Total Petroleum Systems of the Trias/Ghadames 

Province, Algeria, Tunisia, and Libya—The 

Tanezzuft-Oued Mya, Tanezzuft-Melrhir, and 

Tanezzuft-Ghadames

By T.R. Klett

U.S. Geological Survey Bulletin 2202-C

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-c/

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 August 9, 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 ................................................................................................................................. 4

Tectonic History .......................................................................................................................... 4

Stratigraphy.................................................................................................................................. 8

Petroleum Occurrence .............................................................................................................. 12

Regional Exploration History .............................................................................................................. 12

The Tanezzuft-Oued Mya Total Petroleum System (205401)......................................................... 13

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

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

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

Seal Rocks ................................................................................................................................... 13

 Trap Types in Oil and Gas Fields............................................................................................... 13

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

The Tanezzuft-Melrhir Total Petroleum System (205402).............................................................. 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-Ghadames Total Petroleum System (205403)........................................................ 17

 Source Rocks............................................................................................................................... 18

 Overburden Rocks....................................................................................................................... 18

Reservoir Rocks .......................................................................................................................... 18

Seal Rocks ................................................................................................................................... 18

 Trap Types in Oil and Gas Fields............................................................................................... 20

 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 20

Summary................................................................................................................................................ 20

References Cited.................................................................................................................................. 21

Appendices 

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

 Assessment Unit

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

 Assessment Unit

Figures

 1–3. Maps showing approximate locations of:

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

 central Africa............................................................................................................... 3

 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 Trias/Ghadames Province ................ 6

 4. Stratigraphic cross sections through Trias/Ghadames and neighboring

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

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

 Ghadames (Berkine) Basins.............................................................................................. 9
IV

 6–8. Events charts for:

 6. Tanezzuft-Oued Mya Total Petroleum System ...................................................... 14

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

 8. Tanezzuft-Ghadames Total Petroleum System ..................................................... 19

 

Tables

[Tables and Appendices follow References Cited] 

 

1. Abbreviations, names, ages, and lithology of formations used in the total petroleum system

 events chart

2. Reservoir properties of discovered accumulations for each assessment unit through 1995 

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

4. Estimated sizes, number, and coproduct ratios of undiscovered oil and gas fields for each

 assessment unit

5. Estimated 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 Trias/Ghadames 2054

Total Petroleum Tanezzuft-Oued Mya 205401

 Systems Tanezzuft-Melrhir 205402

 Tanezzuft-Ghadames 205403

Assessment Units Tanezzuft-Oued Mya Structural/ 20540101

 Stratigraphic

 Tanezzuft-Melrhir Structural/ 20540201

 Stratigraphic

 Tanezzuft-Ghadames Structural/ 20540301

 Stratigraphic

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, 

Total Petroleum Systems of the Trias/Ghadames Province, 

Algeria, Tunisia, and Libya—The Tanezzuft-Oued Mya, 

Tanezzuft-Melrhir, and Tanezzuft-Ghadames

By T.R. Klett
2 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

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 Trias/Ghadames 

Province (2054) as part of the U.S. Geological Survey World 

Petroleum Assessment 2000. The Trias/Ghadames Province is 

in eastern Algeria, southern Tunisia, and westernmost Libya. 

The province and its total petroleum systems generally coincide 

with the Triassic Basin. The province includes the Oued Mya 

Basin, Melrhir Basin, and Ghadames (Berkine) Basin. Although 

several total petroleum systems may exist within each of these 

basins, only three “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 Trias/Ghadames 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-Oued Mya 830 2,341 110

Tanezzuft-Melrhir 1,875 4,887 269

Tanezzuft-Ghadames 4,461 12,035 908

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, Richard Mast, 

and Michele Tuttle for their editorial review.

Introduction

Undiscovered conventional oil and gas resources were 

assessed within total petroleum systems of the Trias/Ghadames 

Province (2054) as part of the U.S. Geological Survey (USGS) 

World Petroleum Assessment 2000. This study documents the 

geology, undiscovered oil and gas volumes, exploration activity, 

and discovery history of the Trias/Ghadames Province.

The Trias/Ghadames Province is a geologic province delineated by the USGS; it is located in eastern Algeria, southern 

Tunisia, and westernmost Libya (fig. 1). The province area 

encompasses approximately 390,000 km2

 (square kilometers) 

and generally coincides with the Triassic Basin. It contains the 

Melrhir, the Ghadames or Berkine (called Ghadames (Berkine) 

hereafter), and part of the Oued Mya Basins. Neighboring geologic provinces, delineated by the USGS, include the Pelagian 

Basin (2048), Hamra Basin (2047), Illizi Basin (2056), Grand 

Erg/Ahnet Basin (2058), and Atlas Uplift (2053).

More than one total petroleum system may exist within 

each of the basins in the Trias/Ghadames Province (Boote and 

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

adequately determine the relative contribution of each total 
Introduction 3

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

(Berkine)

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

30oN

35o

N

El GassiHassi Messaoud

Ridge

Mouydir

Structural

Terrace
4 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

petroleum 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 composite total petroleum systems are called the Tanezzuft-Oued 

Mya, Tanezzuft-Melrhir, and Tanezzuft-Ghadames Total Petroleum Systems (fig. 2). The Tanezzuft-Melrhir and TanezzuftGhadames Total Petroleum Systems are located almost entirely 

within the Trias/Ghadames Province. The Tanezzuft-Oued Mya 

Total Petroleum System extends into the neighboring Grand Erg/

Ahnet Province. Tanezzuft refers to the Silurian Tanezzuft Formation, which is the oldest major source rock in the total petroleum 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.

The Trias/Ghadames Province contains more than 16,000 

million barrels (MMB) of known (estimated total recoverable, 

that is, cumulative production plus remaining reserves) petroleum liquids (approximately 15,000 million barrels of oil, 

MMBO, and 1,000 million barrels of natural gas liquids, MMBNGL) and approximately 25,000 billion cubic feet of known 

natural gas (109 CFG or BCFG) (Petroconsultants, 1996a). The 

Trias/Ghadames Province contains the giant Hassi Messaoud oil 

field, in the Tanezzuft-Oued Mya Total Petroleum System.

Province Geology

The southern and southwestern boundaries of the Trias/

Ghadames Province represent the approximate extent of Triassic 

and Jurassic evaporites that were deposited within the Mesozoicaged Triassic Basin. The neighboring Hamra Basin is somewhat 

continuous with the Ghadames (Berkine) Basin, but was separated for this study.

A T-shaped anticlinorium, the major structural feature 

within the Trias/Ghadames Province, divides the province into 

the three total petroleum systems (figs.1 and 2). It consists of 

truncated Paleozoic structures beneath a major unconformity 

(the Hercynian unconformity). The anticlinorium can be 

observed on pre-Hercynian unconformity subcrop maps and is 

delineated by the absence of middle and upper Paleozoic rocks. 

A west-to-east- trending arch is located in the northern part of 

the province and consists of the Tilrhemt and the TalemzaneGefara Arches. A southwest-to-northeast-trending structure 

called the Amguid-Hassi Touareg structural axis intersects the 

west-to-east-trending Tilrhemt and Talemzane-Gefara Arches 

(van de Weerd and Ware, 1994). The Amguid-Hassi Touareg 

structural axis is a system of faults and large horst structures 

(Aliev and others, 1971). This fault system deviates eastward 

into the Ghadames (Berkine) Basin, south of the TalemzaneGefara Arch. A secondary structure called the El Gass-Hassi 

Messaoud Ridge lies parallel to part of the Amguid-Hassi 

Touareg structural axis.

The Tanezzuft-Oued Mya Total Petroleum System coincides with the Oued Mya Basin and is bounded on the north by 

the Tilrhemt Arch, on the east by the Amguid-Hassi Touareg 

structural axis, on the south by the Mouydir Structural Terrace, 

and on the west by the Idjerane-M'Zab structural axis. Most of 

the Oued Mya Basin lies within the Grand Erg/Ahnet Province, 

west of the Amguid-Hassi Touareg structural axis. However, 

most of the oil and gas accumulations in this basin had been discovered in the crux of the two westernmost “legs” of the Tshaped anticlinorium (figs. 1 and 2), which had been assigned to 

the Trias/Ghadames Province. The Mouydir Structural Terrace 

is a break or hingeline in the slope of the basement rocks that 

separates the Oued Mya Basin from the perched Mouydir Basin.

