Assessment of Undiscovered Oil and Gas Resources of the Basin Province, North-Central

By Michael E. Brownfield

M ED ATLANTIC ITE RRAN OCEAN EAN SEA

Chad Basin

INDIAN OCEAN

SOUTH

INDIAN OCEAN

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Chapter 6 of Geologic Assessment of Undiscovered Hydrocarbon Resources of Sub-Saharan Africa Compiled by Michael E. Brownfield

\\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_cover.aiDigital Data Series 69–GG

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette 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 Chad Basin Province, north-, 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. 6, 9 p., http://dx.doi.org/10.3133/ds69GG.

ISSN 2327-638X (online) iii

Contents

Abstract...... 1 Introduction...... 1 Tectonic History of Chad Basin Province, North-Central Africa...... 2 Geology...... 6 Petroleum Occurrence in Chad Basin Province, North-Central Africa...... 6 Source Rocks...... 6 Reservoirs, Traps, and Seals...... 6 Exploration...... 7 Geologic Model...... 7 Resource Summary...... 8 For Additional Information...... 8 Acknowledgments...... 8 References...... 9

Figures

1. Map showing locations of the Chad Basin Province and the Cretaceous-Tertiary Rifts Assessment Unit...... 2 2. Geologic map of north-central Africa showing the Chad Province (7066) and the Cretaceous-Tertiary Rifts Assessment Unit (70660101)...... 3 3. Paleotectonic maps showing the evolution of the west and central African rifts...... 4 4. Stratigraphic columns of the west and central African rifts...... 5 5. Schematic cross section showing the sedimentary fill of the southern part of the Termit rift basin in the Chad Basin Province, north-central Africa...... 7 6. Events chart for the Cretaceous-Tertiary Composite Total Petroleum System and the Cretaceous-Tertiary Rifts Assessment Unit...... 8

Table

1. Chad Basin Province assessment results for undiscovered, technically recoverable oil, gas, and natural gas liquids...... 9

Abbreviations Used in This Report km2 square kilometers m meter mg/g milligram per gram 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 Chad Basin Province, North-Central Africa

