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Skua Field Development Plan Team 2.

Skua Field Development Plan Team 2. Justin Dukas Project manager and Economics Agi Burra Geology Nurul Azami Petrophysics Justin Herriman Reserves Lim Ching Wan Reservoir Xiochan Shen Reservoir Wan Zuraidah Ahmad Production

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Skua Field Development Plan Team 2.

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  1. Skua Field Development PlanTeam 2. Justin Dukas Project manager and Economics AgiBurra Geology NurulAzamiPetrophysics Justin Herriman Reserves Lim Ching Wan Reservoir XiochanShen Reservoir Wan Zuraidah Ahmad Production IngveHebnes Drilling and Completions Dylan Stringer Facilities

  2. Executive Summary • Develop southern oil field • Drill 2 new wells, recomplete Skua 3 and 4 • Gas cap blow-down, confirm production rates with simulation • NPV10 =460 Million AUD, NPV/I=1.6 • Payback time 21.5 months • Max Exposure $413 Million

  3. Mission Statement To produce the best field development plan for the Skua field, maximizing the asset value to the company while minimizing the downside risks

  4. Skua Field Location SKUA FIELD

  5. Field Layout Smallersection B 1 MMSTB Largersection A 42 MMSTB

  6. Skua Field - Geology Agi Burra

  7. Regional Geology • Offshore target located approx 700 kms west of Darwin • Extensional environment in NW-SE direction resulting in NE-SW normal faulting • horst / graben features encouraging localised deposition at elevated rates • Numerous faulting events in area with probable moderately recent re-activation of pre-existing structures • Such environments frequently encourage migration of fluids along lineaments Section 1 (Osborne, 1990)

  8. Skua Field Geology • Reservoir limited by major NE trending normal faults in the east, west and north • Additional smaller scale faulting is known – particularly in the lower horizons • Target reservoir dipping toward the SE at 18.5° with an unconformable cap at ~2,300m depth • Full reservoir sequence was intercepted in Skua 6 Section 1 • Main NE fault appears to be sealing – pressure data • Cretaceous tilting of sediments (Osborne, 1990)

  9. (Emery et al, 1996) Stratigraphy • Depositional environment • Fluvial to coastal environments evident from stratigraphical profiles • Reservoir characteristics: • Target reservoir is made up of 6 horizons, 5 of which are HC hosts at different sites • Basal layers massive sandstone with minimal flow barrier units • Younger reservoir rocks are made up of interbedded horizons such as sandstone / shale / siltstone / mudstones (Osborne, 1990)

  10. Depositional history: Fluvial to Coastal sediment deposition Widespread faulting, tilting of sediments and erosion (unconformity) Hydrocarbon emplacement Recent re-activation of major faults GRV = 123MM m3 or 774MM res bbl Good porosity Around 21% Aquifer Strong edge water drive Water influx along impermeable shale unit bedding planes Fluid contacts OWC and GOC intercepted in a number of locations Gas cap identified – 28m height Oil column – 46m height Reservoir Characteristics (Osborne, 1990)

  11. Recommendations: • Acquire 3d seismic for increased resolution to refine location and extent of: • Faults → well location and reserves • Main sealing units→ reservoir dynamics and reserves • Reservoir units → NG ratio and reserves • Drill well in area where full reservoir sequence can be intercepted • Obtain core data to further assess rock and HC properties → refine assumptions into modelling • Generate 3D geological model to assist with understanding reservoir dynamics

  12. PETROPHYSICS NurulAzami

  13. Reservoir properties GOC: 2286.5 m ss OWC: 2333 m ss h: 46.5 m Rock properties Φ: 21% k: 360 – 1700 mD Ave. N/G: 50% HC saturation: 0.82 Residual So: 0.20 Residual Sg: 0.15

  14. Fluid properties • Oil specific gravity: 0.815 • 42º API • Bo: 1.48 • Oil viscosity: 0.30 cP • Oil compressibility: 19.8 microsips • GOR: 900 scf/stb • Gas expansion factor: 200 scf/rcf • Gas viscosity: 0.021 cP • Water viscosity: 0.35 cP * Properties are measured at initial reservoir P and T.

