Total Petroleum Systems of the Illizi Province, Algeria and Libya—Tanezzuft-Illizi

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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–a/

Any use of trade, product, or rmnames in this publicationis for descriptive purposes only and does not imply

endorsement by the U.S. Government



Contents

Foreword................................................................................................................................................ 1Abstract ................................................................................................................................................. 2Acknowledgments ............................................................................................................................... 2Introduction........................................................................................................................................... 2Province Geology................................................................................................................................. 5

Tectonic History.......................................................................................................................... 5Stratigraphy.................................................................................................................................. 8Petroleum Occurrence .............................................................................................................. 11

Regional Exploration History.............................................................................................................. 11 The Tanezzuft-Illizi Total Petroleum System (205601).................................................................... 11 Source Rocks............................................................................................................................... 11 Overburden Rocks....................................................................................................................... 13

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

Trap Types in Oil and Gas Fields............................................................................................... 13 Assessment of Undiscovered Petroleum by Assessment Unit ........................................... 13Summary................................................................................................................................................ 14References Cited.................................................................................................................................. 14Appendix. Exploration-activity and discovery-history plots for the Tanezzuft-IlliziStructural/Stratigraphic Assessment Unit

Figures

1–3. Map showing approximate locations of: 1. USGS-dened 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............................................................................................. 4 3. Areal extent of assessment units within Illizi Province................................................. 6 4. Stratigraphic cross sections through Illizi and neighboring

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



Foreword

This report was prepared as part of the U.S. Geological Sur-vey World Petroleum Assessment 2000. The primary objectiveof World Petroleum Assessment 2000 is to assess the quantitiesof conventional oil, gas, and natural gas liquids outside the

United States that have the potential to be added to reserves inthe next 30 years. Parts of these assessed volumes reside inundiscovered elds whose sizes exceed the stated minimum-eld-size cutoff value for the assessment unit, which is variablebut must be at least 1 million barrels of oil equivalent. Anotherpart of these assessed volumes occurs as reserve growth of eldsalready discovered. However, the contribution from reservegrowth of discovered elds to resources is not covered for theareas treated in this report.

In order to organize, evaluate, and delineate areas to assess,the Assessment Methodology Team of World Petroleum Assess-ment 2000 developed a hierarchical scheme of geographic andgeologic units. This scheme consists of regions, geologic prov-inces, total petroleum systems, and assessment units. For WorldPetroleum Assessment 2000, regions serve as organizationalunits and geologic provinces are used as prioritization tools.Assessment of undiscovered resources was done at the level ofthe total petroleum system or assessment unit.

The world was divided into 8 regions and 937 geologicprovinces. These provinces have been ranked according to thediscovered known oil and gas volumes (Klett and others, 1997).Then, 76 “priority” provinces (exclusive of the United States andh f th i hi h ki ) d 26 “b ti ” i

The total petroleum system includes all genetically relatedpetroleum that occurs in shows and accumulations (discoveredand undiscovered) generated by a pod or by closely related podsof mature source rock. Total petroleum systems exist within alimited mappable geologic space, together with the essentialmappable geologic elements (source, reservoir, seal, and over-burden rocks). These essential geologic elements control the

fundamental processes of

generation, expulsion, migration,entrapment, and preservation of petroleum within the total petro-leum system.

An assessment unit is a mappable part of a total petroleumsystem in which discovered and undiscovered oil and gas eldsconstitute a single relatively homogeneous population such thatthe methodology of resource assessment based on estimation ofthe number and sizes of undiscovered elds is applicable. Atotal petroleum system might equate to a single assessment unit.

If necessary, a total petroleum system may be subdivided intotwo or more assessment units such that each assessment unit issufciently

homogeneous in terms of geology, exploration con-siderations, and risk to assess individually. Differences in thedistributions of accumulation density, trap styles, reservoirs, andexploration concepts within an assessment unit were recognizedand not

assumed to extend homogeneously across an entireassessment unit.

A numeric code identies each region, province, totalpetroleum system, and assessment unit. The criteria for assign-ing codes are uniform throughout the project and throughout allpublications of the project. The numeric codes used in this studyare:

Total PetroleumSystems of the Illizi Province, Algeria andLibya—Tanezzuft-Illizi

T.R. Klett

By



activity within the assessment unit. All four probabilities, orrisking elements, are similar in application and address thequestion of whether at least one undiscovered eld of minimumsize has the potential to be added to reserves in the next 30 yearssomewhere in the assessment unit. Each risking element thusapplies to the entire assessment unit and does not equate to thepercentage of the assessment unit that might be unfavorable interms of charge, rocks, timing, or access.

Estimated total recoverable oil and gas volumes (cumula-tive production plus remaining reserves, called “known” vol-umes hereafter) quoted in this report are derived fromPetroconsultants, Inc., 1996 Petroleum Exploration and Produc-tion database (Petroconsultants, 1996a). To address the fact thatincreases in reported known volumes through time are com-monly observed, the U.S. Geological Survey (Schmoker andCrovelli, 1998) and the Minerals Management Service (Lore andothers, 1996) created a set of analytical “growth” functions thatare used to estimate future reserve growth (called “grown” vol-umes hereafter). The set of functions was originally created forgeologic regions of the United States, but it is assumed that theseregions can serve as analogs for the world. This study appliedthe Federal offshore Gulf of Mexico growth function (developedby the U.S. Minerals Management Service) to known oil and gasvolumes, which in turn were plotted to aid in estimating undis-covered petroleum volumes. These estimates of undiscoveredpetroleum volumes therefore take into account reserve growth ofelds yet to be discovered.

Estimates of the minimum, median, and maximum number,sizes, and coproduct ratios of undiscovered elds were madebased on geologic knowledge of the assessment unit, explorationand discovery history, analogs, and, if available, prospect maps.Probabilistic distributions were applied to these estimates andcombined by Monte Carlo simulation to calculate undiscoveredresources.

Illustrations in this report that show boundaries of the totalpetroleum systems, assessment units, and extent of source rockswere compiled using geographic information system (GIS) soft-

System are 2,814 million barrels of oil (MMBO), 27,785 billion

cubic feet of gas (BCFG), and 873 million barrels of natural gasliquids (MMBNGL).

Acknowledgments

I thank Philip Farfan and Francois Gauthier of AnadarkoAlgeria Corporation, Rob Hoar and Randie Grantham of OryxEnergy Company, and David Boote and Marc Traut of Occiden-tal Oil and Gas Corporation for their suggestions, which greatlyimproved the text. I also thank Katharine Varnes, Gordon Dol-ton, and Gregory Ulmishek for their editorial review.

Introduction

Undiscovered conventional oil and gas resources wereassessed within a total petroleum system of the Illizi Province(2056) as part of the U.S. Geological Survey (USGS) WorldPetroleum Assessment 2000. This study documents the geology,undiscovered oil and gas volumes, exploration activity, and dis-covery history of the Illizi Province.

