m
arin
e, o
pen
mar
ine,
and
mar
gina
l mar
ine
Seychelles
SeychellesEast Africa
Drift
Rift
Lithology
?
?
?
Lithology Lithology Lithology
?
?
?
?
?
W EEE
?Re
stric
ted
mar
ine,
shal
low
mar
ine,
and
ope
n m
arin
eSh
allo
w m
arin
e an
d op
en m
arin
eCo
ntin
enta
l with
min
or m
argi
nal m
arin
e
Envir.
R
R
R
R
R
R
R
R
Age
Rifti
ng a
ndm
argi
nal s
ag
8 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
Figure 6. Cross section across the Mozambique Channel and the Morondava Basin (see index map) showing the top of the oil and gas windows. The Permo-Triassic and Lower Jurassic in Madagascar represent a failed-rift section. Modified from Envoi—Energy Venture Opportunities International (2011).
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INDEX MAP
WEST-NORTHWEST EAST-SOUTHEAST
KILOMETERSSEA LEVEL
4
6
8
10
2
EXPLANATION
Cenozoic
Tertiary
Upper Cretaceous
Lower Cretaceous
Jurassic
Oil field andidentifier
Gas field andidentifier
Triassic to Permian
Basement rock
Volcanic
ContactFault
MnaziBay Field(Offset to
South)
MnaziBay Field
X'
MOZAMBIQUE MADAGASCAR
Île Juan de NovaExclusive Economic Zone
FRENCH SOUTHERN ANDANTARCTIC LANDS
X
IroncladDiscovery(Offset to
North) WindjammerDiscovery(Offset to
North)Manambolo
Gas FieldJuan deNova Island
Shallow anddeepwaterprospect
TsimiroroHeavy Oil
Field BemolangaTar Sands
Top of Oil Window
Top of Gas Window
Davie Fracture Zone Morondava Basin
IroncladDiscovery
MOZAM
BIQUE
MA
DA
GA
SCA
R
MALAWI
Moz
ambiq
ue
Chann
el
RovumaDelta
Majunga Basin
Mor
onda
va B
asin
Mozambique Channel
INDIANOCEAN
X'
X
Line of section
reservoirs (figs. 7, 8). Post-rift Cretaceous sandstone reservoirs include regressive and transgressive marine sandstone, slope turbidite sandstone units, and basin-floor fan sandstone reservoirs (Tamannai and others, 2010). Volcanic events in the Upper Cretaceous and Cenozoic may have degraded potential reservoirs by altering the matrix minerals, but volcanic rocks are generally present in the onshore part of the Majunga Basin (fig. 8) and not in the offshore parts of the basin (Stone and LeRoy, 2003b).
Triassic to Middle Jurassic syn-rift rocks contain traps related to grabens and half-grabens (fig. 8). Lower Cretaceous drift and passive margin post-rift units contain stratigraphic and structural traps such as transgressive and regressive sandstones, salt structures, drape anticlines, and flower structures (Banks and others, 2008). Upper Cretaceous and Paleogene post-rift rocks (drift and passive margin) contain both structural and stratigraphic traps. Structural traps include growth-fault-related structures and rotated fault blocks within the continental shelf. Stratigraphic traps include deep-water fans, turbidite sandstones, and slope truncations along the present day shelf and paleoshelf edge along western Madagascar.
In drift and marginal-marine rocks, the primary reservoir seals are Mesozoic and Cenozoic mudstone and shale. Within the syn-rift section, faults and salt diapirs may act as reservoir seals.
ExplorationAt the time of this 2011 assessment, the Morondava
Province contained one oil field and no oil and gas discover-ies (IHS Energy, 2009); it is considered to be underex-plored on the basis of its exploration effort. The Tsimiroro oil field (fig. 2) is a heavy-oil accumulation with a “grown” size of 229 million barrels of oil (IHS Energy, 2009). Hydrocarbon shows and recent exploration efforts are limited to the Cretaceous-Tertiary offshore drift and marginal-marine rocks.
Exploration wells on the continental shelf and upper slope provide evidence for the existence of an active petroleum system containing Mesozoic source rocks, the migration of hydrocarbons most likely since Late Cretaceous time, and the migration of the hydrocarbons into Cretaceous and Cenozoic reservoirs.
