INTRODUCTION

Shale gas systems are self containing petroleum systems (i.e. source, reservoir and seal all inclusive)

They form continuous accumulation that is being successfully exploited commercially in the US. This is largely driven by government policy, technology and rising natural gas price .

Currently, natural gas production from shale gas plays in the US stands at over 46% and it is projected to rise to 60% in the nearest future.

The successful exploitation of shale gas plays in the US have sparked up exploitation in Europe, North America , etc, where shale gas plays are thought to occur.

showing continuous shale gas accumulation (modified after Shenk and Pollastro, 2002 )

NATURAL GAS IN SHALE PLAYS

The composition of shale gas is dominantly methane, with lesser percentages of propane, butane (Natural gas)

According to Kennedy et al. (2012), natural gas commonly exists in shale reservoirs as:

‘free gas’ (in matrix pore network and natural fractures),

‘Sorbed gas’ (adsorbed to Organic matter and natural fractures or absorbed by the organic matter and matrix pores) and

‘Dissolved gas’ (in liquid hydrocarbons)

NATURAL GAS IN SHALE PLAYS

COMPOSITION OF SHALES

AIM AND OBJECTIVES

• Organic richness (TOC) of Tanezzuft gas shale

• Type of Kerogen present in the gas shale

• Thermal maturity and thermal maturity history / distribution

• Relative proportion of clay minerals, quartz and calcite

• Comparison of Tanezzuft shale properties with established

shale gas plays in the USA

GHADAMES BASIN BACKGROUND• ‘Large Intracratonic - Sag

basin’ (about 350,000km2) covering parts of Tunisia, Algeria and Libya.

• Basin fill: 8000m

• Conventional hydrocarbon Reserves: 32BBOE

• Ongoing exploration for Shale gas resources in the Tunisian end of the basin.

• Estimated resource 80-120TCF (Troudi et.al, 2012)Ghadames Basin

(modified after Underdown and Redfern, 2008)

TANEZZUFT SHALES• Deposited in the Early Silurian

at the onset of widespread flooding in a Passive Margin tectonic setting

• World class source rock– Dominantly Type 2 kerogen – present day TOC (0.5% to >

15%) – HI values (250-450mgHc/g).

• 3 major lithostratigraphic units – Quartz rich upper layer– Calcite rich Intermediate

layer – Basal clay rich hot shale

(best source rock quality)

Tanezzuft Shales

Ghadames Basin Stratigraphy (after Yahi et al, 2001)

Data set available

• Data (TOC data, Maturity data, HI) from 37 wells was used for this study.

• Some data was obtained from Underdown (2006), Basu et al., (1997) and Yahi et al., (2001)

SHALE GAS EXPLORATION WORK FLOW

INITIAL TOC WITH 2% CUT OFF

Initial TOC conversion formula (Daly and Edman, 1987)

Initial TOC generally increases towards the

west

latitude longitude

N

Initial TOC 3D Surface Map

Ro = 0.0180 x Tmax – 7.16 maybe unreliable where S2

values are <0.2(mg HC/g Rock)

THERMAL MATURITY (≥ 1.0% RO)

Latitude

Longitude

Thermal maturity generally increases

towards the west

(Jarvie et al., 2001)

Thermal Maturity 3D Surface Map

SWEET SPOT

Wells used for Basin Modelling

ONE-1 Well

BRD-4 Well

‘Combining initial TOC map (2% TOC cut off) with the thermal maturity map (1% Ro cut-off)’

BASIN MODELLING KEY INPUT PARAMETERS

• Heat flow model

Underdown and Redfern (2008)

Event Begin Age

(Mya)

Eroded thickness

(m)

Alpine 36.7 100

Austrian 120 600

Hercynian 292 3600

Dixon et al., (2010) and Underdown (2006)

• Amount of exhumed overburden

HEAT FLOW MODEL CALIBRATION

BURIAL HISTORY PLOTS

BRD-4

ONE-1

ADSORPTION POTENTIAL SCHEMATIC

Pore Pressure (PSI)

Ads

orp

tion

Pot

entia

l

COMPARISON

After Troudi et al., 2012

COMPARISON

CONCLUSION•Identification of areas with sufficient organic richness (i.e. >2% initial

TOC).

•Tanezzuft gas shale is predominantly of oil prone Type II Kerogen

•1D maturity modelling reveal Tanezzuft shale to be in wet gas stage -

main stage of gas generation around the ‘sweet spot’

•Interbeds of quartz rich silt and fine sands exist in the Tanezzuft shale

stratigraphy. Its thickness increases towards the ‘sweet spot’

•The Tanezzuft shale shares a lot of similarity with the Marcellus and

Utica shales

CONFIDENCE/ PROBABILITY MATRIX

RECOMMENDATIONS Evaluation of the Mineralogy of the Tanezzuft Shale

Investors should bare in mind the following questions:

• Is there adequate supply of water?

• What are the likely environmental issues to face?

• Is there adequate infrastructure?

• Are specialized oil field services readily available?

• Is there political backing for exploration?

ACKNOWLEDGEMENTS•Thanks to God for his grace

•Mr James Armstrong for his wonderful supervision

•Other members of staff for support and encouragement

•Plate River Associates (BasinMod Software)

•TETFUND for sponsorship

Thanks for Listening