By Michael E. Brownfield

Abstract been considered problematic in some areas because of the limited exploration drilling in the province. At the time of the The main objective of the U.S. Geological Survey’s 2010 assessment, the province contained only 58 new-field wildcat wells. Rift-sag and continental analogs were used National and Global Petroleum Assessment Project is to assess for assessment of field sizes and numbers because of similar the potential for undiscovered, technically recoverable oil and source and reservoir rocks and traps. natural gas resources of the and the world. As In this 2010 assessment, the U.S. Geological Survey part of this project, the U.S. Geological Survey completed an estimated mean volumes of undiscovered, technically recover- assessment of the Chad Basin Province in north-central Africa. able conventional oil and gas resources for the Cretaceous- The Chad Basin is the largest intracratonic basin in north-central Tertiary Rifts Assessment Unit in the Chad Basin Province. Africa and is characterized by Cretaceous and Tertiary rifting. The mean volumes are estimated at 2,315 million barrels of The province covers an area of approximately 1,145,000 square oil, 14,648 billion cubic feet of gas, and 391 million barrels kilometers and includes parts of Algeria, , Chad, of natural gas liquids. The estimated mean size of the expected , and . This assessment was based on data from oil largest oil field is 387 million barrels of oil and the estimated and gas wells and fields, field production records, and published mean size of the expected largest gas field is 2,320 billion geologic reports. cubic feet of gas. The Chad Basin Province was assessed because of increased energy exploration and interest in its future oil and gas resource potential. The assessment was based on geology and used the total petroleum system concept. The geologic Introduction elements of a total petroleum system consist of hydrocar- bon source rocks (source-rock maturation and hydrocarbon The main objective of the U.S. Geological Survey’s generation and migration), reservoir rocks (quality and (USGS) National and Global Petroleum Assessment Project is distribution), and traps for hydrocarbon accumulation. Using to assess the potential for undiscovered, technically recover- these geologic criteria, the U.S. Geological Survey defined the able oil and natural gas resources of the United States and the Cretaceous-Tertiary Composite Total Petroleum System with world (U.S. Geological Survey World Conventional Resources one assessment unit, the Cretaceous-Tertiary Rifts Assessment Assessment Team, 2012). As part of this project, the USGS Unit, encompassing about 415,000 square kilometers. The recently completed an assessment of the Chad Basin Province total petroleum system was defined to include Cretaceous in north-central Africa (fig. 1). The Chad Basin, the largest and Tertiary lacustrine and marine source rocks, and the intracratonic basin in north-central Africa, is characterized assessment unit contains Cretaceous and Tertiary clastic by Cretaceous and Tertiary rifting. The province covers an reservoirs, shale seals, and traps that are mostly structural. area of approximately 1,145,000 square kilometers (km2) Hydrocarbons were generated from Cretaceous and and includes parts of Algeria, Cameroon, Chad, Niger, and Tertiary lacustrine and marine source rocks and most likely Nigeria. This assessment was based on data from oil and gas began in the Late Cretaceous. The generated hydrocarbons wells and fields, field production records (IHS Energy, 2009), migrated into Cretaceous and Tertiary reservoirs. Hydrocar- and published geologic reports. Figure 2 is a geologic map bon traps are generally structural and include tilted faulted of north-central Africa showing the Chad Basin Province. blocks, rollover folds, drape anticlines, and reverse-faulted The Chad Basin Province was assessed because of structures. Some inversion features are recognized. Reservoir increased exploratory activity and interest in its future seals are Lower and Upper Cretaceous shale. Oligocene shale potential. The assessment was based on geology and used and other Tertiary shale are seals for the Tertiary reservoirs. the total petroleum system concept. The geologic elements The sometimes limited lateral extents of fluvial seals have of a total petroleum system consist of hydrocarbon source 2 Assessment of Undiscovered Oil and Gas Resources of the Chad Basin Province, North-Central Africa

2°E 4°E 6°E 8°E 10°E 12°E 14°E 16°E 18°E 20°E 22°E 24°E 26°E

26°N

LIBYA EGYPT 24°N

ALGERIA

22°N

20°N

18°N MALI NIGER

CHAD 16°N Chad 7066

A A' 14°N BURKINA FASO 12°N

BENIN NIGERIA 10°N CENTRAL AFRICAN TOGO CAMEROON REPUBLIC SOUTH SUDAN

Base from U.S. Geological Survey digital data, 2002 World Geodetic System 1984 (WGS 84) 0100 200 300 400 KILOMETERS Prime Meridian, Greenwich, 0° 0 100 200 300 400 MILES Chad 7066 EXPLANATION

Chad province boundary AFRICA Cretaceous-Tertiary Rifts Assessment Unit boundary A A' Line of section

INDEX MAP Figure 1. Chad Basin Province and Cretaceous-Tertiary Rifts Assessment Unit. Cross section A–A‘ shown in figure 5.

rocks (source-rock maturation and hydrocarbon generation Tectonic History of Chad Basin and migration), reservoir rocks (quality and distribu- tion), and traps for hydrocarbon accumulation. Using these Province, North-Central Africa geologic criteria, the USGS defined the Cretaceous-Tertiary Composite Total Petroleum System (TPS) with one assessment Rifting and the breakup of west Africa and South unit, the Cretaceous-Tertiary Rifts Assessment Unit (AU) America began in the Early Cretaceous, creating rift basins (figs. 1, 2), encompassing about 415,000 km2. The total (fig. 3) where continental and marine rocks were deposited \\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure01.aipetroleum system was defined to include Cretaceous and (Fairhead and Green, 1989; Genik, 1992, 1993). These Tertiary lacustrine and marine source rocks, and the assessment continental rocks were deposited in the northwest to southeast unit contains Cretaceous and Tertiary clastic reservoirs, shale trending Western African Rift System, reaching thicknesses seals, and traps that are primarily structural. of 2,000 to 5,500 meters (m) (fig. 4) (Genik, 1993). Tectonic History of Chad Basin Province, North-Central Africa 3

