Total Petroleum Systems of the Grand Erg/Ahnet 

Province, Algeria and Morocco—The TanezzuftTimimoun, Tanezzuft-Ahnet, Tanezzuft-Sbaa, 

Tanezzuft-Mouydir, Tanezzuft-Benoud, and 

Tanezzuft-Béchar/Abadla

By T.R. Klett

U.S. Geological Survey Bulletin 2202-B

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Bruce Babbitt, Secretary

U.S. Geological Survey

Charles G. Groat, Director

This report is only available online at:

http://greenwood.cr.usgs.gov/pub/bulletins/b2202-b/

Any use of trade, product, or firm names in this publication

is for descriptive purposes only and does not imply 

endorsement by the U.S. Government

Published in the Central Region, Denver, Colorado

Manuscript approved for publication June 16, 2000

Graphics by the author

Photocomposition by Norma J. Maes

Edited by Lorna Carter
III

Contents

Foreword................................................................................................................................................ 1

Abstract ................................................................................................................................................. 2

Acknowledgments ............................................................................................................................... 2

Introduction........................................................................................................................................... 2

Province Geology ................................................................................................................................. 3

Tectonic History .......................................................................................................................... 9

Stratigraphy.................................................................................................................................. 9

Petroleum Occurrence .............................................................................................................. 13

Regional Exploration History .............................................................................................................. 13

The Tanezzuft-Timimoun Total Petroleum System (205801).......................................................... 13

 Source Rocks............................................................................................................................... 13

 Overburden Rocks....................................................................................................................... 13

Reservoir Rocks .......................................................................................................................... 13

Seal Rocks ................................................................................................................................... 15

 Trap Types in Oil and Gas Fields............................................................................................... 15

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 15

The Tanezzuft-Ahnet Total Petroleum System (205802) ............................................................... 15

 Source Rocks............................................................................................................................... 15

 Overburden Rocks....................................................................................................................... 17

Reservoir Rocks .......................................................................................................................... 17

Seal Rocks ................................................................................................................................... 17

 Trap Types in Oil and Gas Fields............................................................................................... 17

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 17

The Tanezzuft-Sbaa Total Petroleum System (205803).................................................................. 17

 Source Rocks............................................................................................................................... 17

 Overburden Rocks....................................................................................................................... 19

Reservoir Rocks .......................................................................................................................... 19

Seal Rocks ................................................................................................................................... 19

 Trap Types in Oil and Gas Fields............................................................................................... 19

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 19

The Tanezzuft-Mouydir Total Petroleum System (205804) ............................................................ 19

 Source Rocks............................................................................................................................... 19

 Overburden Rocks....................................................................................................................... 21

Reservoir Rocks .......................................................................................................................... 21

Seal Rocks ................................................................................................................................... 21

 Trap Types in Oil and Gas Fields............................................................................................... 21

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 21

The Tanezzuft-Benoud Total Petroleum System (205805) ............................................................. 21

 Source Rocks............................................................................................................................... 21

 Overburden Rocks....................................................................................................................... 23

Reservoir Rocks .......................................................................................................................... 23

Seal Rocks ................................................................................................................................... 23

 Trap Types in Oil and Gas Fields............................................................................................... 23

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 23

The Tanezzuft-Béchar/Abadla Total Petroleum System (205806)................................................ 23

 Source Rocks............................................................................................................................... 23

 Overburden Rocks....................................................................................................................... 25

Reservoir Rocks .......................................................................................................................... 25

Seal Rocks ................................................................................................................................... 25

 Trap Types in Oil and Gas Fields............................................................................................... 25

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 25

Summary................................................................................................................................................ 25

References Cited.................................................................................................................................. 26
IV

Appendices 

1. Exploration-activity and discovery-history plots for the Tanezzuft-Timimoun Structural/Stratigraphic 

 Assessment unit

2. Exploration-activity and discovery-history plots for the Tanezzuft-Ahnet Structural/Stratigraphic 

 Assessment Unit

3. Exploration-activity and discovery-history plots for the Tanezzuft-Sbaa Structural/Stratigraphic 

 Assessment Unit

Figures

 1–3. Maps showing approximate locations of:

 1. USGS-defined geologic provinces and major structures in north-

 central Africa .............................................................................................................. 4

 2. Areal extent of total petroleum systems and Silurian source rocks

 (Tanezzuft Formation), and locations of stratigraphic cross

 sections, north-central Africa.................................................................................. 5

 3. Areal extent of assessment units within Grand Erg/Ahnet Province............... 6

 4. Stratigraphic cross sections through Grand Erg/Ahnet and neighboring

 provinces.............................................................................................................................. 7

 5. Columnar section and stratigraphic nomenclature for Illizi, Triassic, and

 Ghadames (Berkine) Basins ............................................................................................. 11

 6–11. Events charts for:

 6. Tanezzuft-Timimoun Total Petroleum System ....................................................... 14

 7. Tanezzuft-Ahnet Total Petroleum System.............................................................. 16

 8. Tanezzuft-Sbaa Total Petroleum System ............................................................... 18

 9. Tanezzuft-Mouydir Total Petroleum System ......................................................... 20 

 10. Tanezzuft-Benoud Total Petroleum System........................................................... 22

 11. Tanezzuft-Béchar/Abadla Total Petroleum System ............................................. 24 

 

Tables

[Tables and Appendices follow References Cited]

 

1. Reservoir properties of discovered accumulations for each assessment unit 

 through 1995

2. Number and sizes of discovered fields for each assessment unit through 1995 

3. Estimated sizes, number, and coproduct ratios of undiscovered oil and

 gas fields for each assessment unit

4. Calculated mean, grown undiscovered conventional oil, gas, and natural gas liquids 

 volumes for oil and gas fields for each assessment unit
1

Foreword

This report was prepared as part of the U.S. Geological Survey World Petroleum Assessment 2000. The primary objective 

of World Petroleum Assessment 2000 is to assess the quantities 

of conventional oil, gas, and natural gas liquids outside the 

United States that have the potential to be added to reserves in 

the next 30 years. Parts of these assessed volumes reside in 

undiscovered fields whose sizes exceed the stated minimumfield-size cutoff value for the assessment unit, which is variable 

but must be at least 1 million barrels of oil equivalent. Another 

part of these assessed volumes occurs as reserve growth of fields 

already discovered. However, the contribution from reserve 

growth of discovered fields to resources is not covered for the 

areas treated in this report.

In order to organize, evaluate, and delineate areas to assess, 

the Assessment Methodology Team of World Petroleum Assessment 2000 developed a hierarchical scheme of geographic and 

geologic units. This scheme consists of regions, geologic provinces, total petroleum systems, and assessment units. For World 

Petroleum Assessment 2000, regions serve as organizational 

units and geologic provinces are used as prioritization tools. 

Assessment of undiscovered resources was done at the level of 

the total petroleum system or assessment unit.

The world was divided into 8 regions and 937 geologic 

provinces. These provinces have been ranked according to the 

discovered known oil and gas volumes (Klett and others, 1997). 

Then, 76 “priority” provinces (exclusive of the United States and 

chosen for their high ranking) and 26 “boutique” provinces 

(exclusive of the United States) were selected for appraisal of oil 

and gas resources. Boutique provinces were chosen for their 

anticipated petroleum richness or special regional economic or 

strategic importance.

A geologic province is an area having characteristic dimensions of hundreds of kilometers that encompasses a natural geologic entity (for example, a sedimentary basin, thrust belt, or 

accreted terrane) or some combination of contiguous geologic 

entities. Each geologic province is a spatial entity with common 

geologic attributes. Province boundaries were drawn as logically as possible along natural geologic boundaries, although in 

some places they were located arbitrarily (for example, along 

specific water-depth contours in the open oceans).

Total petroleum systems and assessment units were delineated for each geologic province considered for assessment. It is 

not necessary for the boundaries of total petroleum systems and 

assessment units to be entirely contained within a geologic 

province. Particular emphasis is placed on the similarities of 

petroleum fluids within total petroleum systems, unlike geologic 

provinces and plays in which similarities of rocks are emphasized.

The total petroleum system includes all genetically related 

petroleum that occurs in shows and accumulations (discovered 

and undiscovered) generated by a pod or by closely related pods 

of mature source rock. Total petroleum systems exist within a 

limited mappable geologic space, together with the essential 

mappable geologic elements (source, reservoir, seal, and overburden rocks). These essential geologic elements control the 

fundamental processes of generation, expulsion, migration, 

entrapment, and preservation of petroleum within the total petroleum system.

An assessment unit is a mappable part of a total petroleum 

system in which discovered and undiscovered oil and gas fields 

constitute a single relatively homogeneous population such that 

the methodology of resource assessment based on estimation of 

the number and sizes of undiscovered fields is applicable. A 

total petroleum system might equate to a single assessment unit. 

If necessary, a total petroleum system may be subdivided into 

two or more assessment units such that each assessment unit is 

sufficiently homogeneous in terms of geology, exploration considerations, and risk to assess individually. Differences in the 

distributions of accumulation density, trap styles, reservoirs, and 

exploration concepts within an assessment unit were recognized 

and not assumed to extend homogeneously across an entire 

assessment unit.

A numeric code identifies each region, province, total 

petroleum system, and assessment unit. The criteria for assigning codes are uniform throughout the project and throughout all 

publications of the project. The numeric codes used in this study 

are:

 Unit Name Code

Region Middle East and North Africa 2

Province Grand Erg/Ahnet 2058

Total Petroleum 

Systems Tanezzuft-Timimoun 205801

 Tanezzuft-Ahnet 205802

 Tanezzuft-Sbaa 205803

 Tanezzuft-Mouydir 205804

 Tanezzuft-Benoud 205805

 Tanezzuft-Béchar/Abadla 205806

Assessment Tanezzuft-Timimoun Structural/ 

Units Stratigraphic 20580101

Total Petroleum Systems of the Grand Erg/Ahnet Province, 

Algeria and Morocco—The Tanezzuft-Timimoun, TanezzuftAhnet, Tanezzuft-Sbaa, Tanezzuft-Mouydir, TanezzuftBenoud, and Tanezzuft-Béchar/Abadla

By T.R. Klett
2 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

Assessment units—Continued Code 

Tanezzuft-Ahnet Structural/Stratigraphic 20580201

Tanezzuft-Sbaa Structural/Stratigraphic 20580301

Tanezzuft-Mouydir Structural/Stratigraphic 20580401

Tanezzuft-Benoud Structural/Stratigraphic 20580501

Tanezzuft-Béchar/Abadla Structural/Stratigraphic 20580601

A graphical depiction that places the elements of the total 

petroleum system into the context of geologic time is provided in the form of an events chart. Items on the events chart 

include (1) the major rock-unit names; (2) the temporal extent 

of source-rock deposition, reservoir-rock deposition, seal-rock 

deposition, overburden-rock deposition, trap formation, generation-migration-accumulation of petroleum, and preservation 

of petroleum; and (3) the critical moment, which is defined as 

the time that best depicts the generation-migration-accumulation of hydrocarbons in a petroleum system (Magoon and 

Dow, 1994). The events chart serves only as a timeline and 

does not necessarily represent spatial relations.

Probabilities of occurrence of adequate charge, rocks, and 

timing were assigned to each assessment unit. Additionally, an 

access probability was assigned for necessary petroleum-related 

activity within the assessment unit. All four probabilities, or 

risking elements, are similar in application and address the question of whether at least one undiscovered field of minimum size 

has the potential to be added to reserves in the next 30 years 

somewhere in the assessment unit. Each risking element thus 

applies to the entire assessment unit and does not equate to the 

percentage of the assessment unit that might be unfavorable in 

terms of charge, rocks, timing, or access.

Estimated total recoverable oil and gas volumes (cumulative production plus remaining reserves, called “known” volumes hereafter) quoted in this report are derived from 

Petroconsultants, Inc., 1996 Petroleum Exploration and Production database (Petroconsultants, 1996a). To address the fact that 

increases in reported known volumes through time are commonly observed, the U.S. Geological Survey (Schmoker and 

Crovelli, 1998) and the Minerals Management Service (Lore and 

others, 1996) created a set of analytical “growth” functions that 

are used to estimate future reserve growth (called “grown” volumes hereafter). The set of functions was originally created for 

geologic regions of the United States, but it is assumed that these 

regions can serve as analogs for the world. This study applied 

the Federal offshore Gulf of Mexico growth function (developed 

by the U.S. Minerals Management Service) to known oil and gas 

volumes, which in turn were plotted to aid in estimating undiscovered petroleum volumes. These estimates of undiscovered 

petroleum volumes therefore take into account reserve growth of 

fields yet to be discovered.

Estimates of the minimum, median, and maximum number, 

sizes, and coproduct ratios of undiscovered fields were made 

based on geologic knowledge of the assessment unit, exploration 

and discovery history, analogs, and, if available, prospect maps. 

Probabilistic distributions were applied to these estimates and 

combined by Monte Carlo simulation to calculate undiscovered 

resources.

Illustrations in this report that show boundaries of the total 

petroleum systems, assessment units, and extent of source rocks 

were compiled using geographic information system (GIS) software. The political boundaries shown are not politically definitive and are displayed for general reference only. Oil and gas 

field center points were provided by, and reproduced with permission from, Petroconsultants (1996a and 1996b).

Abstract

Undiscovered, conventional oil and gas resources were 

assessed within total petroleum systems of the Grand Erg/Ahnet 

Province (2058) as part of the U.S. Geological Survey World 

Petroleum Assessment 2000. The majority of the Grand Erg/

Ahnet Province is in western Algeria; a very small portion 

extends into Morocco. The province includes the Timimoun 

Basin, Ahnet Basin, Sbaa Basin, Mouydir Basin, Benoud 

Trough, Béchar/Abadla Basin(s), and part of the Oued Mya 

Basin. Although several petroleum systems may exist within 

each of these basins, only seven “composite” total petroleum 

systems were identified. Each total petroleum system occurs in 

a separate basin, and each comprises a single assessment unit.