The Tanezzuft-Melrhir Total Petroleum System coincides 

with the Melrhir Basin (or Trough), bounded on the north by the 

Saharan Flexure, and on the south by the Tilrhemt and Talemzane-Gefara Arches (figs. 1 and 2). The Melrhir Basin is a shallow foredeep.

The Tanezzuft-Ghadames Total Petroleum System coincides with the Ghadames (Berkine) Basin and is bounded on the 

north by the Talemzane-Gefara Arch, on the east by the Hamra 

Basin, on the south by the Illizi Basin, and on the west by the 

Amguid-Hassi Touareg structural axis. The boundary between 

the Ghadames (Berkine) and the Illizi Basins is delineated by a 

break or hingeline in the slope of the basement. This hingeline 

was responsible for separating much of the petroleum generation, migration, and accumulation between two basins (fig. 4A). 

The eastern and southern boundaries approximate the extent of 

the superimposed Triassic Basin.

A portion of another total petroleum system within Cretaceous rocks is present in the Trias/Ghadames Province. It is an 

extension of a total petroleum system from within the Atlas 

Uplift Province (2053) to the north. This total petroleum system 

includes three fields located near the northern province boundary 

close to the Saharan Flexure but is not described in this study.

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 structural 

axes are shown in figures 1 and 4. 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).
Province Geology 5

A

A'

B'

B

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

20o

N

25oN

30oN

35o

N

Total petroleum systems of interest
6 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

TUNISIA

LIBYA

Grand Erg/Ahnet Basin

Tanezzuft-Ghadames 

Structural/Stratigraphic

Tanezzuft-Melrhir 

Structural/Stratigraphic

200 KILOMETERS

Tanezzuft-Oued Mya 

Structural/Stratigraphic

10o

5 E oE

35oN

30oN

Country boundary

Total petroleum system boundary

Silurian source rock boundary

Oil field

Gas field

Geologic province boundary

Mediterranean

Sea

ALGERIA

Hassi

Messaoud

Figure 3. Areal extent of assessment units within the Trias/Ghadames Province (modified from Petroconsultants, 1996b; Persits 

and others, 1997).
Province Geology 7

0 100 KILOMETERS

NORTH SOUTH

GHADAMES (BERKINE)

BASIN

ILLIZI BASIN

0

1

2

3

4

5

6

7

KM

TERTIARY

UPPER CRETACEOUS

LOWER CRETACEOUS

JURASSIC

UPPER TRIASSIC

ORDOVICIAN

BASEMENT

CAMBRIAN

SILURIAN

DEVONIAN

CARBONIFEROUS

SILURIAN

DEVONIAN

A

SALIFEROUS UNITS

Tanezzuft-Ghadames

TPS (205403)

Tanezzuft-Illizi

TPS (205601) A'

TALEMZANE-GEFARA

ARCH

B-B'

A

Regional seal

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

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

B

SALIFEROUS UNITS

B'

Tanezzuft-Ghadames

TPS (205403)

Tanezzuft-Oued Mya

TPS (205401)

A-A'

B

Regional seal

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

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

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

Figure 4. Stratigraphic cross sections through Trias/Ghadames and Illizi Provinces. A, North-to-south stratigraphic cross section

through the Ghadames (Berkine) and Illizi Basins (modified from van de Weerd and Ware, 1994, after Aliev and others, 1971).
8 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

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 Trias/Ghadames 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). Structures that constitute 

the T- shaped anticlinorium were truncated. 

Several transgressive-regressive cycles occurrred 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). 

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 may have 

removed or dispersed petroleum that had accumulated in some 

areas (Boote and others, 1998).

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 the area (Aliev and 

others, 1971; Boudjema, 1987). Sediment deposition gradually 

diminished in the Tertiary (Aliev and others, 1971; Peterson, 

1985; Boudjema, 1987). 

Transpressional movements (wrenching) during Austrian 

deformation reactivated older structures such as those along the 

Amguid-Hassi Touareg structural axis, causing local uplift and 

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

Uplift of the Amguid-Hassi Touareg structural axis as well as the 

Tilrhemt and Talemzane-Gefara Arches of the T-shaped anticlinorium further separated the three total petroleum systems 

within the Trias/Ghadames Province.

 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).

 These movements 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 exist 

were inverted (Aliev and others, 1971). Inversion and tilting 

resulted in the development of the shallow Melrhir and Benoud 

foreland basins (Boote and others, 1998).

Petroleum was generated within the Triassic Basin depocenter throughout the Late Cretaceous and early Tertiary, but 

some spillage or secondary migration subsequently occurred 

(Boote and others, 1998; van de Weerd and Ware, 1994). Many 

structural traps formed by vertical movements of the basement 

during Mesozoic and Tertiary deformational events (Echikh, 

1998).

Stratigraphy

The regional stratigraphy of lower Paleozoic sections 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 (1993), and Echikh (1998). Columnar sections, stratigraphic nomenclature, and correlations are shown in 

figure 5.

Principal source rocks are the Silurian Tanezzuft Formation 

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. Triassic to Jurassic evaporites, mudstone, and 

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 9

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
10 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

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
Province Geology 11

carbonate rocks provide a regional seal for reservoirs. Other seal 

rocks include intraformational Paleozoic marine mudstone and 

Triassic volcanic 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 

the thick Cambrian sandstone of the Mourizidie and Hassaouna 

Formations. The Hassaouna Formation is laterally equivalent to 

the Hassi Messaoud and Hassi Leila Formations, which are 

major oil and gas reservoirs (van de Weerd and Ware, 1994, Petrocosultants, 1996a).

The Lower Ordovician Achebyat and Haouaz Formations 

unconformably overlie the Hassaouna Formation. The Achebyat 

Formation is laterally equivalent to Argile d'El Gassi and Gres 

d'El Atchane. The overlying Haouaz Formation is laterally 

equivalent to the Hamra Formation and Gres de Ouargla. The 

uppermost beds of the Hassi Messaoud and Hassi Leila Formations contain the marine trace fossil Tigillites (also called 

Scolites), which is characteristic of a change from fluvial to shallow marine deposition (van de Weerd and Ware, 1994). The 

Haouaz Formation contains quartz-rich sandstone and mudstone 

that were deposited in marine and marginal marine environments 

and are major oil and gas producing reservoirs (Montgomery, 

1993; van de Weerd and Ware, 1994). The Argile d'El Gassi and 

equivalents may be locally minor source rocks (Makhous and 

others, 1997; Malla and others, 1997).

Above the Haouaz sandstone are Middle Ordovician marine 

mudstone and fine-grained sandstone of the Melez Chograne 

Formation. The Melez Chograne Formation is laterally equivalent to the Argiles d'Azzel and Bir Ben Tartar Formation sandstone. The Argiles d'Azzel and other mudstone equivalents may 

be locally minor source rocks (Makhous and others, 1997; Malla 

and others, 1997). 

Upper Ordovician to Lower Silurian marine and glacial 

mudstone and fine-grained sandstone include the Memouniat 

Formation, the Gres de Remada, the Argile Microconglomerate, 

and the Gres d'Oued Saret. The Ordovician to Silurian M'Kratta 

Complex includes these rocks as well as the underlying Melez 

Chograne and Haouaz Formations.

Overlying the Ordovician sediments is the organic-rich, 

graptolitic, marine mudstone of the Silurian Tanezzuft Formation. 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 percent 

to greater than 17 percent across the Ghadames (Berkine) Basin, 

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

thermal maturity (Daniels and Emme, 1995). The TOC content 

is greatest at the base of the section (Daniels and Emme, 1995). 

The thickness of the Tanezzuft Formation before Hercynian erosion varies from about 200 m to greater than 550 m (Daniels and 

Emme, 1995). The thickness, richness, and kerogen type of this 

source rock are regionally variable and dependent on paleogeography (Daniels and Emme, 1995).

