Well Log Analysis & Consulting

1. Well Log Analysis & Consulting

2. About Us • Everett Petrophysics specializes in mineral-based well log interpretation • For 28 years we have been providing consulting, coaching and analytical services globally; previous 27 years spent with Schlumberger. • Software has been developed to use Nuclear Spectroscopy (elements) and Nuclear Magnetic Resonance (total and free porosity) to derive grain density, exponents m & n, Rw, permeability, porosity and saturation. ROBERT (BOB) EVERETT P.Eng • Over 55 years of experience using petrophysics analytical techniques to interpret oil and gas well logs • Provided consulting services for Unocal, Z and S, Dresser, Baker Hughes, Schlumberger and the University of Texas at Austin, as well as many international Energy companies • B.Sc. In Mechanical Engineering James (Jamie) Everett, B.A., M.Sc. • 30 years experience developing highly specialized software • Development of software for companies such as Verity, Autonomy and Hewlett Packard • B.A. with High Honours in Physics as well as an M.Sc. in Biomedical Engineering

3. Analytical Services • Calculation of full mineralogy: full mineralogy is possible with elements from Nuclear Spectroscopy • Important as the attributes of the minerals are used to provide a unique solution and has value in obtaining the best petrophysical analysis possible • accurate porosity from accurate grain density • Accurate Sw over full range of Sw • Better permeability without special shift-constants • Provides results in same units as core analysis such as weight fractions of minerals • A system that can be relied on

4. Analytical Services • Calculation of full mineralogy: the best way to analyze logs • Aspect of analysis 2: rather than using Vsh, which is not measurable in routine core analysis, use Si, Ca, Al, Fe, Ti, S, Gd which are measurable. Convertible to minerals, CEC, m, n, Grain density etc. • Aspect of analysis 3: logs respond to minerals and elements; makes sense to use them Our PhilosophyMinerals Are the Cornerstone Of Efficient Log Interpretation

5. Conventional Approach vs Our Approach Conventional approach Data Collected Guess Vsh, matrix Use Vsh Guess Sw Type of results: Vsh is empirical, wrong Sw conclusions, uncertainty is high Our approach Derive m, n, Rw Derive grain density Data Collected Sw = core Type of results: Derive from core-based data, best conclusions, lower uncertainty Why use guesswork from 1950’s when better methods available?

6. Example Case 1: Duvernay • Project Details: Duvernay Unconventional • Conventional Vsh results were valid only at low Sw • What services we provided: Offset Nuclear Spectroscopy added • What info we added: cation exchange capacity from each clay family results in full range of Sw • CONCLUSION: Mineral-based interpretation works

7. Example Case 1: Duvernay • Conventional Vsh results were valid only at low Sw

8. Example Case 1: Duvernay • Cation exchange capacity from each clay family results in full range of Sw

9. Example Case 2: Tight gas • Project Details: tight gas environment • Conventional Vsh results missed the zone • Mineral-based results located the zone • We added Nuclear Spectroscopy from offset well • CONCLUSION: Mineral-based interpretation works

10. Example Case 2: Tight Gas • Conventional Vsh results missed the zone: Sw 100%, PHIE < 5%

11. Example Case 2: Tight Gas • Conventional Vsh results missed the zone: Sw 100%, PHIE < 5% WEAKNESS is Rw, m, n, Vsh, Perm All “guessed” with empirical models NOTE: THEPOINT IS SERIOUS ERROR IS POSSIBLE WITH A VSH MODEL. Depends too heavily on analyst’s preconceived ideas of pay/no pay.

12. Example Case 2: Tight gas Mineral-based results located the zone: SW 30%, PHIT 12%: Productive with Frac. STRENGTH is Rw, m, n, GD & Perm: All are Internally calculated, originally from core data Mineral-based Calculation ok elements/minerals Provide cec, GD, perm & constraints for m, n.

13. APPENDIX: Example How to obtain m, n

14. APPENDIX: Example How to obtain Sw

15. APPENDIX: Example How to obtain Rw: step 1

16. APPENDIX: Example How to obtain Rw: step 1 • Rw_SP is derived from an estimated field value and a based lined SP. The trick is how to baseline the SP. • Other methods baseline the SP by drawing a line from whatever is considered shale, called a shale baseline. • This method ‘calculates’ and average zero from the SP equation. This step is important as shales have an SP as they are never zero.

17. APPENDIX: Example How to obtain Rw: step 1a • First, calculate temperature from this equation or any other that provides a geothermal reservoir temperature. Depending on circulation time, the geothermal temperature sis expected to be 10F to 20F above maximum recorded logged temperature. • 0.0198*depth in ft + 42.8 degF • Modify as you see fit.

18. APPENDIX: Example How to obtain Rw: step 1b, SP_ZERO • Next calculate the estimated field Rw using the temperature gradient; standard formula • Rw_known = 0.025*(75+6.77)/(TEMP_DEGF+6.77) • Now calculate Rmf using the same formula 0.04*(87+6.77)/(TEMP_DEGF+6.77) • Then SP_ZERO = (61+0.133*TEMP_DEGF) *LOG(RMF/RW_KNOWN)+add • The “add” is a constant to make the average value zero. This SP_ZERO is the key step.

19. APPENDIX: Example How to obtain Rw: step 1c, SP_shift & SP_baselined • Next, calculate SP_SHIFT = SP + add2 • Where add2 is zero to start with but will be changed later. • Now SP_BASELINED = SP_SHIFT-SP_ZERO • Finally RW_SP = RMF/(10^(SP_BASELINED/(-1*(61+0.133*TEMP_DEGF)))) • Now test to see if Rw_SP comes close to Rw_KNOWN. • If not, supply a new add2 & iterate until they are close. See plot next.

20. APPENDIX: Example How to obtain Rw: step 1c, shift required

21. APPENDIX: Example How to obtain Rw: step 1c, shift made Add2=+40 Now RW_SP_CALC set to RW_SP

22. APPENDIX: Example How to obtain Rw: step 2, compare Ro to Rt; re-shift Dashed Rw_SP_USED After “add2” changed so that Ro=~Rt at arrow i.e. at low Resistivity, water or shale, since Ro has CEC correction.

23. APPENDIX: Example How to obtain Rw: step 2, compare Ro to Rt; re-shift Dashed “Rw_SP_USED” after “add2”changed so that Ro=~Rt at blue arrow. i.e. at low Resistivity, water or shale, since Ro has CEC correction. Now we have a Rw that can be used for the entire well as it is modulated by the SP. This is an oil-base mud & SP was predicted!

24. Conclusion • Why this information is important: log interpretation used to be more art than science; times have changed. • Additional point: with Nuclear Spectroscopy and Nuclear Magnetic Resonance, better science in interpretation has resulted: all parameters initially internally computed without analyst bias. When science-based interpretation is available, why not use it? The conventional Vsh approach was all we had before 1980s but now we have a better, more accurate way to provide Petrophysics Designed to Honour Core

25. Contact Information Robert V Everett PetrophysicsConsulting, Teaching, Coaching AddressPO Box 271 – 1589 Nurmi RoadMerville BCV0R 2M0 Robert: 250-442-9696 / roberteverettsupercomputer@gmail.comJamie: 403-620-2403 / jamie@everett-energysoftware.com