The main source rocks are the Silurian Tanezzuft Formation 

(or lateral equivalents) and Middle to Upper Devonian mudstone. Maturation history and the major migration pathways 

from source to reservoir are unique to each basin. The total 

petroleum systems were named after the oldest major source 

rock and the basin in which it resides.

The estimated means of the undiscovered conventional 

petroleum volumes in total petroleum systems of the Grand Erg/

Ahnet Province are as follows:

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids]

Total Petroleum System MMBO BCFG MMBNGL

Tanezzuft-Timimoun 31 1,128 56

Tanezzuft-Ahnet 34 2,973 149

Tanezzuft-Sbaa 162 645 11

Tanezzuft-Mouydir 12 292 14

Tanezzuft-Benoud 72 2,541 125 

Tanezzuft-Béchar/Abadla 16 441 22 

Acknowledgments

I thank Philip Farfan and Francois Gauthier of Anadarko 

Algeria Corporation, Rob Hoar and Randie Grantham of Oryx 

Energy Company, and David Boote and Marc Traut of Occidental Oil and Gas Corporation for their suggestions, which greatly 

improved the text. I also thank Katharine Varnes, Thaddeus 

Dyman, and Debra Higley for their editorial review.

Introduction

Undiscovered conventional oil and gas volumes were 

assessed within total petroleum systems of the Grand Erg/Ahnet 

Province (2058) as part of the U.S. Geological Survey (USGS) 

World Petroleum Assessment 2000. This study documents the 
Province Geology 3

geology, undiscovered oil and gas volumes, exploration activity, 

and discovery history of the Grand Erg/Ahnet Province.

The Grand Erg/Ahnet Province is a geologic province 

delineated by the USGS; it is located primarily in western Algeria (fig. 1). The northwest tip of the province extends slightly 

into Morocco. The province area encompasses approximately 

700,000 km2 (square kilometers).

The province contains the Timimoun Basin, Ahnet Basin, 

Sbaa Basin, Mouydir Basin, Benoud Trough, Béchar Basin, 

Abadla Basin, and part of the Oued Mya Basin. Neighboring 

geologic provinces, delineated by the USGS, include the Atlas 

Uplift (2053), Trias/Ghadames Basin (2054), Illizi Basin (2056), 

Hoggar (7041), Reggane Basin (2060), and Ougarta Uplift 

(2061).

More than one total petroleum system may exist within 

each of the basins in the Grand Erg/Ahnet Province (Boote and 

others, 1998). Data available for this study are insufficient to 

adequately determine the relative contribution of each system to 

individual accumulations and therefore preclude further subdivision. Consequently only “composite” total petroleum systems 

are described in this report, each of which contains one or multiple total petroleum systems. These systems are coincident with 

the basins in which they exist and are called the Tanezzuft-Timimoun, Tanezzuft-Ahnet, Tanezzuft-Sbaa, Tanezzuft-Mouydir, 

Tanezzuft-Benoud, Tanezzuft-Béchar/Abadla, and TanezzuftOued Mya Total Petroleum Systems (fig. 2). The TanezzuftOued Mya Total Petroleum System extends across both the 

Grand Erg/Ahnet and the neighboring Trias/Ghadames Province, 

and is not described in this study. Tanezzuft refers to the Tanezzuft Formation (Silurian), which is the oldest major source rock 

in the system; in the total petroleum system name, “Tanezzuft” 

is then followed by the basin name in which the total petroleum 

system exists. Due to scarcity of data, province and total petroleum system boundaries can only be approximately delineated 

and therefore are subject to future modification.

One assessment unit was defined for each total petroleum 

system; the assessment units coincide with the total petroleum 

systems (fig. 3). The assessment units are named after the total 

petroleum system with a suffix of “Structural/Stratigraphic.” 

This suffix refers to the progression from a structural and combination trap exploration strategy to a stratigraphic (subtle) trap 

exploration strategy.

Grand Erg/Ahnet Province contains more than 5,500 million barrels (MMB) of known (estimated total recoverable, that 

is cumulative production plus remaining reserves) petroleum liquids (approximately 500 million barrels of oil, MMBO, and 

5,000 million barrels of natural gas liquids, MMBNGL), and 

approximately 114,000 billion cubic feet of known natural gas 

(114×1012 CFG or 114,000 BCFG) (Petroconsultants, 1996a). 

The Grand Erg/Ahnet Province contains the giant Hassi R'Mel 

gas field.

Province Geology

The major structural features of the Grand Erg/Ahnet Province are the Idjerane-M'Zab structural axis; the Tilrhemt Arch, 

Oued Namous Dome, and Maharez Dome (together forming a 

structural axis); and the Ensellement Zousfana (Zousfana Saddle), Maharez Dome, and Ensellement Beni Abbes (Beni Abbes 

Saddle) (fig. 1). The Idjerane-M'Zab structural axis extends 

north to south, generally from the Tilrhemt Arch to the Hoggar 

Massif. A structural axis consisting of the Ensellement Zousfana, Maharez Dome, and Ensellement Beni Abbes extends from 

the Saharan Flexure in the north to the Ougarta Range in the 

south, separating the Béchar and Abadla Basins from the Timimoun Basin (Futyan and Jawzi, 1996). The Tilrhemt-Oued 

Namous-Maharez structural axis extends east to west from the 

Béchar and Abadla Basins into the neighboring Triassic Basin 

(Futyan and Jawzi, 1996).

A total petroleum system (and assessment unit) was identified in each of the basins of the Grand Erg/Ahnet Province. 

Stratigraphic cross sections showing the major structural features and total petroleum systems are shown in figures 2 (locations of cross sections) and 4.

The Tanezzuft-Timimoun Total Petroleum System is 

bounded on the north by the Tilrhemt-Oued Namous-Maharez 

structural axis; on the east by the Idjerane-M'Zab structural axis; 

on the south by the Djoua Saddle, Azzene High, and Ougarta 

Range; and on the west by the Ensellement Beni Abbes (figs. 1 

and 4A).

The Tanezzuft-Ahnet Total Petroleum System is bounded 

on the north by the Djoua Saddle, on the east by the IdjeraneM'Zab structural axis, on the south by the Hoggar Massif, and on 

the west by the Ougarta Range and Sbaa Basin (figs. 1 and 4A). 

Paleozoic rocks, including the major source rocks, crop out 

along the Hoggar Massif (figs. 2 and 3).

The Tanezzuft-Sbaa Total Petroleum System is bounded on 

the north and east by the Azzene High, and on the south and west 

by the Ougarta Range (figs. 1 and 4A).

The Tanezzuft-Mouydir Total Petroleum System is 

bounded on the north by the Oued Mya Basin, on the east by the 

Amguid-Hassi Touareg structural axis, on the south by the Hoggar Massif, and on the west by the Idjerane-M'Zab structural 

axis (fig. 1). The boundary between the Mouydir Basin and the 

neighboring Oued Mya Basin to the north is defined by the 

Mouydir Structural Terrace, a break or hinge line in the slope of 

the basement rocks that separates the two basins (figs. 1, 4B). 

The Mouydir Basin is presently perched on a basement high and 

is not as deep as the neighboring Oued Mya Basin. Like the 

Tanezzuft-Ahnet Total Petroleum System, Paleozoic rocks crop 

out along the Hoggar Massif (figs. 2 and 3).

The Tanezzuft-Benoud Total Petroleum System is bounded 

on the north by the Saharan Flexure, on the east by the Ain Rich 

High and Tilrhemt Arch, on the south by the Tilrhemt-Oued 

Namous-Maharez structural axis, and on the west by the 

Ensellement Zousfana. The Benoud Trough is a shallow foreland basin. The eastern portion is superimposed on part of the 

Triassic Basin. The approximate extent of Triassic Basin is 

defined by the extent of Triassic- to Jurassic-aged evaporites 

(limit of salt shown in fig. 1).

The Béchar and Abadla Basins are partially connected 

with only one minor structure existing between them (Futyan 

and Jawzi, 1996). Therefore, these two basins are treated 

collectively as the Tanezzuft-Béchar/Abadla Total Petroleum 
4 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

Approximate limit of salt

Saharan Flexure

Oued Mya

Basin

Tilrhemt Arch

Hassi Atshan Arch

Gargaf Arch

Triassic

Basin

Illizi

Basin Idjerane-M'Zab Structural Axis

Azzene High

Allal High

Ougarta Range

Antiatlas Range

Hoggar Massif

Ahnet

Basin

Timimoun

Basin

Bechar/

Abadla

Basins

Mouydir

Basin

Sbaa

Basin

ALGERIA

LIBYA

TUNISIA

MOROCCO

Grand Erg/Ahnet

Province 2058

Trias/Ghadames

Province 2054

Illizi

Province 2056

Pelagian

Province 2048

Pelagian

Basin

Country boundary

Province boundary

Structural axis (crest)

Figure 1. North-central Africa, showing USGS-defined geologic provinces and major structures (modified from Aliev and others, 1971; Burollet and others, 

1978; Montgomery, 1994; Petroconsultants, 1996b; Persits and others,1997).

Djoua Saddle

Hamra

Basin

Oued Namous

Dome

Maharez

Dome

Edjeleh

Anticline

Tihemboka Arch

Amguid-Hassi Touareg

Structural Axis

Atlas Mountains

Benoud Trough

Province of interest

Mediterranean Sea

Mediterranean

Sea

Melrhir

Basin

Ghadames

Basin

Talemzane - Gefara Arch

Approximate

limit of salt

Ain Rich

High

Zousfana

Saddle

Beni Abbes

Saddle

Saharan flexure 0 500 KILOMETERS

5

o

W 0

o

5

o

E 10oE 15oE

20o

N

25o

N

30o

N

35oN

Mouydir

Structural

Terrace
Province Geology 5

D'

D

B'

B

C'

C

A'

A

Tanezzuft-Timimoun

TPS

Tanezzuft-Ahnet

TPS

Tanezzuft-Sbaa

TPS

Tanezzuft-Melrhir

TPS

Tanezzuft-Oued

Mya TPS

Tanezzuft-Mouydir

TPS

Tanezzuft-Ghadames

TPS

Tanezzuft-Illizi

TPS

Country boundary

Total petroleum system boundary

Silurian source rock boundary

Oil field

Gas field

ALGERIA

LIBYA

TUNISIA

MOROCCO

T-Shaped Anticlinorium

Figure 2. North-central Africa, showing the areal extent of total petroleum systems and Silurian source rocks (Tanezzuft Formation), and locations of 

stratigraphic cross sections (modified from Petroconsultants, 1996b; Persits and others, 1997; Boote and others, 1998).

Tanezzuft-Benoud

TPS

TanezzuftBechar/Abadla

TPS

0 500 KILOMETERS

5

o

W 0

o

5

o

E 10oE 15oE

20oN

25oN

30o

N

35oN

Total petroleum systems of interest
6 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

ALGERIA

Tanezzuft-Timimoun 

Structural/Stratigraphic

Tanezzuft-Sbaa 

Structural/Stratigraphic

Tanezzuft-Mouydir 

Structural/Stratigraphic

Tanezzuft-Benoud 

Structural/Stratigraphic

Tanezzuft-Ahnet 

Structural/Stratigraphic

200

Silurian absent

Silurian absent

MOROCCO

5

o

W

30o

N

0

o

5

o

E

25oN

Tanezzuft-Bechar/Abadla 

Structural/Stratigraphic

 KILOMETERS

Silurian absent

Country boundary

Total petroleum system boundary

Silurian source rock boundary

Oil field

Gas field

Geologic province boundary

Figure 3. Areal extent of assessment units within the Grand Erg/Ahnet Province (modified from Petroconsultants, 1996b; 

Persits and others, 1997).
Province Geology 7

NORTHEAST SOUTHWEST

0

1

2

3

4

5

6

KM

A

BASEMENT

SBAA

BASIN

OUGARTA

UPLIFT

REGGANE

BASIN

Tanezzuft-Timimoun

TPS (205801)

OUED MYA

BASIN

SILURIAN

DEVONIAN

CARB.

CRETACEOUS-CENOZOIC

BASEMENT

TIMIMOUN

BASIN

IDJERANE-M'ZAB

STRUCTURAL AXIS

TanezzuftSbaa TPS

(205803)

A'

Tanezzuft-Oued Mya

TPS (205401)

TRIASSIC AND JURASSIC

CARB.

DEV.

SIL.

SILURIAN

DEVONIAN

CARBONIFEROUS

CAMBRIANORDOVICIAN

CAMBRIANORDOVICIAN

CAMBRIAN-ORDOVICIAN

SIL.

AZZENE

HIGH

0 100 KILOMETERS

Figure 4. Stratigraphic cross sections through Grand Erg/Ahnet and neighboring provinces. A, North-to-south stratigraphic cross section through the 

Oued Mya, Timimoun, Sbaa, and Reggane Basins (modified from Aliev and others, 1971; Makhous and others, 1997).

A

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

NORTH SOUTH

0

1

2

3

4

5

KM

B

CAMBRIAN-ORDOVICIAN

SILURIAN

DEVONIAN

TRIASSIC

JURASSIC

LOWER CRETACEOUS

UPPER CRETACEOUS

CENOZOIC

OUED MYA BASIN

MOUYDIR BASIN HOGGAR UPLIFT

Tanezzuft-Oued Mya

TPS (205401) B' Tanezzuft-Mouydir

TPS (205804)

C-C'

0 100 KILOMETERS

BASEMENT

DEVONIAN

Figure 4—Continued. Stratigraphic cross sections. B, North-to-south stratigraphic cross section through the Oued Mya and 

Mouydir Basins (modified from Makhous and others, 1997).