The Tanezzuft Formation grades upward into the Upper Silurian Zone de Passage, or its lateral equivalent, the Acacus 

Formation. These formations consist of sandstone and mudstone 

representing marine to marginal marine depositional environments. Erosion during Late Silurian to Early Devonian deformation truncated these rocks on surrounding arches. The Acacus 

sandstone is the predominant oil and gas reservoir in the Libyan 

and Tunisian portion of the province (Petroconsultants, 1996a), 

but it may be an important reservoir elsewhere in the province 

where it has not been removed by erosion.

Devonian rocks unconformably overlie the Upper Silurian 

sediments. Devonian rocks consist of interbedded marine and 

deltaic sandstone and mudstone. The Devonian section includes 

the Tadrart, Hassi Tabankort, Ouan Kasa Formation, Orsine, 

Aouinet Ouenine, Tin Meras, Gara Mas Melouki, and part of the 

Tahara Formations. Sandstone members are each given a code, 

F2 to F6, with F6 being the oldest and F2 the youngest (fig. 5). 

The F6 sandstone (Tadrart Formation) and the Ouan Kasa Formation are important oil and gas reservoirs (Petroconsultants, 

1996a; van de Weerd and Ware, 1994).

Middle to Upper Devonian mudstone is another major 

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

the richest in this interval (Daniels and Emme, 1995). This mudstone, like the Silurian Tanezzuft Formation, 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 TOC 

content generally ranges from about 2 to 4 percent but can be as 

much as 14 percent (Daniels and Emme, 1995). The thickness 

of Middle to Upper Devonian mudstone exceeds 800 m in the 

central Ghadames (Berkine) Basin (Daniels and Emme, 1995). 

Lower Devonian (Emsian) mudstone (laterally equivalent to the 

Ouan Kasa or Orsine Formation) may be a locally minor source 

rock (Makhous and others, 1997).

Caboniferous formations include part of the Tahara Formation, the Mrar Formation (laterally equivalent to the Issendjel 

and the lower part of the Assekaifaf Formations), Assed Jefar 

(laterally equivalent to the upper part of the Assekaifaf Formation and the Oubarakat Formation), and the Dembaba Formation 

(laterally equivalent to the El Adeb Larache and Tiguentourine 

Formations). The Lower to Middle Carboniferous rocks consist 

of cycles of limestone or mudstone, siltstone, sandstone, and 

conglomerate representing deltaic and shallow-marine deposition. Lower Carboniferous mudstone may be locally minor 

source rocks (Makhous and others, 1997). Middle to Upper Carboniferous rocks consist of limestones, marls, dolostones, and 

gypsiferous mudstone that were deposited in evaporitic shallowmarine and tidal environments. Hercynian deformation started 

in Late Carboniferous and lasted through Early Permian. Erosion during this event removed most of the Paleozoic section 

along structural highs.

Permian rocks are only present in the eastern portion of the 

province. These rocks include Lower Permian pelagic limestone 

and mudstone, and Upper Permian bioherms, carbonate, and 

clastic rocks (Rigo, 1995). The Upper Permian Bir Jaja mudstone serves as a seal where present (Boote and others, 1998). 

Due to the limited extent, Permian stratigraphy is not shown in 

figure 5.

Triassic rocks include a lower clastic unit (Middle to Upper 

Triassic) and an upper evaporite unit that grades into the 
12 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

Jurassic section. The clastic unit is subdivided into the Trias 

Argilo-Greseux Inferieur (includes the Nezla Formation, Ouled 

Chebbi Formation, and Ras Hamia Formation, and Kirchaou 

Sandstone), Trias Argilo-Carbonate, and Trias Argilo-Greseux 

Superieur (includes the Gassi Touil Formation and Zarzaitine 

Sandstone). 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). The Triassic clastic interval is thickest to the northeast (approximately 500 m) 

and thins to the south and west (Bishop, 1975). This clastic 

interval may grade into Jurassic sandstone by backstepping 

along the southern margins of the Ghadames and Oued Mya 

Basins (Boote and others, 1998). Some volcanic rocks (spilite, 

basalt, and andesite) are present throughout the Triassic section 

(reaching 150 m in some places) (Hamouda, 1980; Boudjema, 

1987).

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 

thins southward. The combined maximum thickness (Triassic 

and Jurassic sections) exceeds 2,000 m. The southern limit of 

these rocks roughly coincides with the Trias/Ghadames Province 

boundary (fig. 1).

Above the evaporite interval are Middle to Upper Jurassic 

clastic and carbonate rocks. Within the Trias/Ghadames Province, these rocks include the Tigi and Scesciuch Formations, 

which were deposited in a shallow-marine environment (Bishop, 

1975; Montgomery, 1993). 

Lower Cretaceous rocks are represented by nonmarine and 

paralic sandstone. Included in this interval are the Cabao Formation and Continental Intercalaire. The top of the Continental 

Intercalaire is marked by the Austrian unconformity (Aptian) 

(Boudjema, 1987; van de Weerd and Ware, 1994). A thin and 

uniform bed of dolostone was deposited during the transgression 

that followed the erosional event (Bishop, 1975). Continental 

and shallow-marine sandstone and mudstone (Albian) overlay 

the dolostone. Upper Cretaceous to lower Tertiary rocks are 

shallow-marine carbonate rocks and evaporites, which were 

deposited on a north-dipping ramp. This interval includes the 

Nefousa and Al Hamra Groups.

Much of the Upper Cretaceous to Oligocene section was 

eroded during Pyrenean deformation. Miocene to Pliocene nonmarine clastic rocks and gypsum, and Quaternary sediments represent the Cenozoic section.

Petroleum Occurrence

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

the Trias/Ghadames Province are located on subtle, low-relief 

structures within the central and northeast portions of the Ghadames (Berkine) Basin; on low-relief structures along the flank 

of the Tilrhemt Arch in the Oued Mya Basin; and on high-relief 

structures along the Amguid-Hassi Touareg structural axis (fig. 

1). Most of these accumulations are within anticlines, faulted 

anticlines, or fault blocks developed during Hercynian and Austrian deformation (Boote and others, 1998; Petroconsultants, 

1996a). Accumulations in combination traps, those containing 

both structural and stratigraphic components, are common.

Regional Exploration History

Exploration activity was not consistent through time in 

Algeria, Tunisia, and Libya. 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). Tunisia and Libya also experienced fluctuations 

and discontinuities in exploration activity. Between 1963 and 

the late 1980’s, both Algeria and Tunisia had legislation regarding concession contracts and royalties that discouraged exploration by foreign companies (Montgomery, 1994). Since the late 

1980’s, however, Algeria and Tunisia revised their legislation, 

encouraging foreign companies to explore and develop oil and 

gas resources (Davies and Bel Haiza, 1990; SONATRACH, c. 

1992; Montgomery, 1994; Traut and others, 1998).

Not all areas in Algeria, Tunisia, and Libya 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 

the Algerian Grand Erg Oriental where the Ghadames (Berkine) 

and Illizi Basins lie (van de Weerd and Ware, 1994; Macgregor, 

1998).

New discoveries can be easily brought on line without construction of major pipelines because a basic infrastructure has 

been established (SONATRACH, c. 1992). Algeria has an 

extensive pipeline network that connects most of the major producing areas to port cities in Algeria and Tunisia (Pennwell, 

1996). The pipelines allow transportation of oil, gas, and natural gas liquids. In Libya, an oil pipeline connects fields of the 

Ghadames (Berkine) and Hamra Basins to the port city of Az 

Zawiyah. An extension of this pipeline was completed in 1996 

that connects producing areas within the Murzuk Basin with the 

coast (Traut and others, 1998; Pennwell, 1996), and another 

pipeline is planned to connect the Libyan portion of the Trias/

Ghadames Province to the coast (Arab Petroleum Research 

Center, 1996).
The Tanezzuft-Oued Mya Total Petroleum System (205401) 13

The Tanezzuft-Oued Mya Total Petroleum System 

(205401)

The Tanezzuft-Oued Mya Total Petroleum System is an 

important total petroleum system with respect to known oil volumes, containing about 70 percent of the discovered oil in the 

province. This total petroleum system extends into the neighboring Grand Erg/Ahnet Province (figs. 1 and 2). An events 

chart (fig. 6) summarizes the timing of sources, reservoirs, seals, 

trap development, and generation and migration of petroleum. 