The Illizi Province is a geologic province delineated by theUSGS; it is located in eastern Algeria and extreme westernLibya (g. 1). The province encompasses approximately200,000 km

2

(square kilometers) and coincides with the IlliziBasin. Neighboring geologic provinces, delineated by theUSGS, are the Trias/Ghadames Basin (2054), Hamra Basin(2047), Tihemboka Uplift (2057), Hoggar (7041), and GrandErg/Ahnet Basin (2058).

More than one total petroleum system may exist within theIllizi Basin (Boote and others, 1998). Data available for thisstudy are insufcient to adequately determine the relative contri-bution of each system to individual accumulations and thereforepreclude further subdivision. Consequently only one “compos-ite” total petroleum system is described in this report which



A p p r o x i m a t e l i m i t o f s a l t

Saharan Flexure

Oued MyaBasin

T i l r h e m t A r c h

H a s s i A t s h a n A r c h

Gargaf Arch

TriassicBasin

IlliziBasin

I d j e r a n e - M ' Z a b S

t r u c t u r a l A

x i s

A

z z e n e

H i g h

A l l a l H i g h

Ougarta Range

Antiatlas Range

Hoggar Massif

AhnetBasin

TimimounBasin

Bechar/ AbadlaBasins

MouydirBasin

SbaaBasin

ALGERIA

LIBYA

TUNISIA

MOROCCO

Grand Erg/AhnetProvince 2058

Trias/GhadamesProvince 2054

Illizi

Province 2056

PelagianProvince 2048

PelagianBasin

Country boundaryProvince boundary

Djoua Saddle

HamraBasin

Oued NamousDome

MaharezDome

EdjelehAnticline

T i h

em

b ok

aA r c h

A m

g u i d - H a s s i T o u a r e g

S t r u c t u r a l A x i s

Atlas Mountains

Benoud Trough

f

Mediterranean Sea

Mediterranean Sea

MelrhirBasin

Ghadames(Berkine)

Basin

Talemzane - Gefara Arch

A p p r o x i m

a t e

l i m i t o f s

a l t

Ain RichHigh

Z o u s

f a n a

S a

d d l e

B e n

i A b b e s

S a

d d l e

5oW 0o 5oE 10 oE 15 oE

25 oN

30 oN

35 oN

Mou y d irS truc tura l Terrace



A

A' B'

B

Tanezzuft-TimimounTPS

Tanezzuft-AhnetTPS

Tanezzuft-SbaaTPS

Tanezzuft-MelrhirTPS

Tanezzuft-OuedMya TPS

Tanezzuft-MouydirTPS

Tanezzuft-GhadamesTPS

Tanezzuft-IlliziTPS

Country boundaryTotal petroleum system boundary

ALGERIA

LIBYA

TUNISIA

MOROCCO

T-Shaped AnticlinoriumTanezzuft-Benoud

TPS

Tanezzuft-Bechar/Abadla

TPS

5oW 0o 5oE 10 oE 15 oE

25 oN

30 oN

35 oN



Province contains the giant Tin Fouye-Tabankort and Zarza-itine oil elds.

Province Geology

The Tanezzuft-Illizi Province coincides with the Illizi Basinand is bounded on the north by the Ghadames (Berkine) Basin,on the east by the Tihemboka Arch, on the south by the HoggarMassif, and on the west by the Amguid-Hassi Touareg structuralaxis.

The south-to-north plunging Tihemboka Arch separates theIllizi Basin from the Hamra Basin to the east (g. 1) and islocated near the Algerian-Libyan border. Along the westernboundary, the Amguid-Hassi Touareg structural axis separatesthe Illizi Basin from the Mouydir Basin of the Grand Erg/AhnetProvince.

The boundary between the Illizi and Ghadames (Berkine)Basins is dened by a break or hinge line in the slope of thebasement rocks. This hinge line was responsible for separatingmuch of the petroleum generation, migration, and accumulationbetween the two basins (g. 4

A

). The Illizi Basin is presentlyperched on a basement high and is not as deep as the neighbor-ing Ghadames (Berkine) and Hamra Basins. The Illizi-Gha-dames (Berkine) Basin boundary represents the approximateextent of Triassic and Jurassic evaporites that were depositedwithin the Mesozoic-aged Triassic Basin.

Tectonic History

The regional stratigraphy is continuous across North Africa,but petroleum generation, migration, and entrapment withineach total petroleum system have been controlled by the tectonichistory of individual basins. Deformational events in the region,most of them minor, are recorded by unconformities reectingbasin tilting uplift and erosion of intracratonic structural axes at

earlier structures (Peterson, 1985). Later, in the Middle to LateDevonian, the initial collision of Laurasia and Gondwana beganresulting in erosion and further modication of preexisting struc-tures (Boote and others, 1998).

Repeated minor uplift of the Tihemboka Arch and Amguid-Hassi Touareg structural axis occurred in the Late Silurianthrough the Devonian, with resulting local erosion and gradualdevelopment of the Illizi as a discrete basin (Aliev and others,1971; van de Weerd and Ware, 1994; Boote and others, 1998).

The Hercynian event marks the collision between Laurasiaand Gondwana and caused regional uplift, folding, and erosion(Aliev and others, 1971; Boote and others, 1998). Paleozoicbasins that were delineated by earlier tectonic events were modi-ed, resulting in the development of several intracratonic sagand foreland basins (Aliev and others, 1971; van de Weerd andWare, 1994; Boote and others, 1998).

Several transgressive-regressive cycles occurrred through-out the Paleozoic. Two major ooding events, one in the Sil-urian and the other in the Late Devonian, were responsible forthe deposition of source rocks (Aliev and others, 1971; Boud-

jema, 1987). Many of the prograding uvial, estuarine, deltaic,and shallow marine sands that were deposited during thesecycles are now reservoirs (Aliev and others, 1971).

Some petroleum may have been generated during the Car-boniferous Period within the Paleozoic depocenter southwest ofthe Illizi Basin, but uplift caused petroleum generation to cease.Subsequent erosion probably removed or dispersed most petro-leum that had accumulated (Tissot and others, 1973).

