Otter Paper


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Otter Paper

  1. 2. Introduction <ul><li>Introduction to Otter </li></ul><ul><li>Drilling Targets & Requirements </li></ul><ul><li>GeoVision Images and Geosteering </li></ul><ul><li>Data-flow and Communication in the decision process </li></ul><ul><li>Case Study </li></ul><ul><ul><li>Otter 210/15a-T1 </li></ul></ul><ul><li>Conclusions </li></ul>
  2. 3. Field Location
  3. 4. Otter Field Summary 36.5 api Oil density 443 scf/bbl GOR 78.5 C Temp 1970m SS 92m Standoff 2062m SS Crest OWC Oct. 2002 subsea tie-back to Eider First Oil Approval 2001 Dev. Plan 2000 TotalFina 210/15a-6 Appraisal 1997 Fina 210/15a- DST 7650 BOPD Appraisal 1994 3D Seismic 1977 Philips 210/15-2 DST 4746 BOPD Discovery Brent Gp. Sandstones (98m thick N:G 90% Phi 24% Sw 32% Perm 400 mD Reservoir Easterly tilted fault block 4.3 km 2 Trap
  4. 5. Stratigraphy
  5. 6. Well T1
  6. 7. Otter Well T1
  7. 8. Geoteering Targets – Well T1 210 m 8 m T10 Sand 3000 m OWC N S
  8. 9. Geosteering Objectives <ul><li>Maintain Standoff from OWC </li></ul><ul><li>Target Best Quality Rock (T10 sands) </li></ul><ul><ul><li>8m target (upper part 4 m target) </li></ul></ul><ul><li>Avoid poor quality sandstones above T10 </li></ul><ul><li>Avoid Coals in Top Ness immediately below T10 </li></ul><ul><li>Reinterpret structure real time and adjust trajectory to account for sub-seismic faults </li></ul>
  9. 10. Geosteering Issues <ul><li>Lag time </li></ul><ul><ul><li>Time between receiving data and making the decision (analysis time) </li></ul></ul><ul><ul><li>Time between making the decision and achieving the target objective (trajectory adjustment time) </li></ul></ul><ul><ul><ul><li>4 deg per 30m, if you want to change the trajectory by 6 deg then 45 m is required </li></ul></ul></ul><ul><ul><li>Distance between the bit and the measurement device </li></ul></ul><ul><li>Things can change during the lag time </li></ul><ul><ul><li>Be prepared for the unexpected </li></ul></ul><ul><li>No real ‘look ahead’. You can look up and look down but not ahead </li></ul>
  10. 11. GeoVision Resistivity Logging PowerDrive VADN PowerPulse MWD 6 bps for real-time image GVR Gamma Ray Azimuthal Ring resistivity electrode for high resolution laterolog resistivity Button Resistivity electrodes for azimuthal images (deep, medium, shallow) PDC bit 3.5 m 21 m
  11. 12. GeoVision Resistivity Logging Recorded Mode Image 70 ft
  12. 13. GeoVision Resistivity Logging
  13. 14. Data Flow and Communication Operations Geology & Petrophysics (TFEE UK) Geosteering Specialist Schlumberger (War Room) Well Site Geologist INTERACT Real Time Data
  14. 15. T1 Trajectory and Areas of Uncertainty Top Brent Sub-seismic faults Throw on main fault Coal? N S
  15. 16. Forward Model N S
  16. 17. Staying in the Target Zone OUT OF TOLERANCE Target Zone 330 m of pay Ness plots as T20-T30 Caution
  17. 18. Landing the Well 9m low to prognosis Resistive Conductive
  18. 19. Landing the Well N S Dip = 4.7 deg Azimuth = 294
  19. 20. Landing the well Good quality T10 Poorer quality T10 Actual Prognosis Good quality T10 Poorer quality T10 T20 T30 T20 T30
  20. 21. Faults 2770m 2770 m
  21. 22. Tagging The Coal In the Ness RHOBB RHOBU Penetrating Coal From Top Below Coal Above Coal Below Coal Above Coal 2810m 2770m Fault
  22. 23. Sub-Horizontal to Coal
  23. 24. Top Ness Coal & Sub-Seismic Faults N S
  24. 25. Problematic (Shaley?) Section Encountered 2840 m 2812 m Ness T10 Fault 2854 m N S Increased GR Decrease RT Separation of ROBB and ROBU – close to bed boundary- thin bed
  25. 26. Tagged Heather? 2810m 2854m T20/T30 L Heather T10 Prognosis Actual
  26. 27. Based on Image Dips - Structural Cross-Section Indicates Silty T10 Unit not Heather. N S
  27. 28. Based on Image Dips - Structural Cross-Section Indicates Silty T10 Unit not Heather. N S
  28. 29. Main Fault BN/BS
  29. 30. Logging Response Into BS BN - Silty T10 BS Prognosis Into T10 Prognosis Into NESS
  30. 31. Dip as Expected – Maintain Pay Zone N S
  31. 32. Tagged Coal at TD (Top Ness Confirmed)
  32. 33. Pre-Drill N S
  33. 34. Post Drill Interpretation OWC 50 m Sand N/G: 95% (218 m) Pay N/G: 91% (210 m) Average Permeability: 1500 mD Average Porosity: 25% N S
  34. 35. Conclusions – Real Time Images <ul><li>Real time images and log data allow rapid adjustment of the structural model </li></ul><ul><li>The well trajectory can be continually adjusted to maximise pay </li></ul><ul><ul><li>4 deg per 30 m </li></ul></ul><ul><li>Side tracks can be avoided </li></ul><ul><li>Reduced rig time </li></ul><ul><li>Reduced well time </li></ul><ul><li>Value added data for structural review and reservoir interpretation </li></ul>
  35. 36. Acknowledgements Logicom for 3D visualisation of RAB images Otter Partnership