National and Global Petroleum Assessment

Assessment of Conventional Oil Resources 

of the East African Rift Province, East Africa, 2016

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2017–3006

March 2017 Printed on recycled paper

Using a geology-based assessment methodology, the U.S. Geological Survey estimated undiscovered, technically recoverable mean 

conventional resources of 13.4 billion barrels of oil and 4.6 trillion cubic feet of gas in the East African Rift Province of east Africa.

For this assessment, we used a minimum undiscovered field size 

of 5 million barrels of oil (MMBO). In the Uganda part of the Albertine 

Graben AU, 15 oil fields are equal to or greater than minimum assessment field size, and in the Kenya part of the Eastern Arm Rift Basins 

AU, 8 fields equal to or greater than the minimum assessment field 

size have been discovered (IHS MarkitTM, 2015). No fields have been 

discovered in the other AUs. Assessment input data for the four conventional assessment units in the East African Rift Province are shown 

in table 1. Numbers and sizes of undiscovered oil accumulations are 

guided by data from geologic analogs.

Introduction

The U.S. Geological Survey (USGS) recently completed an assessment of undiscovered, technically recoverable conventional oil resources within the East African Rift 

Province (fig. 1), a geologically complex region of approximately 2,916,160 square kilometers in east Africa. The rifts 

are commonly described as forming an “Eastern Branch” and 

a “Western Branch.” The East African Rift System (EARS) 

developed in the late Oligocene in the Afar region of Ethiopia 

shortly after an Eocene–Oligocene flood basalt event in the 

Lake Turkana and South Lokichar Basin area in the Eastern 

Branch of EARS (fig. 1) where extensional faults developed 

within the Precambrian craton. During the middle to late 

Miocene, rifts developed between Ethiopia and Mozambique in 

the Western Branch of the EARS within the Precambrian craton 

(fig. 1) (Davison and others, 2014; Abeinomugisha, 2015). As 

much as 5,000 meters of Oligocene-to-Holocene sedimentary 

rocks are present in the rift basins of the province. At the time 

of this assessment, the province contained 30 oil fields in the 

rift basins—18 in Uganda and 12 in Kenya—and the province 

is considered underexplored (IHS MarkitTM, 2015).

Total Petroleum System and Assessment Units

The East African Rift Province was assessed because of 

its potential for undiscovered oil resources. 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 the Oligocene–Pleistocene TPS 

with four assessment units (AUs): the Albertine Graben AU, 

Tanganyika-Rukwa AU, Lake Malawi AU, and Eastern Arm 

Rift Basins AU (fig. 1). The AUs include parts of Burundi, 

Democratic Republic of the Congo, Ethiopia, Kenya, Malawi, 

Mozambique, Rwanda, South Sudan, Tanzania, Uganda, and 

Zambia (fig. 1). The TPS was defined to include (1) Oligoceneto-Pleistocene lacustrine source rocks with total organic content ranging from 1 to 17 weight percent; (2) porosity values 

ranging from 15 to 30 percent in Oligocene-to-Pleistocene 

clastic reservoirs; (3) permeability values ranging from 

50 millidarcies to several darcies; (4) shale seals; and (5) traps 

that are primarily structural with extensional faulting and minor 

inversion, although some stratigraphic traps are also present. 

Oil generation and migration began in the Miocene and most 

likely continues today (Talbot and others, 2004; Curd and 

others, 2013).

Figure 1. Location of the East African Rift Province and the four assessment 

units (AUs) defined in this study.

20° 25° 30° 35° 40° 45°

10°

5°

0°

–5°

–10°

–15°

Lake

Turkana

Lake

Victoria

RED SEA

INDIAN OCEAN

SOUTH

LOKICHAR

BASIN Western Branch

Eastern Branch

MALAWI

Western Branch

Afar

Region

DEMOCRATIC 

REPUBLIC OF 

THE CONGO RWANDA

UGANDA

BURUNDI

TANZANIA

CENTRAL

AFRICAN

REPUBLIC

REPUBLIC OF

THE CONGO

KENYA

CHAD

ETHIOPIA

ZAMBIA

ANGOLA

NAMBIA BOTSWANA

ZIMBABWE

ZAMBIA

SOUTH

SUDAN

MOZAMBIQUE

SOMALIA

Source: U.S. Department of the Interior National Park Service

Asia

AFRICA

Asia EUROPE Asia ASIA

ATLANTIC

OCEAN

INDIAN Map area OCEAN

0 150 300 MILES

0 150 300 KILOMETERS

EXPLANATION

Albertine Graben AU

Tanganyika-Rukwa AU

Lake Malawi AU

Eastern Arm Rift Basins AU

East African Rift Province
ISSN 2327-6916 (print) ISSN 2327-6932 (online) https://doi.org/10.3133/fs20173006

Undiscovered Resources Summary

The USGS quantitatively assessed 

undiscovered, technically recoverable 

conventional oil resources within four 

assessment units in the East African Rift 

Province (table 2). The estimated total 

mean resources are 13,438 million barrels 

of oil (MMBO), or 13.4 billion barrels of 

oil, with an F95–F5 range from 4,808 to 

25,373 MMBO; 4,648 billion cubic feet 

of gas (BCFG), or 4.6 trillion cubic feet of 

gas, with an F95–F5 range from 1,674 to 

9,072 BCFG; and 24 million barrels of natural gas liquids (MMBNGL) with an F95–F5 

range from 9 to 46 MMBNGL. For oil and 

gas accumulations, zeros at F95 reflect the 

chance that oil and gas might not exist in the 

AU, and the geologic AU probability (risk) 

was estimated to be less than one.

