PDOs EOR Screening Methodology for Heavy-Oil Fractured Carbonate Fields - a Case Study

Transcription

1 PDOs EOR Screening Methodology for Heavy-Oil Fractured Carbonate Fields - a Case Study Georg Warrlich, Ibrahim Al-Waili, Dhiya Said, Mohamed Diri, Nabil Al-Bulushi, Jonathan Strauss, Mohammed Al-Kindi, Fahad Al- Hadhrami, Ton van Heel, John van Wunnik (PDO) Bert-Rik de Zwart, Carl Blom, Rifaat Al-Mjeni, Paul Boerrigter (Shell Technology Oman) SPE

2 Talk Outline Introduction heavy-oil fractured carbonates in PDO & field under study EOR Screening Methodology Global Analogues Key Technical Risks to developments De-risking EOR recovery methods with Appraisal Conclusions

3 Introduction 6 fields in PDO's portfolio of heavy-oil fractured carbonate reservoirs in Ghaba Salt Basin Recovery methods: Cold & steam-assisted gasoil gravity drainage Fractured Shuaiba Fields in the Ghaba Salt Basin C: Cold GOGD A: SAGOGD 8cp Development projects in various stages of maturity Focus on finding a suitable recovery mechanism for Field F Salt-withdrawal syncline 250cp 500cp B: SAGOGD E: SAGOGD D Cold GOGD 9/30cp 5000cp N 10000cp F: This paper 10 km Top Haushi structure map - blue is deep, red is shallow ( courtesy of M. Lawati)

4 Kharaib Water-filled Reservoir rocks Hawar Tight Limestone Shuaiba Reservoir Field F Summary Understanding at Study Start GR Porosit y Sat. Oil Res. Zone RZ 4 Field D F-8 F-2 F-5 F10 F-9 F-3 F-7 F-1 Field F Large STOIIP 400m column, but only 30m thick reservoir Fractured Carbonate Reservoir (Shuaiba) High porosity (28%), low perm.(5-20 md) Very viscous oil cp (@ 50 degc) Low oil saturations (80% - 20%) F-6 THSU AGS-3H3 AGS-3H2 FU2 THKH Base Hawar AGS-3H1 F-3 AGS-1H1 F-1 THSU FU2 THSU THKH Base Hawar FU m Oil Sat logs 1:16000 FU2 THKH Base Ha AGS-1H

5 EOR Screening Methodology Fullfield feasibility study carried out to screen all potentially applicable recovery mechanisms within one year 1. Global benchmarking against analogue field developments & studies 2. Initial identification of potential recovery mechanisms & key risks + highlevel screening 3. Targeted appraisal campaign to address key risks to developments => phased field trials 4. Technical evaluation of do-ability of considered recovery mechanisms in field F 5. Economic screening to define required commercial conditions to make a fullfield project viable

6 Detailed EOR Screening Gradio Interference testing Key Technical risks identified Analogue studies

7 Analogues Studies Gradio Interference testing Analogue studies

8 Permeability [md] Word-wide Successful Steam Project Matrix Properties & Viscosities 100,000 10,000 1,000 Steam Projects Wordwide Fields with similar viscosity as F, non fractured, Sand Colour-coding by Viscosity 1-10 cp cp cp cp cp + (Unconsolidated Sand) Data from Moritis, Oil & Gas Journal, 2010 Porosity [%] F Global ongoing thermal EOR projects: 90% steam, sandstone reservoirs Similar viscosities as F: Only in un-fractured sandstone reservoirs with permeabilities > 1 D 2 orders of magnitude greater than F matrix permeabilities

9 Comparison with Carbonate Heavy Oil fields F thinner than any other reservoir Thickness Viscosities <1000cp Only 5 other fields with viscosities >1000cp => F very unique & unfavourable reservoir properties F Data from Oil & Gas Journal s 2010 worldwide EOR project review (Moritis, 2010), C&C Reservoirs online proprietary data bases and Buza, 2008 Viscosity