Table 1 shows the formation names, ages, and lithology for 

abbreviations used in the events chart.

Source Rocks

The principal source rock in the Tanezzuft-Oued Mya 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 basin (Makhous and others, 1997; 

Boote and others, 1998). Devonian source rocks were truncated 

by erosion during Hercynian deformation and are present only in 

the southwestern part of the total petroleum system.

In the Oued Mya Basin, the present-day TOC content of 

Silurian (and Lower Devonian) rocks ranges from 1 to 10 percent, but content of the Silurian rocks can reach 16 percent 

(Makhous and others, 1997). Middle to Upper Devonian and 

Carboniferous rocks contain from 0.5 to 2.5 percent TOC (Makhous and others, 1997). In the Takhoukht area west of and adjacent to Hassi Messaoud field (fig. 3), equivalent vitrinite 

reflectance value of Silurian source rocks is 0.7 percent Ro (calculated, Makhous and others, 1997). Silurian source rocks are 

more mature in western and southern portions of the Oued Mya 

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

the southern portion of the basin, equivalent vitrinite reflectance 

values of Silurian source rocks range from 1.3 to 1.7 percent Ro

(calculated, Makhous and others, 1997). Equivalent vitrinite 

reflectance values of the Middle to Upper Devonian and the Carboniferous range from 0.7 to 1.5 percent Ro (calculated, Makhous and others, 1997).

Minor amounts of petroleum may have been generated in 

the southern portion of the Oued Mya Basin during the Carboniferous when the Paleozoic section was thickest, but generation 

was halted during Hercynian deformation (Makhous and others, 

1997; Boote and others, 1998). The main phase of oil generation 

occurred after Hercynian deformation with the development of 

the new Triassic Basin depocenter, superimposed on the northern part of the Oued Mya Basin. Oil generation and migration 

most likely started no earlier than Late Triassic and peaked in 

Late Cretaceous to early Tertiary (Makhous and others, 1997; 

Boote and others, 1998). Oil generated in the Oued Mya Total 

Petroleum System also charged the Hassi R'Mel area on the Tilrhemt Arch. (The Hassi R'Mel area was either simultaneously or 

subsequently charged with gas from the north and west and is 

therefore included in another total petroleum system.) Pyrenean 

uplift and erosion terminated petroleum generation in the Oued 

Mya Basin (Boote and others, 1998). Petroleum most likely 

migrated laterally into adjacent or juxtaposed migration conduits 

and reservoirs. Some vertical migration may have occurred 

along faults or fractures in structurally deformed areas (Boote 

and others, 1998).

Overburden Rocks

Overburden rocks are variable across the area mainly due to 

nondeposition and erosion during the Hercynian, Austrian, and 

Pyrenean deformational events (fig. 4B). Large portions of Paleozoic section were removed by erosion during Hercynian deformation, as much as 2,200 m of Silurian and Devonian sediments 

(Makhous and others, 1997). Mesozoic rocks comprise most of 

the overburden and unconformably overlie the Paleozoic section 

throughout the total petroleum system. Only small sections of 

Mesozoic rocks were removed by erosion. Both Paleozoic and 

Mesozoic rocks are thickest in the central part of the basin 

between the Tilrhemt Arch and the Amguid-Hassi Touareg 

structural axis (fig. 4B) (Boudjema, 1987; van de Weerd and 

Ware, 1994). A thin Cenozoic section is present over part of the 

total petroleum system.

Reservoir Rocks

Known reservoir rocks in the Tanezzuft-Oued Mya Total 

Petroleum System are predominately Cambrian-Ordovician and 

Triassic sandstone (Petroconsultants, 1996a). Cambrian-Ordovician reservoirs include fluvial to marine sandstone of the Cambrian Hassi Messaoud and Ordovician Gres d'El Atchane (van de 

Weerd and Ware, 1994; Petroconsultants, 1996a). The Triassic 

reservoirs include fluvial sandstone of the Trias Argilo-Greseux 

Inferieur and Trias Argilo-Greseux Carbonate (Petroconsultants, 

1996a). Other reservoirs include fluvial, deltaic, and marine 

sandstone within the Ordovician to Silurian M'Kratta Complex. 

Names of laterally equivalent rock units are shown in figure 5, 

and known reservoir properties are given in table 2.

Seal Rocks

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

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

Mya Total Petroleum System. The Triassic to Jurassic seal 

extends from the Saharan Flexure in the north where the thickest 

section is present to approximately the southern boundary of the 

Trias/Ghadames Province (fig. 1). Triassic volcanic rocks provide the primary seal for some reservoirs, and intraformational 

Paleozoic marine mudstone provides secondary, lateral seals 

when in conjunction with the regional top seal (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 (Boote and others, 1998; 

Petroconsultants, 1996a, van de Weerd and Ware, 1994). Some 
14 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya 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-Oued Mya (205401) Province Name: Trias/Ghadames Basin (2054)

Author(s): Timothy R. Klett Date: 3-23-99

CARB

E O

M

SU

TAG

MR

AO

TZ

MK

EA

HS

AZ

EG

Figure 6. Events chart for Tanezzuft-Oued Mya Total Petroleum System. Names for

abbreviations used in rock unit column are given in table 1. 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-Melrhir Total Petroleum System (205402) 15

accumulations within combination traps are present (Petroconsultants, 1996a). 

The typical trapping style is structures directly overlain by 

or capped with Triassic to Jurassic evaporite sequence. Other 

proven and potential traps include (1) stratigraphic traps against 

volcanic rocks (Hamouda, 1980); (2) lateral sealing of reservoir 

rocks by impermeable formations due to lithofacies change, particularly Paleozoic reservoirs, or juxtaposed in fault blocks; and 

(3) incised valley fills associated with the Hercynian Unconformity.

All of the discovered petroleum accumulations in the 

Tanezzuft-Oued Mya Total Petroleum System are oil and are 

located in three groups along the flanks of the T-shaped anticlinorium (fig. 3). In the northwestern portion of the total petroleum system, along the Tilrhemt Arch, a cluster of several small 

oil accumulations is present in low-relief structures. These accumulations are more gas rich than others within the total petroleum system (Boote and others, 1998). In the northeast portion 

of the total petroleum system, where the Tilrhemt Arch intersects 

the Amguid-Hassi Touareg structural axis in the area surrounding the town of Ouargla, a cluster of larger, linearly oriented 

accumulations is present. The linear arrangement of these accumulations reflects the orientation of structural highs (Boote and 

others, 1998). The third group of accumulations is aligned on 

top of the Amguid-Hassi Touareg structural axis and includes the 

giant Hassi Messaoud oil field. Presumably, spillage from Hassi 

Messaoud charged other fields southwest along the structure 

(Boote and others, 1998).

Assessment of Undiscovered Petroleum by 

Assessment Unit

One assessment unit was identified for the Tanezzuft-Oued 

Mya Total Petroleum System, called Tanezzuft-Oued Mya Structural/Stratigraphic Assessment Unit (fig. 3). As of 1996, it contained 36 fields. Of these discovered fields, 34 are oil fields, and 

2 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 10,843 

MMBO and 8,973 BCFG, as known volumes (table 3) (Petroconsultants, 1996a). No gas fields have yet been discovered, and 

no natural gas liquids (NGL) volumes were reported. Minimum 

field sizes of 10 MMBO and 60 BCFG were chosen for this 

assessment unit based on the field-size distribution of discovered 

fields.

The exploration density as of 1996 was approximately 

seven new-field wildcat wells per 10,000 km2. The overall success rate as of 1996 was approximately 24 discoveries per 100 

new-field wildcat wells (or about one discovery per four newfield wildcat wells). Plots showing exploration activity and discovery history are presented in Appendix 1.