For the Albertine Graben AU, 

the estimated mean resources are 

1,594 MMBO with an F95–F5 range from 

560 to 3,251 MMBO, 435 BCFG with an 

F95–F5 range from 136 to 964 BCFG, and 

2 MMBNGL with an F95–F5 range from 

1 to 5 MMBNGL. For the TanganyikaRukwa AU, the estimated mean resources 

are 3,218 MMBO with an F95–F5 range 

from 1,284 to 6,042 MMBO, 880 BCFG 

with an F95–F5 range from 320 to 

1,780 BCFG, and 5 MMBNGL with an 

F95–F5 range from 2 to 9 MMBNGL. 

For the Lake Malawi AU, the estimated 

mean resources are 1,937 MMBO with an 

F95–F5 range from 0 to 4,114 MMBO, 

529 BCFG with an F95–F5 range from 0 

to 1,224 BCFG, and 3 MMBNGL with an 

F95–F5 range from 0 to 6 MMBNGL. For 

the Eastern Arm Rift Basins AU, the estimated mean resources are 6,689 MMBO 

with an F95–F5 range from 2,964 to 

11,966 MMBO, 2,804 BCFG with an 

F95–F5 range from 1,218 to 5,104 BCFG, 

and 14 MMBNGL with an F95–F5 range 

from 6 to 26 MMBNGL.

Assessment input data Albertine Graben AU Tanganyika-Rukwa AU

Minimum Median Maximum Calculated mean Minimum Median Maximum Calculated mean

Number of oil fields 1 45 130 47 1 90 270 95

Sizes of oil fields (MMBO) 5 10 2,000 33 5 10 2,000 33

AU probability 1.0 1.0

Assessment input data Lake Malawi AU Eastern Arm Rift Basins AU

Minimum Median Maximum Calculated mean Minimum Median Maximum Calculated mean

Number of oil fields 1 60 180 63 1 160 450 168

Sizes of oil fields (MMBO) 5 10 2,000 33 5 10 2,800 40

AU probability 0.9 1.0

Table 1. Key assessment input data for four conventional assessment units in the East African Rift Province, east Africa.

[AU, assessment unit; MMBO, million barrels of oil. Shading indicates not applicable]

Total petroleum system 

and assessment units (AUs)

AU 

probability

Accumulation 

type

Expected

largest

mean

field size

Total undiscovered resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Oligocene–Pleistocene Total Petroleum System

Albertine Graben AU 1.0 Oil 449 560 1,416 3,251 1,594 136 365 964 435 1 2 5 2

Tanganyika-Rukwa AU 1.0 Oil 635 1,284 2,951 6,042 3,218 320 778 1,780 880 2 4 9 5

Lake Malawi AU 0.9 Oil 523 0 1,809 4,114 1,937 0 467 1,224 529 0 2 6 3

Eastern Arm Rift Basins AU 1.0 Oil 1,098 2,964 6,234 11,966 6,689 1,218 2,599 5,104 2,804 6 13 26 14

Total undiscovered conventional 

resources 4,808 12,410 25,373 13,438 1,674 4,209 9,072 4,648 9 21 46 24

Table 2. Assessment results for four conventional assessment units in the East African Rift Province, east Africa.

[Expected largest mean field size in MMBO. MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. 

Results shown are fully risked estimates. F95 represents a 95-percent chance of at least the amount tabulated; other fractiles are defined similarly. Fractiles are 

additive under the assumption of perfect positive correlation. Shading indicates not applicable]

References Cited

Abeinomugisha, Dozith, 2015, Hydrocarbon exploration in the Albertine Graben of the East African Rift 

System, in East African Rift System Planning Workshop, Morristown, New Jersey, October 25–27, 2012, 

Proceedings: GeoPRISMS (Geodynamic Processes at Rifting and Subducting Margins), 19 p., accessed 

January 30, 2017, at http://geoprisms.org/wp-content/uploads/2015/02/019_EARS2012_Dozith.pdf.

Curd, S.R., Downie, R., Logan, P.C., and Holley, P., 2013, The Kingfisher Field, Uganda—A bird in the 

hand! [abs.], in SAMPLE (South Atlantic Margin Processes and Links with Onshore Evolution) Colloquium 2013, Heidelberg, Germany, June 11–14, 2013, Proceedings: South Atlantic Margin Processes and 

Links with Onshore Evolution, 16 p., accessed December 15, 2016, at http://www.sample-spp.de/internal/

london/Posters_Strat%20Studies,%20Reservoirs%20and%20Reserves/Downie_The%20Kingfisher%20

Field,%20Uganda%20-%20A%20Bird%20in%20the%20Hand.pdf.

Davison, Ian; Steel, Ian; Taylor, Matthew; Beirne, E.O.; and Faull, Theodore, 2014, Exploration in the East 

African Rift System: GeoExPro, v. 11, no. 5, p. 26–32.

IHS MarkitTM, 2015, International petroleum exploration and production database [current through 2015]: 

IHS Markit, 15 Inverness Way East, Englewood, CO 80112.

Talbot, M.R., Morley, C.K, Tiercelin, J.-J., Le Hérissé, A., Potdevin, J.-L., and Le Gall, B., 2004, Hydrocarbon potential of the Meso–Cenozoic Turkana Depression, northern Kenya. II. Source rocks—Quality, 

maturation, depositional environments and structural control: Marine and Petroleum Geology, v. 21, no. 1, 

p. 63–78.

For More Information

Assessment results also are available 

at the USGS Energy Resources Program 

website at http://energy.usgs.gov.

East African Rift Province 

Assessment Team

Michael E. Brownfield, Christopher 

J. Schenk, Timothy R. Klett, Tracey J. 

Mercier, Stephanie B. Gaswirth, Kristen 

R. Marra, Thomas M. Finn, Phuong A. Le, 

and Heidi M. Leathers-Miller