B

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION
8 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

WEST EAST

0

1

2

3

4

5

KM

C

TERTIARY

UPPER CRETACEOUS

DEVONIAN

SILURIAN

CAMBRIAN-ORDOVICIAN

BASEMENT

SILURIAN

DEVONIAN

CARBONIFEROUS

BASEMENT

LOWER CRETACEOUS

AHNET

BASIN

IDJERANE-M'ZAB

STRUCTURAL AXIS

AMGUID-HASSI TOUAREG

STRUCTURAL AXIS

TIHEMBOKA

ARCH

ILLIZI

BASIN

MOUYDIR

BASIN

Tanezzuft-Mouydir C'

TPS (205804)

Tanezzuft-Illizi

TPS (205601)

B-B'

0 100 KILOMETERS

TRIASSIC-JURASSIC

TRIASSIC-JURASSIC

CAMBRIANORDOVICIAN

CAMBRIANORDOVICIAN

Figure 4—Continued. Stratigraphic cross sections. C, West-to-east stratigraphic cross section through the Mouydir and Illizi Basins (modified from 

Makhous and others, 1997).

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

C

Tanezzuft-Benoud

TPS (205805)

0 100 KILOMETERS

0

1

2

3

4

5

6

7

KM

WEST EAST

TILRHEMT ARCH OUED MYA BASIN AMGUID-HASSI TOUAREG

STRUCTURAL AXIS

GHADAMES (BERKINE)

BASIN

TERTIARY

UPPER CRETACEOUS

LOWER CRETACEOUS

JURASSIC

TRIASSIC

TRIASSIC

ORDOVICIAN

ORDOVICIAN

CAMBRIAN

BASEMENT

SILURIAN

DEVONIAN

CARBONIFEROUS CAMBRIAN

D

SALIFEROUS UNITS

D' Tanezzuft-Ghadames

TPS (205403)

Tanezzuft-Oued Mya

TPS (205401)

Figure 4.—Continued. Stratigraphic cross sections. D, West-to-east stratigraphic cross section through the Benoud, Oued Mya, and 

Ghadames (Berkine) Basins (modified from van de Weerd and Ware,1994, after Aliev and others, 1971).

Regional seal

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

D
Province Geology 9

System. The Béchar/Abadla Basin is bounded on the north by 

the Antiatlas Range, on the east by the Ensellement ZousfanaMaharez Dome-Ensellement Beni Abbes structural axis, and on 

the south and west by the Ougarta Range (fig. 1).

Tectonic History

The regional stratigraphy is continuous across North 

Africa, but petroleum generation, migration, and entrapment 

within each total petroleum system have been controlled by the 

tectonic history of individual basins. Deformational events in 

the region, most of them minor, are recorded by unconformities 

reflecting basin tilting, uplift, and erosion of intracratonic structural axes at various times throughout the Phanerozoic. The 

main deformational events occurred in the Precambrian to Early 

Cambrian (Pan African event), Late Silurian to Early Devonian, 

Late Devonian (Frasnian event), Carboniferous to Permian (Hercynian event), Early Jurassic, Early Cretaceous (Aptian, Austrian event), Late Cretaceous, and Tertiary (Eocene to Oligocene, 

Pyrenean event) (Aliev and others, 1971; Peterson, 1985; Boudjema, 1987; van de Weerd and Ware, 1994).

Throughout most of the Paleozoic, North Africa was a single depositional basin on the northern shelf of the African craton 

(Aliev and others, 1971; van de Weerd and Ware, 1994). The 

basin generally deepened northward where deposition and 

marine influence were greater (Daniels and Emme, 1995). Some 

gentle but large structures existed in this area throughout the 

Paleozoic and affected the thickness of the sedimentary cover 

(Aliev and others, 1971; van de Weerd and Ware, 1994). There 

was a general conformity of structure throughout most of the 

Paleozoic until the Hercynian event. In the Late Silurian and 

Early Devonian, Laurasia separated from Gondwana resulting in 

minor deformation, uplift, and local erosion (Aliev and others, 

1971; Boote and others, 1998). Many of the basins and uplifts 

preserved today were initially developed during this event from 

earlier structures (Peterson, 1985). Later, in the Middle to Late 

Devonian, the initial collision of Laurasia and Gondwana began 

resulting in erosion and further modification of preexisting structures (Boote and others, 1998).

Minor deformation occurred in the Late Silurian through 

the Devonian, resulting in uplift and local erosion (Aliev and 

others, 1971; van de Weerd and Ware, 1994; Boote and others, 

1998). Within the Grand Erg/Ahnet Province, uplift and erosion 

occurred on and near the Amguid-Hassi Touareg structural axis.

The Hercynian event marks the collision between Laurasia and Gondwana and caused regional uplift, folding, and 

erosion (Aliev and others, 1971; Boote and others, 1998). 

Paleozoic basins that were delineated by earlier tectonic events 

were modified, resulting in the development of several intracratonic sag and foreland basins (Aliev and others, 1971; van de 

Weerd and Ware, 1994; Boote and others, 1998). Petroleum 

was generated during the Carboniferous Period within deeper 

portions of the basins, but uplift caused generation to cease 

(Tissot and others, 1973; Daniels and Emme, 1995; Makhous 

and others, 1997). Subsequent erosion probably removed or 

dispersed petroleum that had accumulated in some areas (Boote 

and others, 1998).

During the Hercynian event, many of the structural traps 

within the Grand Erg/Ahnet Province resulted from vertical 

movement of the basement and charged with petroleum (Aliev 

and others, 1971; Boote and others, 1998). The structural highs 

separating total petroleum systems within the province, the 

Idjerane-M'Zab, the Tilrhemt-Oued Namous-Maharez, and the 

Ensellement Zousfana-Maharez Dome-Ensellement Beni Abbes 

structural axes, were uplifted at this time. Inversion of the Sbaa 

Basin also resulted from this event.

Several transgressive-regressive cycles occurred throughout 

the Paleozoic. Two major flooding events, one in the Silurian 

and the other in the Late Devonian, were responsible for the deposition of source rocks (Aliev and others, 1971; Boudjema, 

1987). Many of the prograding fluvial, estuarine, deltaic, and 

shallow marine sands that were deposited during these cycles are 

now reservoirs (Aliev and others, 1971).

During the early Mesozoic, extensional movements caused 

by the opening of the Tethys and Atlantic oceans developed a 

cratonic sag basin called the Triassic Basin. The depocenter was 

superimposed on some of the Paleozoic basins (Aliev and others, 

1971; Boudjema, 1987). Triassic fluvial sands followed by a 

thick Triassic to Jurassic evaporite section were deposited within 

the sag basin (Aliev and others, 1971; Boudjema, 1987). Sandstones resulting from the fluvial deposition are major reservoirs, 

and the evaporites provide a regional seal for these fluvial reservoirs as well as Paleozoic reservoirs (Aliev and others, 1971). 

Clastic then carbonate deposition occurred throughout the 

remainder of the Mesozoic over much of central North Africa 

(Aliev and others, 1971; Boudjema, 1987). Sediment deposition 

gradually diminished in the Tertiary over most of the area (Aliev 

and others, 1971; Peterson, 1985; Boudjema, 1987). 

Transpressional movements (wrenching) during Austrian 

deformation reactivated older structures causing local uplift and 

erosion (Claret and Tempere, 1967; Aliev and others, 1971). 

The initial stages of the Africa-Arabia and Eurasia collision during Late Cretaceous to middle Tertiary caused compressional 

movements and uplift (Peterson, 1985; Guiraud, 1998). 

Compressional movements during the Late Cretaceous and 

Pyrenean deformation tilted the Triassic Basin to its present configuration (Aliev and others, 1971; Boote and others, 1998). 

Basins that existed where the present-day Atlas Mountains lie 

were inverted by these events (Aliev and others, 1971). Inversion and tilting at this time resulted in the development of the 

shallow Melrhir and Benoud foreland basins (Boote and others, 

1998).

Stratigraphy

The stratigraphy of the lower Paleozoic is generally continuous, but the Devonian and overlying sections show more 

localized depositional systems. Stratigraphic nomenclature varies among the Saharan basins and countries. This study primarily uses nomenclature given in Boudjema (1987), Montgomery 
10 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

during a major regional flooding event and contains mostly 

sapropelic and mixed (type I and II) kerogen (Daniels and 

Emme, 1995; Makhous and others, 1997). In the Timimoun, 

Ahnet, and Mouydir Basins, present-day TOC content ranges 

from about 1 to 8 percent (Makhous and others, 1997). Equivalent vitrinite reflectance values range from 1 to 4 percent Ro (calculated, Makhous and others, 1997). The TOC content in Upper 

Devonian mudstone generally decreases westward across the 

Illizi and Grand Erg/Ahnet Provinces (Makhous and others, 

1997).

Upper Devonian to Carboniferous formations include the 

Strunian-Tournaisian Sbaa Formation and overlying unnamed 

mudstone deposited in deltaic and nearshore marine environments. No Permian rocks are present in the Grand Erg/Ahnet 

Province. Hercynian deformation started in Late Carboniferous 

and lasted through Early Permian. Erosion during this event 

removed most of the Paleozoic section along structural highs.

The Mesozoic rock section is thin across much of the 

Grand Erg/Ahnet Province, but thickens to the northeast in the 

Oued Mya and Benoud Basins (fig. 4A, B). Triassic rocks 

include a lower clastic unit (Middle to Upper Triassic) and an 

upper evaporite unit that grades into the Jurassic section. The 

clastic unit is subdivided into the Trias Argilo-Greseux Inferieur, 

Trias Argilo-Carbonate, and Trias Argilo-Greseux Superieur. 

Sandstone within this clastic unit is a major oil and gas reservoir. 

The lowermost Triassic rocks were deposited as continental (fluvial) sandstone and mudstone (Boudjema, 1987; Echikh, 1998). 

Because these beds were deposited over a dissected erosional 

surface of the Hercynian unconformity, thickness is variable 

(Bishop, 1975). The lowermost beds, Trias Argilo-Greseux 

Inferieur, were deposited as transgressive fluvial sandstone (Ford 

and Scott, 1997). These lower beds grade upward into dolostone, dolomitic mudstone, and anhydrite beds of the Trias 

Argilo-Carbonate (Boudjema, 1987; Montgomery, 1993). 

Rocks of the Trias Argilo-Greseux Superieur consist of alluvial 

mudstone, siltstone, and fine- to medium-grained sandstone 

(Boudjema, 1987; Montgomery, 1993). This clastic interval 

may grade into Jurassic sandstone by backstepping along the 

southern margins of the Oued Mya Basin (Boote and others, 

1998).

Overlying the Triassic clastic unit is an Upper Triassic and 

Lower Jurassic cyclic sequence of interbedded salt, anhydrite, 

gypsum, dolostone, and mudstone, called the Saliferous Units 

(fig. 5) (Bishop, 1975). These rocks form a regional seal for 

many oil and gas reservoirs (van de Weerd and Ware, 1994). The 

sequence is thickest near the Saharan Flexure in the north, and it 

thins southward. The combined maximum thickness (Triassic 

and Jurassic sections) exceeds 2,000 m.

 The Cretaceous section includes nonmarine clastic rocks 

grading upward into marginal marine clastic rocks, and then 

into marine carbonate rocks. The thickest Mesozoic section is 

to the northeast; the section thins to the south and west. 

(1993), and Echikh (1998). Columnar sections, stratigraphic 

nomenclature, and correlations are shown in figure 5.

Principal source rocks are the Silurian Tanezzuft Formation 

(or its lateral equivalents) and Middle to Upper Devonian mudstone (Givetian to Famennian) (Tissot and others, 1973; Daniels 

and Emme, 1995). Other minor or relatively unimportant source 

rocks are also present but contributed significantly less petroleum than did the Silurian or Middle to Upper Devonian mudstone (Daniels and Emme, 1995; Boote and others, 1998). 

Reservoir rocks include sandstone of Cambrian-Ordovician, Silurian, Devonian, Carboniferous, and Triassic age. Intraformational Paleozoic marine mudstone provides the primary seals. In 

the Benoud trough, seal rocks also include Triassic to Jurassic 

evaporites, mudstone, and carbonate rocks.

During the late Precambrian and Early Cambrian, erosion 

of a preexisting craton to the south occurred due to uplift during 

the Pan African deformational event. Eroded sediments were 

deposited northward as alluvial and fluvial deposits and make up 

a thick Cambrian sandstone section. This sandstone is laterally 

equivalent to the Hassi Messaoud and Hassi Leila Formations, 

which are major oil and gas reservoirs in the neighboring Trias/

Ghadames and Illizi Provinces (van de Weerd and Ware, 1994; 

Petroconsultants, 1996a).

Ordovician sandstone and mudstone deposited in marine 

and marginal marine environments overlie the Cambrian sandstone (Montgomery, 1993; van de Weerd and Ware, 1994). 

Mudstone laterally equivalent to Argile d'El Gassi, Argiles 

d'Azzel, and Argile Microconglomerate may be locally important source rocks in the Grand Erg/Ahnet Province (Makhous 

and others, 1997; Malla and others, 1997).

The organic-rich, graptolitic, marine mudstone of the Silurian Tanezzuft Formation (or its lateral equivalents) overlies the 

Ordovician section. The Tanezzuft Formation, a principal source 

rock, was deposited during a major regional flooding event and 

contains mostly sapropelic and mixed (type I and II) kerogen 

(Daniels and Emme, 1995; Makhous and others, 1997). The 

present-day total organic carbon (TOC) content ranges from 

about 2 to 4 percent across the Timimoun, Ahnet, and Mouydir 

Basins (Makhous and others, 1997). The TOC content is presumably greatest at the base of the section as in the neighboring 

Ghadames (Berkine) and Illizi Basins (Daniels and Emme, 

1995). The TOC content of the Tanezzuft Formation, however, 

may be reduced by as much as one-half due to increased thermal 

maturity (Daniels and Emme, 1995). Equivalent vitrinite reflectance values of the Silurian source rock within the Timimoun, 

Ahnet, and Mouydir Basins range from 1.2 to 1.6 percent Ro (calculated, Makhous and others, 1997). The thickness, richness, 

and kerogen type of this source rock are regionally variable and 

dependent on paleogeography (Daniels and Emme, 1995).

