U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2012–3039

April 2012

World Petroleum Resources Project

Assessment of Undiscovered Oil and Gas Resources of Four 

East Africa Geologic Provinces

Introduction

The main objective of the U.S. Geological Survey’s (USGS) 

World Petroleum Resources Project is to assess the potential for 

undiscovered, technically recoverable oil and natural gas resources 

of the world, exclusive of the United States. As part of this program, 

the USGS recently completed an assessment of four geologic provinces: three along the eastern part of the African coast and one more 

than 900 miles east of the African coast and extending to water depths 

ranging from 2,000−3,000 meters (m) (fig. 1). From north to south, 

the provinces are as follows: (1) the Tanzania Coastal, containing rift, 

marginal sag, and passive margin rocks of Middle Jurassic to Holocene 

age; (2) Seychelles, characterized by rift, marginal sag, and drift rocks; 

(3) the Morondava, containing failed rift, marginal sag, and passive 

margin rocks; and (4) the Mozambique Coastal, described by rift, marginal sag, and passive margin rocks. These assessments were based on 

data from oil and gas exploration wells and published geologic reports.

The four provinces were related to the breakup of Gondwana 

(fig. 2) in the late Paleozoic and Mesozoic (Reeves and others, 2002), 

and developed similarly through two tectonic phases (fig. 3): (1) a 

syn-rift phase that was started during the Permo–Triassic and continued 

REUNION

MAURITIUS

COMOROS

MAYOTTE

TANZANIA

ZAMBIA

MALAWI

ZIMBABWE MADAGASCAR

LESOTHO

SWAZILAND

SOUTH 

AFRICA

MOZAMBIQUE

SEYCHELLES

KENYA

BURUNDI

2° RWANDA

4°

6°

8°

10°

12°

14°

16°

18°

20°

22°

24°

26°

28°

30°

32°

34°

!

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! !

!

!

0 300 600 MILES

 INDIAN OCEAN

MOZAMBIQUE

COASTAL PROVINCE 

MORONDAVA

PROVINCE 

SEYCHELLES

PROVINCE

TANZANIA COASTAL

PROVINCE

AFRICA

MADAGASCAR

 INDIAN

 OCEAN

SOUTH

ATLANTIC

OCEAN

EXPLANATION

Mesozoic-Cenozoic Reservoirs AU 

Gas field

Oil field

Province

!

!

Mesozoic-Cenozoic Reservoirs AU

Seychelles Rifts AU 

Mesozoic-Cenozoic Reservoirs AU 

MOZAMBIQUE

CHANNEL AREA

0 300 600 KILOMETERS 

28° 30° 32° 34° 36° 38° 40° 42° 44° 46° 48° 50° 52° 54° 56° 58° 60° 62° 64° 66° 68° 70° 72°

Figure 1. Locations of the four assessed geologic provinces and assessment units (AU) along the central coast 

of east Africa.

Four geologic provinces along the east coast of Africa recently were assessed for undiscovered, technically recoverable oil, 

natural gas, and natural gas liquids resources as part of the U.S. Geological Survey’s (USGS) World Oil and Gas Assessment. 

Using a geology-based assessment methodology, the USGS estimated mean volumes of 27.6 billion barrels of oil, 441.1 trillion 

cubic feet of natural gas, and 13.77 billion barrels of natural gas liquids.
into the Jurassic, resulting in the formation of grabens and half-grabens 

and (2) a drift phase that began in the mid-Jurassic and continued into 

the Paleogene. A later passive margin phase began in the late Paleogene and continues to the present in the Morondava, Mozambique, 

and Tanzania Coastal Provinces, whereas in the Seychelles Province 

the drift phase continues to the present because there is no significant 

sediment source after the Seychelles-India breakup. The total thickness 

of the Mesozoic to Cenozoic stratigraphic section is more than 5,000 

m on the outer parts of the continental shelf along the east Africa coast 

in the Morondava and Mozambique Coastal Provinces and more than 

4,000 m in the Seychelles Province.

The four provinces and associated assessment units (AU) were 

assessed for the first time because of increased exploratory activity, 

recent discoveries, and increased interest in their future potential. The 

assessment was geology based and used the total petroleum system 

(TPS) concept. The geologic elements of a TPS 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 USGS defined four TPSs and 

one AU for each TPS (table 1). The TPSs were defined to include 

Mesozoic to Paleocene source rocks and conventional reservoirs (fig. 

