U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3029

March 2011

World Petroleum Resources Project

Assessment of Undiscovered Oil and Gas Resources of the 

Sud Province, North-Central Africa

Printed on recycled paper

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 the 

Sud Province (fig. 1), an area of approximately 978,800 square 

kilometers (km2) that covers parts of the Central African Republic, 

Chad, Ethiopia, Camaroon, and Sudan. This assessment was based 

on data from oil and gas wells and fields, field production records, 

and published geologic reports. At the time of the assessment, the 

The Sud Province located in north-central Africa recently was 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 7.31 billion barrels of oil, 13.42 trillion 

cubic feet of natural gas, and 353 million barrels of natural gas liquids.

province contained 113 oil fields—18 in Chad and 95 in Sudan—

and was considered to be underexplored for its size. There was one 

gas field in the province but several discoveries reported associated gas in oil fields. The producing oil fields and recent petroleum 

discoveries were limited to the Cretaceous-Tertiary rift basins.

The Sud Province was assessed for the first time because of 

increased exploratory activity and interest in its future potential for 

energy 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 

16°N

12°N

8°N

4°N

0°

4°S

12°E 16°E 20°E 24°E 28°E 32°E 36°E 40°E 44°E

TANZANIA

KENYA

SOMALIA

SOMALIA

ETHIOPIA

ERITREA

DJIBOUTI

YEMEN

SUDAN

CASZ

SUDAN

UGANDA

RWANDA

BURUNDI

DEMOCRATIC REPUBLIC

OF THE CONGO

CENTRAL AFRICAN REPUBLIC

CHAD

NIGER

NIGERIA

CAMEROON

GABON

EQUATORIAL

GUINEA

REPUBLIC

OF THE

CONGO

ANGOLA

SAUDI ARABIA

0 60 120 180 KILOMETERS

EXPLANATION

Sud Province boundary

Central African Rifts AU 

boundary

International boundary

0 50 100 150 MILES

Map

area

RED SEA

GULF OF

ADEN

INDIAN

OCEAN ATLANTIC

OCEAN

A

A'

B

B'

C

C'

D

D'

Anza

Basin

Melut

Basin

Muglad

Basin

Doseo

Basin

Bongor

Basin

Figure 1. Locations of the Sud Province, Central African Rifts Assessment Unit (AU), and approximate locations of 

cross sections shown in figures 2 and 4. CASZ, Central African shear zone.
these geologic criteria, the USGS defined the Cretaceous-Cenozoic 

Composite Total Petroleum System (TPS) with one assessment unit 

(AU), the Central African Rifts AU (fig. 1), encompassing about 

848,825 km2, that extends beyond the Sud Province boundary. The 

AU includes parts of the Central African Republic, Chad, Ethiopia, Kenya, Sudan, and Tanzania (fig. 1). The TPS was defined to 

include Cretaceous and Paleogene lacustrine and marine source 

rocks and the AU contains Cretaceous and Paleogene clastic reservoirs, shale seals, and traps that mostly are associated structurally 

with extensional and transtensional faulting and minor compressional inversion.

The Central African Rift system was initiated during the Early 

Cretaceous, during the opening of the south Atlantic and the commencement of regional northwest-southeast extension. The rifting 

continued into the Neogene and can be divided into two rifting 

events in the western part and three rifting events in the eastern 

part. The rift basins of central Africa are linked along the Central African shear zone (CASZ) right-lateral fault system (fig. 1). 

Several thousand meters of Lower Cretaceous clastic sediments, 

mostly lacustrine clays, silts, and sands, were deposited during this 

rifting phase (Genik, 1992, 1993).

The Cretaceous-Tertiary rift basins of the western part of the 

Sud Province (fig. 1) are extensional and transtensional and are 

filled with Lower Cretaceous to Neogene sedimentary rocks, ranging in thickness from about 3,000 meters (m) to more than 7,500 m 

(fig. 2) that were deposited in fluvial and lacustrine environments 

(Genik, 1992; 1993). During the Early Cretaceous, the first rifting 

phase occurred and fluvial and lacustrine sediments were deposited 

in the rift basins of southern Chad and the Central African Republic 

(fig. 2). In the Late Cretaceous (Cenomanian to Turonian) there was 

a regional rifting event that deposited thick continental clastic sediments. During the Late Cretaceous and Paleogene, transtensional 

faulting and sag events occurred in the western part of the Sud 

Province and fluvial and lacustrine sediments were deposited.