The Devonian rocks unconformably overlie the Upper Silurian sediments. Devonian rocks consist of interbedded marine 

sandstone and mudstone. Sandstone members are each given a 

code, F2 to F6 with F6 being the oldest and F2 the youngest (fig. 

5). These sandstone members are principal oil and gas reservoirs in the province.

Middle to Upper Devonian mudstone is another major 

source rock, particularly the Frasnian-aged mudstone, which is 

the richest in the section (Daniels and Emme, 1995). This mudstone, like the Silurian Tanezzuft Formation, was deposited 

Figure 5 (next two pages). Columnar section and stratigraphic nomenclature for Illizi, Triassic, and Ghadames (Berkine) Basins (modified from 

Boudjema, 1987). Major reservoir rocks are shown in yellow, source 

rocks in gray, and seals in red.
Province Geology 11

InfraCambrian Cambrian Ordovician Silurian Devonian Carboniferous System

Stage

Stephanian

Westphalian

Namurian

Visean

Tournaisian

Famen. -Frasnian

Givetian -

Eifelian

Emsian

Siegenian -

Gedinnian

Cardocian

Llandeilian -

Llanvirnian

Arenigian

Tremadocian

Cambrian-Ordovician

Triassic Basin

(Boudjema,

1987)

Ghadames

(Berkine) and

Hamra Basins

(Montgomery,

1994; Echikh, 1998)

Tiguentourine

El Adeb Larache

Dembaba

Assed Jeffar Oubarakat

Assekaifaf

Issendjel

Mrar

Gara Mas Melouki Tahara (Shatti)

Tin Meras Aouinet Ouenine

Ouan Kasa Orsine

Hassi Tabankort Tadrart

Acacus

Oued Imirhou Tanezzuft

Gres de Remada

Argile Microcgl.

Memouniat

Melez Chograne

Gres d'Oued Saret

Argiles d'Azzel

Gres de Ouargla

Haouaz Quartzites De

Hamra

Gres d'El Atchane

Argile d'El Gassi

Zone des Alternances

Ri

Ro

R2

R3

Socle Infra Tassilian/

Mourizidie

Hassaouna

and

Mourizidie

Illizi Basin

(van de Weerd

and Ware,

1994)

"Argileux"

Gara Louki

Edjeleh

Hamra

In Kraf

Hassi Leila

General

lithology

(Boudjema,

1987)

Description

(Boudjema, 1987)

Hercynian Unconformity

Mudstone, limestone, and gypsum

Limestone, gypsum, and mudstone

Limestone and sandstone

Limestone and sandstone with concretions

Mudstone and sandstone

Limestone and mudstone

Sandstone

Mudstone Frasnian Unconformity

Sandstone

Mudstone and limestone

Mudstone and sandstone

Sandstone

Late Silurian-Early Devonian Unconformity

Sandstone and mudstone

Black mudstone with graptolites

Sandstone

Microconglomeratic mudstone Glacial Unconformity

Limestone, sandstone, and mudstone

Silty black mudstone

Sandstone

Sandstone

Sandstone and mudstone

Mudstone

Sandstone and mudstone

Sandstone

Sandstone and conglomerate

Pan-African Unconformity

Metamorphic and magmatic rocks

Hassi Messaoud

F6

F4-5

F3

F2

A

B

C

D

E

F

M'Kratta Complex

(Sbaa)

Zone de Passage

Strunian

Bir Tlacsin

Achebyat
12 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco System

Stage

Cretaceous

Lias

Dogger

Malm

Neocomian

Barremian

Aptian

Albian

Triassic Jurassic

Cenomanian

Turonian

Senonian

Paleog. Eocene Neogene

Miocene

Pliocene

General

lithology

(Boudjema,

1987)

Description

(Boudjema, 1987)

Conglomerate

Marl, gypsum, and sandstone

Gypsum, marl, limestone, sandstone,

and conglomerate

Pyrenean Unconformity Sandstone and marl

Limestone and marl

Anhydrite, limestone, dolostone, marl,

and mudstone

Limestone and dolostone

Anhydrite, dolostone, and marl

Austrian Unconformity

Sandstone, mudstone, and dolostone

Sandstone and mudstone

Sandstone and dolomitic mudstone

Anhydrite, limestone, dolostone, marl,

and sandstone

Mudstone, sandstone, limestone,

and anhydrite

Salt, anhydrite, and mudstone

Sandstone, mudstone, salt,

and volcanic rocks

Hercynian Unconformity

Triassic, Ghadames (Berkine),

and Hamra Basins

(Montgomery, 1994)

Al Hamra Group

Nefousa Group

Continental

Intercalaire

Scesciuch

(Shakshuk)

Tigi

Saliferous

Units

Argilo-Greseux

Superieur

(Gassi Touil)

Argilo-Carbonate

(Oulad Nsir)

Argilo-Greseux

Inferieur

(Nezla)

Cabao

Paleocene

Zarzaitine

Inferieur

Zarzaitine

Superieur

Zarzaitine

Moyen

Serie

de Taouratine

Serie

D'In Akamil

Argile Gypse

Calcaire

Calcaire

Marnes

Illizi Basin

(Chaouchi and

others, 1998)

Oligocene
Regional Exploration History 13

Cenozoic rocks are represented by thin, discontinuous 

Miocene-Pliocene nonmarine rocks and Quaternary sediments.

Petroleum Occurrence

Most of the oil and gas fields found by the end of 1995 in 

the Grand Erg/Ahnet Province are associated with anticlines or 

faulted anticlines that developed during Hercynian deformation (Petroconsultants, 1996a). Many fields are within highamplitude folds on or near the Djoua Saddle and Azzene High 

within the Ahnet, Sbaa, and southern Timimoun Basins (fig. 1). 

Some accumulations are within combination traps, those containing both structural and stratigraphic components, such as 

Hassi R'Mel and surrounding fields on the broad Tilrhemt 

Arch.

Regional Exploration History

Exploration activity was not consistent through time in 

Algeria. Exploration activity in Algeria fluctuated due to its 

war for independence from 1954 to 1962, nationalization of the 

oil industry from 1963 to 1971, political and economic problems into the 1980’s, and more favorable contractual terms in 

the late 1980’s (Traut and others, 1998; Montgomery, 1994). 

Since 1963, Algeria had legislation regarding concession contracts and royalties that discouraged exploration by foreign 

companies (Montgomery, 1994). Since the late 1980’s, however, Algeria revised its legislation, encouraging foreign companies to explore and develop oil and gas resources 

(SONATRACH, c. 1992; Montgomery, 1994; Traut and others, 

1998).

Not all areas in Algeria were accessible for exploration. 

Shifting sand of Saharan Africa deserts presents technical difficulties in exploration and hazards in production operations 

(Echikh, 1998). Since the 1980’s, some of these technical difficulties in exploration have been resolved. Recent advances in 

gathering, processing, and reprocessing of seismic data allow 

exploration beneath sand-sea environments such as Grand Erg 

Occidental where the Timimoun Basin lies (van de Weerd and 

Ware, 1994; Macgregor, 1998). As of 1996, no pipelines connect the fields of the Timimoun and Ahnet Basins to the existing 

infrastructure.

Plots showing exploration activity and discovery history for 

each of the assessment units are presented in the appendices. 

Due to limited data, however, exploration-activity and discovery-history plots are provided for only the Tanezzuft-Timimoun 

Structural/Stratigraphic, Tanezzuft-Ahnet Structural/Stratigraphic, and Tanezzuft-Sbaa Structural/Stratigraphic assessment units.

The Tanezzuft-Timimoun Total Petroleum System 

(205801)

The Tanezzuft-Timimoun Total Petroleum System is an 

important total petroleum system with respect to known gas 

volumes. Excluding the contribution from the Hassi R'Mel 

field, the Tanezzuft-Timimoun Total Petroleum System contains about 50 percent of the discovered gas in the province. 

An events chart (fig. 6) summarizes the timing of sources, 

reservoirs, seals, trap development, and generation and migration of petroleum.

Source Rocks

The principal source rocks in the Tanezzuft-Timimoun 

Total Petroleum System are the Silurian Tanezzuft Formation (or 

lateral equivalents), and Middle to Upper Devonian mudstone 

(Makhous and others, 1997; Boote and others, 1998). The 

present-day TOC content of the Silurian rocks ranges from 2 to 4 

percent TOC for the Timimoun, Ahnet, and Mouydir Basins 

(Makhous and others, 1997). Upper Devonian rocks in the Timimoun Basin contain from 1 to 1.8 percent TOC (Makhous and 

others, 1997).

Petroleum is presumed to have been generated during the 

Carboniferous, when the Paleozoic section was thickest, but generation was halted during uplift associated with Hercynian 

deformation (Makhous and others, 1997; Boote and others, 

1998). Migration and charge are presumed to have occurred 

during the early stages of Hercynian deformation, prior to major 

uplift and erosion (Boote and others, 1998). Petroleum most 

likely migrated vertically along faults or fractures (Boote and 

others, 1998). A later phase of dry gas generation is hypothesized to have occurred due to igneous activity in the Late Triassic, about 200 million years ago (Logan and Duddy, 1998). 

Some of the petroleum generated prior to or during the early 

stages of the Hercynian event may have been removed or dispersed by erosion during the late stages of Hercynian and subsequent deformational events.

Overburden Rocks

Overburden rocks are variable across the area mainly due to 

nondeposition and erosion during the Hercynian and Pyrenean 

deformational events (fig. 4A). Along structural highs, large portions of the Paleozoic section were removed by erosion during 

Hercynian deformation. Elsewhere, Paleozoic rocks comprise 

most of the overburden. The Paleozoic section is thickest in the 

center of the Timimoun Basin. This section thins to the north 

and east over the Tilrhemt-Oued Namous-Maharez and IdjeraneM'Zab structural axes, and thins to the south over the Azzene 

High and Djoua Saddle (fig. 4A). Mesozoic rocks comprise only 

a small portion of the overburden. The Mesozoic section is 

thickest to the north and east and thins to the south and west (fig. 

4A). A thin Cenozoic section is present over the northeast part of 

the total petroleum system.

Reservoir Rocks

The known major reservoir rocks in the Tanezzuft-Timimoun Total Petroleum System are Ordovician marine and glacial sandstone, Devonian shallow marine sandstone, and 

Carboniferous deltaic to marine sandstone (including the Sbaa 

Formation) (Petroconsultants, 1996a). Names of laterally 

equivalent rock units are shown in figure 5, and known reservoir properties are given in table 1.
14 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Timimoun (205801) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 12-1-98

CARB

E O

M

Figure 6. Events chart for Tanezzuft-Timimoun Total Petroleum System. Gray boxes

indicate secondary or possible occurrences.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
The Tanezzuft-Ahnet Total Petroleum System (205802) 15

Seal Rocks

Intraformational Paleozoic marine mudstone is the primary 

seal for most reservoirs in the Tanezzuft-Timimoun Total Petroleum System (Boote and others, 1998).

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 are 

within high-amplitude anticlines and faulted anticlines (Boote 

and others, 1998; Petroconsultants, 1996a). Accumulations 

within combination traps (those containing both structural and 

stratigraphic components) are assumed to be present; however, 

none have yet been reported.

The typical trapping style is anticlines containing intraformational Paleozoic mudstone seals. Other proven or potential 

trap types include lateral sealing of reservoir rocks by impermeable formations due to either faulting or lithofacies changes. 

Potential traps may occur where the main Paleozoic reservoir 

rocks subcrop and pinch out beneath Mesozoic and Cenozoic 

rocks in the northern portion of the total petroleum system; however, overlying rocks may not provide adequate seals (fig. 4A).

Most of the discovered petroleum accumulations are gas 

and are present in the southern portion of the province, near the 

Djoua Saddle (fig. 3). As of 1996, one gas accumulation exists 

on top of the Allal High.

Assessment of Undiscovered Petroleum by

Assessment Unit

One assessment unit was identified for the Tanezzuft-Timimoun Total Petroleum System, called Tanezzuft-Timimoun 

Structural/Stratigraphic Assessment Unit (fig. 3). As of 1996, it 

contained 11 fields, all of which are gas fields (based on USGS oil 

and gas field definitions). Combined, these fields contained 4,200 

BCFG, as known volumes (table 2) (Petroconsultants, 1996a). 

No volumes of oil or NGL were reported. Minimum field sizes of 

4 MMBO and 24 BCFG were chosen for this assessment unit 

based on the field-size distribution of discovered fields.

The exploration density as of 1996 was approximately 

three new-field wildcat wells per 10,000 km2. The overall success rate as of 1996 was approximately 11 discoveries per 62 

new-field wildcat wells (or about one discovery per six new-field 

wildcat wells). The greatest success in terms of discoveries per 

number of new-field wildcat wells drilled occurred since 1985. 

Plots showing exploration activity and discovery history are presented in Appendix 1.

Exploration activity was not consistent through time: peaks 

in activity occurred in the mid-1950’s, early 1960’s, and early 

1990’s. The sizes of gas fields discovered have decreased 

through time and with respect to exploration activity, although 

much of the area north of the Djoua Saddle experienced little 

exploration.

Until recently, only structural traps have been explored for 

oil and gas. Continued exploration of structural and combination traps is expected for the next 30 years, and many more small 

gas fields could potentially be discovered along the Djoua 

Saddle and Idjerane-M'Zab structural axis, particularly around 

the Allal High. New exploration concepts include the search for 

both structural and stratigraphic traps in the northern portion of 

the total petroleum system. Potential for discoveries exists 

within stratigraphic pinchouts in shallow marine or deltaic 

deposits due to lateral changes of lithofacies.