5°E 10°E 15°E 20°E 25°E

EGYPT

25°N

ALGERIA

20°N

MALI

CHAD SUDAN Chad NIGER 7066 15°N

Lake Chad BURKINA FASO NIGERIA

BENIN CAMEROON 10°N TOGO CENTRAL AFRICAN SOUTH SUDAN REPUBLIC Base from U.S. Geological Survey digital data, 2002 0 150 300 KILOMETERS Geology by Persits and others, 2002 World Geodetic System 1984 (WGS 84) Prime Meridian, Greenwich, 0° 0 150 300 MILES

EXPLANATION

Quaternary Contact Chad Province boundary Tertiary Cretaceous-Tertiary Rifts Assessment Unit boundary Cretaceous Oil Fields1995 and Older Paleozoic-Mesozoic Oil Fields1996 and Younger Chad Precambrian Province identifier 7066 Volcanic

Figure 2. Geology of north-central Africa showing the Chad Basin Province (7066) and the Cretaceous Tertiary-Rifts Assessment Unit (70660101). Modified from Klett and others (1997) and Persits and others (2002).

\\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure02.ai 4 Assessment of Undiscovered Oil and Gas Resources of the Chad Basin Province, North-Central Africa

A. 126 million years ago, Neocomian B. 108 million years ago, late Aptian

ARABIA ARABIA

SOUTH SOUTH AMERICA AFRICA AMERICA AFRICA

INDIAN INDIAN OCEAN OCEAN

C. 96 million years ago, late Albian D. 90–84 million years ago, Turonian - Santonian ARABIA ARABIA

AFRICA SOUTH AMERICA ATLANTIC ATLANTIC SOUTH

AFRICA INDIAN INDIAN OCEAN AMERICA OCEAN

E. 74 million years ago, late Campanian F. 54 million years ago, early Eocene ARABIA ARABIA

AFRICA AFRICA ATLANTIC ATLANTIC SOUTH

AMERICA INDIAN OCEAN

G. 30–0 million years ago, Miocene to recent ARABIA

RED SEA EXPLANATION Continental sediment Adamawa uplift

Marine transgression with East African rift system marine deposition Direction of active extension Chad Province boundary Major fault or block boundary— Direction of possible compression Dashed where uncertain AFRICA Direction of marine incursion Strike-slip fault—Arrows show Area of Paleogene rifting ATLANTIC sense of movement Contact—Dashed where uncertain Incipient rift—Longer dash where ±10 million years younger INDIAN OCEAN

Figure 3. Paleotectonic maps showing the evolution of the west and central African rifts. Approximate location of the Chad Basin Province outlined in red. Modified from Genik (1993).

\\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure03.ai Tectonic History of Chad Basin Province, North-Central Africa 5

A West African Rift Subsystem–Chad and Niger Depth Age in Lithology meters Grein Kafra Tenere Termit Bongor H H H Holocene- M M M Miocene Neogene P Oligocene 1,000 P

Tertiary P Eocene

Paleocene UK 2,000 UK Maastrichtian UK

3,000 LK Upper Cretaceous Paleogene Senonian

4,000 LK

MZ

Albian Cretaceous PZ 5,000 Less than LK 5,000 meters Aptian-

Barremian- Lower Cretaceous Less than Neocomian 6,000 Less than 6,000 meters 6,000 Less than meters = 13,000 meters Mesozoic-Paleozoic 7,000 Precambrian

B LIBYA EXPLANATION ALGERIA KAFRA

Marine GREIN TÉNÉRÉ West and Central Shale African Rift Sandstone TEFIDET MALI System NIGER Carbonate Volcanic TERMIT CHAD N’DGEL EDGI Nonmarine Basement Uncertain fault BURKINA BORNU Shale-claystone NIGERIA Contact FASO BONGOR BIDA YOLA Siltstone and Unconformity DOBA

BENIN DOSEO sandstone Tested oil/gas BENOUE

TOGO Fault

GHANA CENTRAL Shaly limestone Tested oil AFRICAN REPUBLIC ATLANTIC Sandstone and OCEAN CAMEROON shale INDEX MAP Figure 4. A, Stratigraphic columns of selected rift basins in the west African rifts, Chad and Niger. H, Holocene; M, Miocene; P, Paleogene; UK, Upper Cretaceous, LK, Lower Cretaceous; Mz, Mesozoic; PZ, Paleozoic, =, Precambrian. B, Location of rift basins of Chad and Niger and stratigraphic columns shown in 4A. Modified from Genik (1992, 1993).

