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Geosteering

Geosteering

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  • Hi Dr. Stromberg, May I please ask to get the NMR course file that you have uploaded in the website?

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Otter Paper Otter Paper Presentation Transcript

  •  
  • Introduction
    • Introduction to Otter
    • Drilling Targets & Requirements
    • GeoVision Images and Geosteering
    • Data-flow and Communication in the decision process
    • Case Study
      • Otter 210/15a-T1
    • Conclusions
  • Field Location
  • 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
  • Stratigraphy
  • Well T1
  • Otter Well T1
  • Geoteering Targets – Well T1 210 m 8 m T10 Sand 3000 m OWC N S
  • Geosteering Objectives
    • Maintain Standoff from OWC
    • Target Best Quality Rock (T10 sands)
      • 8m target (upper part 4 m target)
    • Avoid poor quality sandstones above T10
    • Avoid Coals in Top Ness immediately below T10
    • Reinterpret structure real time and adjust trajectory to account for sub-seismic faults
  • Geosteering Issues
    • Lag time
      • Time between receiving data and making the decision (analysis time)
      • Time between making the decision and achieving the target objective (trajectory adjustment time)
        • 4 deg per 30m, if you want to change the trajectory by 6 deg then 45 m is required
      • Distance between the bit and the measurement device
    • Things can change during the lag time
      • Be prepared for the unexpected
    • No real ‘look ahead’. You can look up and look down but not ahead
  • 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
  • GeoVision Resistivity Logging Recorded Mode Image 70 ft
  • GeoVision Resistivity Logging
  • Data Flow and Communication Operations Geology & Petrophysics (TFEE UK) Geosteering Specialist Schlumberger (War Room) Well Site Geologist INTERACT Real Time Data
  • T1 Trajectory and Areas of Uncertainty Top Brent Sub-seismic faults Throw on main fault Coal? N S
  • Forward Model N S
  • Staying in the Target Zone OUT OF TOLERANCE Target Zone 330 m of pay Ness plots as T20-T30 Caution
  • Landing the Well 9m low to prognosis Resistive Conductive
  • Landing the Well N S Dip = 4.7 deg Azimuth = 294
  • Landing the well Good quality T10 Poorer quality T10 Actual Prognosis Good quality T10 Poorer quality T10 T20 T30 T20 T30
  • Faults 2770m 2770 m
  • Tagging The Coal In the Ness RHOBB RHOBU Penetrating Coal From Top Below Coal Above Coal Below Coal Above Coal 2810m 2770m Fault
  • Sub-Horizontal to Coal
  • Top Ness Coal & Sub-Seismic Faults N S
  • 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
  • Tagged Heather? 2810m 2854m T20/T30 L Heather T10 Prognosis Actual
  • Based on Image Dips - Structural Cross-Section Indicates Silty T10 Unit not Heather. N S
  • Based on Image Dips - Structural Cross-Section Indicates Silty T10 Unit not Heather. N S
  • Main Fault BN/BS
  • Logging Response Into BS BN - Silty T10 BS Prognosis Into T10 Prognosis Into NESS
  • Dip as Expected – Maintain Pay Zone N S
  • Tagged Coal at TD (Top Ness Confirmed)
  • Pre-Drill N S
  • 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
  • Conclusions – Real Time Images
    • Real time images and log data allow rapid adjustment of the structural model
    • The well trajectory can be continually adjusted to maximise pay
      • 4 deg per 30 m
    • Side tracks can be avoided
    • Reduced rig time
    • Reduced well time
    • Value added data for structural review and reservoir interpretation
  • Acknowledgements Logicom for 3D visualisation of RAB images Otter Partnership