1

Enhanced Oil Recovery Studies in the Tirrawarra Oil Field, Cooper Basin, South

Australia

Ian Pedler23 September 2009

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Enhanced Oil Recovery Studies in the Tirrawarra Oil Field, Cooper Basin, South Australia

The Tirrawarra oil field is located in north-eastern South Australia in the Cooper Basin.  The field was discovered in 1970 and is the largest onshore Permian oilfield in Australia.  Primary production commenced in 1983 and from 1984 to 1996 the field was subjected to a miscible flood initially using raw satellite gas and subsequently, ethane injection.  With the commencement of ethane sales from the Cooper Basin the EOR scheme was shut-down and the field was has been produced on blowdown since 1996.

In 2008 a study team was established to re-evaluate the field and review the potential for the re-establishment of and EOR scheme using CO2 or another suitable fluid with particular attention to the under-developed areas of the field.  The study was an integrated review of the subsurface, well construction and facilities aspects of an EOR project and included the construction of a modern static reservoir model and fully compositional dynamic simulation model.  This presentation will review some of the results from the 2008 study and the implications for the implementation of a future EOR scheme in the field.

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Cooper Basin Unit Partners

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Contents

1. Tirrawarra Field Review- Discovery

- Development

- Recent Performance

2. 2008 EOR Studies- Reservoir Modelling

- EOR Screening Results

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1. Tirrawarra Field Review

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Tirrawarra Location

Queensland

NewSouth Wales

GunnedahBasin

GunnedahBasin

BowenBasin

BowenBasinCooper

BasinCooperBasin

SouthAustralia

Brisbane

SydneyAdelaide

Moomba

Santos acreage Basin outline Oil pipeline Gas pipeline

Pt Bonython

50km

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Cooper Basin Operations

Typical Gas Wellhead Terrain Near Moomba

Tirrawarra SatelliteMoomba Plant

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Tirrawarra Discovery and Appraisal

1969 : First gas sales from Cooper Basin

1970 : Tirrawarra-1- Gas and oil discovery well

- TD 10,200 ft- Volatile oil in Tirrawarra formation

- 592 bopd max test rate- Liquids rich gas in multiple stacked

sands in overlying Patchawarra formation- 6.9 MMscf/d max test rate

1970 – 1972 Tirrawarra 2-11- Patchawarra/Tirrawarra

appraisal - Toolache formation gas discovery

1973 – 1979- No activity, pending

development of Cooper Basin Liquids Project

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Tirrawarra Field Summary

Tirrawarra Field Tirrawarra

Reservoir Properties

OOIP: 150 MMstbCrest : 9300 feet SSClosure : 550 feetThickness : 100 - 180 feetArea : 12,000 acresPorosity : 6 – 10%Permeability : 0.05 – 1 md

Fluid Properties

Initial Pressure : 4260 psiaBubble Point : 3000 psiaTemperature : 140 oCSolution GOR : 2700 scf/stbFVF : 2.7 rbbl/stbViscosity : 0.09 cP

Component Mol %

H2S 0.0

CO2 16.66

N2 1.72

Methane (C1) 31.95

Ethane (C2) 12.20

Propane (C3) 9.47

Iso Butane (iC4) 1.98

n-Butane (nC4) 3.72

Iso Pentane (iC5) 1.31

n-Pentane (nC5) 1.77

Hexanes (C6) 2.47

Heptanes+ (C7+) 16.75

100.00

API at 60oF 44.5

Tirrawarra Oil Composition

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Tirrawarra Field

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Tirrawarra Field Development

1981 : Commencement of Cooper Basin Liquids Project

1983 : First oil production from Tirrawarra (depletion)

1984 : Pilot EOR miscible flood project commenced based on raw gas injection- Total 10 Bcf inj from ’84-’88

1986 : Ethane injection commenced as part of basin ethane storage commitment

1997 : Ethane injection ceased with the commencement of ethane sales from the basin- Total 90 Bcf inj from ’86-’97

2007/8 : Multiwell appraisal programme and EOR Project Team established

TI15TI38

TI18

TI60

TI61

TI50

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Tirrawarra Field Production

27 MMstb produced to date

’84SG injection

’87C2 injection

’97 Cease Injection + Blowdown

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2. 2008 EOR Studies

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Current Operations

CO2 Remova

l

DeH2OLiquids Recover

y

Ethane Treatmen

t

Liquids to Pt Bonython

Ethane and Sales Gas to SydneySales Gas to Adelaide

CO2 to Vent

Moomba PlantCooper

Basin Gas Fields

Tirrawarra Oil Field

Tirrawarra

Satellite

Gas Satellite

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Proposed MCS1/EOR Project

CO2 Remova

l

DeH2OLiquids Recover

y

Ethane Treatmen

tCooper

Basin Gas Fields

Liquids to Pt Bonython

Ethane and Sales Gas to SydneySales Gas to Adelaide

Moomba Plant

De H2O Compression

New CO2 FacilitiesTirrawarra Oil

Field

Tirrawarra

Satellite

Gas Satellite

Upgrade

Upgrade

New Dense Phase Pipeline

New Inj & Prod Wells

New Fuel Gas Line

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Subsurface Workflow

Static Reservoir Model- First use of modern 3D reservoir

modelling tool in Tirrawarra- Integrate nearly 40 years of core,

log and stratigraphic data from >80 wells to create 3D geocelluar model- 120m x 120m x 1 ft (6,000,000 cells)

Dynamic Reservoir Model- Upscale Static Model to size suitable

for dynamic numerical modelling- 50,000 – 100,000 active cells

- Fully compositional reservoir model with 8 component PVT model

History Matching Process- Make ‘reasonable’ changes to a

base model to approximate past performance

- Matching >25 years of observed pressures, rates, ratios

- Iterative, time consuming & non-unique process

Outcome is a matched model that can be used to test various EOR and development scenarios