\\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure04.ai 6 Assessment of Undiscovered Oil and Gas Resources of the Chad Basin Province, North-Central Africa

During the Early Cretaceous, fluvial and lacustrine greater than 40 API and high gas-to-oil ratios. The oils have rocks were deposited in the rift basins of the Chad Basin (Genik, low viscosities, moderate wax, and low sulfur values. Oils of 1992, 1993; Zanguina and others, 1998). A regional sag event in lacustrine origin have medium to high API gravities around the Late Cretaceous (Cenomanian to Maastrichtian) formed a 35 API. The oils have low gas-to-oil ratios, low viscosities, broad basin resulting in a marine transgression in which shallow low sulfur, and high wax contents. Oils in shallower reservoirs marine to marginal marine and coastal plain rocks accumulated. have been degraded and exhibit low API gravities and high During the Late Cretaceous to Oligocene, the last rifting phase viscosities (Genik, 1992). occurred in the Chad Basin and thick fluvial and lacustrine The oil window in the Cretaceous-Tertiary rifts in the rocks were deposited (Genik, 1993). Chad Basin is between 2,500 m and 4,000 m depth (Genik, Gravity modeling of the Chad Basin shows the extent 1993). In the Niger part of the Chad Basin the oil window and thickness of the Mesozoic and Cenozoic sedimentary rocks begins at a depth ranging from 2,200 to 2,900 m (Zanguina in the rift basins of the Chad Province (Fairhead and Green, and others, 1998). 1989). The extent of the rift basin sedimentary rocks was used to define the Cretaceous-Tertiary Rifts Assessment Unit (fig. 2). Reservoirs, Traps, and Seals

