The document discusses the importance of petrophysics in analyzing well logs and reservoirs. It explains that petrophysics goes beyond basic log analysis by seeking to understand why rocks hold fluids in certain ways based on their properties. This allows petrophysicists to better quantify remaining oil in existing fields and determine whether oil is movable or trapped as residual saturation. With aging fields and marginal developments, advanced petrophysical analysis is needed to understand fluid distributions and plan future well performance and recovery.

1. Petrophysics: More Important Than Ever Graham Davis Chief Petrophysicist President - Aberdeen Formation Evaluation Society (AFES)

3. Petrophysics – The Customers Calgary Mappers Drillers Geophysicists Geologists Model Builders Petrophysicist Engineers Corporate

4. Well Logging – making measurements in our Wellbores Photo courtesy of Reeves Wireline

5. Routine Log Acquisition

6. Routine Log Analysis Oil Leg Average Sw = 44% -10,060 TVDSS “OWC?” Eyeball Sw 30%

7. Routine Log Analysis – Parameter Sensitivity Eyeball Sw 20% Oil Leg Average Sw = 38% -10,110 TVDSS “OWC?”

8. Routine Log Analysis – SWH Modelling Now we’re getting a bit more petrophysical! Saturation height functions require an understanding of how much oil a rock is capable of holding at any height (depth) in the reservoir

9. Routine Log Analysis + Core Some think of Log + Core = Petrophysics (but really core is just another log unless you “learn” from it) Too much Water in the Core? WBM invasion? Too much Water in the log? Shaly sand?

10. Petrophysical Analysis – Flow Prediction Even a Geologist could pick the Perfs here (but might be surprised at lack of flow from upper interval) Tarbert & Rannoch are the “Tricky” Brent reservoirs!

11. Petrophysical Analysis – Moveable Oil? If taken this far, this is probably where the petrophysics would have stopped in days gone by RESIDUAL

12. Petrophysical Analysis – What if drilled today? Hypothetical swept profile – typical of the logs seen today Now things get complicated!

13. Petrophysical Analysis – Where’s the water now? We know, from the SWH, what the initial oil saturation would have been, so we can infer where water influx (CYAN) has occurred … ..but can we determine whether residual saturation has been reached?

14. Petrophysical Analysis – Where’s the water now? We know, from the SWH, what the initial oil saturation would have been, so we can infer where water influx (CYAN) has occurred … ..but can we determine whether residual saturation has been reached? By the way – we rarely get new core in old fields (except for special studies)

15. Petrophysical Analysis – Residual or Moveable? Obviously it’s not simple – there are even more uncertainties and errors in evaluating saturations at this end of the spectrum The salinity of the sweep water mix is uncertain

16. Petrophysical Analysis – Residual or Moveable? Electrical (Archie) Parameters in the secondary imbibition cycle are often poorly understood Obviously it’s not simple – there are even more uncertainties and errors in evaluating saturations at this end of the spectrum

17. Log Analysis – Residual or Moveable? If you just did the “Log Analysis” you may not know whether the oil saturation was swept-residual (so not producible) or poorly charged but still producible.

20. Aberdeen Formation Evaluation Society (AFES) www.afes.org.uk

22. It Seems Like a Lifetime in Petrophysics! When you first hear that your project is in Petrophysics ..you’re young and naturally a bit apprehensive!

23. It Seems Like a Lifetime in Petrophysics! Then, with experience, older and wiser, you can look back on your time in Petrophysics with happy memories You made a difference!!

24. The Premium Value, Defined Growth Independent The Future Clearly Defined St. Magnus House, Guild Street, Aberdeen AB11 6NJ www.cnrl.com