This study estimates that about half of the total number of 

fields (discovered and undiscovered) of at least the minimum 

size has been discovered. Only a small number of undiscovered 

oil fields containing small volumes of oil was estimated. The 

estimated median size and number of undiscovered oil fields are 

10 MMBO and 2 fields; the same values for undiscovered gas 

fields are 60 BCFG and 10 fields. The ranges of number, size, 

and coproduct-ratio estimates for undiscovered fields are given 

in table 3.

The estimated means of the undiscovered conventional 

petroleum volumes are 31 MMBO, 1,128 BCFG, and 56 MMBNGL (table 4). In addition, the mean sizes of the largest anticipated undiscovered oil and gas fields are 21 MMBO and 309 

BCFG, respectively.

The Tanezzuft-Ahnet Total Petroleum System 

(205802)

The Tanezzuft-Ahnet Total Petroleum System is an important petroleum system in the Grand Erg/Ahnet Province with 

respect to known gas volumes. Excluding the contribution from 

the Hassi R'Mel field, this total petroleum system contains about 

35 percent of the discovered gas in the province. An events chart 

(fig. 7) summarizes the timing of sources, reservoirs, seals, trap 

development, and generation and migration of petroleum.

Source Rocks

The principal source rocks in the Tanezzuft-Ahnet Total 

Petroleum System are the Silurian Tanezzuft Formation (or lateral equivalents), and Middle to Upper Devonian mudstone 

(Makhous and others, 1997; Boote and others, 1998; Macgregor, 

1998). In the Timimoun, Ahnet, and Mouydir Basins, presentday TOC content ranges from 2 to 4 percent TOC for Silurian 

source rocks and from 1 to 8 percent TOC for Middle to Upper 

Devonian source rocks (Makhous and others, 1997).

Petroleum is presumed to have been generated during the 

Carboniferous, when the Paleozoic section was thickest, but generation was halted during uplift associated with Hercynian 

deformation (Makhous and others, 1997; Boote and others, 

1998). Migration and charge are presumed to have occurred 

during the early stages of Hercynian deformation (Boote and 

others, 1998). Petroleum most likely migrated vertically along 

faults or fractures (Boote and others, 1998). A later phase of dry 

gas generation is hypothesized to have occurred due to igneous 

activity in the Late Triassic, about 200 million years ago (Logan 

and Duddy, 1998). Some of the petroleum generated prior to or 

during the early stages of the Hercynian event may have been 

removed or dispersed by erosion during the late stages of Hercynian and subsequent deformational events.
16 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Ahnet (205802) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 12-1-98

CARB

E O

M

Figure 7. Events chart for Tanezzuft-Ahnet Total Petroleum System. Gray boxes

indicate secondary or possible occurrences.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
The Tanezzuft-Sbaa Total Petroleum System (205803) 17

as known volumes (table 2) (Petroconsultants, 1996a). Minimum field sizes of 4 MMBO and 24 BCFG were chosen for this 

assessment unit based on the field-size distribution of discovered 

fields.

The exploration density as of 1996 was approximately five 

new-field wildcat wells per 10,000 km2. The overall success rate 

as of 1996 was approximately 24 discoveries per 58 new-field 

wildcat wells (or about one discovery per two new-field wildcat 

wells). Plots showing exploration activity and discovery history 

are presented in Appendix 2.

Exploration activity was not consistent through time, occurring in the mid- to late 1950’s, mid-1970’s, and late 1980’s to 

early 1990’s. The sizes of gas fields discovered have not significantly decreased through time, and exploration appears to be 

only moderately mature across much of the area.

Until recently, only structural traps have been explored for 

oil and gas. Continued exploration of structural and combination traps is expected for the next 30 years and many more gas 

fields could be discovered. Potential for discoveries exists 

within stratigraphic pinchouts in shallow marine or deltaic 

deposits due to lateral changes of lithofacies.

This study estimates that about half of the total number of 

fields (discovered and undiscovered) of at least the minimum 

size has been discovered. Little potential exists for significant 

oil discoveries. The estimated median size and number of undiscovered oil fields are 10 MMBO and 2 fields; the same values 

for undiscovered gas fields are 60 BCFG and 26 fields. The 

ranges of number, size, and coproduct-ratio estimates for undiscovered fields are given in table 3.

The estimated means of the undiscovered conventional 

petroleum volumes are 34 MMBO, 2,973 BCFG, and 149 

MMBNGL (table 4). In addition, the mean largest anticipated 

undiscovered oil and gas fields are 23 MMBO and 557 BCFG, 

respectively.

The Tanezzuft-Sbaa Total Petroleum System 

(205803)

The Tanezzuft-Sbaa Total Petroleum System is the only 

area in the province that contains significant volumes of oil, 

containing more than 75 percent of the discovered oil. An 

events chart (fig. 8) summarizes the timing of sources, 

reservoirs, seals, trap development, and generation and migration of petroleum.

Source Rocks

The principal source rocks in the Tanezzuft-Sbaa Total 

Petroleum System are the Silurian Tanezzuft Formation (or lateral equivalents), and Middle to Upper Devonian mudstone 

(Makhous and others, 1997; Boote and others, 1998). The mean 

present-day TOC content of the Silurian source rocks is 3 percent TOC and mean equivalent vitrinite reflectance values are 

from 0.9 to 1.0 percent Ro (calculated, Makhous and others, 

1997). Petroleum generation occurred during the early stages of 

Hercynian deformation (Boote and others, 1998) but ceased 

when the basin was uplifted and eroded during the later stages of 

this event. Because rocks within the Sbaa Basin were never 

Overburden Rocks

The age and thickness of overburden rocks are variable 

across the area mainly due to nondeposition and erosion during 

the Hercynian and Pyrenean deformational events (fig. 4A). 

Although in some areas large portions of Paleozoic section were 

removed by erosion during Hercynian deformation, Paleozoic 

rocks comprise most of the overburden, as much as about 4,000 

m (Boote and others, 1998). Paleozoic rocks are thickest in the 

center of the Ahnet Basin (fig. 4A). Mesozoic rocks comprise 

only a small portion of the overburden.

Reservoir Rocks

Known reservoir rocks in the Tanezzuft-Ahnet Total Petroleum System include Cambrian-Ordovician marine and glacial 

sandstone, Silurian marine sandstone, Devonian sandstone, 

including the Devonian F6 Member shallow marine sandstone, 

and Carboniferous deltaic to marine sandstone (Petroconsultants, 1996a). Names of laterally equivalent rock units are shown 

in figure 5, and known reservoir properties are given in table 1.

Seal Rocks

Intraformational Paleozoic marine mudstone is the primary 

seal for reservoirs in the Tanezzuft-Ahnet Total Petroleum System (Boote and others, 1998).

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 are 

within high-amplitude anticlines that formed during Hercynian 

deformation (Boote and others, 1998; Petroconsultants, 1996a). 

Accumulations within combination traps are assumed to be 

present; however, none have yet been reported.

The typical trapping style is anticlines containing intraformational Paleozoic mudstone seals. Other proven or potential 

trap types include lateral sealing of reservoir rocks by impermeable formations due to lithofacies changes or by juxtaposition of 

fault blocks.

Most of the discovered petroleum accumulations in the Tanezzuft-Ahnet Total Petroleum System are gas and are present 

across the entire area, except in the southern portion where Paleozoic rocks are shallow and crop out (fig. 3).

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the Tanezzuft-Ahnet 

Total Petroleum System, called Tanezzuft-Ahnet Structural/

Stratigraphic Assessment Unit (fig. 3). As of 1996, it contained 

24 fields. Of the 24 fields discovered, 1 is an oil field, 20 are gas 

fields, and 3 fields are not classified because they contain less 

than 1 million barrels of oil equivalent (MMBOE) (based on 

USGS oil and gas field definitions). Combined, these fields contain a negligible amount of oil, 3,117 BCFG, and 90 MMBNGL, 
18 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Sbaa (205803) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 12-1-98

CARB

E O

M

Figure 8. Events chart for Tanezzuft-Sbaa Total Petroleum System.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
The Tanezzuft-Mouydir Total Petroleum System (205804) 19

buried too deeply, source rocks are less mature than those in the 

surrounding basins, and oil rather than gas was preserved. 

Petroleum most likely migrated vertically along faults or fractures (Boote and others, 1998).

Overburden Rocks

Overburden rocks are variable across the area mainly due 

to nondeposition and erosion during the Hercynian and Pyrenean deformational events (fig. 4A). Large portions of the 

Paleozoic section were removed by erosion during Hercynian 

deformation. Paleozoic rocks comprise most of the overburden and are thickest in the center of the basin (fig. 4A). Mesozoic rocks comprise a smaller portion of the overburden.

Reservoir Rocks

Known reservoir rocks in the Tanezzuft-Sbaa Total Petroleum System include Cambrian-Ordovician marine and glacial 

sandstone, Devonian marine sandstone, and the Carboniferous 

deltaic to marine sandstone (including the Sbaa Formation) 

(Petroconsultants, 1996a; Baghdadli, 1988). Strunian-aged reservoir rocks have been reported (Baghdadli, 1988), and are 

included with the Devonian or Carboniferous rocks previously 

mentioned. Names of laterally equivalent rock units are shown 

in figure 5, and known reservoir properties are given in table 1.

Seal Rocks

Intraformational Paleozoic marine mudstone is the primary 

seal for reservoirs in the Tanezzuft-Sbaa Total Petroleum System (Boote and others, 1998).

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 are 

within anticlines and faulted anticlines that formed during 

Hercynian deformation (Petroconsultants, 1996a; Baghdadli, 

1988). Depositional pinchouts have also been reported. Other 

proven or potential trap types include lateral sealing of reservoir rocks by impermeable formations due to lithofacies 

changes or by juxtaposition of fault blocks. Most of the discovered petroleum accumulations are oil, and are present generally across the entire area.

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the TanezzuftSbaa Total Petroleum System, called Tanezzuft-Sbaa Structural/Stratigraphic Assessment Unit (fig. 3). As of 1996, it 

contained 15 fields. Seven fields are oil fields, five are gas 

fields, and three fields are not classified because they contain 

less than 1 MMBOE (based on USGS oil and gas field definitions). Combined, these fields contain 284 MMBO, 1,490 

BCFG, and 10 MMBNGL, as known volumes (table 2) (Petroconsultants, 1996a). Minimum field sizes of 10 MMBO 

and 60 BCFG were chosen for this assessment unit.

The exploration density as of 1996 was approximately 17 

new-field wildcat wells per 10,000 km2

. The overall success 

rate as of 1996 was approximately 15 discoveries per 25 newfield wildcat wells (or about 1 discovery per 2 new-field wildcat wells). The success in terms of discoveries per number of 

new-field wildcat wells drilled remained somewhat constant 

through time. Plots showing exploration activity and discovery history are presented in Appendix 3.

Exploration activity was not consistent through time: most 

of the activity occurred since the mid-1980’s through the early 

1990’s. Although exploration appears to be mature across much 

of the area, field sizes have not significantly decreased through 

time.

Until recently, only structural traps have been explored for 

oil and gas. Continued exploration of structural and combination traps is expected for the next 30 years and more fields could 

be discovered.

This study estimates that about half of the total number of 

fields (discovered and undiscovered) of at least the minimum 

size has been discovered. The estimated median size and number of undiscovered oil fields are 30 MMBO and four fields; the 

same values for undiscovered gas fields are 80 BCFG and four 

fields. The ranges of number, size, and coproduct-ratio estimates for undiscovered fields are given in table 3.

The estimated means of the undiscovered conventional 

petroleum volumes are 162 MMBO, 645 BCFG, and 11 MMBNGL (table 4). In addition, the mean sizes of the largest anticipated undiscovered oil and gas fields are 63 MMBO and 259 

BCFG, respectively.

The Tanezzuft-Mouydir Total Petroleum System 

(205804)

Little information is available for the Tanezzuft-Mouydir 

Total Petroleum System. This basin has only been partially 

explored for oil and gas and has not been thoroughly studied 

(SONATRACH, c. 1992). An events chart (fig. 9) summarizes 

the assumed timing of sources, reservoirs, seals, trap development, and generation and migration of petroleum.

Source Rocks

The principal source rocks in the Tanezzuft-Mouydir Total 

Petroleum System are assumed to be similar to those in the 

neighboring Ahnet and Illizi Basins, that is, mudstone of the Silurian Tanezzuft Formation (or lateral equivalents), and Middle to 

Upper Devonian mudstone. In the Timimoun, Ahnet, and Mouydir Basins, present-day TOC content ranges from 2 to 4 percent 

TOC for Silurian source rocks and from 1 to 8 percent TOC for 

Middle to Upper Devonian source rocks (Makhous and others, 

1997). Upper Devonian rocks in the Mouydir Basin contain 

from 1 to 3.5 percent TOC (Makhous and others, 1997).

Oil generation probably started in the Carboniferous, but 

generation was halted by uplift and erosion during the Hercynian 
20 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Mouydir (205804) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 1-1-99

CARB

E O

M

Figure 9. Events chart for Tanezzuft-Mouydir Total Petroleum System. Gray boxes

indicate secondary or possible occurrences.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
The Tanezzuft-Benoud Total Petroleum System (205805) 21

deformational event (Makhous and others, 1997; Boote and others, 1998). Potential source rocks within the Mouydir Basin were 

never again sufficiently buried to generate petroleum. Most of the 

petroleum that had accumulated prior to or during the early stages 

of the Hercynian event was probably removed or dispersed by erosion (Boote and others, 1998; van de Weerd and Ware, 1994). 

Although unproven, if petroleum was generated within the southern portion of the Oued Mya Basin, the possibility exists that some 

petroleum may have migrated updip across the Mouydir Structural Terrace and charged traps within the Mouydir Basin.

Overburden Rocks

Overburden rocks are variable across the area because of 

nondeposition and erosion during Hercynian and Pyrenean 

deformation (fig. 4B and C). Both Paleozoic and Mesozoic 

rocks comprise the overburden. Paleozoic rocks are thickest in 

the southern portion of the Mouydir Basin and thin northward. 