Exploration activity was not consistent through time: peaks 

in activity occurred during the early 1960’s and mid- to late 

1970’s. The first major discovery was the giant Hassi Messaoud 

field in 1956. The sizes of oil fields discovered have generally 

decreased through time and with respect to exploration activity. 

Nevertheless, exploration appears to be relatively immature 

across much of the area. Fields equivalent in size to those found 

recently may yet be discovered. Discoveries of large fields, similar in size to those found early in the discovery history, are not 

likely. Oil will most likely be found along the anticlinorium, 

whereas gas would only be present in the southern and western 

portions of the total petroleum system. Adequate traps may not 

exist beyond the flanks of the anticlinorium.

Until recently, only structural traps had been explored for 

oil and gas. Before 1996, no discoveries have been made 

beyond the regional seal in the southern and western portions of 

the total petroleum system.

Continued exploration of structural and combination traps 

is expected for the next 30 years, and many more smaller oil 

fields could potentially be discovered along the flanks of the 

anticlinorium. New exploration concepts could include the 

search for both structural and stratigraphic traps in the southern portion of the total petroleum system, where perhaps some 

pre-Hercynian-generated petroleum, probably as gas, may be 

preserved.

This study estimates that about one-third of the total number of fields (discovered and undiscovered) of at least the minimum size has been discovered. Only a small number of 

undiscovered gas fields containing small volumes of gas was 

estimated. The estimated median size and number of undiscovered oil fields are 16 MMBO and 34 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 4.

The estimated means of the undiscovered conventional 

petroleum volumes are 830 MMBO, 2,341 BCFG, and 110 

MMBNGL (table 5). In addition, the mean size of the largest 

anticipated undiscovered oil field is 114 MMBO and gas field, 

405 BCFG.

The Tanezzuft-Melrhir Total Petroleum System 

(205402)

As of 1996, the Tanezzuft-Melrhir Total Petroleum System 

was not a major oil and gas producing entity, although it was 

immature in terms of exploration. An events chart (fig. 7) summarizes the timing of sources, reservoirs, seals, trap development, and generation and migration of petroleum. Table 1 

shows the formation names, ages, and lithology for abbreviations used in the events chart.

Source Rocks

The principal source rock in the Tanezzuft-Melrhir Total 

Petroleum System is the Silurian Tanezzuft Formation (or lateral 

equivalents). The extent and continuity of this source rock in the 

Melrhir Basin are not well defined (D. Boote, oral commun., 

1999). The present-day TOC content of the Silurian source 

rocks in the Melrhir Basin ranges from 1.0 to 5.0 percent 

(Cunningham, 1988; Hammill and Robinson, 1992). Oil may 

have generated as early as Carboniferous or Permian time due to 

a thick wedge of Carboniferous to Permian sediments that was 

deposited in the northeastern portion of the Melrhir Basin (D. 

Boote, oral commun., 1999). The main phase of oil generation 
16 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya 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-Melrhir (205402) Province Name: Trias/Ghadames Basin (2054)

Author(s): Timothy R. Klett Date: 3-23-99

CARB

E O

M

SU

TAG

TZ

HM

Figure 7. Events chart for Tanezzuft-Melrhir Total Petroleum System. Names for 

abbreviations used in rock unit column are given in table 1. 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-Ghadames Total Petroleum System (205403) 17

probably began in the Cretaceous and continued into the Tertiary 

(Rigo, 1996). The geochemistry of oils and source rocks of the 

Melrhir Basin is not well documented in literature available to 

the public. Petroleum most likely migrated laterally into adjacent or juxtaposed migration conduits and reservoirs. Some vertical migration may have occurred 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, Austrian, and 

Pyrenean deformational events. The largest portions of Paleozoic section were removed by erosion during Hercynian deformation. Paleozoic rocks are thickest to the north and thin to the 

south over the T-shaped anticlinorium. Mesozoic rocks comprise most of the overburden and unconformably overlie the 

Paleozoic section throughout the province. Only small sections 

of Mesozoic rocks were removed by erosion. A thin Cenozoic 

section is present over some parts of the area. Approximately 

4,000 to more than 6,000 m of Mesozoic and Cenozoic overburden is present over the Tanezzuft-Melrhir Total Petroleum System (Cunningham, 1988; Hammil and Robinson, 1992; Rigo, 

1996).

Reservoir Rocks

Known reservoir rocks in the Tanezzuft-Melrhir Total 

Petroleum System are predominately fluvial to marine sandstone 

of the Ordovician Hamra Formation and fluvial sandstone of the 

Triassic Kirchaou Formation, the lateral equivalent of the Trias 

Argilo-Greseux (Petroconsultants, 1996a). Names of other laterally equivalent rock units are given in figure 5. Known reservoir properties for the Tanezzuft-Melrhir Total Petroleum 

System are not shown in table 2 due to insufficient data.

Seal Rocks

Triassic to Jurassic evaporites, mudstone, and carbonate 

rocks (Saliferous Units, fig. 5) provide a regional top seal, and 

the Tanezzuft mudstone provides a secondary lateral seal when 

in conjunction with the top seal (Hammill and Robinson, 1992).

Trap Types in Oil and Gas Fields

Accumulations in three of the four fields discovered prior to 

1996 are within tilted fault blocks, and in the fourth, within an 

arched stratigraphic trap (Hammill and Robinson, 1992; Rigo, 

1996). The typical trapping style is structures directly overlain 

by or capped with Triassic to Jurassic evaporite sequence. Additional tilted fault blocks or other structures containing 

accumulations may exist along the Tilrhemt and TalemzaneGefara Arches. 

Assessment of Undiscovered Petroleum by 

Assessment Unit

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

contained a total of four fields, two oil fields and two gas fields 

(based on USGS oil and gas field definitions). Combined, these 

fields contain 6 MMBO, 125 BCFG, and 9 MMBNGL, as 

known volumes (table 3) (Petroconsultants, 1996a). Minimum 

field sizes of 1 MMBO and 6 BCFG were chosen for this assessment unit due to the relatively small sizes of discovered fields.

The exploration density as of 1996 was approximately four 

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

as of 1996 was four discoveries with 47 new-field wildcat wells 

(or about one discovery per 12 new-field wildcat wells). 

Exploration activity was sparse and not consistent through 

time. Exploration is immature across the area. As more areas 

are explored, field sizes equivalent to those found recently may 

be discovered. Discoveries of large fields, similar in size to 

those found early in the discovery history, are likely, but adequate traps may not exist beyond the flanks of the anticlinorium.

Until recently, only structural traps had been explored for 

oil and gas. Continued exploration of structural and perhaps 

combination traps is expected for the next 30 years, and more 

discoveries could be made along the flanks of the Tilrhemt and 

Talemzane-Gefara Arches. Permian-aged reefs containing Silurian-sourced petroleum accumulations may exist in the eastern 

part of this total petroleum system, in Tunisia (Rigo, 1995), but 

many of these reefs have been tested with little or no success (D. 

Boote, oral commun., 1999).

This study estimates that only a very small fraction 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 16 MMBO and 31 

fields; the same values for undiscovered gas fields are 70 BCFG 

and 15 fields. The ranges of number, size, and coproduct-ratio 

estimates for undiscovered fields are given in table 4.

The estimated means of the undiscovered conventional 

petroleum volumes are 1,875 MMBO, 4,887 BCFG, and 269 

MMBNGL (table 5). In addition, the mean of the largest anticipated undiscovered oil field is 550 MMBO and undiscovered gas 

field, 686 BCFG.

The Tanezzuft-Ghadames Total Petroleum 

System (205403)

The Tanezzuft-Ghadames Total Petroleum System is an 

important total petroleum system with respect to known oil and 

gas volumes, containing about 30 percent of the discovered oil 

and 60 percent of the discovered gas in the province. A small 

portion of this total petroleum system extends into the neighboring Illizi, Hamra, and Pelagian Provinces. Although Middle to 
18 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

Upper Devonian-aged mudstone may be the primary source 

rock, the naming convention requires that the oldest source rock, 

Tanezzuft, must be used in the total petroleum system name. An 

events chart (fig. 8) summarizes the timing of sources, reservoirs, seals, trap development, and generation and migration of 

petroleum. Table 1 shows the formation names, ages, and lithology for abbreviations used in the events chart.