During the early Mesozoic, extensional movements causedby the opening of the Tethys and Atlantic oceans developed acratonic sag basin called the Triassic Basin. The depocenter wassuperimposed on some of the Paleozoic basins (Aliev and others,1971; Boudjema, 1987). Triassic uvial sands followed by athick Triassic to Jurassic evaporite section were deposited withinthe sag basin (Aliev and others, 1971; Boudjema, 1987). Sand-stones resulting from the uvial deposition are major reservoirs,and the evaporites provide a regional seal for these uvial and



LIBYA

Illizi Basin

Tanezzuft-IlliziStructural/Stratigraphic

ALGERIA

10 oE8oE6oE

28oN

30oN

Silurian absent



0 100 KILOMETERS

NORTH SOUTH

GHADAMES (BERKINE)BASIN

ILLIZI BASIN

0

1

2

3

4

5

6

7KM

TERTIARY

UPPER CRETACEOUS

LOWER CRETACEOUS

JURASSIC

UPPER TRIASSIC

ORDOVICIAN

BASEMENT

CAMBRIAN

SILURIAN

DEVONIAN

CARBONIFEROUS

SILURIAN

DEVONIAN

A

SALIFEROUS UNITS

Tanezzuft-GhadamesTPS (205403)

Tanezzuft-IlliziTPS (205601) A'

TALEMZANE-GEFARAARCH

B-B'

Figure 4. Stratigraphic cross sections through Trias/Ghadames and Illizi Provinces. A, North-to-south stratigraphic cross sectionthrough the Ghadames (Berkine) and Illizi Basins (modified from van de Weerd and Ware, 1994, after Aliev and others, 1971).

Regional seal

Sections containing source rocks

Sections containing reservoir rocks

Fault

Unconformity

EXPLANATION

A

WEST EAST

B

TERTIARY

AHNETBASIN

IDJERANE-M'ZABSTRUCTURAL AXIS

AMGUID-HASSI TOUAREGSTRUCTURAL AXIS

TIHEMBOKAARCH

ILLIZIBASIN

MOUYDIRBASIN

B' Tanezzuft-MouydirTPS (205804)

Tanezzuft-IlliziTPS (205601)

A-A'



Petroleum was generated within the Illizi Basin from theMiddle to Late Jurassic to early Tertiary (Daniels and Emme,1995). Some spillage or secondary migration occurred (Booteand others, 1998; van de Weerd and Ware, 1994). Many of thestructural traps were formed by vertical movements of the base-ment during Mesozoic and Tertiary deformational events(Echikh, 1998).

Stratigraphy

The regional stratigraphy of lower Paleozoic sections isgenerally continuous, but the Devonian and overlying sectionsshow more localized depositional systems. Stratigraphicnomenclature varies among the Saharan basins and countries.This study primarily uses nomenclature given in Boudjema

(1987), Montgomery (1993), and Echikh (1998). Columnar sec-tions, stratigraphic nomenclature, and correlations are shown ingure 5.

Principal source rocks are the Silurian Tanezzuft Formationand Middle to Upper Devonian mudstone (Givetian to Famen-nian) (Tissot and others, 1973; Daniels and Emme, 1995). Otherminor or relatively unimportant source rocks are also present butcontributed signi cantly less petroleum than did the Silurian orMiddle to Upper Devonian mudstone (Daniels and Emme, 1995;

Boote and others, 1998). Reservoir rocks include sandstone ofCambrian-Ordovician, Silurian, Devonian, and Carboniferousage. Intraformational Paleozoic marine mudstone provides theprimary seals.

During the late Precambrian and Early Cambrian, erosionof a preexisting craton to the south occurred due to uplift duringthe Pan African deformational event. Eroded sediments weredeposited northward as alluvial and uvial deposits and make upthe thick Cambrian sandstone of the Hassi Leila Formation. TheHassi Leila Formation and its lateral equivalents, the Hassaounaand Hassi Messaoud Formations, are major oil and gas reser-voirs (Petroconsultants, 1996a; van de Weerd and Ware, 1994).

The Lower Ordovician In Kraf Formation unconformably

kerogen (Daniels and Emme, 1995; Makhous and others, 1997).The present-day total organic carbon (TOC) content ranges fromless than 2 to 9 percent across the Illizi Basin, but may bereduced by as much as one-half due to increased thermal matu-rity (Daniels and Emme, 1995). The TOC content is greatest atthe base of the section (Daniels and Emme, 1995). The thick-ness, richness, and kerogen type of this source rock are region-ally variable and dependent on paleogeography (Daniels andEmme, 1995). The thickness of the Tanezzuft Formation, beforeHercynian erosion, ranged from about 200 m to greater than 500m (Boote and others, 1998).

The Tanezzuft Formation grades upward into sandstone andmudstone of the Silurian Zone de Passage. These sedimentswere deposited in marine to marginal marine environments andare laterally equivalent to the Acacus sandstone.

Devonian rocks unconformably overlie the Upper Siluriansediments. Devonian rocks consist of interbedded marine sand-stone and mudstone. Sandstone members within the Devoniansection are each given a code, F2 to F6 with F6 being the oldestand F2 the youngest ( g. 5). These sandstone members are prin-cipal oil and gas reservoirs in the Illizi Province.

Middle to Upper Devonian mudstone is another majorsource rock, particularly the Frasnian-aged mudstone, which isthe richest in this interval (Daniels and Emme, 1995). This mud-stone, like the Silurian Tanezzuft Formation, was deposited dur-ing a major regional ooding event and contains mostlysapropelic and mixed (type I and II) kerogen (Daniels andEmme, 1995; Makhous and others, 1997). Distribution of rich-ness and kerogen type were presumably controlled by paleo-geography. The present-day TOC content generally ranges fromabout 2 to 4 percent but can reach 7 percent (Daniels and Emme,1995). Thickness of Middle to Upper Devonian mudstoneranges from about 200 m to more than 400 m near the HoggarMassif (Daniels and Emme, 1995).

The Lower to lower Middle Carboniferous rocks consist ofcycles of limestone or mudstone, siltstone, sandstone, and con-glomerate representing deltaic and shallow marine deposition



S i l u r i a n

D e v o n

i a n

C a r b o n

i f e r o u s

S y s

t e m

Stage

Stephanian

Westphalian

Namurian

Visean

Tournaisian

Famen. -FrasnianGivetian -

Eifelian

EmsianSiegenian -Gedinnian

Cardocian

Llandeilian -Llanvirnian

A igi

Triassic Basin(Boudjema,

1987)

Ghadames(Berkine) andHamra Basins(Montgomery,

1994; Echikh, 1998)

Tiguentourine

El Adeb LaracheDembaba

Assed JeffarOubarakat

Assekaifaf

IssendjelMrar

Tahara (Shatti)Gara Mas Melouki

Tin Meras Aouinet Ouenine

Ouan KasaOrsine

Hassi Tabankort Tadrart

Acacus

Oued Imirhou Tanezzuft

Gres de RemadaArgile Microcgl.