Mesozoic rocks are thickest in the northern portion and thin 

southward. A thin section of Cenozoic rocks is present over the 

northern part of the area.

Reservoir Rocks

Based on interpretations of the regional geology, reservoir 

rocks in the Tanezzuft-Mouydir Total Petroleum System are 

assumed to be similar to those of the neighboring Ahnet and 

Illizi Basins, that is, Cambrian-Ordovician and Devonian 

sandstone.

Seal Rocks

Based on the petroleum geology of neighboring total petroleum systems, intraformational Paleozoic marine mudstone is 

the most likely primary seal for reservoirs in the TanezzuftMouydir Total Petroleum System. 

Trap Types in Oil and Gas Fields

Expected trap types should be similar to those within the 

Ahnet and Illizi Basins. These include anticlines and faulted 

anticlines, some possibly having stratigraphic components. As 

with the Timimoun Basin, some potential exists for traps to be 

present where the main Paleozoic reservoir rocks subcrop 

beneath Mesozoic and Cenozoic rocks. This potential is mainly 

in the northern portion of the total petroleum system; however, 

the overlying rocks may not provide adequate seals (fig. 4B

and C).

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the TanezzuftMouydir Total Petroleum System, called Tanezzuft-Mouydir 

Structural/Stratigraphic Assessment Unit (fig. 3). As of 1996, no 

fields greater than 1 MMBO or 6 BCFG were discovered. Minimum field sizes of 5 MMBO and 30 BCFG were chosen for this 

assessment unit.

The exploration density as of 1996 was approximately one 

new-field wildcat well per 10,000 km2

. Only four new-field 

wildcat wells had been drilled in this assessment unit. Until 

recently, only structural traps have been explored for oil and gas 

(Aliev and others, 1971).

Only a small number of undiscovered oil and gas fields, 

each containing small volumes of oil or gas, was estimated. The 

estimated median size and number of undiscovered oil fields are 

10 MMBO and two fields; the same values for undiscovered gas 

fields are 60 BCFG and six fields. The ranges of number, size, 

and coproduct-ratio estimates for undiscovered fields are given 

in table 3. A probability of 0.4 was given for the existence of at 

least one undiscovered field of at least minimum size in this 

assessment unit.

The estimated means of the undiscovered conventional 

petroleum volumes are 12 MMBO, 292 BCFG, and 14 MMBNGL (table 4). In addition, the mean sizes of the largest anticipated oil and gas fields are 21 MMBO and 230 BCFG, 

respectively.

The Tanezzuft-Benoud Total Petroleum System 

(205805)

The Tanezzuft-Benoud Total Petroleum System is an 

important petroleum system with respect to known oil and gas 

volumes, containing about 24 percent of the discovered oil and 

92 percent of the discovered gas in the province. The giant 

Hassi R'Mel gas field resides in this total petroleum system. An 

events chart (fig. 10) summarizes the timing of sources, reservoirs, seals, trap development, and generation and migration of 

petroleum.

Source Rocks

The principal source rock in the Tanezzuft-Benoud Total 

Petroleum System is the Silurian Tanezzuft Formation (or lateral 

equivalents) (Boote and others, 1998). Middle to Upper Devonian mudstone may provide another source of petroleum but is 

not present over most of the total petroleum system (Makhous 

and others, 1997; Boote and others, 1998). Middle to Upper 

Devonian source rocks were truncated by erosion during Hercynian deformation and are present only in the western portions 

of this total petroleum system. No TOC content or equivalent 

vitrinite reflectance values were available for the source rock at 

the time of this study.

Petroleum was generated during the Late Cretaceous into 

the Tertiary (Boote and others, 1998). In most of the Tanezzuft-Benoud Total Petroleum System, accumulations were 

charged with gas generated within the Benoud Trough. In the 

Hassi R'Mel area on the Tilrhemt Arch, however, two sources 

of petroleum are presumed; gas may have been derived from 

the Benoud Trough in the north and west whereas oil may have 

migrated from the Oued Mya Basin in the south (Boote and 

others, 1998). Petroleum most likely migrated laterally 

through permeable Paleozoic and Triassic sandstone (Boote 

and others, 1998).
22 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Benoud (205805) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 12-1-98

CARB

E O

M

Figure 10. Events chart for Tanezzuft-Benoud Total Petroleum System. Gray box

indicates secondary or possible occurrences.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
The Tanezzuft-Béchar/Abadla Total Petroleum System (205806) 23

Structural/Stratigraphic Assessment Unit (fig. 3). As of 1996, it 

contained four fields. One field is an oil field, two are gas fields, 

and one field is not classified because it contains less than 1 

MMBOE (based on USGS oil and gas field definitions). Combined, these fields contain 88 MMBO, 105,050 BCFG, and 

4,935 MMBNGL, as known volumes (table 2) (Petroconsultants, 1996a). Minimum sizes of 4 MMBO and 24 BCFG were 

chosen for this assessment unit.

The exploration density as of 1996 was approximately six 

new-field wildcat wells per 10,000 km2. The overall success 

rate as of 1996 was approximately four discoveries per 56 newfield wildcat wells (or about one discovery per 14 new-field 

wildcat wells). Because only a few fields are present in this total 

petroleum system, no appendix of plots of exploration activity 

and discovery history is presented in order not to release proprietary data.

Exploration activity was not consistent through time: 

peaks occurred in the mid-1950’s to mid-1960’s and again 

around 1970. Until recently, only structural traps have 

been explored for oil and gas. Continued exploration of 

structural and combination traps is expected for the next 30 

years and many more small oil fields could potentially be 

discovered.

This study estimates that about one-fifth of the total number of fields (discovered and undiscovered) of at least the minimum size has been discovered. The estimated median size and 

number of undiscovered oil fields are 12 MMBO and 4 fields; 

the same values for undiscovered gas fields are 100 BCFG and 

10 fields. The ranges of number, size, and coproduct-ratio estimates for undiscovered fields are given in table 3.

The estimated means of the undiscovered conventional 

petroleum volumes are 72 MMBO, 2,541 BCFG, and 125 

MMBNGL (table 4). In addition, the mean sizes of the largest 

anticipated undiscovered oil and gas fields are 34 MMBO and 

823 BCFG, respectively.

The Tanezzuft-Béchar/Abadla Total Petroleum 

System (205806)

As of 1996, no oil or gas fields have been discovered and 

little geologic information is available for the TanezzuftBéchar/Abadla Total Petroleum System. An events chart (fig. 

11) summarizes the timing of sources, reservoirs, seals, trap 

development, and generation and migration of petroleum.

Source Rocks

Potential source rocks in the Tanezzuft-Béchar/Abadla 

Total Petroleum System are assumed to be similar to those in 

the neighboring Benoud Trough and Timimoun Basin, that is, 

mudstone of the Silurian Tanezzuft Formation (or lateral equivalents), and possibly Middle to Upper Devonian mudstone. 

No TOC content or equivalent vitrinite reflectance values for 

any of the potential source rocks were available at the time of 

this study.

Overburden Rocks

Overburden rocks are variable across the area mainly due to 

nondeposition and erosion during the Hercynian, Austrian, and 

Pyrenean deformational events (fig. 4A). Large portions of the 

Paleozoic section were removed by erosion that occurred during 

Hercynian deformation. Both Paleozoic and Mesozoic rocks 

comprise most of the overburden; they are thickest along the 

Saharan Flexure (Peterson, 1985). A thin Cenozoic interval is 

present over parts of the area.

Reservoir Rocks

Known reservoir rocks in the Tanezzuft-Benoud Total 

Petroleum System are Lower Devonian and Carboniferous 

nearshore marine sandstone and Triassic fluvial sandstone (Petroconsultants, 1996a). Triassic reservoirs are basal fluvial 

sandstone directly beneath a Triassic to Jurassic evaporite section. Names of laterally equivalent rock units are shown in figure 5, and known reservoir properties are given in table 1.

Seal Rocks

As much as 2,000 m of Triassic to Jurassic evaporites, mudstone, and carbonate rocks (Saliferous Units, fig. 5) provide a 

regional top seal for reservoirs in most of the Tanezzuft-Benoud 

Total Petroleum System. The Triassic to Jurassic seal rocks, predominantly salt, extend from the Saharan Flexure in the north 

where the thickest section is present to approximately the Idjerane-M'Zab structural axis (fig. 1). Intraformational Paleozoic 

marine mudstone is the inferred primary seal for some reservoirs 

and secondary, lateral seals for others.

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 are 

within anticlines (Boote and others, 1998; Petroconsultants, 

1996a). Accumulations within combination traps, those containing both structural and stratigraphic components, are present and 

include the Hassi R'Mel gas field.

Except for the Hassi R'Mel field, the typical trapping style 

includes Paleozoic reservoir rocks within anticlines sealed by 

intraformational mudstone. Other proven or potential trap 

types include lateral sealing of reservoir rocks by impermeable 

formations due to lithofacies changes or by juxtaposition of 

fault blocks. Potential accumulations may be trapped in Paleozoic reservoir rocks that subcrop directly beneath Triassic to 

Jurassic evaporites in the northeastern portion of the total petroleum system (fig. 4D). The presence of an overlying basal Triassic sandstone, however, would preclude the existence of such 

traps.

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the TanezzuftBenoud Total Petroleum System, called Tanezzuft-Benoud 
24 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco ROCK UNIT SOURCE ROCK RESERVOIR ROCK SEAL ROCK OVERBURDEN ROCK TRAP FORMATION

GENERATIONPRESERVATION

CRITICAL MOMENT

PETROLEUM

SYSTEM EVENTS

GEOLOGICTIMESCALE CEN. MESOZOIC

TERT TR

E. L. E. E. L. L. E. E. E. M. M. M. L. L. L. L. E. E. M. L. L.

JUR CRET

ACCUMULATION MIGRATIONPALEOZOIC CAM ORD SIL DEV P PreC

0 100 200 300 400 500 600 150 250 350 450 550 50

TPS Name: Tanezzuft-Bechar/Abadla (205806) Province Name: Grand Erg/Ahnet Basin (2058)

Author(s): Timothy R. Klett Date: 12-1-98

CARB

E O

M

Figure 11. Events chart for Tanezzuft-Béchar/Abadla Total Petroleum System. Gray boxes

indicate secondary or possible occurrences.

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS
Summary 25

Petroleum generation probably started during the Carboniferous. Accumulations are presumed to be charged with gas 

because the potential source rocks may be deeply buried (as 

much as 5,000 m) in the central part of the basin (Conrad and 

Lemosquet, 1984; Aliev and others, 1971).

Overburden Rocks

Overburden rocks are variable across the area mainly due to 

nondeposition and erosion during the Hercynian, Austrian, and 

Pyrenean deformation events. Both Paleozoic and Mesozoic 

rocks comprise the overburden. Paleozoic rocks are thickest in 

the western portion of the Béchar and Abadla Basins thinning 

eastward (Conrad and Lemosquet, 1984).

Reservoir Rocks

Reservoir rocks in the Tanezzuft-Béchar/Abadla Total 

Petroleum System are assumed to be similar to those of the 

neighboring Benoud Trough and Timimoun Basins, that is, 

Cambrian-Ordovician fluvial to marine sandstone; and Devonian nearshore marine sandstone. Additionally, Wausortiantype bioherm mounds of Carboniferous (Visean) age may be 

potential reservoirs (Bourque and others, 1995; Madi and others, 1998). Names of laterally equivalent rock units are given 

in figure 5.

Seal Rocks

Intraformational Paleozoic marine mudstone is presumed to 

be the primary seal for reservoirs in the Tanezzuft-Béchar/

Abadla Total Petroleum System.

Trap Types in Oil and Gas Fields

Expected trap types should be similar to those within the 

western portion of the Benoud Trough. These include anticlines and faulted anticlines, some possibly having stratigraphic 

components.

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the TanezzuftBéchar/Abadla Total Petroleum System, called TanezzuftBéchar/Abadla Structural/Stratigraphic Assessment Unit (fig. 3). 

As of 1996, it contained no discoveries greater than 1 MMBO or 

6 BCFG. Minimum field sizes of 1 MMBO and 6 BCFG were 

chosen for this assessment unit.

The exploration density as of 1996 of the TanezzuftBéchar/Abadla Structural/Stratigraphic Assessment Unit was 

approximately one new-field wildcat well per 10,000 km2. 

Only six new-field wildcat wells were drilled in this total 

petroleum system, five of which were in the Moroccan 

portion. Exploration is relatively immature across much of the 

area.

The estimated median size and number of undiscovered 

oil and gas fields within the Tanezzuft-Béchar/Abadla Structural/Stratigraphic Assessment Unit are 5 MMBO and 5 fields; 

the same values for undiscovered gas fields are 30 BCFG and 

15 fields. The ranges of number, size, and coproduct-ratio estimates for undiscovered fields are given in table 3. A probability of 0.4 was given for the existence of at least one 

undiscovered field of at least minimum size in this assessment 

unit.

The estimated means of the undiscovered conventional 

petroleum volumes are 16 MMBO, 441 BCFG, and 22 MMBNGL (table 4). In addition, the mean sizes of the largest anticipated undiscovered oil and gas fields are 18 MMBO and 303 

BCFG, respectively.

Summary

Seven “composite” total petroleum systems were identified, 

each coinciding with a separate basin and each comprising a single assessment unit. These total petroleum systems are called 

the Tanezzuft-Timimoun, Tanezzuft-Ahnet, Tanezzuft-Sbaa, 

Tanezzuft-Mouydir, Tanezzuft-Benoud, Tanezzuft-Béchar/

Abadla, and Tanezzuft-Oued Mya. The Tanezzuft-Oued Mya 

Total Petroleum System was not assessed here.