3). The Permian to Triassic contains fluvial and lacustrine source 

rocks, and the Jurassic contains restricted marine Type II kerogen 

source rocks and marginal marine and deltaic Types II and III kerogen 

source rocks. Types II and III kerogen source rocks of Cretaceous 

age have been identified in the Morondava, Mozambique, Seychelles, 

and Tanzania Provinces, and Types II and III kerogen source rocks of 

Paleogene age have been identified in Mozambique, Seychelles, and 

Tanzania Provinces. Permian to Triassic source rocks contain 1.0 to 

6.7 weight percent total organic carbon (TOC), with some samples 

having as much as 17.4 percent. The Early to Middle Jurassic restricted 

marine Type II source rocks contain as much as 12 weight percent 

TOC. Upper Jurassic and Cretaceous marine strata include (1) Aptian 

source containing Type II kerogen, ranging from 2.0 to 4.28 weight 

percent TOC; and (2) Cenomanian–Turonian source rocks containing Type II kerogen, ranging from 1.0 to 3.0 weight percent TOC. All 

four AUs contain Mesozoic and Cenozoic clastic reservoirs. Traps 

are mostly structural within the syn-rift rock units and both structural 

and stratigraphic in the postrift-rock units. The east African provinces 

(Mozambique, Morondava, and Tanzania, fig. 1) contain reservoirs that 

mostly are associated with growth-fault-related structures, rotated fault 

blocks within the continental shelf, deep water fans, turbidite channels and sandstones, slope truncations along the present-day shelf and 

paleoshelf edge. Permian to Triassic sandstone and Late Jurassic reefs 

and platform limestone also are possible reservoirs. The primary seals 

are Mesozoic and Cenozoic mudstones and shales. The Seychelles 

Province contains possible reservoirs in Permian to Middle Jurassic 

rift-related sandstones, Middle Jurassic carbonates, Lower and Upper 

Cretaceous turbidite sandstones, and Tertiary carbonates. The primary 

seals are intraformational shales.

0 125 250 MILES

0 125 250 KILOMETERS

HORN OF AFRICA

KENYA

TANZANIA

NORTH

MAZAMBIQUE

MADAGASCAR

INDIA

INDIA

SRI LANKA

EAST ANTARCTICA

SEYCHELLES

Mikume Rift

Cambay Rift

SAURASTRA Anza Rift

NARMADA-SON

Selous

Basin

Figure 2. Reconstruction of the early breakup of Gondwana during the Early Jurassic 

(200 Ma) showing the Precambrian crustal fragments in yellow and the rift-related rocks 

in light green. Modified after Reeves and others (2002).
At the time of the assessment, the four east African provinces 

contained 1 oil and 11 gas accumulations (HIS Energy, 2009), thus 

exceeding the minimum size of 5 million barrels of oil equivalent and 

30 billion cubic feet of gas; these provinces are considered to be underexplored for their size. The Seychelles Province contained no discoveries and was also underexplored.

Exploration wells and discovered accumulations on the continental shelf and upper slope (IHS Energy, 2009) provide evidence for 

(1) the existence of an active petroleum system containing Mesozoic 

source rocks, (2) the migration of the hydrocarbons most likely since 

the Late Cretaceous, and (3) the migration of the hydrocarbons into 

Cretaceous and Cenozoic reservoirs.

Resource Summary

The results of the USGS assessment of undiscovered, technically recoverable conventional oil and gas resources in the east Africa 

provinces are listed in table 1. The mean volumes are estimated at 

(1) 10,750 million barrels of oil (MMBO), 167,219 billion cubic 

feet of gas (BCFG), and 5,176 million barrels of natural gas liquids (MMBNGL) for the Mesozoic-Cenozoic Reservoirs AU in the 

Morondava Province; (2) 11,682 MMBO, 182,349 BCFG, and 5,645 

MMBNGL for the Mesozoic-Cenozoic Reservoirs AU in the Mozambique Coastal Province; (3) 2,394 MMBO, 20,376 BCFG, and 739 

MMBNGL for the Seychelles Rifts AU in the Seychelles Province; 

and (4) 2,806 MMBO, 71,107 BCFG, and 2,212 MMBNGL for the 

Mesozoic-Cenozoic Reservoirs AU in the Tanzania Coastal Province. 

For this assessment, a minimum undiscovered field size of 5 million 

barrels of oil equivalent (MMBOE) was used. No attempt was made to 

estimate economically recoverable reserves.

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 

(mbrownfield@usgs.gov).

East Africa Provinces Assessment Team

Michael E. Brownfield, Christopher J. Schenk, Ronald R. Charpentier, Timothy R. Klett, Troy A. Cook, Richard M. Pollastro, and 

Marilyn E. Tennyson.