Memouniat

Melez Chograne

Gres d'Oued Saret

Argiles d'Azzel

G d O gl

Illizi Basin(van de Weerd

and Ware,1994)

"Argileux"

Gara Louki

Edjeleh

Generallithology

(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

SandstoneMudstone Frasnian Unconformity SandstoneMudstone and limestoneMudstone and sandstone

Sandstone

Late Silurian-Early Devonian Unconformity Sandstone and mudstone

Black mudstone with graptolites

SandstoneMicroconglomeratic mudstone Glacial Unconformity

Limestone, sandstone, and mudstone

Silty black mudstone

S d t

F6

F4-5

F3

F2

A

B

C

D

E

F

a C o m p

l e x

(Sbaa)

Zone de Passage

Strunian

Bir Tlacsin





into marine carbonate rocks forming a north-facing sedimentarywedge. The Cenozoic section is represented by thin, discontinu-ous Miocene-Pliocene nonmarine rocks and Quaternarysediments.

PetroleumOccurrence

Most of the oil and gas elds found by the end of 1995 inthe Illizi Province are located in the north-central part of theIllizi Basin and along the Tihemboka Arch, near the TriassicBasin where Mesozoic generation and migration occurred.Most of these accumulations are within low-relief, commonlyfaulted anticlines (Boote and others, 1998; Petroconsultants,1996a). The number of accumulations in the southern and west-

ern portions of the province had been destroyed by uplift, inac-tive generation, erosion of reservoir and seal rocks, and waterushing during and following Hercynian deformation (Booteand others, 1998; Macgregor, 1998). There is a lower potentialfor new discoveries in these areas compared to the northern andeastern portions of the Illizi Basin.

Regional Exploration History

Exploration activity in Algeria uctuated through time dueto its war for independence from 1954 to 1962, nationalizationof the oil industry from 1963 to 1971, and political and eco-nomic problems into the 1980 ’s (Traut and others, 1998; Mont-gomery, 1994). Libya also experienced uctuations anddiscontinuities. Between 1963 and late 1980 ’s, Algeria had leg-islation regarding concession contracts and royalties that dis-couraged exploration by foreign companies (Montgomery,

1994). Since the late 1980 ’s, however, Algeria revised its legis-lation, encouraging foreign companies to explore and developoil and gas resources (Davies and Bel Haiza, 1990;SONATRACH, c. 1992; Montgomery, 1994; Traut and others,

coast (Traut and others, 1998; Pennwell, 1996), and anotherpipeline is planned to connect the Libyan portion of the Trias/ Ghadames Province to the coast (Arab Petroleum ResearchCenter, 1996).

The Tanezzuft-Illizi Total PetroleumSystem(205601)

The Tanezzuft-Illizi Total Petroleum System is coincidentwith most of the Illizi Basin and Province. Paleozoic rocks,including the major source rocks, crop out along the HoggarMassif ( gs. 2 and 3). An events chart ( g. 6) summarizes thetiming of sources, reservoirs, seals, trap development, and gener-

ation and migration of petroleum. Table 1 shows the formationnames, ages, and lithology for abbreviations used in the eventschart.

Source Rocks

The principal source rocks in the Tanezzuft-Illizi TotalPetroleum System are the Silurian Tanezzuft Formation and

Middle to Upper Devonian mudstone (Tissot and others, 1973;Daniels and Emme, 1995). In the Illizi Basin, the present-dayTOC content of the Silurian Tanezzuft source rock typicallyranges from 0.5 to 8 percent, but can be as much as 16 percent(Daniels and Emme, 1995; Makhous and others, 1997). Middleto Upper Devonian source rocks typically contain from 2 to 8percent TOC (Daniels and Emme, 1995; Makhous and others,1997). Equivalent vitrinite re ectance of Silurian source rocksranges from 1.1 to 1.75 percent (Daniels and Emme, 1995) and

the Middle to Upper Devonian, 1.1 to 1.3 percent R

o

(Danielsand Emme, 1995). In the north-central, central, and southeasternportions of the total petroleum system, Silurian and Middle toUpper Devonian source rocks are presently in the peak to late oil



P R E S E R V A T I O N

C R I T I C A L M O M E N T

G E N E R A T I O

N -

T R A P F O R M A T I O N

O V E R B U R D E N

R O C K

R E S E R V O I R

R O C K

S E A L R O C K

S O U R C E R

O C K

R O C K U N I T

P E T R O L E U M

S Y S T E M

E V E N T S

G E O L O G I C

T I M E

S C A L E

C E N

.

M E S O Z O I C

T E R T

T R

L .

E .

E .

L .

L .

E .

M .

L .

L .

L .

E .

E .

M .

L .

J U R

C R E T

A C C U M U L A T I O N

M I G R A T

I O N -

E O Z O I C

IL D E V

P

0

1 0 0

2 0 0

3 0 0

4 0 0

1 5 0

2 5 0

3 5 0

5 0

T P S N a m e :

T a n e z z u

f t - I l l i z i ( 2 0 5 6 0 1 )

s i n ( 2 0 5 6 )

le t t

D a

t e :

1 1 - 1

5 - 9

8

C A R B

E

O M

F4-6

F3

F2

A, B

D

Pyrenean EventLate Cretaceous Event

Austrian Event

Hercynian Event

Frasnian Event

Late Silurian-

TECTONIC EVENTS

AO



from Silurian source rocks in the central and southeastern por-tions of the total petroleum system peaked during the middleCretaceous, whereas in the northern and eastern portions, gener-ation probably peaked during the Middle to Late Jurassic(Daniels and Emme, 1995). Oil generation from Middle toUpper Devonian source rocks peaked during the Eocene in thecentral portion of the total petroleum system and Early to LateCretaceous in the northern and eastern portions (Daniels andEmme, 1995). Petroleum most likely migrated laterally intoadjacent or juxtaposed migration conduits and reservoirs. Somevertical migration occurred along faults or fractures in structur-ally deformed areas (Boote and others, 1998).

Overburden Rocks

Overburden rocks are variable across the area mainly due tonondeposition and erosion during the Hercynian, Austrian, andPyrenean deformational events ( g. 4

A

and B

). Carboniferousand Mesozoic rocks comprise most of the overburden for theTanezzuft-Illizi Total Petroleum System. Large portions of Pale-ozoic section were removed by erosion during Hercynian defor-mation. Mesozoic rocks thin southward as a result of bothoriginal deposition and Tertiary uplift and unroo ng in the south.

As a result, Paleozoic rocks are thickest in the center of the basin(approximately 2,500 m, while the Mesozoic is thickest to thenorth and west ( g. 4

A

and B

) (Bishop, 1975; Chiarelli, 1978;Boudjema, 1987; Montgomery, 1993; D. Boote, oral commun.,1999). A thin Cenozoic section is present over the northern partof the total petroleum system.