Source Rocks

Two major source rocks generated petroleum in the Tanezzuft-Ghadames Total Petroleum System, the Silurian Tanezzuft 

Formation (or lateral equivalents) and Middle to Upper Devonian mudstone (Tissot and others, 1973; Daniels and Emme, 

1995). Based on regional stratigraphic architecture of the Ghadames (Berkine) Basin and geochemical analysis, Daniels and 

Emme (1995) indicated that the Upper Devonian (Frasnian) 

mudstone may be the primary source rock.

In the Ghadames (Berkine) Basin, mean present-day TOC 

content of Silurian source rocks ranges from 0.5 to 2.0 percent 

(individual values as high as 17 percent), and that of Middle to 

Upper Devonian source rocks ranges from 2.0 to 8.0 percent 

(individual values as high as 14 percent) (Daniels and Emme, 

1995; Makhous and others, 1997). Equivalent vitrinite reflectance of Silurian source rocks ranges from 1.1 to 2.0 percent Ro

and Upper Devonian, from 1.1 to 1.3 percent Ro (Daniels and 

Emme, 1995). Source rock maturity is variable across the total 

petroleum system. In the northern part of the total petroleum 

system, Silurian source rocks are presently in the peak to late oil 

generation phase, whereas Middle to Upper Devonian source 

rocks are presently in the early to peak oil generation window 

(Daniels and Emme, 1995). In the central part, Silurian rocks 

are presently in the wet to dry gas generation phase, whereas 

Middle to Upper Devonian source rocks are presently in the late 

oil to early wet gas generation phase (Daniels and Emme, 1995).

Petroleum generation in the Ghadames (Berkine) Basin 

may have taken place in two pulses, the first occurring in the 

Carboniferous before Hercynian deformation and the second 

occurring after Hercynian deformation and the development of 

the Triassic Basin (Daniels and Emme, 1995; Makhous and others, 1997). Peak oil generation from Silurian source rocks began 

in the middle Cretaceous in the northern portion of the total 

petroleum system (Daniels and Emme, 1995). In the central portion, peak oil generation from Silurian source rocks began as 

early as the Carboniferous, was interrupted by the Hercynian 

event, then resumed until Late Jurassic (Daniels and Emme, 

1995). Oil generation from Middle to Upper Devonian source 

rocks peaked in early Tertiary in the northern portion of the total 

petroleum system and peaked in Early Cretaceous in the central 

portion (Daniels and Emme, 1995). Petroleum most likely 

migrated laterally into adjacent or juxtaposed migration conduits 

and reservoirs. Some vertical migration may have occurred 

along faults or fractures in structurally deformed areas (Boote 

and others, 1998).

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 and B). Large portions 

of Paleozoic section were removed by erosion during Hercynian 

deformation, between 380 and 3,000 m of sediments, or more, 

were eroded during Hercynian deformation (Malla and others, 

1997). Paleozoic rocks are thickest to the southeast (approximately 2,300 m) and thin to the west and north over the T-shaped 

anticlinorium. Mesozoic rocks comprise most of the overburden 

and overlie the Paleozoic section above the Hercynian Unconformity throughout the province. Only small sections of Mesozoic 

rocks were removed by erosion. Mesozoic rocks are thickest to 

the north and west and thin to the southeast (fig. 4A and B) 

(Bishop, 1975; Chiarelli, 1978; Boudjema, 1987; Montgomery, 

1993). A thin Cenozoic section is present over part of the area.

Reservoir Rocks

The known major reservoir rocks in the Tanezzuft-Ghadames Total Petroleum System are fluvial to marine sandstone 

of the Cambrian-Ordovician and fluvial sandstone of the Triassic 

(Trias Argilo-Greseux). Cambrian-Ordovician reservoirs 

include the Cambrian Hassi Messaoud Formation, Hassi Leila 

Formation, and Quartzites de Hamra (laterally equivalent to the 

Haouaz Formation) (Petroconsultants, 1996a; van de Weerd and 

Ware, 1994). The Triassic lower clastic unit reservoirs include 

sandstone of the Trias Argilo-Greseux Inferieur (Nezla Formation, Ouled Chebbi Formation, and Ras Hamia Formation) as 

well as sandstone of the Trias Argilo-Greseux Superieur (Gassi 

Touil Formation and Zarzaitine Sandstone), the Kirchaou Sandstone, and the Tartrat Sandstone (Petroconsultants, 1996a).

The marginal marine to marine sandstone of the Upper Silurian Acacus Formation is a predominant reservoir in the eastern 

portion of the Tanezzuft-Ghadames Total Petroleum System 

(Petroconsultants, 1996a). Other reservoir rocks in the Tanezzuft-Ghadames Total Petroleum System include glacial and 

marine sandstone of the Ordovician to Silurian M'Kratta Complex; the paralic to marine Lower Devonian F6 sandstone 

(Tadrart Formation) and Upper Devonian Ouan Kasa Formation; 

and the deltaic and marine Lower Carboniferous Tahara Formation (Petroconsultants, 1996a). Names of some laterally equivalent rock units are shown in figure 5, and known reservoir 

properties are given in table 2.

Seal Rocks

Triassic to Jurassic evaporites, mudstone, and carbonate 

rocks (Saliferous Units, fig. 5) provide a regional top seal. 

Intraformational Paleozoic marine mudstone is the primary seal 

for some reservoirs (Boote and others, 1998).
The Tanezzuft-Ghadames Total Petroleum System (205403) 19

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-Ghadames (205403) Province Name: Trias/Ghadames Basin (2054)

Author(s): Timothy R. Klett Date: 3-23-99

CARB

E O

M

SU

TAG

MR

TS

OK

F6

AC

TZ

MK

HM

HS

EG

AZ

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

Names for abbreviations used in rock unit column are given in table 1. 

Gray boxes indicate secondary or possible occurrences.

Glacial Unconformity

Pan-African Event

Pyrenean Event

Late Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late SilurianEarly Devonian Event

TECTONIC EVENTS

AO
20 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 are 

within anticlines, faulted anticlines, or fault blocks (Echikh, 

1998; Boote and others, 1998; Petroconsultants, 1996a, van de 

Weerd and Ware, 1994). A few accumulations within combination traps are present (Echikh, 1998). 

The typical trapping style is structures directly overlain by 

or capped with Triassic to Jurassic evaporite sequence. Other 

proven or potential traps include combination traps in association with intraformational mudstone or volcanic rocks, if 

present, and incised valley fills associated with the Hercynian 

Unconformity.

The discovered petroleum accumulations in the TanezzuftGhadames Total Petroleum System exist in low-relief structures 

in the central and northeast portions of the total petroleum system and in high-relief structures along the Amguid-Hassi 

Touareg structural axis (fig. 1). Three accumulations along the 

Amguid-Hassi Touareg structural axis are more gas rich than 

others within the total petroleum system (fig. 1). Several small 

fields are producing from Silurian Acacus reservoirs in lowrelief structures in the extreme eastern part of the total petroleum 

system (in Libya and Tunisia) (fig. 2). In the northern part of the 

total petroleum system, along the Talemzane-Gefara Arch, some 

undiscovered accumulations might be present in tilted fault 

blocks that mirror those across the arch in the Tanezzuft-Melrhir 

Total Petroleum System.

Assessment of Undiscovered Petroleum by 

Assessment Unit

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

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

it contained 93 fields. Of these discovered fields, 66 are oil 

fields, 21 are gas fields, and 6 fields are not classified because 

they contain less than 1 MMBOE. Combined, these fields contain 4,538 MMBO, 16,484 BCFG, and 1,011 MMBNGL, as 

known volumes (table 3) (Petroconsultants, 1996a). Minimum 

field sizes of 1 MMBO and 6 BCFG were chosen for this 

assessment unit based on the field-size distribution of discovered fields.