Petroleum Occurrence in the Morondava Province, Madagascar, East Africa 9
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EXPLANATION
Unconformity
Coal and lignite
Probable reservoir interval
Productive gas zone
Tar/heavy oil deposit
Davie Fracture ZoneDFZ
Zone of probable bituminous/oil-prone organic matter
Contact
Oceanic crust
R
R
RR
R
R
R
R
R
R
RR
R
Era
Ceno
zoic
Mes
ozoi
cPa
leoz
oic
Perm
ian
Tria
ssic
Jura
ssic
Cret
aceo
usPa
leog
ene
Neo
gene
Quat
.Sy
stem
Epoch Stage
HolocenePleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Upper
MaastrichtianCampanianSantonianConiacianTuronian
CenomanianAlbianAptian
BarremianHauterivianValanginianBerriasianTithonian
KimmeridgianOxfordianCallovian
BathonianBajocianAalenian
PliensbachianSinemurianHettangian
RhaftianNorianCarnianLadinianAnisian
Induan
Lower
Upper
Middle
Lower
Upper(Malm)
Middle(Dogger)
Lower(Lias)
?
?
West EastDavieFracture
Zone(South)
MorondovaBasin
Coast
Potentialsource rock Tectonic
eventsTectonicactivityMaturity
chronology
Passive marginsubsidence
Drift Phase
N-S SeparationMadagascar, India,and Antarctic PlateFrom Africaalong DavieFracture Zone(DFZ)
Drift Phase
Pre-DriftSubsidence
KarooRift Phase
RecurrentNE-SW to N-Sextension
Uplift,Transpression andTranstension- Central DFZ andMadagascarMargins
Uplift andExtension- DFZ andCoastal Bas
RejuvenateUplift andExtension- Central andSouth DFZ
Transtension andTranspression-DFZ
-Alongfuture plateboundaries
Gas
Oil
Oil
Oil
Imm
atur
e
Imm
atur
e
Imm
atur
e
Imm
atur
e
Gas
Gas
-Grabens andhalf-grabens
?
?
?
Oil
Separation Indiaand Seychellesfrom Madagascar
Clastics
Sandstone
Siltstone
Coastal plain to shallow marine
Clastics
ContinentalDepositional Systems
Carbonates
Evaporites including salt
Lagoonal to restricted shallow marine
Outer shelf to basinal
Carbonates
Clastics
Volcanic
Igneous intrusive
Figure 7. Generalized stratigraphic column of the Morondava Basin, western Madagascar. Red and black lines are the approximate duration of the tectonic events and activity. Modified from Matchette-Downes (2009). Quat., Quaternary; ?, extent uncertain.
10 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
Figure 8. Schematic cross section across the Majunga Basin, northwest Madagascar. Modified from Banks and others (2008).
KILOMETERSSea Level
NORTHWEST SOUTHEAST
Lower JurassicRift Basin and
Mid-Jurassic-TertiaryPassive Margin
Failed Karroo Rift
Sofia-1 Tuilerie-1Ihopy-1
Belobaka-1
Coast Maravoay-1Mariarano-1
Mariarano-1
Ankara-1
Ankara-1
1
2
3
4
5
6
7
8
9
10
Q-MI
OL
EO-PC
KU
KU
KLJM
KL
JLu
JLu
JLL
JLL
JLu
JLu
JLL
JLL
KL
JU
JU
JU
�P-�
�P-�?
?
?
?
Geographic identifierQuaternaryQMioceneMIOligoceneOLEocene-PaleoceneEO-PCUpper CretaceousKULower CretaceousKLUpper JurassicJUMiddle JurassicJMLower Jurassic undifferentiatedJLuLowest Lower JurassicJLL
Permian-TriassicP-�
Unconformity
FaultGas show
Oil show
Contact—Dashed where approximate
Well and identifier
Offshore well and identifier
EXPLANATION
Tertiary
Upper Cretaceous
Lower Cretaceous
Middle and Upper Jurassic
Lower Jurassic
Salt
Karoo-age rock
Basement
Volcanic
Carbonate
Sandstone
Uncertain
0 10 20 30 40 KILOMETERS
0 10 20 30 40 MILES
Shale—Karoo, lacustrine?
Resource Summary 11
Figure 9. Events chart for the Mesozoic Composite Petroleum System (737301) and the Mesozoic-Cenozoic Reservoirs Assessment Unit (73730101). Gray, rock units present; yellow, age range of reservoir rock; green, age ranges of source, seal, and overburden rocks and the timing of trap formation and generation, migration, and preservation of hydrocarbons; wavy line, unconformity. Divisions of geologic time conform to dates in U.S. Geological Survey Geologic Names Committee (2010). Plio, Pliocene; Mio, Miocene; Olig, Oligocene; Eoc, Eocene; Pal, Paleocene, L, Late; E, Early; M, Middle; ?, uncertain.