The rift basins in the eastern part of the province are extensional and transtensional and filled with Lower Cretaceous to 

Neogene sedimentary rocks, ranging in thickness from 6,000 m 

to more than 13,000 m that were deposited in fluvial and lacustrine environments (Mohamed and others, 2000, 2002; Dou and 

others, 2007). The initial rifting event began in the latest Jurassic 

and continued through the Early Cretaceous (fig. 3), resulting in 

the deposition of Lower Cretaceous lacustrine source sediments 

(figs. 3, 4). The second rifting event began in the Turonian and 

continued into the Senonian, and the third stage of rifting occurred 

during the Paleogene, contemporaneous with the commencement of 

the Red Sea rifting (Mohamed and others, 2000). Each rifting event 

was followed by a sag event, during which thick continental clastic 

sediments were deposited (fig. 3).

The central African rift basins are known to contain Cretaceous to Paleogene lacustrine and marine source rocks that have 

generated hydrocarbons since the Late Cretaceous (Genik, 1992, 

1993; Mohamed and others, 2002). The generated hydrocarbons 

migrated into Cretaceous and Paleogene reservoirs and structural 

traps.

Resource Summary

Using a geology-based assessment, the USGS estimated mean 

volumes of undiscovered, technically recoverable conventional oil 

and gas resources for the Central African Rifts AU in the Sud Province (table 1). The mean volumes are estimated at 7,310 million 

barrels of oil (MMBO), 13,418 billion cubic feet of gas (BCFG), 

and 353 million barrels of natural gas liquids. The estimated mean 

size of the largest oil field that is expected to be discovered is 1,112 

MMBO, and the estimated mean size of the expected largest gas 

field is 3,677 BCFG. A minimum undiscovered field size of 1 million barrels of oil equivalent (MMBOE) was used for this assessment. No attempt was made to estimate economically recoverable 

reserves.

Figure 2. Schematic geologic cross sections of the western part of the Bongor and Doseo 

Basins showing sedimentary fill in the western part of the Sud Province, north-central Africa. 

Location of cross sections shown in figure 1. Pe, Precambrian; Kl, Lower Cretaceous; Ku, 

Upper Cretaceous; HMi, Holocene to Miocene. Modified after Genik (1992).

0

2,500

5,000

7,500

Depth, in meters

South Bongor Basin North

A A'

0 5 MILES

0 5 KILOMETERS

HMi HMi

0 5 MILES

0 5 KILOMETERS

2,500

0

5,000

7,500

Southeast Doseo Basin Northwest

B B'

Depth, in meters

Pe

Pe

Pe

Pe

Kl

Kl

Ku

Ku

HMi
Figure 3. Generalized stratigraphic columns for the Muglad and Melut Basins, southern Sudan (see fig. 1). Modified after 

Mohamed and others (2000) and Dou and others (2007). Cretaceous Kordofan Group Darfur Gp

Rifting event 1 Rifting event 2 Rifting event 3 Sag

Tertiary Jurassic?

Holocene–Miocene

760 m

Oligocene–upper

Eocene

4,115 m

Paleocene

760 m

Upper Senonian–

Turonian

1,830 m

Cenomanian–

upper Albian 

1,525 m

Albian–Aptian

1,830 m

Barremian–

Neocomian

760 m

Tithonian–

older

90 m

Zeraf

Adok

Tendi

Nayil

Amal

Baraka

Ghazal

Zarga

Aradeiba

Bentiu

Abu

gabra

Sharaf

Precambrian basement

Lacustrine source rock

Clay and shale, minor Type I 

and Type III source rocks present

Sandstone and siltstone 

EXPLANATION

Group/ Lithology

Formation

Muglad Basin Melut Basin

Tectonic

event

Time-rock units

(thickness in meters)