The main source rocks are the Silurian Tanezzuft Formation 

(or lateral equivalents) and Middle to Upper Devonian mudstone. Petroleum generation and migration occurred in the Carboniferous, but ceased during the Hercynian deformational 

event. In northern portions of the province, petroleum generation and migration occurred during the Cretaceous and into the 

Tertiary with the development of the Triassic and Benoud 

Basins. The major reservoir rocks are Cambrian-Ordovician, 

Ordovician, Silurian, Devonian, Carboniferous, and Triassic 

sandstone. Intraformational Paleozoic marine mudstone is the 

primary seal. In the northeastern part of the province, Triassic to 

Jurassic evaporites, mudstone, and carbonate rocks provide seals 

for reservoir rocks. Of the fields discovered thus far, traps are 

primarily structural and associated with anticlines and faulted 

anticlines.

The estimated means of the undiscovered conventional 

petroleum volumes in the Tanezzuft-Timimoun Total Petroleum System are 31 MMBO, 1,128 BCFG, and 56 MMBNGL; volumes in the Tanezzuft-Ahnet Total Petroleum System 

are 34 MMBO, 2,973 BCFG, and 149 MMBNGL; volumes in 

the Tanezzuft-Sbaa Total Petroleum System are 162 MMBO, 

645 BCFG, and 11 MMBNGL; volumes in the TanezzuftMouydir Total Petroleum System are 12 MMBO, 292 BCFG, 

and 14 MMBNGL; volumes in the Tanezzuft-Benoud Total 

Petroleum System are 72 MMBO, 2,541 BCFG, and 125 

MMBNGL; and volumes in the Tanezzuft-Béchar/Abadla Total 

Petroleum System are 16 MMBO, 441 BCFG, and 22 MMBNGL. The estimated means of the undiscovered conventional 
26 Total Petroleum Systems of the Grand Erg/Ahnet Province, Algeria and Morocco

volumes for these total petroleum systems in Grand Erg/Ahnet 

Province (excluding the Tanezzuft-Oued Mya Total Petroleum 

System) are 328 MMBO, 8,018 BCFG, and 377 MMBNGL.

References Cited

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E., Mkrtchiane, O., Moustafinov, R., Oriev, L., Oroudjeva, D., Oulmi, 

M., and Saïd, A., 1971, Geological structures and estimation of oil 

and gas in the Sahara in Algeria: Spain, Altamira-Rotopress, S.A., 

265 p.

Baghdadli, S.M., 1988, Sbaa Basin—A new oil producing region in Algeria [abs.]: American Association of Petroleum Geologists Bulletin, v. 

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Bishop, W.F., 1975, Geology of Tunisia and adjacent parts of Algeria and 

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Boote, D.R.D., Clark-Lowes, D.D., and Traut, M.W., 1998, Palaeozoic 

petroleum systems of North Africa, in Macgregor, D.S., Moody, 

R.T.J., and Clark-Lowes, D.D., eds., Petroleum geology of North Africa: Geological Society, London, Special Publication 132, p. 7–68.

Boudjema, A., 1987, Evolution structurale du bassin petrolier «Triasique»

du Sahara Nord Oriental (Algerie): Thèse a l'Université de ParisSud, Centre d’Orsay, 290 p.

Bourque, P.-A., Madi, A., and Mamet, B.L., 1995, Waulsortian-type bioherm development and response to sea-level fluctuations—Upper 

Visean of Béchar Basin, western Algeria: Journal of Sedimentary 

Research, v. B65, no. 1, p. 80–95.

Burollet, P.F., Mugniot, J.M., and Sweeney, P., 1978, The geology of the 

Pelagian block—The margins and basins off southern Tunisia and 

Tripolitania, in Nairn, A.E.M., Kanes, W.H., and Stehli, F. G., eds., The 

ocean basins and margins: New York, Plenum Press, v. 4B, p. 331–

359.

Chaouchi, R., Malla, M.S., and Kechou, F., 1998, Sedimentological evolution of the Givetian-Eifelian (F3) sand bar of the West Alrar field, Illizi 

Basin, Algeria, in Macgregor, D.S., Moody, R.T.J., and Clark-Lowes, 

D.D., eds., Petroleum geology of North Africa: Geological Society, 

London, Special Publication 132, p. 187–200.

Claret, J., and Tempere, C., 1967, Une nouvelle region productrice au 

Sahara Algerien—l’anticlinorium d'Hassi Touareg: Proceedings of 

the Seventh World Petroleum Congress, v. 2, Origin of oil, geology 

and geophysics, p. 81–100.

Conrad, J., and Lemosquet, Y., 1984, Du craton vers sa marge—Évolution 

sédimentaire et structurale du bassin Ahnet-Timimoun-Béchar 

(Sahara algérien) au cours du Carbonifère; données paléoclimatiques: Bulletin de la Société Géologique de France, v. 7, no. 6, p. 

987–994.

Daniels, R.P., and Emme, J.J., 1995, Petroleum system model, eastern 

Algeria, from source rock to accumulation; when, where, and how?: 

Proceedings of the Seminar on Source Rocks and Hydrocarbon 

Habitat in Tunisia; Entreprise Tunisienne d'Activités Petrolieres 

Memoir 9, p. 101–124.

Echikh, K., 1998, Geology and hydrocarbon occurrences in the Ghadames 

Basin, Algeria, Tunisia, and Libya, in Macgregor, D.S., Moody, R.T.J., 

and Clark-Lowes, D.D., eds., Petroleum geology of North Africa: 

Geological Society, London, Special Publication 132, p. 109–129.

Ford, G.W., and Scott, A.J., 1997, A depositional model and sequence 

stratigraphy of the Trias Argilo-Greseux Inferieur (T.A.G.I.) in the 

Ghadames Basin, Algeria [abs.]: Dallas, Texas, American Association of Petroleum Geologists Midyear Meeting, May 1997.

Futyan, A., and Jawzi, A.H., 1996, The hydrocarbon habitat of the oil and 

gas fields of north Africa with emphasis on the Sirt Basin, in Salem, 

M.J., El-Hawat, A.S., and Sbeta, A.M., eds., The geology of Sirt 

Basin, Volume II: Amsterdam, The Netherlands, Elsevier Science 

B.V., p. 287–308.

Guiraud, R., 1998, Mesozoic rifting and basin inversion along the northern 

African Tethyan margin—An overview, in Macgregor, D.S., Moody, 

R.T.J., and Clark-Lowes, D.D., eds., Petroleum geology of North Africa: Geological Society, London, Special Publication 132, p. 217–229.

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, 1 CD-ROM.

Logan, P., and Duddy, I., 1998, An investigation of the thermal history of 

the Ahnet and Reggane Basins, Central Algeria, and the consequences for hydrocarbon generation and accumulation, in Macgregor, D.S., Moody, R.T.J., and Clark-Lowes, D.D., eds., Petroleum 

geology of North Africa: Geological Society, London, Special Publication 132, p. 131–155.

Lore, G.L., Brooke, J.P., Cooke, D.W., Klazynski, R.J., Olson, D.L., and 

Ross, K.M., 1996, Summary of the 1995 assessment of conventionally 

recoverable hydrocarbon resources of the Gulf of Mexico and Atlantic Outer Continental Shelf: Minerals Management Service OCS 

Report MMS 96-0047, 67 p.

Macgregor, D.S., 1998, Giant fields, petroleum systems and exploration 

maturity of Algeria, in Macgregor, D.S., Moody, R.T.J., and ClarkLowes, D.D., eds., Petroleum geology of North Africa: Geological 

Society, London, Special Publication 132, p. 79–96.

Madi, A.C., Savard, M.M., Benderra, F., and Hopkins, N., 1998, Hydrocarbon potential of the Mississippian carbonate platform, Bechar 

Basin, Algerian Sahara [abs.]: Salt Lake City, Utah, American Association of Petroleum Geologists Midyear Meeting, May 1998.

Magoon, L.B., and Dow, W.G., 1994, The petroleum system, in Magoon, 

L.B., and Dow, W.G., eds., The petroleum system—From source to 

trap: American Association of Petroleum Geologists Memoir 60, p. 

3–24.

Makhous, M., Galushkin, Y., and Lopatin, N., 1997, Burial history and 

kinetic modeling for hydrocarbon generation, part II, Applying the 

GALO model to Saharan basins: American Association of Petroleum 

Geologists Bulletin, v. 81, no. 10, p. 1679–1699.

Malla, M.S., Khatir, B., and Yahi, N., 1997, Review of the structural evolution and hydrocarbon generation in Ghadames and Illizi Basins: Proceedings of the 15th World Petroleum Congress, p. 1–11.

Montgomery, S., 1993, Ghadames Basin of north central Africa; Stratigraphy, geologic history, and drilling summary: Petroleum Frontiers, 

v. 10, no. 3, 51 p.
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———1994, Ghadames Basin and surrounding areas; Structure, tectonics, geochemistry and field summaries: Petroleum Frontiers, v. 

10, no. 4, 79 p.

Persits, F., Ahlbrandt, T., Tuttle, M., Charpentier, R., Brownfield, M., and 

Takahashi, K., 1997, Maps showing geology, oil and gas fields and 

geologic provinces of Africa: U.S. Geological Survey Open-File 

Report 97-470A, CD-ROM.

Peterson, J.A., 1985, Geology and petroleum resources of north-central 

and northeastern Africa: U.S. Geological Survey Open-File Report 

85-709, 54 p.

Petroconsultants, 1996a, Petroleum exploration and production database: Houston, Texas, Petroconsultants, Inc. [Database available 

from Petroconsultants, Inc., P.O. Box 740619, Houston, TX 77274-

0619.]

———1996b, PetroWorld 21: Houston, Texas, Petroconsultants, Inc. 

[Database available from Petroconsultants, Inc., P.O. Box 740619, 

Houston, TX 77274-0619.]

Schmoker, J.W., and Crovelli, R.A., 1998, A simplified spreadsheet program for estimating future growth of oil and gas reserves: Nonrenewable Resources, v. 7, no. 2, p. 149–155.

SONATRACH, c. 1992, Exploration in Algeria: Algeria, Sur Presses Speciales U.A.F., 36 p.

Tissot, B., Espitalié, J., Deroo, G., Tempere, C., and Jonathan, D., 1973, 

Origin and migration of hydrocarbons in the eastern Sahara (Algeria): 6th International Meeting of Organic Geochemistry, reprinted 

in Demaison, G., and Murris, R.J., eds., Petroleum geochemistry and 

basin evaluation, American Association of Petroleum Geologists 

Memoir 25, p. 315–334.

Traut, M.W., Boote, D.R.D., and Clark-Lowes, D.D., 1998, Exploration history of the Palaeozoic petroleum systems of North Africa, in

Macgregor, D.S., Moody, R.T.J., and Clark-Lowes, D.D., eds., Petroleum geology of North Africa: Geological Society, London, Special 

Publication 132, p. 69–78.

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Sahara oil and gas province (Triassic, Ghadames and Illizi Basins): 

First Break, v. 12, no. 7, p. 363–373.
ufficient data]

Permeability

(millidarcies)

Mean Maximum Number

450450 2

1,125 2,000 8

nd nd 0

240450 2

820 2,000 15

nd nd 0

73 110 14

450450 5

1,625 2,000 4

nd nd 0

nd nd 0

1,000 1,000 1

nd nd 0
USGS Code

Number of 

fields Known (discovered) volumes

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

205801 Tanezzuft-Timimoun Total Petroleum System

20580101 Tanezzuft-Timimoun Structural/Stratigraphic Assessment Unit

Oil fields 0 00 0

Gas fields 11 0 4,200 0

Fields < 1 MMBOE 0 00 0

All fields 11 0 4,200 0

205802 Tanezzuft-Ahnet Total Petroleum System

20580201 Tanezzuft-Ahnet Structural/Stratigraphic Assessment Unit

Oil fields 1 NA NA NA

Gas fields 20 0 3,105 85

Fields < 1 MMBOE 3 0 12 5

All fields 24 NA 3,117 90

205803 Tanezzuft-Sbaa Total Petroleum System

20580301 Tanezzuft-Sbaa Structural/Stratigraphic Assessment Unit

Oil fields 7 278 105 0

Gas fields 5 5 1,380 10

Fields < 1 MMBOE 3 15 0

All fields 15 284 1,490 10

Table 2. Number and sizes of discovered fields for each assessment unit through 1995. The Tanezzuft-Oued Mya 

Total Petroleum System contains the greatest volume of discovered oil whereas the Tanezzuft-Ghadames Total 

Petroleum System contains the greatest volume discovered gas and natural gas liquids. The Tanezzuft-Sbaa Total 

Petroleum System contains the greatest volume of oil wheras the Tanezzuft-Benoud Total Petroleum System contains 

the greatest volume of discovered gas and natural gas liquids due to the giant Hassi R'Mel gas field. [MMBO, million 

barrels of oil; BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of NGL. Volumes 

reported are summed for oil and gas fields (USGS defined). Oil and gas fields containing known volumes below 1 

million barrels of oil or 6 billion cubic feet of gas (BCFG) are grouped. NA, not available. Data from 

Petroconsultants (1996a)] 
Table 2. Continued.