Reservoir Rocks

The primary known reservoir rocks in the Tanezzuft-IlliziTotal Petroleum System are Devonian sandstone. Devonian res-ervoirs include paralic to marine sandstone of the F2, F3, F4, F5,and F6 members (Petroconsultants, 1996a). Other known reser-

Trap Types in Oil and Gas Fields

Most of the accumulations discovered prior to 1996 arewithin anticlines and faulted anticlines (Echikh, 1998; Boote andothers, 1998; Petroconsultants, 1996a, van de Weerd and Ware,1994). Accumulations within combination traps are present inthe Illizi Basin. These are generally unconformity-related reser-voir pinchouts across Hercynian or Austrian structures (Echikh,1998). Hydrodynamic traps may also be present but are notcommon (Echikh, 1998; Chiarelli, 1978; Aliev and others,1971). Accumulations within one of the largest oil elds of theIllizi Basin, Tin Fouye-Tabankort, are presumed hydrodynami-cally trapped (Echikh, 1998; Alem and others, 1998).

Assessment of Undiscovered PetroleumbyAssessment Unit

One assessment unit was identi ed for the Tanezzuft-IlliziTotal Petroleum System, called Tanezzuft-Illizi Structural/Strati-graphic Assessment Unit ( g. 3). As of 1996, it contained 102elds. Of these discovered elds, 51 are oil elds, 38 are gaselds, and 13 elds are not classi ed because they contain lessthan 1 million barrels of oil equivalent (MMBOE) (based onUSGS oil and gas eld de nitions). Combined, these elds con-tain 3,670 MMBO, 45,061 BCFG, and 898 MMBNGL, asknown volumes (table 3) (Petroconsultants, 1996a). Minimumeld sizes of 10 MMBO or 60 BCFG were chosen for thisassessment unit based on the eld-size distribution of discoveredelds.

The exploration density as of 1996 was 16 new- eld wild-cat wells per 10,000 km

2

. The overall success rate as of 1996was 32 discoveries per 100 new- eld wildcat wells (or about onediscovery per three new- eld wildcat wells). The success rate interms of discoveries per number of new- eld wildcat wellsdrilled remained relatively constant through time. Plots showingexploration activity and discovery history are presented in the



size and number of undiscovered oil elds are 25 MMBO and67 elds; the same values for undiscovered gas elds are 200BCFG and 45 elds. The ranges of number, size, and coprod-uct-ratio estimates for undiscovered elds are given in table 4.

The estimated means of the undiscovered conventionalpetroleum volumes are 2,814 MMBO, 27,785 BCFG, and 873MMBNGL (table 5). In addition, the mean largest anticipatedundiscovered oil and gas elds are 222 MMBO and 1,842 BCFG,respectively.

Summary

One total petroleum system and a corresponding assessment

unit were identi ed, both coinciding with the Illizi Basin. Thistotal petroleum system is called the Tanezzuft-Illizi.

The primary source rocks are the Silurian Tanezzuft F orma-tion and Middle to Upper Devonian mudstone. In the southernand western portions, the source rocks reached peak generativephases during the Carboniferous. Elsewhere, peak oil generationoccurred from the Middle to Late Jurassic to the Eocene. Theprimary reservoir rocks include Cambrian-Ordovician, Silurian,Devonian, and Carboniferous sandstone. Intraformational Paleo-

zoic marine mudstone is the primary seal. Most of the knownaccumulations are within anticlines and faulted anticlines.

The estimated means of the undiscovered conventionalpetroleum volumes in the Tanezzuft-Illizi Total Petroleum Sys-tem are 2,814 MMBO, 27,785 BCFG, and 873 MMBNGL.

References Cited

Alem, N., Assassi, S., Benhebouche, S., and Kadi, B., 1998, Controls onhydrocarbon occurrence and productivity in the F6 reservoir, TinFouyé-Tabankort area, NW Illizi Basin, in

Macgregor, D.S., Moody,R TJ andClark-Lowes D D eds PetroleumgeologyofNorthAfri-

Burollet, P.F., Mugniot, J .M., and Sweeney, P., 1978, The geology of thePelagian block: The margins and basins off southern Tunisia and

Tripolitania, in

Nairn, A.E.M., Kanes, W.H., and Stehli, F. G., eds., Theocean basins and margins: New York, Plenum Press, v. 4B, p. 331–359.

Chaouchi, R., Malla, M.S., and Kechou, F., 1998, Sedimentological evolu-

tion of the Givetian-Eifelian (F3) sand bar of the West Alrar field, IlliziBasin, Algeria, in

Macgregor, D.S., Moody, R.T.J ., and Clark-Lowes,D.D., eds., Petroleum geology of North Africa: Geological Society,London, Special Publication 132, p. 187–200.

Chiarelli, A., 1978, Hydrodynamic framework of Eastern Algerian Sahara- Influence on hydrocarbon occurrence: American Association ofPetroleum Geologists Bulletin, v. 62, no. 4, p. 667–685.

Claret, J ., and Tempere, C., 1967, Une nouvelle region productrice auSahara Algerien; l’anticlinorium d'Hassi Touareg: Proceedings ofthe Seventh World Petroleum Congress, v. 2, Origin of oil, geology

and geophysics, p. 81–100.Daniels, R.P., and Emme, J .J ., 1995, Petroleum system model, eastern

Algeria, from source rock to accumulation; when, where, and how?:Proceedings of the Seminar on Source Rocks and HydrocarbonHabitat in Tunisia; Entreprise Tunisienne d’Activités PetrolieresMemoir 9, p. 101–124.

Davies, W.C., and Bel Haiza, A., 1990, Sweeter E and P terms, CretaceousAbiod chalk oil play lead to busier exploration in Tunisia: Oil and Gas

J ournal, December 10, p. 50–53.Echikh, K., 1998, Geology and hydrocarbon occurrences in the Ghadames

Basin, Algeria, Tunisia, and Libya, in

Macgregor, D.S., Moody, R.T.J .,and Clark-Lowes, D.D., eds., Petroleum geology of North Africa:Geological Society, London, Special Publication 132, p. 109–129.

Guiraud, R., 1998, Mesozoic rifting and basin inversion along the northernAfrican Tethyan margin—An overview, in

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

Klett, T.R., Ahlbrandt, T.S., Schmoker, J .W., and Dolton, G.L., 1997, Rank-ing of the world’s oil and gas provinces by known petroleum vol-umes: 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., andRoss, K.M., 1996, Summary of the 1995 assessment of conventionallyrecoverable hydrocarbon resources of the Gulf of Mexico and Atlan-ticOuterContinental Shelf: MineralsManagement ServiceOCS



———1994, Ghadames Basin and surrounding areas; Structure, tecton-ics, geochemistry and field summaries: Petroleum Frontiers, v. 10,no. 4, 79 p.

Pennwell Publishing Company, 1996, International petroleum encyclope-dia: 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 andgeologic provinces of Africa: U.S. Geological Survey Open-FileReport 97-470A, CD-ROM.