10 Permeability [md] Permeability [md] F permeabilities lowest (matrix and fracture) => F very unique and unfavourable matrix and fracture properties Carbonate Analogues S F Fracture Perms Reported matrix-only Production Issaran p 0cp 000cp rm cp cp cp >1000 Frac Perm Frac Perm Grosmont Ku-e-Mond AG F S Matrix Porosity [%] Matrix Porosity [%] Matrix Perms

11 Key Risks Gradios Key Technical risks identified Analogue studies Eliminated by Initial Screening

12 400m Rank SAGOGD Alt Thermal ISC Chemical Key Risks to EOR developments in Field F Pre Appraisal UNCERTAINTIES underlying the Risks identified pre Appraisal Risk/Opp Fault Leak Base seal leak Fracture Density Mobile water Low matrix perm N D Main Boundary Fault Hi So Lo?? 1 So ~ 80%???? 2 F 5? 4 3? So ~ 20% 6 S 30m 6 Sat. Oil 7 Water supply and disposal Showstopper Hi Risk Risk N/A Opportunity per Recovery Process

13 Targeted Appraisal Campaign Gradio Interference testing Key Technical risks identified Analogue studies

14 Gradio Surveys F-3 F-2 F-5 F-6 GR GR GR GR Air column m Foreign fluid (brine) in F-2,3 and 5 Formation water in F-2,5,6 No Oil column was observed => Water-filled fracture network likely Air Brine Formation water

15 Interference Testing F-10 total losses while drilling (interference with 4 wells): F-2,3,7,8 F-10/F-2 max. Keff= 700 md F-10/F-3 max. Keff= 700 md Field D F-8 F-2 F10 F-7 F-9 F-3 F-1 F-3/F-2 Interference: Max. Keff: 300 md Field F Connected network of faults and fracture corridors Very low fracture permeability (~500mD) Main Boundary Fault non-sealing

16 Pressure (kpa) (kpa) Main Boundary Fault Non-Sealing F-8 F-10 F-3 Natih F-8 Natih Shuaiba No vertical exaggeration Effect of AGS10 Total Losses AGS8 AGS3 AGS2 F-9 F Drilling with losses in F-10 Acid induced losses F F-9 total losses after acid job was observed in F-3 and F F-3 Direct pressure communication across the Main Boundary Fault F-8 F-2 7-Jan Jan Jan-11 6-Feb-11 Date 16-Feb Feb-11 8-Mar Mar-11

17 Bottom-Seal Capacity of Hawar Special interference testing set-up to test seal capacity of Hawar Delayed signal arrival in Kharaib F-10 Gauge F-9 Packer Inject

18 Shuaiba Conceptual Fracture Model from New Data Acquired Conceptual Fracture model developed to explain the static and dynamic observation (wells, seismic Interefence testing, drilling) Connected Fracture corridors with isolated background fractures Hawar Background Fractures Fracture Corridor Orientation (N=27) Fracture corridor Permeability 300 to 700mD Water-filled Fracture corridor Spacing ~300 to 400m Length weighted Frequency

19 Rank SAGOGD Alt Thermal ISC Chemical SAGOGD Alt Thermal ISC Chemical Evolution of Risks with Appraisal Pre Appraisal Risk/Opp Hi Risk per Recovery N/A Process Opportunity Increase in likelihood of risk materialising Risk evolution with new data and study work Post Appraisal Risk/Opp 1 Fault Leak Fracture appear water filled only water produced cold Gradio surveys show no oil-in from fractures in 12 months Extended Cold production: only water Direct pressure communicatio n across fault Fault leaking Fault Leak 2 Base Seal Leak No analogue for Hawar as pressure seal Total losses across major fracture zones Lateral interference signal Base seal breached by major fracs spacing under analysis Base seal leak 3 Fracture Density Observed spacing much larger than field A Only one major fracture set; low frac. perm ~500mD Total losses in F- 7 fracture corridors continue to mid flank Detailed fracture spacing analysis and comparison with all fields in GSB Too sparse for GOGD but pos. OK for chemical Fracture Density 4 Mobile Water Only water produced in all (5) well tests Mobile water (in matrix also) Mobile water 5 Low Matrix Perm Leaching-prone rudist facies missing in F Plugs show <20mD; avg 3mD Can match F-1 build-up with < 5mD matrix rel. perm Incr. risk low matrix perm Low matrix perm 6 Sat. Oil Calculated log saturations confirmed by Dean Stark Measurements Sat. Oil 7 Water Supply and Disposal Water supply and disposal