  15. Skua-3 GOC 2286.5 OWC 2333 1 2 3 4 5 6 7 Skua-3 cross section

  16. Skua-4 cross section Skua-4 GOC 2286.5 OWC 2333 1 2 3 4 5 6 7

  17. Skua-3

  18. Skua-4

  19. Skua-3 Skua-4 Skua-6 Bayfill Mouthbar estuary Channel Mouthbar Delta front (lagoon) Skua field facies

  20. Depositional environment – k vs Φ

  21. Skua Field Insitu k-Φ crossplot 104 103 102 101 100 Deltaic environment – high energy Skua-3 Skua-4 Overburden core perm 0 15.00 30.00 Overburden core porosity

  22. Skua-3 #1 Estuarine / marine #2 Lagoonal interdistrib. bay #3 Fluvial - Estuarine #4

  23. Skua-4 Lacustrine/ alluvial #1 Coastal plain/ alluvial lagoonal Lacustrine alluvial #2 Bay margin delta plain #3 Marginal marine lagoonal #4

  24. Skua-3 core properties

  25. Skua-4 core properties

  26. Relative Permeability • From SCAL of Skua 3 core

  27. *Ave. Φ *Ave. Sw *N/G Petrophysical properties

  28. Reserves Estimation Justin Herriman

  29. Significance of Estimation Ultimate goal to define return on investment Uncertainty exists and must be managed Required component of reservoir modelling and economics

  30. Inputs and Assumptions GRV from Area vs. Depth plot N:G, porosity, Sw estimated from logs, core, analysis Bo, Bg from PVT Minima and Maxima as recommended, triangular distributions Each layer treated separately

  31. OOIP Distribution

  32. OOIP Influence Sand unit 1 N:G and GRV most influence

  33. Top 5 Sensitivity

  34. Correlation between Parameters Sw and porosity correlated by -0.7 Reduction in Std. Dev.

  35. OOIP and Gas Cap Estimates

  36. Recovery Factor Analogue fields 55-65% (Wallace & Balnaves, 1988; Edwards & Behrenbruch, 1998) MBAL Model predicted 63% Assumption: “no doubts are held for full and strong aquifer” (Skua Aquifer Report) Chosen Distribution: Uniform 35-65% Accounts for aquifer/connectivity uncertainties suggested by geologist

  37. Reserves Estimates

  38. RESERVOIR & PRODUCTION ENGINEERING Chan Wan Zuraidah Ching Lim

  39. MAIN FOCUS Compare development alternatives - Theoretical (data given) - Preliminary simulations Choose development alternatives Decide on number of wells Decide on well locations/likely perforation depths Run sensitivities

  40. DEVELOPMENT ALTERNATIVES Gas Cap Blowdown Dev. Well Gas Cap Initial Oil Column Conventional Oil Rim Dev. Aquifer Well Well Gas Cap Remaining Gas Cap Gas Flooded Zone Oil Resaturated Zone Final Oil Rim Remaining Oil Rim Water Flooded Zone Final Oil Rim Water Flooded Zone

  41. CONVENTIONAL DEVELOPMENT The effective oil thickness is located between a gas cap and a water zone For conventional development, both gas and water coning will pose a problem The critical oil rate Qoc for combined gas and water coning can be calculated with the Meyer-Garder Correlation

  42. GCB DEVELOPMENT • Assume gas cap has been produced • The critical oil rate can be estimated by applying the equation for water-coning system. Gas cap produced

  43. Qoc RESULTS • Coning problem will occur when wells are produced above Qoc • If critical rate is lower, coning will be more severe • Wells have higher Qoc in GCB than conventional

  44. PITFALL OF CONVENTIONAL DEVELOPMENT Expected high water cut compared to GCB May need re-perforation in later life of reservoir Increased cost

  45. IMPORTANT FACTORS FOR ‘GCB’ Reservoir Energy Production Policy – Flaring Perforation Depths Most suitable for reservoirs with: - strong aquifer - small gas cap

  46. DRIVE MECHANISM Plover Formation Aquifer Support Information Provided: Plover formation section average thickness of 800 m Conservative estimation – semi-circular with radius of 30 km Volume of Connected Aquifer to Reservoir 5.2 million to 1 Aquifer support in Skua Field is very strong Justification? Based on Gross Rock Volume in Skua Field 142 x 106 m3 To guarantee adequate support: Aquifer : Reservoir → 1000 : 1 Required aquifer radius → 10.6 km Additional Information: Analogue → Jabiru field has strong aquifer support (SPE 17602)

  47. GAS CAP SIZE For all low, base and high case reserves, the relative gas cap size is calculated to be approximately 0.09 Relatively small gas cap size (m < 0.1) GCB theoretically suitable for Skua

  48. SIMULATIONS

  49. CONVENTIONAL GAP

  50. GAS CAP BLOWDOWN MBAL

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