Peterson, J .A., 1985, Geology and petroleum resources of north-centraland northeastern Africa: U.S. Geological Survey Open-File Report85-709, 54 p.

Petroconsultants, 1996a, Petroleum exploration and production data-base: Houston, Tex., Petroconsultants, Inc. [database availablefrom 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].

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

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

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

Origin and migration of hydrocarbons in the eastern Sahara (Alge-ria): 6th International Meeting of Organic Geochemistry, reprinted inDemaison, G., and Murris, R.J ., eds., Petroleum geochemistry andbasin evaluation, American Association of Petroleum GeologistsMemoir 25, p. 315–334.

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

Macgregor, D.S., Moody, R.T.J ., and Clark-Lowes, D.D., eds., Petro-leum geology of North Africa: Geological Society, London, SpecialPublication 132, p. 69–78.

van de Weerd, A.A., and Ware, P.L.G., 1994, A review of the East AlgerianSahara 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 petroleumsystem events chart.________________________________________________________________________

Code Formation name Age Lithology________________________________________________________________________

A, B A and B Sandstone Lower Carboniferous SandstoneMembers

AO Aouinet Ouenine Middle to Upper Devonian Mudstone

D D Sandstone Member Lower Carboniferous Sandstone

ED Edjeleh Middle Ordovician Sandstone

F2 F2 Sandstone Member Upper Devonian Sandstone

F3 F3 Sandstone Member Middle Devonian Sandstone

F4-6 F4 to F6 Sandstone Lower Devonian Sandstone

Members

GL Gara Louki Upper Ordovician to Sandstone andLower Silurian mudstone

HM Hamra Lower Ordovician Sandstone

HL Hassi Leila Cambrian-Ordovician Sandstone

TZ Tanezzuft Silurian Mudstone________________________________________________________________________



Table 2. Reservoir properties of discovered accumulations for the Tanezzuft-Illizi Structural/Stratigraphic Assessment Unit through 1995. [nd,represents either no data or insufficient data. Data from Petroconsultants (1996a)]

USGS Code Depth Gross thickness Porosity Permeability

(meters) (meters) (percent) (millidarcies)

Minimum Mean Max imum N u mb er Min imum Mean Max imum N u mb er Min imu m Mean Max imum N u mb er Min imu m Mean Max imum N umber

2 05 60 1 Tanezzuft-Illizi Total Petroleum System20560101 Tanezzuft-Illizi Structural/Stratigraphic Assessment Unit

Carboniferous 243 533 975 10 11 41 107 9 10 22 25 8 30 420 1,150 7Devonian 152 1,522 2,955 41 4 43 396 91 11 21 30 38 2 892 7,000 24

Silurian 200 800 1,399 2 16 16 16 1 4 4 4 1 nd nd nd 0Cambrian-Ordovician 453 1,817 3,100 120 7 55 176 28 4 9 15 103 10 552 800 102





USGSCode Size of accumulations Number of accumulations Gas-to-oil ratio NGL-to-gas ratio

(MMBO or BCFG) (CFG/BO) (BNGL/MMCFG)

Minimum Median Maximum Mean Shifted mean Minimum Median Maximum Mean Mode Minimum Median Maximum Mean Mode Minimum Median Maximum Mean Mode

205601 Tanezzuft-Illizi Total Petroleum System20560101 Tanezzuft-Illizi Structural/Stratigraphic Assessment Unit

Oil fields 10 25 500 28 38 10 67 200 75 14 2,350 4,700 7,050 4,705 4,700 11 22 33 22 22Gas fields 60 200 4,800 263 323 8 45 84 45 44 20 40 60 40 40

Table 4. Estimated sizes, number, and coproduct ratios of undiscovered oil and gas fields for the Tanezzuft-Illizi Structural/Stratigraphic Assessment Unit. [MMB O, million barrels of oil; BCFG, billioncubic feet of gas; CFG/BO, cubic feet of gas per barrel oil, not calculated for gas fields; BNGL/M MCFG or BL/MMCFG, barrels of natural gas liquids or barrels of total liquids per million cubic feet ofgas. BNGL/M MCFG was calculated for USGS-defined oil fields whereas BL/MM CFG was calc ulated for USGS-defined gas fields. Shifted mean, the mean size of the accumulation within alognormal distribution of field sizes for which the origin is the selected minimum field size]



USGSCode 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

205601 Tanezzuft-Illizi Total Petroleum System

20560101 Tanezzuft-Illizi Structural/Stratigraphic Assessment UnitOil fields 10 1.00 601 2,520 6,000 2,814 2,655 11,444 29,734 13,235 55 244 685 291 86 205 419 222

Gas fields 60 1.00 5,809 14,241 24,286 14,550 213 551 1,055 582 753 1,633 3,696 1,842

All fields 601 2,520 6,000 2,814 8,464 25,685 54,020 27,785 269 795 1,740 873

2056 To tal

Oil fields 601 2,520 6,000 2,814 2,655 11,444 29,734 13,235 55 244 685 291

Gas fields 5,809 14,241 24,286 14,550 213 551 1,055 582

All fields 601 2,520 6,000 2,814 8,464 25,685 54,020 2 7,785 269 795 1,740 873

Table 5. Estimated undiscovered conventional oil, gas, and natural gas liquids volumes for oil and gas fields for the Tanezzuft-Illizi Structural/Stratigraphic Assessment Unit.[MM BO, million barrels of oil; BCFG, billion cubic feet of gas; NGL, natural gas liquids; MMBNGL, million barrels of natural gas liquids. Volumes of undiscovered NGL werecalculated for oil fields whereas volumes of total liquids (oil plus NGL) were calculated for USGS-defined gas fields. Largest anticipated undiscovered field is in units of MM BO

for oil fields and BCFG for gas fields. Results shown are estimates that are fully risked with respect to geology and accessibility. Undiscovered volumes in fields smaller thanthe selected minimum field size are excluded from the assessment. M eans can be summed, but fractiles (F95, F50, and F5) can be summed only if a correlation coefficient of+1.0 is assumed]



APPENDIX

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



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

Wildcat Wells

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

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

Wildcat Wells

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

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

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

• Number of Reservoirs in Oil Fields vs. API Gravity (Degrees)





Tanezzuft-Illizi Structural/Stratigraphic, Assessment Unit20560101

0

5

10

15

20

25

30

35

40

45

50

1 9 5 6

1 9 5 8

1 9 6 0

1 9 6 2

1 9 6 4

1 9 6 6

1 9 6 8

1 9 7 0

1 9 7 2

1 9 7 4

1 9 7 6

1 9 7 8

1 9 8 0

1 9 8 2

1 9 8 4

1 9 8 6

1 9 8 8

1 9 9 0

1 9 9 2

1 9 9 4

DRILLING-COMPLETION YEAR

N E W - F I E

L D W I L D C A T W

E L L S ( N o . )