USGS Code

Number of 

fields Known (discovered) volumes

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

205804 Tanezzuft-Mouydir Total Petroleum System

20580401 Tanezzuft-Mouydir Structural/Stratigraphic Assessment Unit

Oil fields 0 00 0

Gas fields 0 00 0

Fields < 1 MMBOE 0 00 0

All fields 0 00 0

205805 Tanezzuft-Benoud Total Petroleum System

20580501 Tanezzuft-Benoud Structural/Stratigraphic Assessment Unit

Oil fields 1 NA NA NA

Gas fields 2 82 105,050 4,935

Fields < 1 MMBOE 1 NA NA NA

All fields 4 88 105,050 4,935

205806 Tanezzuft-Bechar/Abadla Total Petroleum System

20580601 Tanezzuft-Bechar/Abadla Structural/Stratigraphic Assessment Unit

Oil fields 0 00 0

Gas fields 0 00 0

Fields < 1 MMBOE 0 00 0

All fields 0 00 0

2058 Total

Oil fields 9 284 105 0

Gas fields 38 87 113,735 5,030

Fields < 1 MMBOE 7 1 17 5

All fields 54 372 113,857 5,035
205802 Tanezzuft-Ahnet Total Petroleum System

20580201 Tanezzuft-Ahnet Structural/Stratigraphic Assessment Unit

Oil fields 4 10 252 12 16 1 2 4 2 1 275 550 825 

Gas fields 24 60 2,000 80 104 8 26 67 28 10 

205803 Tanezzuft-Sbaa Total Petroleum System

20580301 Tanezzuft-Sbaa Structural/Stratigraphic Assessment Unit

Oil fields 10 30 250 28 38 1 4 10 4 2 275 550 825 

Gas fields 60 80 3,000 69 129 1 4 10 4 2 

205804 Tanezzuft-Mouydir Total Petroleum System

20580401 Tanezzuft-Mouydir Structural/Stratigraphic Assessment Unit

Oil fields 5 10 200 10 15 1 2 4 2 1 1,875 3,750 5,625 

Gas fields 30 60 1,500 64 94 1 6 15 6 3 

205805 Tanezzuft-Benoud Total Petroleum System

20580501 Tanezzuft-Benoud Structural/Stratigraphic Assessment Unit

Oil fields 4 12 200 13 17 1 4 8 4 3 1,875 3,750 5,625 

Gas fields 24 100 5,000 180 204 2 10 28 11 3 

205806 Tanezzuft-Bechar/Abadla Total Petroleum System

20580601 Tanezzuft-Bechar/Abadla Structural/Stratigraphic Assessment Unit

Oil fields 1 5 100 7 8 1 5 10 5 4 1,875 3,750 5,625 

Gas fields 6 30 1,500 55 61 2 15 30 15 14 
onventional volumes Largest anticipated undiscovered field

 (BCFG) NGL (MMBNGL) (MMBO or BCFG)

F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

0 307 118 1 5 19 7 6 15 59 21

0 1,942 1,010 17 43 98 48 95 241 765 309

0 2,249 1,128 18 48 117 56

4 50 1 9 0 1 3 1 6 1 6 67 23

8 5,963 2,955 40 130 316 148 166 457 1,324 557

1 6,013 2,973 40 131 319 149

8 194 89 1 5 12 5 25 55 132 63

3 1,360 555 1 4 14 6 72 159 792 259

1 1,553 645 3 9 26 11

as liquids volumes for oil and gas fields for each assessment unit. [MMBO, million 

ids; MMBNGL, million barrels of natural gas liquids. Volumes of undiscovered 

oil plus NGL) were calculated for USGS-defined gas fields. Largest anticipated 

gas fields. Results shown are estimates that are fully risked with respect to geology 

elected minimum field size are excluded from the assessment. Means can be 

rrelation coefficient of +1.0 is assumed]
ered conventional volumes Largest anticipated undiscovered field

Gas (BCFG) NGL (MMBNGL) (MMBO or BCFG)

F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

0 203 47 0 0 12 3 7 14 56 21

0 1,056 245 0 0 51 12 61 170 620 230

0 1,259 292 0 0 63 14

233 607 272 4 14 38 16 10 26 84 34

1,880 5,483 2,268 16 88 273 109 144 590 2,363 823

2,113 6,090 2,541 20 102 311 125

0 256 59 0 0 16 4 5 14 44 18

0 1,571 382 0 0 77 18 71 230 812 303

0 1,827 441 0 0 93 22

415 1,616 604 7 24 100 36

5,920 17,375 7,414 75 265 830 340

6,335 18,991 8,018 81 290 930 377
APPENDICES

Exploration-activity and discovery-history plots for each of the assessment units. Two sets of 

plots and statistics are provided, one set showing known field sizes (cumulative production plus 

remaining reserves) and another showing field sizes upon which a reserve-growth function was 

applied (labeled grown). Within each set of plots, oil fields and gas fields are treated separately. 

The plots include:

• Cumulative Number of New-Field Wildcat Wells vs. Drilling-Completion Year

• Number of New-Field Wildcat Wells vs. Drilling-Completion Year

• Oil- or Gas-Field Size (MMBO or BCFG) vs. Oil- or Gas-Field Rank by Size (With 

Respect to Discovery Halves or Thirds)

• Number of Oil or Gas Fields vs. Oil- or Gas-Field Size Classes (MMBO or BCFG) (With

Respect to Discovery Halves or Thirds)

• Volume of Oil or Gas (MMBO or BCFG) vs. Oil- or Gas-Field Size Classes 

(MMBO or BCFG)

• Oil- or Gas-Field Size (MMBO or BCFG) vs. Field-Discovery Year

• Oil- or Gas-Field Size (MMBO or BCFG) vs. Cumulative Number of New-Field 

Wildcat Wells

• Cumulative Oil or Gas Volume (MMBO or BCFG) vs. Field-Discovery Year

• Cumulative Oil or Gas Volume (MMBO or BCFG) vs. Cumulative Number of NewField Wildcat Wells

• Cumulative Number of Oil or Gas Fields vs. Field-Discovery Year
• Cumulative Number of Oil or Gas Fields vs. Cumulative Number of New-Field 

Wildcat Wells

• Reservoir Depth, Oil or Gas Fields (m) vs. Field-Discovery Year

• Reservoir Depth, Oil or Gas Fields (m) vs. Cumulative Number of New-Field 

Wildcat Wells

• Gas/Oil, Oil Fields (CFG/BO) vs. Mean Reservoir Depth (m)

• NGL/Gas, Oil Fields (BNGL/MMCFG) vs. Mean Reservoir Depth (m)

• Liquids/Gas, Gas Fields (BL/MMCFG) vs. Mean Reservoir Depth (m)

• Number of Reservoirs in Oil Fields vs. API Gravity (Degrees)
Appendix 1. Exploration-activity and discovery-history plots for the Tanezzuft-Timimoun 

Structural/Stratigraphic Assessment Unit.
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

10

20

30

40

50

60

70

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

DRILLING-COMPLETION YEAR

CUM. NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1

2

3

4

5

6

7

8

1953195519571959196119631965196719691971197319751977197919811983198519871989199119931995

DRILLING-COMPLETION YEAR

NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

0 1 2 3 4 5 6

GAS-FIELD RANK BY SIZE

KNOWN GAS-FIELD SIZE (BCFG)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1

2

3

4

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1,000

2,000

3,000

4,000

5,000

6,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1,000

2,000

3,000

4,000

5,000

6,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

2

4

6

8

10

12

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

0 1 2 3 4 5 6

GAS-FIELD RANK BY SIZE

GROWN GAS-FIELD SIZE (BCFG)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1

2

3

4

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

1

10

100

1,000

10,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1,000

2,000

3,000

4,000

5,000

6,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

1,000

2,000

3,000

4,000

5,000

6,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

2

4

6

8

10

12

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Timimoun Structural/Stratigraphic, Assessment 

Unit 20580101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 10 20 30 40 50 60 70

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Appendix 2. Exploration-activity and discovery-history plots for the Tanezzuft-Ahnet 

Structural/Stratigraphic Assessment Unit.
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

10

20

30

40

50

60

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

DRILLING-COMPLETION YEAR

CUM. NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1

2

3

4

5

6

7

8

9

195419561958196019621964196619681970197219741976197819801982198419861988199019921994

DRILLING-COMPLETION YEAR

NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

0 1 2 3 4 5 6 7 8

GAS-FIELD RANK BY SIZE

KNOWN GAS-FIELD SIZE (BCFG)

First third of fields discovered

Second third of fields discovered

Third third of fields discovered
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1

2

3

4

5

6

7

8

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

200

400

600

800

1,000

1,200

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1,000

2,000

3,000

4,000

5,000

6,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1,000

2,000

3,000

4,000

5,000

6,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

2

4

6

8

10

12

14

16

18

20

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

500

1,000

1,500

2,000

2,500

3,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

100

200

300

400

500

600

700

800

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

LIQUIDS/GAS, GAS FIELDS (BL/MMCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

0 1 2 3 4 5 6 7 8

GAS-FIELD RANK BY SIZE

GROWN GAS-FIELD SIZE (BCFG)

First third of fields discovered

Second third of fields discovered

Third third of fields discovered
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1

2

3

4

5

6

7

8

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

500

1,000

1,500

2,000

2,500

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

1

10

100

1,000

10,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1,000

2,000

3,000

4,000

5,000

6,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

1,000

2,000

3,000

4,000

5,000

6,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

5

10

15

20

25

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

5

10

15

20

25

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

500

1,000

1,500

2,000

2,500

3,000

0 10 20 30 40 50 60

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Ahnet Structural/Stratigraphic, Assessment Unit 

20580201

0

100

200

300

400

500

600

700

800

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

LIQUIDS/GAS, GAS FIELDS (BL/MMCFG)
Appendix 3. Exploration-activity and discovery-history plots for the Tanezzuft-Sbaa 

Structural/Stratigraphic Assessment Unit.
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

5

10

15

20

25

30

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

DRILLING-COMPLETION YEAR

CUM. NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

19561958196019621964196619681970197219741976197819801982198419861988199019921994

DRILLING-COMPLETION YEAR

NEW-FIELD WILDCAT WELLS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

0 1 2 3 4

OIL-FIELD RANK BY SIZE

KNOWN OIL-FIELD SIZE (MMBO)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

1 to <22 to <44 to <8

8 to <16

16 to <3232 to <64

64 to <128

128 to <256256 to <512

512 to <1,024

1,024 to <2,0482,048 to <4,0964,096 to <8,192

8,192 to <16,384

16,384 to <32,76832,768 to <65,536

65,536 to <131,072

131,072 to <262,144

>=262,144

KNOWN OIL-FIELD SIZE (MMBO)

OIL FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

20

40

60

80

100

120

140

160

180

200

1 to <22 to <44 to <8

8 to <16

16 to <3232 to <64

64 to <128

128 to <256256 to <512

512 to <1,024

1,024 to <2,0482,048 to <4,0964,096 to <8,192

8,192 to <16,384

16,384 to <32,76832,768 to <65,536

65,536 to <131,072

131,072 to <262,144

>=262,144

KNOWN OIL-FIELD SIZE (MMBO)

VOLUME OF OIL (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

KNOWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

KNOWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

50

100

150

200

250

300

350

400

450

500

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. KNOWN OIL VOLUME (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

50

100

150

200

250

300

350

400

450

500

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. KNOWN OIL VOLUME (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

7

8

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

7

8

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

100

200

300

400

500

600

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

0 to <10 10 to

<20

20 to

<30

30 to

<40

40 to

<50

50 to

<60

60 to

<70

70 to

<80

80 to

<90

90 to

<100

>=100

API GRAVITY (DEGREES)

RESERVOIRS IN OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

0 1 2 3 4

GAS-FIELD RANK BY SIZE

KNOWN GAS-FIELD SIZE (BCFG)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

200

400

600

800

1,000

1,200

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

KNOWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

KNOWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. KNOWN GAS VOLUME (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

10

20

30

40

50

60

70

80

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

LIQUIDS/GAS, GAS FIELDS (BL/MMCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

0 1 2 3 4

OIL-FIELD RANK BY SIZE

GROWN OIL-FIELD SIZE (MMBO)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

1 to <22 to <44 to <8

8 to <16

16 to <3232 to <64

64 to <128

128 to <256256 to <512

512 to <1,024

1,024 to <2,0482,048 to <4,0964,096 to <8,192

8,192 to <16,384

16,384 to <32,76832,768 to <65,536

65,536 to <131,072

131,072 to <262,144

>=262,144

GROWN OIL-FIELD SIZE (MMBO)

OIL FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

50

100

150

200

250

300

1 to <22 to <44 to <8

8 to <16

16 to <3232 to <64

64 to <128

128 to <256256 to <512

512 to <1,024

1,024 to <2,0482,048 to <4,0964,096 to <8,192

8,192 to <16,384

16,384 to <32,76832,768 to <65,536

65,536 to <131,072

131,072 to <262,144

>=262,144

GROWN OIL-FIELD SIZE (MMBO)

VOLUME OF OIL (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

50

100

150

200

250

300

350

400

450

500

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

50

100

150

200

250

300

350

400

450

500

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

7

8

9

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

7

8

9

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

0 to <10 10 to

<20

20 to

<30

30 to

<40

40 to

<50

50 to

<60

60 to

<70

70 to

<80

80 to

<90

90 to

<100

>=100

API GRAVITY (DEGREES)

RESERVOIRS IN OIL FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

0 1 2 3 4

GAS-FIELD RANK BY SIZE

GROWN GAS-FIELD SIZE (BCFG)

First half of fields discovered

Second half of fields discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

GAS FIELDS (No.)

Second half

of fields

discovered

First half of

fields

discovered
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

6 to <12

12 to <2424 to <4848 to <96

96 to <192

192 to <384384 to <768

768 to <1,536

1,536 to <3,0723,072 to <6,144

6,144 to <12,288

12,288 to <24,57624,576 to <49,15249,152 to <98,304

98,304 to <196,608

196,608 to <393,216393,216 to <786,432

786,432 to <1,572,864

>=1,572,864

GROWN GAS-FIELD SIZE (BCFG)

VOLUME OF GAS (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

1

10

100

1,000

10,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN GAS-FIELD SIZE (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN GAS VOLUME (BCFG)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GAS FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

1

2

3

4

5

6

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GAS FIELDS (No.)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

500

1,000

1,500

2,000

2,500

3,000

0 5 10 15 20 25 30

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, GAS FIELDS (m)
Tanezzuft-Sbaa Structural/Stratigraphic, Assessment Unit 

20580301

0

10

20

30

40

50

60

70

80

0 500 1,000 1,500 2,000 2,500 3,000

MEAN RESERVOIR DEPTH (m)

LIQUIDS/GAS, GAS FIELDS (BL/MMCFG)