The generated hydrocarbons migrated into Cretaceous Geology and Tertiary sandstone reservoirs and mostly into Cretaceous and Tertiary structural traps (Genik, 1993; Warren, 2009). The Cretaceous-Tertiary rift basins are filled with Lower Cretaceous lacustrine sandstone reservoirs are poorly Lower Cretaceous to Neogene sedimentary rocks, ranging in defined in terms of their distribution, net thickness, and thickness from about 3,000 m to more than 12,000 m (fig. 4), reservoir quality because of the limited number of exploration which were deposited in fluvial, lacustrine, and marine holes in the Cretaceous-Tertiary Rifts AU. At the time of the environments (Genik, 1992, 1993; Zanguina and others, 1998). 2010 assessment, the province contained only 58 new-field The Termit Basin, which is filled with more than 12,000 m of wildcat wells. sediment (fig. 5) (Genik, 1993), contains producing oil fields Lower Cretaceous sandstone reservoirs include stacked (Mbendi International Services, 2010). fluvial channels and lacustrine-deltaic units (Genik, 1993). Individual reservoir beds are generally less than 5 m thick; however, stacked channels can range up to 20 m thick. Porosities range from 12 to 35 percent in shallow reservoirs Petroleum Occurrence in Chad Basin and decrease to 10 to 12 percent at depths of 3,000 to 3,500 m Province, North-Central Africa (Genik, 1993). Permeabilities range considerably, in Lower Cretaceous units from 3 to 525 millidarcies (mD) and in Source Rocks Upper Cretaceous units from 35 to 500 mD. The Maastrichtian sandstone reservoirs, which are fluvial in origin, have The rift basins that traverse Chad are known to contain excellent reservoir quality with porosity ranging from 25 to Cretaceous and Tertiary lacustrine and marine source rocks 35 percent (Zanguina and others, 1998). An Upper Cretaceous that have generated hydrocarbons since the Late Cretaceous channel sandstone reservoir in southern Chad has porosities (Genik, 1993). Primary source rocks for hydrocarbons in the up to 32 percent and permeabilities up to 10 Darcies (Genik, Chad Province are in the Cretaceous lacustrine and marine shale 1993). The limited vertical and lateral extents of the reservoirs section within the grabens. Source rocks are identified in Lower influence preservation of possible hydrocarbon. Cretaceous lacustrine shale, Upper Cretaceous marine shale, Fluvial sandstone reservoirs of Eocene age are generally and Eocene and Oligocene lacustrine shale. Lower Cretaceous thin, but stacked reservoirs may be as much as several hundred lacustrine shale contains Type I kerogen whose total organic meters thick. Fluvial sandstones are generally of limited lateral carbon (TOC) content ranges from 1.0 to 14.0 weight percent extent and are interbedded with thick shale units. Reservoir and averages 2.0 to 3.0 weight percent. Its hydrogen index characteristics are good to excellent; porosities range from values are greater than 600 milligrams per gram (mg/g) (Genik, 16 to 35 percent and permeabilities average 500 mD (Genik, 1993). Late Cretaceous marine source rocks contain Type II 1993). Porosity decreases with depth. Vertical and lateral seals and Type III kerogen whose TOC ranges from 0.8 to 1.5 weight may not be present in some areas. percent. Oligocene lacustrine shale contains Type 1 and Type II Marine reservoirs include Upper Cretaceous deltaic to kerogen with TOC values up to 4.5 weight percent. tidal sandstone. Reservoir rocks are generally thin bedded and Two main types of oil have been identified in the have limited lateral extent. The stacked reservoirs are as much Cretaceous-Tertiary AU: oil with a marine-paralic source, as 70 m thick. Porosities range from less than 10 percent to and oil with a lacustrine source (Genik, 1992). Oils of marine about 32 percent and permeabilities range from 35 to 500 mD origin have American Petroleum Institute (API) gravities (Genik, 1993). Porosity decreases with depth. Geologic Model 7

West Sedigi-1 Kumia-1 A 1975 1976 East KILOMETERS Termit Basin HM A’ 0 P P Ku Kl 5 Ku

 Kl 10

 15 0 201030 KILOMETERS

0 2010 30 MILES

EXPLANATION

HM Holocene to Miocene

P Paleogene

Ku Upper Cretaceous

Kl Lower Cretaceous

 Precambrian Fault Contact—Dashed where inferred Sedigi-1 1975 Oil /gas well and identifier

Kumia-1 1976 Oil well and identifier

Figure 5. Sedimentary fill of the southern part of the Termit rift basin in the Chad Basin Province, north-central Africa. Line of section shown in figure 1. Modified from Genik (1993).

Hydrocarbon traps, which are generally structural, 100 billion cubic feet of associated gas (Mbendi International include tilted faulted blocks, rollover folds, drape anticlines, Services, 2010). In southeastern Niger, 9 oil discoveries and and reverse-faulted structures. Some inversion features are 1 gas discovery have been estimated to be about 500 million recognized (Warren, 2009). barrels of oil equivalent (TG World Petroleum LTD., 2009). In the lacustrine and marine section, Lower and Upper The Cretaceous rifts of the Chad Basin Province remain

\\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure05.aiCretaceous shale act as the hydrocarbon seals. Oligocene shale underexplored despite the discovered oil fields and despite an and other Tertiary shale seal Tertiary reservoirs (Genik, 1993). identified petroleum system with its source rocks, potential The lateral extents of fluvial mudstone and shale seals are reservoirs, and structural targets. considered problematic in some areas.