1

10

100

1,000

0 2 4 6 8 10 12 14 16 18

OIL-FIELD RANK BY SIZE

K N O W N O I L - F

I E L D S I Z E ( M M B O )

First third of fields discoveredSecond third of fields discoveredThird third of fields discovered




0

2

4

6

8

10

12

1 t o < 2

2 t o < 4

4 t o < 8

8 t o < 1 6

1 6 t o

< 3 2

3 2 t o

< 6 4

6 4 t o

< 1 2

8

1 2 8 t o

< 2 5

6

2 5 6 t o

< 5 1

2

5 1 2 t o

< 1 ,

0 2 4

1 , 0 2

4 t o < 2 ,

0 4 8

2 , 0 4

8 t o < 4 ,

0 9 6

4 , 0 9

6 t o < 8 ,

1 9 2

8 , 1 9

2 t o < 1 6

, 3 8 4

1 6 , 3 8 4

t o < 3 2

, 7 6 8

3 2 , 7 6

8 t o < 6 5

, 5 3 6

6 5 , 5 3

6 t o < 1 3

1 , 0 7

2

1 3 1 ,

0 7 2 t o

< 2 6

2 , 1 4

4

> = 2 6

2 , 1 4

4

KNOWN OIL-FIELD SIZE (MMBO)

O I L F I E L D S ( N o .

)

Third third of fieldsdiscovered

Second third

of fieldsdiscovered

First third of fieldsdiscovered




0

100

200

300

400

500

600

700

800

900

1,000

1 t o < 2

2 t o < 4

4 t o < 8

8 t o < 1 6

1 6 t o

< 3 2

3 2 t o

< 6 4

6 4 t o

< 1 2

8

1 2 8 t o

< 2 5

6

2 5 6 t o

< 5 1

2

5 1 2 t o

< 1 ,

0 2 4

1 , 0 2

4 t o < 2 ,

0 4 8

2 , 0 4

8 t o < 4 ,

0 9 6

4 , 0 9

6 t o < 8 ,

1 9 2

8 , 1 9

2 t o < 1 6

, 3 8 4

1 6 , 3 8 4

t o < 3 2

, 7 6 8

3 2 , 7 6

8 t o < 6 5

, 5 3 6

6 5 , 5 3

6 t o < 1 3

1 , 0 7

2

1 3 1 ,

0 7 2 t o

< 2 6

2 , 1 4

4

> = 2 6

2 , 1 4

4

KNOWN OIL-FIELD SIZE (MMBO)

V O L U M E O F O

I L ( M M B O )




1

10

100

1,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIELD-DISCOVERY YEAR

K N O W N O I L - F





1

10

100

1,000

0 50 100 150 200 250 300 350 400

CUM. NEW-FIELD WILDCAT WELLS (No.)

K N O W N O I L - F





0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. K N O W N O I L V O L U M E ( M M B O )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 50 100 150 200 250 300 350 400


C U M

. K N O W N O I L V O L U M E ( M M B O )




0

10

20

30

40

50

60

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. O I L F I E L D S ( N o . )




0

10

20

30

40

50

60

0 50 100 150 200 250 300 350 400


C U M

. O I L F I E L D S ( N o . )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0001950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


R E S E R V O I R D E P T H

, O I L F I E L D S ( m )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0000 50 100 150 200 250 300 350 400



, O I L F I E L D S ( m )




0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

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

MEAN RESERVOIR DEPTH (m)

G A S / O I L , O I L F I E L D S ( C F G / B O )




0

200

400

600

800

1,000

1,200

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


N G L / G A S

, O I L F I E L D S ( B N

G L / M M C F G )






1

10

100

1,000

10,000

0 2 4 6 8 10 12 14

GAS-FIELD RANK BY SIZE

K N

O W N G A S - F I E

L D S I Z E ( B C F G )





0

2

4

6

8

10

12

14

6 t o < 1 2

1 2 t o

< 2 4

2 4 t o

< 4 8

4 8 t o

< 9 6

9 6 t o

< 1 9 2

1 9 2 t o

< 3 8 4

3 8 4 t o

< 7 6 8

7 6 8 t o

< 1 , 5 3 6

1 , 5 3

6 t o < 3 , 0 7 2

3 , 0 7

2 t o < 6 , 1 4 4

6 , 1 4

4 t o < 1 2

, 2 8 8

1 2 , 2 8 8

t o < 2 4

, 5 7 6

2 4 , 5 7

6 t o < 4 9

, 1 5 2

4 9 , 1 5 2

t o < 9 8

, 3 0 4

9 8 , 3 0 4

t o < 1 9

6 , 6 0 8

1 9 6 ,

6 0 8 t o

< 3 9

3 , 2 1 6

3 9 3 ,

2 1 6 t o

< 7 8

6 , 4 3 2

7 8 6 ,

4 3 2 t o

< 1 , 5 7

2 , 8 6 4

> = 1 , 5 7

2 , 8 6 4

KNOWN GAS-FIELD SIZE (BCFG)

G A S F I E L D S ( N o . )


Second thirdof fieldsdiscovered





0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

6 t o < 1 2

1 2 t o

< 2 4

2 4 t o

< 4 8

4 8 t o

< 9 6

9 6 t o

< 1 9 2

1 9 2 t o

< 3 8 4

3 8 4 t o

< 7 6 8

7 6 8 t o

< 1 , 5 3

6

1 , 5 3

6 t o < 3 , 0 7

2

3 , 0 7

2 t o < 6 , 1 4

4

6 , 1 4

4 t o < 1 2

, 2 8 8

1 2 , 2 8 8

t o < 2 4

, 5 7 6

2 4 , 5 7

6 t o < 4 9

, 1 5 2

4 9 , 1 5 2

t o < 9 8

, 3 0 4

9 8 , 3 0 4

t o < 1 9

6 , 6 0 8

1 9 6 ,

6 0 8 t o

< 3 9

3 , 2 1 6

3 9 3 ,

2 1 6 t o

< 7 8

6 , 4 3 2

7 8 6 ,

4 3 2 t o

< 1 , 5 7

2 , 8 6 4

> = 1 , 5 7

2 , 8 6 4

KNOWN GAS-FIELD SIZE (BCFG)

V O L U M E O F G A S ( B C F G )




1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


K N

O W N G A S - F I E





1

10

100

1,000

10,000

0 50 100 150 200 250 300 350 400


K N

O W N G A S - F I E





0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. K N O W N G A S V O L U M E ( B C F G )






0

5

10

15

20

25

30

35

40

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. G A S F I E L D S

( N o . )




0

5

10

15

20

25

30

35

40

0 50 100 150 200 250 300 350 400


C U M

. G A S F I E L D S

( N o . )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0001950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000



, G A S

F I E L D S ( m )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0000 50 100 150 200 250 300 350 400



