assessment of undiscovered oil and gas resources of libyaand tunisia

7/29/2019 Assessment of Undiscovered Oil and Gas Resources of Libyaand Tunisia

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Assessment of Undiscovered Oil and Gas Resources of Libyaand Tunisia, 2010Printed on recycled paper

IntroductionThe U.S. Geological Survey (USGS) assessed the potential

-

logicprovinces of North AfricaSirte Basin in Libya and Pela-

gian Basin in Tunisia and western Libyaas part of the USGSWorld Petroleum Resources Project1). The Sirte Basinoriginated as a Cretaceous rift that evolved into a post-rift basindominated by

-grained clastic

deposition introughs (Ahlbrandt, 2001; Hallett, 2002). The Pelagian Basin wasdominated by Mesozoic

and Cenozoic subsidence related to tecto-

nism along the northern margin of the African plate (Klett, 2001).One total petroleum system (TPS)

PelagianBasin Province.

The SirteRachmat Composite TPS in the SirteBasin Province contains the post-rift

ConiacianCampanianSirteRachmat organic-rich shale/marl, which was deposited introughs across

the Sirte Basin during the early phase of thermalsubsidence (Ahlbrandt, 2001; Hallett, 2002). Major

reservoirs inthe Sirte Basin Province include syn-rift continental sandstonesand post-rift shallow-marine carbonates, with shales and evapo

-rites acting as seals for hydrocarbon reservoirs (Ahlbrandt, 2001;Hallett, 2002). Two assessment units

withinthe SirteRachmat Composite TPS: the Onshore Sirte Carbon-

Klett(2001) were retained for this assessment. The JurassicCretaceousComposite TPS consists of

-marine shales that migrated into JurassicCretaceous shal-

low marine limestones and Upper Cretaceous fractured deep-water chalks. Seals include Jurassic and

this TPS, the JurassicCre-

taceous Structural/Stratigraphic AU, based on Klett (2001). TheBou Dabbous Cenozoic TPS containsthe Eocene Bou Dabbousorganic-rich shale, with hydrocarbons that migrated into lower and middle

Eocene shallow-water limestones that are sealed by

Using a geology-based assessment methodology, the U.S.Geological Survey estimatedmeans of 3.97 billion barrels of undiscovered oil, 38.5 trillion cubic feet of undiscovered

natural gas, and 1.47 billion barrels of undiscovered natural gas liquids in two provinces ofNorth Africa.

Figure 1.Locations of the Sirteand Pelagian Basin Provinces,North Africa. AU, assessment unit.


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t


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Assess

ment

of

Undisc

overed


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Oil and

Gas

Resour

ces of

Libyaa


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nd

Tunisia

, 2010Printed on recycled paperIntroductionThe U.S. GeologicalSurvey (USGS)


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assessed the

potentialfor undiscovered

conventional oil and

two geo

-logic provinces of

North AfricaSirte

Basin in Libya and

Pela

-


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gian Basin in

Tunisia and westernLibyaas part of

the USGSWorldPetroleum

Resources Project

1). The SirteBasinoriginated as a

Cretaceous rift thatevolved into a post-

rift basindominated

by thermal


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subsidence; it is

characterized bycarbonatedeposition

on high blocks and-grained clastic

deposition introughs

(Ahlbrandt, 2001;Hallett, 2002). The

Pelagian Basinwasdominated by

Mesozoic and

Cenozoic


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subsidence related

to tecto-

nism along thenorthern margin of

the African plate

(Klett, 2001).Onetotal petroleum

system (TPS) wasthe

SirteBasin Province,

and two TPSs were


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the PelagianBasinProvince. The

SirteRachmatComposite TPS in

the SirteBasin

Province containsthe post-rift

ConiacianCampan

ianSirteRachmat

organic-rich

shale/marl, which


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was deposited

introughs across theSirte Basin during

the early phase ofthermalsubsidence

(Ahlbrandt, 2001;

Hallett, 2002).Major reservoirs

inthe Sirte BasinProvince include

syn-rift continental

sandstonesand post-


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rift shallow-marine

carbonates, withshales and evapo

-rites acting as sealsfor hydrocarbon

reservoirs(Ahlbrandt,

2001;Hallett, 2002).Two assessment

units (AU) were

withinthe


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SirteRachmat

Composite TPS: theOnshore Sirte

Carbon-ateClastic AU and

the Offshore SirteBasin AU.Within

the Pelagian Basin,two TPSs as

Klett(2001) were


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retained for this

assessment. TheJurassicCretaceous

Composite TPS

from Jurassic and

Cretaceousdeep-marine shales that

migratedinto JurassicCretac

eous shal

-


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low marine

limestones andUpper Cretaceous

fractured deep-water chalks. Seals

include Jurassic and

Cretaceous shalesandevaporites. One

for this TPS, the

JurassicCre

-


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taceous

Structural/Stratigraphic AU, based

on Klett (2001).TheBou Dabbous

Cenozoic TPS

contains the EoceneBou

Dabbousorganic-rich shale, with

hydrocarbons that

migrated into


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lower and middle

Eocene shallow-water limestones

that are sealed byUsing a geology-based

assessmentmethodology, theU.S.GeologicalSurvey estimatedmeans of 3.97

billion barrels


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of undiscovered

oil, 38.5 trillioncubic fe

assessment of undiscovered oil and gas resources of libyaand tunisia

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