Exploration Geologic Model Hydrocarbon discoveries and fields are limited to the The geologic model developed for the assessment of Cretaceous-Tertiary rift basins of Chad and Niger, and oil and conventional oil and gas in the Chad Province and the Coastal gas shows have been recorded in most of the wells drilled in Plain and Offshore AU is as follows: the assessment unit. At the time of the 2010 assessment, the 1. Hydrocarbons were generated from Cretaceous and province contained 8 oil fields: 3 in Chad and 5 in Niger; in Tertiary lacustrine and marine source rocks. Generation addition, 58 new-field wildcat wells had been drilled (IHS most likely began in the Late Cretaceous. Energy, 2009). There are currently no gas fields, but several oil discoveries in the Chad Basin have reported tests that include 2. The generated hydrocarbons migrated into Cretaceous associated gas. For example, Chad’s Sedigi field (125 million and Tertiary reservoirs. Migration paths are generally barrels of oil) in the Termit rift basin (fig. 5) has an estimated fault controlled. 8 Assessment of Undiscovered Oil and Gas Resources of the Chad Basin Province, North-Central Africa

3. Hydrocarbon traps are primarily structural and include PETROLEUM tilted faulted blocks, rollover folds, drape anticlines, and SYSTEM EVENTS reverse-faulted structures. Some inversion features have

been recognized. ACCUMULATION 4. Reservoir seals are Lower and Upper Cretaceous shale. Oligocene shale and other Tertiary shale seals the Tertiary

reservoirs. The limited lateral extents of fluvial seals are MIGRATION- considered problematic in some areas.

ROCK UNIT RESERVOIR ROCK

OVERBURDEN ROCK GENERATION- PRESERVATION 5. Rift-sag and continental analogs (Charpentier and others, Age in million years (Ma) SOURCE ROCK SEAL ROCK TRAP FORMATION 0 2007) were used to estimate field sizes and umbersn because Plio their source and reservoir rocks and traps are similar. Neogene Mio An events chart (fig. 6) for the Cretaceous-Tertiary 24 Olig Composite TPS and the Cretaceous-Tertiary Rifts AU summarizes the age of the source, seal, and reservoir rocks and Paleogene Eoc the timing of trap development and generation and migration 50 of hydrocarbons. Pal 65

L

Resource Summary Cretaceous 100 Using a geology-based assessment, the U.S. Geological Survey estimated mean volumes of undiscovered, technically E recoverable conventional oil and gas resources for the Cretaceous-Tertiary Rifts AU in the Chad Basin Province (table 1). The mean volumes are estimated at 2,315 million 146 150 barrels of oil, 14,648 billion cubic feet of gas, and 391 million L barrels of natural gas liquids. The estimated mean size of M the expected largest oil field is 387 million barrels of oil and Jurassic the estimated mean size of the expected largest gas field is 2,320 billion cubic feet of gas. E 200 200

For Additional Information Triassic L

Assessment results are available at the USGS Central M 245 E Energy Resources Science Center website: http://energy.usgs. 250 L gov/oilgas/ or contact Michael E. Brownfield, the assessing Permian geologist ([email protected]). E

Figure 6. Events chart for the Cretaceous-Tertiary Composite Acknowledgments Total Petroleum System (706601) and the Cretaceous-Tertiary Rifts Assessment Unit (70660101). Gray, rock units present; yellow, age The author wishes to thank Mary-Margaret Coates, range of reservoir rock; green, age ranges of source, seal, and Jennifer Eoff, Christopher Schenk, and David Scott for their overburden rocks and the timing of trap formation and generation, suggestions, comments, and editorial reviews, which greatly and migration and preservation of hydrocarbons; wavy line, improved the manuscript. The author thanks Wayne Husband unconformity. Divisions of geologic time conform to dates in for his numerous hours drafting many of the figures used U.S. Geological Survey Geological Names Committee (2010). Ma, in this manuscript, and Chris Anderson, who supplied the million years ago; Plio, Pliocene; Mio, Miocene; Olig, Oligocene; Eoc, Geographic Information System files for this assessment. Eocene; Pal, Paleocene, L, Late; E, Early; M, Middle. \\IGSKAHCMVSFS002\Pubs_Common\Jeff\den13_cmrm00_0129_ds_brownfield\dds_69_gg_ch06_figures\ch06_figures\ch06_figure06.ai References 9