The exploration density as of 1996 was approximately 15 

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

as of 1996 was approximately 32 discoveries per 100 new-field 

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

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

of new-field wildcat wells drilled occurred since the mid-1980’s 

through 1995. Plots showing exploration activity and discovery 

history are presented in Appendix 2.

Exploration activity was not consistent through time: peaks 

occurred in activity from the early 1960’s to the early 1970’s, 

and again in the 1980’s. The sizes of oil and gas fields discovered have generally decreased through time and with respect to 

exploration activity, but some large accumulations are still being 

discovered. Exploration appears to be moderately mature across 

much of the area.

Until recently, only structural traps had been explored 

for oil and gas. Continued exploration of structural and 

combination traps is expected for the next 30 years, and 

many more fields, both oil and gas, could be discovered, 

especially in deeper sections within the center of the Ghadames (Berkine) Basin (Macgregor, 1998). New exploration 

concepts could include the search for both structural and 

stratigraphic traps. Additionally, pinchouts within the Silurian Acacus sandstone have some potential, but seals are 

lacking in much of the total petroleum system due to erosional truncation (Echikh, 1998). Potential for discoveries 

exists in stratigraphic traps, due to the abundance of clastic 

reservoirs and unconformities (Macgregor, 1998) and in possible tilted fault block traps along the Talemzane-Gefara Arch 

(similar to those in the Tanezzuft-Melrhir Total Petroleum 

System).

This study estimates that about one-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 16 MMBO and 73 fields; the 

same values for undiscovered gas fields are 70 BCFG and 38 

fields. The ranges of number, size, and coproduct-ratio estimates for undiscovered fields are given in table 4.

The estimated means of the undiscovered conventional 

petroleum volumes are 4,461 MMBO, 12,035 BCFG, and 908 

MMBNGL (table 5). In addition, the mean size of the largest 

anticipated undiscovered oil and gas fields are 817 MMBO and 

1,014 BCFG, respectively.

Summary

Three “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-Oued Mya, Tanezzuft-Melrhir, and TanezzuftGhadames.

The main source rocks are the Silurian Tanezzuft Formation 

(or lateral equivalents) and Middle to Upper Devonian mudstone. Petroleum generation and migration may have started as 

early as the Carboniferous Period but was halted during the Hercynian deformational event. Peak generation and migration 

occurred from the Cretaceous to the Tertiary. The major reservoir rocks are Cambrian to Ordovician, Silurian, Devonian, Carboniferous, and Upper Triassic sandstone. Triassic to Jurassic 

evaporites, mudstone, carbonate rocks, and volcanic rocks provide a regional top seal for most of the accumulations, while 

Paleozoic marine mudstone locally provides seals. In 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-Oued Mya Total Petroleum 

System are 830 MMBO, 2,341 BCFG, and 110 MMBNGL; volumes in the Tanezzuft-Melrhir Total Petroleum System are 1,875 

MMBO, 4,887 BCFG, and 269 MMBNGL; and volumes in the 

Tanezzuft-Ghadames Total Petroleum System are 4,461 MMBO, 

12,035 BCFG, and 908 MMBNGL. The combined estimated 

means of the undiscovered conventional volumes for these total 
References Cited 21

petroleum systems in the Trias/Ghadames Province are 7,167 

MMBO, 19,262 BCFG, and 1,288 MMBNGL.

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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.

Hammill, M., and Robinson, N.D., 1992, Nearby oil discoveries add interest to licensing rounds in Algerian basins: Oil and Gas Journal, 

November 9, p. 99–101.

Hamouda, A., 1980, Oil and gas potential of Algeria's Ouargla region: Oil 

and Gas Journal, March 17, p. 206–224.

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.

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.

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.

———1994, Ghadames Basin and surrounding areas—Structure, tectonics, geochemistry and field summaries: Petroleum Frontiers, v. 

10, no. 4, 79 p.

Pennwell Publishing Company, 1996, International petroleum encyclopedia: Tulsa, Okla., Pennwell Publishing Company, v. 29, 335 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, Tex., Petroconsultants, Inc. [database available 

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

0619].

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

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

Houston, TX 77274-0619].
22 Total Petroleum Systems of the Trias/Ghadames Province, Algeria, Tunisia, and Libya

Rigo, F., 1995, Overlooked Tunisia reef play may have giant field potential: 

Oil and Gas Journal, v. 93 (January 2, 1995), p. 56–60.

———1996, N. Tunisian Sahara hosts giant Triassic, L. Paleozoic prospects: Oil and Gas Journal, v. 94 (January 15, 1996), p. 52–57.

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.A., 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.

van de Weerd, A.A., and Ware, P.L.G., 1994, A review of the East Algerian 

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

First Break, v. 12, no. 7, p. 363–373.
Table 1. Abbreviations, names, ages, and lithology of formations used in the total petroleum system events chart.

________________________________________________________________________

Code Formation name Age Lithology

________________________________________________________________________

AC Acacus Upper Silurian Sandstone

AO Aouinet Ouenine Middle to Upper Devonian Mudstone

AZ Argiles D'Azzel Middle Ordovician Mudstone

SU Saliferous Units Lower Jurassic Salt and anhydrite

EA Gres D'El Atchane Lower Ordovician Sandstone

EG Argile D'El Gassi Lower Ordovician Mudstone

F6 F6 Sandstone Member Lower Devonian Sandstone

HM Hamra Lower Ordovician Sandstone

HS Hassaouna Cambrian-Ordovician Sandstone

MK M'Kratta Complex Middle to Upper Sandstone and

Ordovician mudstone

MR Mrar Lower Carboniferous Mudstone and

sandstone

OK Ouan Kasa Middle Devonian Mudstone and

sandstone

TAG Trias Argilo-Greseux Upper Triassic Sandstone

TS Tahara (Shatti) Upper Devonian to Sandstone

Lower Carboniferous

TZ Tanezzuft Silurian Mudstone

________________________________________________________________________
Cambrian-Ordovician 2,900 3,312 4,000 11 18 80 145 8 10 17 25 9 9 408 1,000 

205402 Tanezzuft-Melrhir Total Petroleum System

20540201 Tanezzuft-Melrhir Structural/Stratigraphic Assessment Unit

Triassic nd nd nd 1 nd nd nd 1 nd nd nd 1 nd nd nd 

Cambrian-Ordovician nd nd nd 3 nd nd nd 3 nd nd nd 2 nd nd nd 

205403 Tanezzuft-Ghadames Total Petroleum System

20540301 Tanezzuft-Ghadames Structural/Stratigraphic Assessment Unit

Triassic 100 2,461 4,188 49 12 85 365 28 9 20 35 47 25 756 1,400 4

Carboniferous 1,829 2,810 3,400 3 30 30 30 1 20 22 25 3 100 200 250 

Devonian 2,217 3,435 4,000 16 12 95 200 4 15 20 23 4 20 1,039 2,000 

Silurian 1,219 2,729 3,127 33 15 51 163 33 14 19 30 31 50 118 300 3

Cambrian-Ordovician 152 2,860 4,000 10 14 201 759 7 6 9 12 9 0.2 254 1,000 
USGS Code

Number of 

fields Known (discovered) volumes

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

205401 Tanezzuft-Oued Mya Total Petroleum System

20540101 Tanezzuft-Oued Mya Structural/Stratigraphic Assessment Unit

Oil fields 34 10,842 8,970 0

Gas fields 0 0 0 0

Fields < 1 MMBOE 2 1 3 0

All fields 36 10,843 8,973 0

205402 Tanezzuft-Melrhir Total Petroleum System

20540201 Tanezzuft-Melrhir Structural/Stratigraphic Assessment Unit

Oil fields 2 6 0 0

Gas fields 2 0 125 9

Fields < 1 MMBOE 0 0 0 0

All fields 4 6 125 9

205403 Tanezzuft-Ghadames Total Petroleum System

20540301 Tanezzuft-Ghadames Structural/Stratigraphic Assessment Unit

Oil fields 66 4,385 5,327 63

Gas fields 21 151 11,154 948

Fields < 1 MMBOE 6 2 3 0

All fields 93 4,538 16,484 1,011

2054 Total

Oil fields 102 15,233 14,297 63

Gas fields 23 151 11,279 957

Fields < 1 MMBOE 8 2 6 0

All fields 133 15,384 25,576 1,020

Mya Total Petroleum System contains the greatest volume of discovered oil, whereas the TanezzuftGhadames Total Petroleum System contains the greatest volume discovered gas and natural gas liquids. 