Sag

Rifting event 3

Sag

Rifting event 2

Sag

Rifting event 1

Period and

Epoch

Formation Lithology Tectonic

event

Precambrian

Al Gayger

Galhak

Melut

Samma

Yabus

Adar

Lau

Jimidi

Miadol

Daga

Agor

Early

Late

Paleogene Neogene

Quaternary

Pleistocene

Miocene

Oligocene

Eocene

Paleocene

Cretaceous

Province, 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

Sud Province–Cretaceous-Cenozoic Composite TPS

Central African Rifts AU

Oil 1,112 3,141 6,809 13,222 7,310 531 1,321 3,169 1,522 14 35 87 41

Gas 3,677 2,824 9,822 26,776 11,696 73 259 732 312

Total conventional

resources 3,141 6,809 13,222 7,310 3,355 11,143 29,915 13,418 87 294 819 353

Table 1. Sud Province and Central African Rifts Assessment Unit 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. AU, assessment unit;

AU probability is the chance of at least one accumulation of minimum size within the AU. NGL, natural gas liquids. Gray shading indicates not applicable]
Figure 4. Schematic geologic cross sections of the Muglad and Melut Basins showing sedimentary 

fill in the southern Sudan. Location of cross sections shown in figure 1. Pe, Precambrian; Kl, Lower 

Cretaceous; Ku, Upper Cretaceous; T, Tertiary; TK, Tertiary to Upper Cretaceous; Pa, Paleocene; EPa, 

Eocene to Paleocene; Mi, Miocene; HMi, Holocene to Miocene. Modified after Mohamed and others 

(2002) and Dou and others (2007).

D D'

0

3

6

9

12

Depth, in meters

SW NE

C C'

Rakuba sub basin Sharaf-Abu Gabra ridge Nugara sub basin

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Depth, in meters

0 10 MILES

0 10 KILOMETERS

Abanus-1 Hashab-1

T T

TK

TK

Ku Ku

Pe

Kl Kl

HMi HMi

0 10 MILES

0 15 KILOMETERS

Melut Basin

Muglad Basin

Pe

Ku Pe Kl

Pa

EPa

Mi

HMi

For Additional Information

Assessment results are available at the USGS Central Energy 

Resources Science Center Web site: http://energy.cr.usgs.gov/

oilgas/noga/ or contact Michael E. Brownfield, the assessing geologist (mbrownfield@usgs.gov).

Sud Basin Province Assessment Team

Michael E. Brownfield, Timothy R. Klett, Christopher J. Schenk, 

Ronald R. Charpentier, Troy A. Cook, Richard M. Pollastro, and 

Marilyn E. Tennyson.

References Cited

Dou, L., Xiao, K., Cheng, D., Shi, B., and Li, Z., 2007, Petroleum 

geology of the Melut Basin and the Great Palogue field, Sudan: 

Marine and Petroleum Geology, v. 24, no. 3, p. 129–144.

Genik, G.J., 1992, Regional framework, structural and petroleum 

aspects of rift basins in Niger, Chad and the Central African 

Republic (C.A.R.): Tectonophysics, v. 213, no. 1, 

p. 169–185.

Genik, G.J., 1993, Petroleum geology of the Cretaceous-Tertiary 

rift basins in Niger, Chad, and Central African Republic: American Association of Petroleum Geologists Bulletin, v. 73, no. 8, 

p. 153–168.

Mohamed, A.Y., Iliffe, J.E., Ashcroft, W.A., and Whiteman, A.J., 

2000, Burial and maturation history of the Heglig field area, 

Muglad Basin, Sudan: Journal of Petroleum Geology, v. 23, 

no. 1, p. 107–128.

Mohamed, A.Y., Pearson, M.J., Ashcroft, W.A., and Whiteman, 

A.J., 2002, Petroleum maturation modeling, Abu Gabra-Sharaf 

area, Muglad Basin, Sudan: Journal of African Earth Sciences, 

v. 35, no. 2, p. 331–344.