Table 1. Chad Basin 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] Largest Total undiscovered resources Total Petroleum Systems (TPS) Field expected Oil (MMBO) Gas (BCFG) NGL (MMBNGL) and Assessment Units (AU) type mean F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean field size Chad Province–Cretaceous—Tertiary Composite TPS Oil 387 794 2,082 4,637 2,315 228 657 1,665 766 6 18 46 21 Cretaceous-Tertiary Rifts AU Gas 2,320 4,786 12,443 28,002 13,882 125 330 751 570 Total Conventional Resources 794 2,082 4,637 2,315 5,014 13,108 29,667 14,643 131 348 797 391 References Persits, F.M., Ahlbrandt, T.S., Tuttle, M.L., Charpentier, R.R., Brownfield, M.E., and Takahashi, K.I., 2002, Map show- ing geology, oil and gas fields, and geologic provinces of Charpentier, R.R., Klett, T.R., and Attanasi, E.D., 2007, Data- base for assessment of unit-scale analogs (exclusive of the Africa: U.S. Geological Survey Open-File Report 97–470A, United States), Version 1.0: U.S. Geological Survey Open- Version 2.0, CD–ROM. File Report 2007–1404, 36 p., CD–ROM. TG World Energy Corporation, 2009, The Ténéré Project, Fairhead, J.D., and Green, C.M., 1989, Controls on rifting in Niger: http://www.tgworldenergy.com/niger.html. Last Africa and the regional tectonic model for the Nigeria and accessed April 16, 2010, 4 p. east Niger rift basins: Journal of African Earth Science, v. 8, U.S. Geological Survey Geologic Names Committee, 2010, no. 2, 3, 4, p. 231–249. Divisions of geologic time: U.S. Geological Survey Fact Genik, G.J., 1992, Regional framework, structural and petroleum Sheet 2010−3059, 2 p. Available at http://pubs.usgs.gov/ aspects of rift basins in Niger, Chad and the Central African fs/2010/3059/. Republic (C.A.R.): Tectonophysics, v. 213, no. 1, p. 169–185. U.S. Geological Survey World Conventional Resources Genik, G.J., 1993, Petroleum geology of the Cretaceous- Assessment Team, 2012, An estimate of undiscovered Tertiary rifts basins in Niger, Chad, and Central African conventional oil and gas resources of the world, 2012: Republic: American Association of Petroleum Geologists U.S. Geological Survey Fact Sheet 2012–3042, 6 p. Bulletin v. 73, no. 8, p. 153–168. Available at http://pubs.usgs.gov/fs/2012/3042/. IHS Energy, 2009, International petroleum exploration and Warren, M.J., 2009, Tectonic inversion and petroleum sys- production database [current through December 2009]: available from IHS Energy, 15 Inverness Way East, Engle- tem implications in the rifts of central Africa: Frontiers + wood, Colo. 80112, USA. Innovation, 2009 Canadian Society of Petroleum Geol- ogy, Canadian Society of Exploration Geophysicists, and Klett, T.R., Ahlbrandt, T.A., Schmoker, J.W., and Dolton, Canadian Well Logging Society Convention, Calgary, G.L., 1997, Ranking of the world’s oil and gas provinces by May 4–6, 2009, Proceedings, p. 461–464. Available at known petroleum volumes: U.S. Geological Survey Open- http://www.cspg.org/documents/Conventions/Archives/ File Report 97–463, unpaged, CD–ROM. Annual/2009/266.pdf. Last accessed March 5, 2012. MBendi Information Services, 2010, Crude petroleum and natural gas extraction in Chad—Overview: Available at Zanguina, M., Bruneton, A., and Gonnard, R., 1998, An http://www.mbendi.com/indy/oilg/ogus/af/ch/p0005.htm. introduction to the petroleum potential of Niger: Journal Last accessed April 8, 2010, 2 p. of Petroleum Geology, v. 21, no. 1, p. 83–103.

M ED ATLANTIC ITE RRAN OCEAN EAN SEA

Chad Basin

INDIAN OCEAN

SOUTH ATLANTIC OCEAN

INDIAN OCEAN

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