Geologic ModelThe geologic model developed for the assessment of
conventional oil and gas in the Morondava Province and the Coastal Plain and Offshore AU, Madagascar, is as follows:1. Oil and gas were generated from Permian to Juras-
sic Karoo lacustrine and continental rocks (rift stage). Lacustrine rocks contain TOC values averaging 4.0 to 5 weight percent; Early to Middle Jurassic restricted marine rocks as much as 9 weight percent TOC, and Cretaceous source rocks contain Type II kerogen with TOC values as much as 12 weight percent. Hydrocar-bon generation of syn-rift sources (Upper Jurassic) most likely began in the Early Cretaceous. Oil genera-tion began in the Late Cretaceous for the early post-rift sources. Post-rift (Turonian) sources in parts of the offshore most likely are generating oil today.
2. Hydrocarbons migrated into mostly Cretaceous and Paleogene reservoirs and traps. Possible reservoirs could exist in the syn-rift section.
3. Hydrocarbon traps are structural within the syn-rift rock units and both structural and stratigraphic in the post-rift rocks.
4. The primary reservoir seals are Mesozoic and Cenozoic mudstone and shale.
5. Rifted passive margin analog (Charpentier and others, 2007) was used for assessment sizes and numbers because of similar source, reservoirs, and traps.
An events chart (fig. 9) for the Mesozoic Composite TPS and the Mesozoic-Cenozoic AU summarizes the age of the source, seal, and reservoir rocks and the timing of trap development, generation, and migration of hydrocarbons.
Resource SummaryAt the time of the 2011 assessment, the Morondava Province
contained one oil accumulation exceeding the minimum size of 5 million barrels of oil equivalent; the province is considered to be underexplored on the basis of its exploration activity.
Using a geology-based assessment, the U.S. Geological Survey estimated mean volumes of undiscovered, technically recoverable conventional oil and gas resources for the Mesozoic-Cenozoic Reservoirs Assessment Unit in the Morondava Province (table 1). Mean volumes are estimated at 10,750 million barrels of oil, 167,219 billion cubic feet of gas, and 5,176 million barrels of natural gas liquids. The estimated mean size of the largest oil field that is expected to be discovered is 1,016 million barrels of oil, and the estimated mean size of the expected largest gas field is 7,837 billion cubic feet of gas. For this assessment, a minimum undiscovered field size of 5 million barrels of oil equivalent was used. No attempt was made to estimate economically recoverable reserves.
Deltaic
Delta
ic
Rift
Cont
inen
tal
Rest
ricte
d an
dop
en m
arin
eOp
en a
nd m
argi
nal m
arin
e
Marine
0
100
200
50
150
250
Paleogene
Cretaceous
Jurassic
Triassic
Permian
65
146
200
251 E
E
E
E
M
M
L
L
L
L
Neogene
23
Pal
Eoc
Olig
Mio
Plio
PRES
ERVA
TION
Gen
erat
iom
n-
TRAP
FOR
MAT
ION
OVER
BURD
EN R
OCKS
RESE
RVOI
R RO
CKS
SEAL
ROC
KS
SOUR
CE R
OCKS
ROCK
UN
ITS
Acc
umul
atio
nM
igra
tion-
AgeMa
Petroleumsystemevents
?
12 Assessment of Undiscovered Oil and Gas Resources of the Morondava Province, Madagascar, East Africa
For Additional Information
Assessment results are available at the USGS Central Energy Resources Science Center website: http://energy.cr.usgs.gov/oilgas/noga/ or contact Michael E. Brownfield, the assessing geologist ([email protected]).
Acknowledgments
The author wishes to thank Mary-Margaret Coates, Jennifer Eoff, Christopher Schenk, and David Scott for their suggestions, comments, and editorial reviews, which greatly improved the manuscript. The author thanks Wayne Husband for his numerous hours drafting many of the figures used in this manuscript, and Chris Anderson, who supplied the Geographic Information System files for this assessment.
References
Banks, Nigel, Cooper, Bernard, Jenkins, Steven, and Razafindrakoto, Edmond, 2008, Evidence for the onshore extension of the deep water Jurassic salt basin in the Majunga Basin, northwest Madagascar: American Association of Petroleum Geologists Search and Discovery article 10155 (2008), 20 p.
Charpentier, R.R., Klett, T.R., and Attanasi, E.D., 2007, Data-base for assessment unit−scale analogs (exclusive of the United States), Version 1.0: U.S. Geological Survey Open-File Report 2007−1404, 36 p., CD–ROM.
Cope, Michael, 2000, Tanzania’s Mafia deepwater basin indi-cates potential on new seismic data: Oil and Gas Journal, v. 98, no. 33. Available at http://www.ogj.com/articles/print/volume-98/issue-33/exploration-development/tanzanias-mafia-deepwater-basin-indicates-potential-on-new-seismic-data.html. Last accessed February 28, 2013.