PetrophysicsStatic

Model

Dynamic

ModelUpscale

History Match

OOIP Sensitivities

New Dep. ModelPVT

Res. Eng. StudiesFracture / production / log KH / single well modelling etc

Feedback

Fieldwide Basic Data

Review

Appraisal Results Pr

oduc

tion,

Pres

sure

Dat

a

3D Seismic BasedStructural Interpretation

Matched Dynamic

Model to Test EOR and

Development Scenarios

SubsurfaceReservoir Modelling

ProductionFacilities

WellConstruction

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The Importance of Compositional Modelling

Comp. Mol %

CO2 16.66

N2 1.72

C1 31.95

C2 12.20

C3 9.47

iC4 1.98

nC4 3.72

iC5 1.31

nC5 1.77

C6 2.47

C7-C10

16.75C11-C16

C16+

Vent

Sales Gas

Ethane

LPG

Oil

3

1

2

4

5

678

Mol % Mol % Mol % Comp.

99.1 28.8 1.8 CO2

0.9 50.0 93.9N2

C1

- 13.4 3.9 C2

- 6.8 0.4

C3

iC4

nC4

1.0 - iC5

- - nC5

C6

C7-C10

C11-C16

C16+

Tirrawarra Reservoir

Fluid Prod

uct St

ream

Des

tina

tion

PVT

Com

pone

nt

EOR Injectants Studied

CO2

Sat. G

as

Sales

Gas

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Tirrawarra History Match - HCPV

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Tirrawarra History Match - Pressure

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Tirrawarra : Current Day Conditions

2009 HCPV 2009 Pressure

2009 StatusCore Area RF : 33%North Flank RF : 10%

Core, Brownfields AreaHigh on StructureLow pressure, swept

Northern, Greenfields AreaLower on structure,Higher pressure, unswept

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Tirrawarra : Current Day Conditions

2009 HCPV Reservoir kh

Core, Brownfields AreaHigh on StructureLow pressure, swept

Northern, Greenfields AreaLower on structure,Higher pressure, unswept

Core, Brownfields AreaGenerally higher kh and well productivity

Northern, Greenfields AreaGenerally lower kh and well productivity

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CO2 EOR Alternatives

600 ktpa CO2Greenfields Area“Oil Focussed” CO2 EOR52 New Wells•37 new prod•15 new injectors

600 ktpaBrownfields Area“Storage Focussed” CO2 EOR•no new wells, recreate original injection patterns

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Tirrawarra 600 ktpa CO2 EOR Cases

Net C5+ Production

0

2000

4000

2009 2014 2019 2024 2029 2034

bbl/

d

Net C5+ Production

0

2000

4000

2009 2014 2019 2024 2029 2034

bbl/

d

Net CO2 Production

-750

-500

-250

0

250

2009 2014 2019 2024 2029 2034

kT/Yr

Net CO2 Production

-750

-500

-250

0

250

2009 2014 2019 2024 2029 2034

kT/Yr

CO2 Balance

0

500

1000

2009 2014 2019 2024 2029 2034

kT C

O2

Produced CO2

Injected CO2

CO2 Balance

0

500

1000

2009 2014 2019 2024 2029 2034

kT C

O2

Produced CO2

Injected CO2

Brownfields Area“Storage Focussed”CO2 EOR

Greenfields Area“Oil Focussed”CO2 EOR

Incremental Recovery

0

10

20

30

Oil EOR S'age EOR

MM

boe

Oil

LPG

C2C1

Oil

CO2 Storage

0

5

10

Mt CO

2

Tota

l In

j.

Tota

l In

j.

Net

S’a

ge

Net

S’a

ge

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The Fuel Gas Challenge …..

Capture Process Compression

Moomba Plant

1 Mtpa CO2 to EOR

1 Mtpa CO2 to Vent

Sales Gas

100 ktpa CO2 to Atmosphere

Gas Turbine

•To inject 1 Mtpa of CO2 for EOR, 0.1 Mtpa of new CO2 emissions are generated. For EOR, CO2 is cycled through the reservoir and plant several times and each time this happens new CO2 emissions are generated.

•For pure MCS this only happens once

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The Fuel Gas Challenge …..

Capture Process Compression

Moomba Plant

1 Mtpa CO2 to EOR

1 Mtpa CO2 to Vent

Electric DriverGeothermal

Power Station

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EOR Fluid Evaluation

0%

10%

20%

30%

40%

0.0 0.5 1.0 1.5 2.0 2.5

HCPV of EOR Fluid Injected

Incr

em

enta

l Reco

very

Fact

or

CO2

Satellite Gas

Sales Gas

Initial Depletion Phase

Sales Gas Blowdown

Satellite Gas Blowdown

Basis:Greenfields AreaNorthern Injection Only600ktpa CO2(e)

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Conclusions

Pre FEED Studies successfully completed in early 2009

Cooper Basin JV has chosen to place a large scale Tirrawarra CO2 EOR project on hold pending clarity on carbon pricing and oil price recovery

New development drilling in Northern Tirrawarra is proposed for 2010 to prove reservoir performance of this area

Australia’s only EOR Project is currently underway in nearby Fly Lake field- Pilot scale project using Tirrawarra satellite gas to increase

oil recovery

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Acknowledgements

TEOR Subsurface Pre-FEED Team- David Grybowski, Bich Thuy Ngo Hoang, Adam Little,

Serge Toulekima and Alan Waldron

Cooper Basin Joint Venture Partners