, G A S

F I E L D S ( m )






1

10

100

1,000

0 2 4 6 8 10 12 14 16 18

OIL-FIELD RANK BY SIZE

G R O W N O I L - F I E

L D S I Z E ( M M B O )





0

2

4

6

8

10

12

1 t o < 2 2 t o

< 4 4 t o

< 8

8 t o < 1 6

1 6 t o

< 3 2

3 2 t o

< 6 4

6 4 t o

< 1 2 8

1 2 8 t o

< 2 5 6

2 5 6 t o

< 5 1 2

5 1 2 t o

< 1 ,

0 2 4

1 , 0 2

4 t o < 2 ,

0 4 8

2 , 0 4

8 t o < 4 ,

0 9 6

4 , 0 9

6 t o < 8 ,

1 9 2

8 , 1 9

2 t o < 1 6

, 3 8 4

1 6 , 3 8 4

t o < 3 2

, 7 6 8

3 2 , 7 6

8 t o < 6 5

, 5 3 6

6 5 , 5 3

6 t o < 1 3

1 , 0 7 2

1 3 1 ,

0 7 2 t o

< 2 6

2 , 1 4 4

> = 2 6

2 , 1 4 4

GROWN OIL-FIELD SIZE (MMBO)

O I L F I E L D S ( N o .

)


Second third

of fieldsdiscovered





0

200

400

600

800

1,000

1,200

1,400

1,600

1 t o < 2

2 t o < 4

4 t o < 8

8 t o < 1 6

1 6 t o

< 3 2

3 2 t o

< 6 4

6 4 t o

< 1 2 8

1 2 8 t o

< 2 5 6

2 5 6 t o

< 5 1 2

5 1 2 t o

< 1 ,

0 2 4

1 , 0 2

4 t o < 2 ,

0 4 8

2 , 0 4

8 t o < 4 ,

0 9 6

4 , 0 9

6 t o < 8 ,

1 9 2

8 , 1 9

2 t o < 1 6

, 3 8 4

1 6 , 3 8 4

t o < 3 2

, 7 6 8

3 2 , 7 6

8 t o < 6 5

, 5 3 6

6 5 , 5 3

6 t o < 1 3

1 , 0 7 2

1 3 1 ,

0 7 2 t o

< 2 6

2 , 1 4 4

> = 2 6

2 , 1 4 4

GROWN OIL-FIELD SIZE (MMBO)

V O L U M E O F O I L ( M M B O )






1

10

100

1,000

0 50 100 150 200 250 300 350 400


G R O W N O I L - F I E

L D S I Z E ( M M B O )






0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 50 100 150 200 250 300 350 400


C U M

. G R O W N O I L V O L U M E ( M M B O )




0

10

20

30

40

50

60

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. O I L F I E L D S

( N o . )




0

10

20

30

40

50

60

0 50 100 150 200 250 300 350 400


C U M

. O I L F I E L D S

( N o . )






0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0000 50 100 150 200 250 300 350 400



, O I L

F I E L D S ( m )




0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

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


G

A S / O I L , O I L F I E L D S ( C F G / B O )




0

200

400

600

800

1,000

1,200

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


N G L / G A S

, O I L F I E L D S ( B N G L / M M C F G )








0

2

4

6

8

10

12

14

6 t o < 1 2

1 2 t o < 2

4

2 4 t o < 4

8

4 8 t o < 9

6

9 6 t o

< 1 9 2

1 9 2 t o

< 3 8 4

3 8 4 t o

< 7 6 8

7 6 8 t o

< 1 , 5 3

6

1 , 5 3

6 t o < 3 , 0 7

2

3 , 0 7

2 t o < 6 , 1 4

4

6 , 1 4

4 t o < 1 2 , 2 8

8

1 2 , 2 8 8

t o < 2 4 , 5 7

6

2 4 , 5 7

6 t o < 4 9 , 1 5

2

4 9 , 1 5 2

t o < 9 8 , 3 0

4

9 8 , 3 0 4

t o < 1 9

6 , 6 0 8

1 9 6 ,

6 0 8 t o

< 3 9

3 , 2 1 6

3 9 3 ,

2 1 6 t o

< 7 8

6 , 4 3 2

7 8 6 ,

4 3 2 t o

< 1 , 5 7

2 , 8 6 4

> = 1 , 5 7

2 , 8 6 4

GROWN GAS-FIELD SIZE (BCFG)

G A S F I E L D S ( N o . )


Second thirdof fields

discovered





0

5,000

10,000

15,000

20,000

25,000

6 t o < 1 2

1 2 t o < 2

4

2 4 t o < 4

8

4 8 t o < 9

6

9 6 t o

< 1 9 2

1 9 2 t o

< 3 8 4

3 8 4 t o

< 7 6 8

7 6 8 t o

< 1 , 5 3

6

1 , 5 3

6 t o < 3 , 0 7

2

3 , 0 7

2 t o < 6 , 1 4

4

6 , 1 4

4 t o < 1 2 , 2 8

8

1 2 , 2 8 8

t o < 2 4 , 5 7

6

2 4 , 5 7

6 t o < 4 9 , 1 5

2

4 9 , 1 5 2

t o < 9 8 , 3 0

4

9 8 , 3 0 4

t o < 1 9

6 , 6 0 8

1 9 6 ,

6 0 8 t o

< 3 9

3 , 2 1 6

3 9 3 ,

2 1 6 t o

< 7 8

6 , 4 3 2

7 8 6 ,

4 3 2 t o

< 1 , 5 7

2 , 8 6 4

> = 1 , 5 7

2 , 8 6 4

GROWN GAS-FIELD SIZE (BCFG)

V O L U M E O F G A S ( B C F G )




1

10

100

1,000

10,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


G R O W N G A S - F I E





1

10

100

1,000

10,000

0 50 100 150 200 250 300 350 400


G R O W N G A S - F I E





0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. G R O W N G A S V O L U M E ( B C F G )




0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

0 50 100 150 200 250 300 350 400


C U M

. G R O W N G A S V O L U M E ( B C F G )




0

5

10

15

20

25

30

35

40

45

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


C U M

. G A S F I E L D S ( N o . )




0

5

10

15

20

25

30

35

40

45

0 50 100 150 200 250 300 350 400


C U M

. G A S F I E L D S ( N o . )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0001950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000


R E S

E R V O I R D E P T H

, G A S F I E L D S ( m )




0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,0000 50 100 150 200 250 300 350 400


R E S

E R V O I R D E P T H

, G A S F I E L D S ( m )




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


L I Q U I D S / G A S

, G A S F I E L D S ( B L / M M C F G )

Date post:	02-Jun-2018
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Total Petroleum Systems of the Illizi Province, Algeria and Libya—Tanezzuft-Illizi

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