Envoi—Energy Venture Opportunities International, 2011, Mozambique Channel (Offshore S.E. Africa), Juan de Nova Est Permit, Morondava Basin: Envoi Limited, London, http://envoi.co.uk/wp-content/uploads/2012/11/ P191WessexSEAfricaJuanDeNovaSynopsis.pdf. Last accessed August 1, 2011.
IHS Energy, 2009, International petroleum exploration and production database [current through December 2009]: Available from IHS Energy, 15 Inverness Way East, Engle-wood, Colo. 80112 USA.
Klett, T.R., Ahlbrandt, T.S., Schmoker, J.W., and Dolton, G.L., 1997, Ranking of the world’s oil and gas provinces by known petroleum volumes: U.S. Geological Survey Open-File Report 97−463, CD–ROM.
Matchette-Downes, C.J., 2009, The east African petroleum systems: East African Petroleum Conference, March 11−13, 2009, Mombasa, Kenya, 22 p. http://www.mdoil.co.uk/pdfs/EAPC09-eafrica_petroleum-systems.pdf.
Ophir Energy Company, 2007, Hydrocarbon prospectivity of deepwater southern Tanzania: East African Petroleum Con-ference, Arusha, Tanzania, March 7–9, 2007, 26 p.
PetroSeychelles, 2013, The Seychelles licensing initia- tives: NAPE, February 5–8, Houston, Texas, 46 p. http://www.internationalpavilion.com/NAPE%202013%20Presentations/Seychelles.pdf.
Plummer, Ph.S., Joseph, P.R., and Samson, P.J., 1998, Deposi-tional environments and oil potential of Jurassic/Cretaceous source rocks within the Seychelles microcontinent: Marine and Petroleum Geology, v. 15, no. 5, p. 385–401.
Reeves, C.V., Sahu, B.K., and de Wit, M., 2002, A re-examina-tion of the paleo-position of Africa’s eastern neighbours in Gondwana: Journal of African Earth Sciences, v. 34, no. 1, p. 101–108.
Rusk, Bertagne & Associates, 2003, Petroleum geology and geophysics of the Mozambique Channel, executive summary: Available at http://www.petrocommunicators.com/moz/index.htm. Accessed March 6, 2012.
Table 1. Morondava Province assessment results for undiscovered, technically recoverable oil, gas, and natural gas liquids.
[Largest expected mean field size, in million barrels of oil and billion cubic feet of gas; MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas accumulations, all liquids are included as natural gas liquids (NGL). Undiscovered gas resources are the sum of nonassociated and associated gas. F95 represents a 95-percent chance of at least the amount tabulated; other fractiles are defined similarly. Fractiles are additive under assumption of perfect positive correlation. AU, assessment unit; AU probability is the chance of at least one accumulation of minimum size within the AU. TPS, total petroleum system. Gray shading indicates not applicable]
Total Petroleum Systems (TPS) and Assessment Units (AU)
Field type
Largest expected
mean field size
Total undiscovered resourcesOil (MMBO) Gas (BCFG) NGL (MMBNGL)
F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean
Morondava-Mesozoic Composite TPS
Mesozoic-Cenozoic Reservoirs AU Oil 1,016 5,701 10,256 17,455 10,750 7,686 14,325 25,322 15,123 205 386 693 409Gas 7,837 85,291 145,683 242,887 15,2096 2,667 4,569 7,618 4,767
Total Conventional Resources 5,701 10,256 17,455 10,750 92,977 160,008 268,210 167,219 2,872 4,955 8,311 5,176
References 13
Stone, R.A., and LeRoy, S.D., 2003a, Madagascar deep-water–1: Oil and Gas Journal, v. 101, no. 9, p. 35–39.
Stone, R.A., and LeRoy, S.D., 2003b, Madagascar deepwater–2: Oil and Gas Journal, v. 101, no. 10, p. 42–45.
Tamannai, M.S., Winstone, D., Deighton, I., and Conn, P., 2010, Geological and geophysical evaluation of offshore Morondava frontier basin based on satellite gravity, well and regional 2D seismic data interpretation: American Association of Petroleum Geologists Search and Discovery article 10229 (2010), 7 p.
U.S. Geological Survey Geologic Names Committee, 2010, Divisions of geologic time: U.S. Geological Survey Fact Sheet 2010–3059, 2 p. Available at http://pubs.usgs.gov/fs/2010/3059/.
U.S. Geological Survey World Conventional Resources Assessment Team, 2012, An estimate of undiscovered conventional oil and gas resources of the world, 2012: U.S. Geological Survey Fact Sheet 2012–3042, 6 p. Available at http://pubs.usgs.gov/fs/2012/3042/.
ATLANTIC OCEAN
SOUTHATLANTIC
OCEAN
INDIAN OCEAN
INDIAN OCEAN
MEDITERRANEAN SEA
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Morondava
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