1. 1 Enhanced Oil Recovery Studies in the Tirrawarra Oil Field, Cooper Basin, South Australia Ian Pedler 23 September 2009

2. 2 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.

3. 3 Cooper Basin Unit Partners

4. 4 Contents 1. Tirrawarra Field Review -Discovery -Development -Recent Performance 2. 2008 EOR Studies -Reservoir Modelling -EOR Screening Results

5. 5 1. Tirrawarra Field Review

6. 6 Tirrawarra Location Queensland New South Wales Gunnedah Basin Bowen Basin Cooper Basin South Australia Brisbane Sydney Adelaide Moomba Santos acreage Basin outline Oil pipeline Gas pipeline Pt Bonython 50km

7. 7 Cooper Basin Operations Typical Gas Wellhead Terrain Near Moomba Tirrawarra Satellite Moomba Plant

8. 8 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

9. 9 Tirrawarra Field Summary Tirrawarra Field Tirrawarra Reservoir Properties OOIP:  150 MMstb Crest : 9300 feet SS Closure :  550 feet Thickness : 100 - 180 feet Area :  12,000 acres Porosity : 6 – 10% Permeability : 0.05 – 1 md Fluid Properties Initial Pressure : 4260 psia Bubble Point : 3000 psia Temperature : 140 o C Solution GOR : 2700 scf/stb FVF : 2.7 rbbl/stb Viscosity : 0.09 cP ComponentMol % H2S0.0 CO216.66 N21.72 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 60 o F44.5 Tirrawarra Oil Composition

10. 10 Tirrawarra Field

11. 11 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

12. 12 Tirrawarra Field Production

13. 13 2. 2008 EOR Studies

14. 14 Current Operations CO 2 Removal DeH 2 O Liquids Recovery Ethane Treatment Liquids to Pt Bonython Ethane and Sales Gas to Sydney Sales Gas to Adelaide CO2 to Vent Moomba Plant Cooper Basin Gas Fields Tirrawarra Oil Field Tirrawarra Satellite Gas Satellite

15. 15 Proposed MCS1/EOR Project CO 2 Removal DeH 2 O Liquids Recovery Ethane Treatment Cooper Basin Gas Fields Liquids to Pt Bonython Ethane and Sales Gas to Sydney Sales Gas to Adelaide Moomba Plant De H 2 O Compression New CO2 Facilities Tirrawarra Oil Field Tirrawarra Satellite Gas Satellite Upgrad e New Dense Phase Pipeline New Inj & Prod Wells New Fuel Gas Line

16. 16 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 Petrophysics Static Model Dynami c Model Upscale History Match OOIP Sensitivities New Dep. Model PVT Res. Eng. Studies Fracture / production / log KH / single well modelling etc Feedback Fieldwide Basic Data Review Appraisal Results Production, Pressure Data 3D Seismic Based Structural Interpretation Matched Dynamic Model to Test EOR and Development Scenarios

17. 17 The Importance of Compositional Modelling Comp.Mol % CO216.66 N21.72 C131.95 C212.20 C39.47 iC41.98 nC43.72 iC51.31 nC51.77 C62.47 C7-C10 16.75 C11-C16 C16+ Vent Sales Gas Ethane LPG Oil 3 1 2 4 5 6 7 8 Mol % Comp. 99.128.81.8CO2 0.950.093.9 N2 C1 -13.43.9C2 -6.80.4 C3 iC4 nC4 1.0-iC5 --nC5 C6 C7-C10 C11-C16 C16+ Tirrawarra Reservoir Fluid Product Stream Destination PVT Component EOR Injectants Studied CO2 Sat. Gas Sales Gas

18. 18 Tirrawarra History Match - HCPV

19. 19 Tirrawarra History Match - Pressure

20. 20 Tirrawarra : Current Day Conditions 2009 HCPV 2009 Pressure 2009 Status Core Area RF : 33% North Flank RF : 10% Core, Brownfields Area High on Structure Low pressure, swept Northern, Greenfields Area Lower on structure, Higher pressure, unswept

21. 21 Tirrawarra : Current Day Conditions 2009 HCPV Reservoir kh Core, Brownfields Area High on Structure Low pressure, swept Northern, Greenfields Area Lower on structure, Higher pressure, unswept Core, Brownfields Area Generally higher kh and well productivity Northern, Greenfields Area Generally lower kh and well productivity

22. 22 CO2 EOR Alternatives 600 ktpa CO2 Greenfields Area “Oil Focussed” CO2 EOR 52 New Wells 37 new prod 15 new injectors 600 ktpa Brownfields Area “Storage Focussed” CO2 EOR no new wells, recreate original injection patterns

23. 23 Tirrawarra 600 ktpa CO2 EOR Cases Brownfields Area “Storage Focussed” CO2 EOR Greenfields Area “Oil Focussed” CO2 EOR Oil LPG C2 C1 Oil Total Inj. Net S’age

24. 24 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

25. 25 The Fuel Gas Challenge ….. Capture Process Compression Moomba Plant 1 Mtpa CO2 to EOR 1 Mtpa CO2 to Vent Electric Driver Geothermal Power Station

26. 26 EOR Fluid Evaluation Initial Depletion Phase Sales Gas Blowdown Satellite Gas Blowdown Basis: Greenfields Area Northern Injection Only 600ktpa CO2(e)

27. 27 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

28. 28 Acknowledgements  TEOR Subsurface Pre-FEED Team -David Grybowski, Bich Thuy Ngo Hoang, Adam Little, Serge Toulekima and Alan Waldron  Cooper Basin Joint Venture Partners