[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. Data from 

Petroconsultants (1996a)] 
Oil fields 10 16 362 14 24 4 34 70 35 31 434 868 1,302 867 868 20 40 60 40 

Gas fields 60 100 2,000 85 145 1 10 30 11 2 25 50 75 50 

205402 Tanezzuft-Melrhir Total Petroleum System

20540201 Tanezzuft-Melrhir Structural/Stratigraphic Assessment Unit

Oil fields 1 16 2,488 55 56 3 31 81 34 17 686 1,372 2,058 1,372 1,372 20 40 60 40 

Gas fields 6 70 3,144 136 142 2 15 38 16 9 36 72 108 72 

205403 Tanezzuft-Ghadames Total Petroleum System

20540301 Tanezzuft-Ghadames Structural/Stratigraphic Assessment Unit

Oil fields 1 16 2,488 55 56 14 73 202 80 25 686 1,372 2,058 1,371 1,372 20 40 60 40 

Gas fields 6 70 3,110 136 142 6 38 105 42 14 56 112 168 112 
USGS 

Code MFS Prob. Undiscovered conventional volumes Largest anticipated undiscovered field

(0-1) Oil (MMBO) Gas (BCFG) NGL (MMBNGL) (MMBO or BCFG)

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

205401 Tanezzuft-Oued Mya Total Petroleum System

20540101 Tanezzuft-Oued Mya Structural/Stratigraphic Assessment Unit

Oil fields 10 1.00 292 802 1,450 830 233 673 1,355 720 9 26 58 29 40 96 255 11

Gas fields 60 1.00 269 1,417 3,640 1,621 13 69 192 81 111 318 1,030 40

All fields 292 802 1,450 830 502 2,090 4,994 2,341 21 95 250 110

205402 Tanezzuft-Melrhir Total Petroleum System

20540201 Tanezzuft-Melrhir Structural/Stratigraphic Assessment Unit

Oil fields 1 1.00 348 1,629 4,224 1,875 450 2,175 6,079 2,574 17 84 252 103 96 403 1,557 55

Gas fields 6 1.00 495 2,032 5,060 2,313 33 142 382 166 160 539 1,756 68

All fields 348 1,629 4,224 1,875 945 4,206 11,139 4,887 50 226 635 269

205403 Tanezzuft-Ghadames Total Petroleum System

20540301 Tanezzuft-Ghadames Structural/Stratigraphic Assessment Unit

Oil fields 1 1.00 990 3,993 9,520 4,461 1,274 5,292 13,733 6,110 48 206 576 244 197 679 1,939 81

Gas fields 6 1.00 1,403 5,311 12,469 5,925 148 576 1,480 664 299 865 2,285 1,01

All fields 990 3,993 9,520 4,461 2,677 10,603 26,201 12,035 196 782 2,055 908
Table 5. Continued.

USGS 

Code MFS Prob. Undiscovered conventional volumes Largest anticipated undiscovered field

(0-1) Oil (MMBO) Gas (BCFG) NGL (MMBNGL) (MMBO or BCFG)

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

2054 Total

Oil fields 1,630 6,424 15,194 7,167 1,957 8,140 21,166 9,403 74 316 886 376

Gas fields 2,167 8,759 21,168 9,859 194 786 2,054 911

All fields 1,630 6,424 15,194 7,167 4,125 16,899 42,334 19,262 268 1,102 2,940 1,288
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
• 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-Oued Mya 

Structural/Stratigraphic Assessment Unit.
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

20

40

60

80

100

120

140

160

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

DRILLING-COMPLETION YEAR

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

Unit 20540101

0

2

4

6

8

10

12

14

195419561958196019621964196619681970197219741976197819801982198419861988199019921994

DRILLING-COMPLETION YEAR

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

Unit 20540101

1

10

100

1,000

10,000

0 2 4 6 8 10 12

OIL-FIELD RANK BY SIZE

KNOWN OIL-FIELD SIZE (MMBO)

First third of fields discovered

Second third of fields discovered

Third third of fields discovered
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2

4

6

8

10

12

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.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

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-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

KNOWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

1

10

100

1,000

10,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

KNOWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. KNOWN OIL VOLUME (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. KNOWN OIL VOLUME (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

30

35

40

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. OIL FIELDS (No.)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. OIL FIELDS (No.)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

1,000

2,000

3,000

4,000

5,000

6,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

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-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

1

10

100

1,000

10,000

0 2 4 6 8 10 12

OIL-FIELD RANK BY SIZE

GROWN OIL-FIELD SIZE (MMBO)

First third of fields discovered

Second third of fields discovered

Third third of fields discovered
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

1

2

3

4

5

6

7

8

9

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.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2,000

4,000

6,000

8,000

10,000

12,000

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-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

1

10

100

1,000

10,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

30

35

40

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. OIL FIELDS (No.)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. OIL FIELDS (No.)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 20 40 60 80 100 120 140 160

CUM. NEW-FIELD WILDCAT WELLS (No.)

RESERVOIR DEPTH, OIL FIELDS (m)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

1,000

2,000

3,000

4,000

5,000

6,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Oued Mya Structural/Stratigraphic, Assessment 

Unit 20540101

0

5

10

15

20

25

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.)
Appendix 2. Exploration-activity and discovery-history plots for the Tanezzuft-Ghadames 

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

Unit 20540301

0

50

100

150

200

250

300

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

DRILLING-COMPLETION YEAR

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

Unit 20540301

0

5

10

15

20

25

19561958196019621964196619681970197219741976197819801982198419861988199019921994

DRILLING-COMPLETION YEAR

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

Unit 20540301

1

10

100

1,000

10,000

0 5 10 15 20 25 30

OIL-FIELD RANK BY SIZE

KNOWN OIL-FIELD SIZE (MMBO)

First third of fields discovered

Second third of fields discovered

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

Unit 20540301

0

2

4

6

8

10

12

14

16

18

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.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

500

1,000

1,500

2,000

2,500

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

1

10

100

1,000

10,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

10

20

30

40

50

60

70

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

10

20

30

40

50

60

70

80

90

100

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

NGL/GAS, OIL FIELDS (BNGL/MMCFG)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

5

10

15

20

25

30

35

40

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

1

2

3

4

5

6

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

1

10

100

1,000

10,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

5

10

15

20

25

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

100

200

300

400

500

600

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

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

Unit 20540301

1

10

100

1,000

10,000

0 5 10 15 20 25 30

OIL-FIELD RANK BY SIZE

GROWN OIL-FIELD SIZE (MMBO)

First third of fields discovered

Second third of fields discovered

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

Unit 20540301

0

2

4

6

8

10

12

14

16

18

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.)

Third third of

fields

discovered

Second third

of fields

discovered

First third of

fields

discovered
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

1

10

100

1,000

10,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

GROWN OIL-FIELD SIZE (MMBO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

CUM. GROWN OIL VOLUME (MMBO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

10

20

30

40

50

60

70

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

GAS/OIL, OIL FIELDS (CFG/BO)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

10

20

30

40

50

60

70

80

90

100

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

NGL/GAS, OIL FIELDS (BNGL/MMCFG)
Tanezzuft-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

5

10

15

20

25

30

35

40

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

1

2

3

4

5

6

7

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

1

10

100

1,000

10,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

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-Ghadames Structural/Stratigraphic, Assessment 

Unit 20540301

0

5

10

15

20

25

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

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

Unit 20540301

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 50 100 150 200 250 300

CUM. NEW-FIELD WILDCAT WELLS (No.)

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

Unit 20540301

0

100

200

300

400

500

600

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

MEAN RESERVOIR DEPTH (m)

LIQUIDS/GAS, GAS FIELDS (BL/MMCFG)