Total petroleum systems

(TPS) and assessment 

units (AU) 

Field 

type

Largest 

expected 

mean

field size

Total undiscovered resources

Oil (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

1,041 6,268 11,174 8,423 15,615 27,238 16,425 225 421 744 444

Gas

7,976 93,486 158,654 263,301 165,924 2,915 4,978 8,270 5,201

Total conventional

resources

6,268 11,174 18,857 11,682 101,909 174,269 290,539 182,349 3,140 5,399 9,014 5,645

Mozambique Coastal–Mesozoic Composite TPS

Mesozoic-Cenozoic

Reservoirs AU

Oil

1,016 5,701 10,256 17,455 10,750 7,686 14,325 25,323 15,123 205 386 693 409

Gas

7,837 85,291 145,683 242,887 152,096 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

Seychelles–Mesozoic-Cenozoic Composite TPS

Seychelles Rifts AU

Oil 793 585 1,984 5,574 2,394 1,328 4,760 15,038 6,044 28 100 324 129

Gas 4,765 3,538 11,781 33,660 14,332 146 496 1,467 610

Total conventional

resources 585 1,984 5,574 2,394 4,866 16,541 48,698 20,376 174 596 1,791 739

Tanzania Coastal–Mesozoic-Cenozoic Composite TPS

Mesozoic-Cenozoic

Reservoirs AU

Oil 594 1,223 2,608 5,064 2,806

1,223 2,608 5,064 2,806

35,902 64,054 108,925 67,174

42 95 208 106

Gas 6,162 1,118 2,006 3,433 2,106

Total conventional

resources 37,485

1,583

67,609 116,496 71,107 1,160 2,101 3,641 2,212

–

Total conventional

resources 13,777 26,022 46,950 27,632 237,237 418,427 723,943 441,051 7,346 13,051 22,757 13,772

3,555 7,571 3,933

18,857 11,682

[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 he amount tabulated; other fractiles are defined similarly. 

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]

Table 1. Morondava, Mozambique Coastal, Seychelles, and Tanzania Coastal Provinces assessment results for undiscovered, technically 

recoverable oil, gas, and natural gas liquids.
References Cited

Fugro Multi Client Services, 2010, New Seychelles, non-exclusive 2D 

seismic survey: Accessed March 6, 2012, at http://www.fugromcs.

com.au/Fliers/Flier_Seychelles.pdf.

IHS Energy, 2009, International petroleum exploration and production 

database [current through December 2009]: Available from IHS 

Energy, 15 Inverness Way East, Englewood, CO 80112 USA.

Reeves, C.V., Sahu, B.K., and de Wit, M., 2002, A re-examination 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: Accessed March 6, 

2012, at http://www.petrocommunicators.com/moz/index.htm.

Coastal

Mozambique Tectonic events Tectonic events Mozambique Channel

and Coastal Tanzania

Coastal

Morandava Basin

W Envir. W Envir.

Tertiary Cretaceous Jurassic Triassic Permian Carb. Precambrian

Basement

Neogene Paleogene Upper Lower Upper Upper MLUL Middle- Upper Midddle Lower

Fluvial

deltaic

Deltaic

marine

?

?

Continenta with minor marginal marine

Zones of reservoir potential

Marine Marine Continental with minor marginal marine Shallow marine

Deltaic

to

cont. Shallow marine to continental Shallow marine lagoonal to continental

Marginal Sag and passive margin

Rift, marginal sag and drift Marginal sag and drift

Rift and

marginal sag

Recurrent rifting

and uplift

Recurrent Rifting and uplift

Seychelles-India

breakup

MadagascarSeychelles-Indiabreakup from Africa

MadagascarSeychelles-Indiabreakup from Africa

Restricted marine, open marine, and marginal marine

Seychelles

East Africa Seychelles Drift Rift

Lithology

?

E Lithology Lithology E W Lithology E

?

Salt

Restricted marine, shallow

marin, and open marine Shallow marine and open marine Continental with minor marginal marine Envir.

R

R

R

R

R

R

R

R

Age

Sandstone Shale

Salt

Calcareous

 shaley marl

Igneous rocks-

 extrusive

Igneous rocks–

 oceanic crust

Sandstone and Sandy shale Basement rocks

 conglomerate

Reservoir rock

 zones, east

Limestone Source rock

Potential reservoir–

 Seychelles Province

Oil field

Gas field

EXPLANATION

R

Africa

Figure 3. Generalized stratigraphic columns for Mozambique Coastal, the Mozambique Channel and Tanzania Coastal, and 

the Morondava and Seychelles Provinces along the east coast of Africa (see fig. 1). Carb., Carboniferous; cont., continental; 

Envir., environment; L, Lower; M, Middle; U, Upper; ?, questionable extent. Modified after Fugro Multi Client Services (2010) 

and Rusk, Bertagne & Associates (2003).