20 Conclusions In field F approach demonstrated to be effective for rapid appraisal that should be applied to other discoveries entering the maturation funnel In the case of field F, a fast-pace maturation campaign was executed & key risks for thermal developments have materialised: Seal: fault leak, water-filled fracture system =>breached accumulation Reservoir: matrix blocksize too large, fracture & matrix permeability too low Saturation too low, reservoir too thin, oil viscosity too high => Heating efficiency too low Novel-chemical flooding techniques might provide a way to unlock other heavy-oil accumulations in carbonates. They are further evaluated for field F. Dynamic data are critical to characterize fracture networks. Total losses during a drilling operation are a good signal for interference testing

21 Petroleum Development Oman

22 Analogues Methodology Extensive research has been carried out to find analogues for F Analysis of general energy measures for steam projects Data base & literature research for heavy all heavy oil developments (SPE, CC data base, Oil & Gas Journal) Scanning of field data from the heavy-oil Carbonate provinces (Middle East, Europe, Canada, Mexico)

23 Numerical Fracture model Integrating All Data Large areas without connected fractures

24 Possible Outcomes Scenario Definition Probabilistic Screening of Subsurface Scenarios Boundary Fault No Seal (0.9) Seal (0.1) EOR Options and Showstoppers Key Subsurface properties Base Seal/ Fracture Rock Leaching Fracture spacing orientation upper Flow Unit 10 m DIP parallel & Fault Cr(0.2) Fl(0.05) parallel Cr (0.35), Fl (0.8) 40 m DIP parallel Patchy leaching Cr(0.5) Fl(0.35) Cr (0.65), Fl (0.2) (0.2) 400 m Extensive leaching Cr(0.3) Fl(0.6) (0.05) Water Mobility Sw No leaching (0.75) Sw < 0.3 Cr (0.8) Fl (0.3) Sw > 0.3 Cr (0.2), Fl (0.7) Development options Showstopper Technology Commercial showstopper SA-GOGD Energy efficiency CSS Boundary Fault not sealing and sparse fracture spacing (>40 m) and low fracture permeability Very slow process, low recovery Steam Drive Fracture Spacing < 400 m Energy efficiency, challenging in low permeability environment TA-WOGD (hot water) - Very slow process SAGD Low matrix permeability ISC Boundary Fault not sealing, effective fracture permeability <1D and fracture spacing >10 m Chemical drive Lack of Base Seal (Fracture Spacing < 400 m) Low injectivity, slow process

25 Results 1 Probabilistic Screening of Subsurface Scenarios SAGOGD SAGOGD CSS Steam CSS Drive Steam SAGDrive ISC SAGD (quasi Solvent ISC (quasi Drive SAGOGD) SAGOGD) Solvent Chemical Ass. Drive GOGD Drive Solvent TAWOGD Ass. GOGD TAWOGD Crest Flank Crest Flank Probabilistic score per recovery method for both crest and flank Zero score: at least one technical showstopper in all subsurface combinations Only CSS, steam drive, hot water oil gravity drainage (TAWOGD) novel-chemical drive appear technically possible

26 Warrlich, GEO12 Acknowledgements The Authors thank Petroleum Development Oman and Sultanate of Oman Ministry of Oil and Gas for permission to present this work Petroleum Development Oman