Well Log Analysis & Consulting Lost your card! Your logo would go at the top instead of the text.

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 A basic introduction

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 Text points need to be short, to the point.

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 I just grabbed a core image from a google search. Best to get a photo you have, or can get permission to use Our Philosophy Minerals Are the Cornerstone Of Efficient Log Interpretation

Conventional Approach vs Our Approach Data Collected Guess Vsh, matrix Use Vsh Guess Sw Type of results: Vsh is empirical, wrong Sw conclusions, uncertainty is high Our approach Data Collected Derive grain density Derive m, n, Rw Sw = core The purpose of this slide is to get a bit more involved in the technical aspects of the analyses to demonstrate the added information you provide. The image at the right would show the typical information that is analyzed, then the information and plots you provide would fade in/ overlay.. Type of results: Derive from core-based data, best conclusions, lower uncertainty Why use guesswork from 1950’s when better methods available?

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

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

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

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

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

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: THE POINT IS SERIOUS ERROR IS POSSIBLE WITH A VSH MODEL. Depends too heavily on analyst’s preconceived ideas of pay/no pay.

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.

APPENDIX: Example How to obtain m, n

APPENDIX: Example How to obtain Sw

APPENDIX: Example How to obtain Rw: step 1

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.

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.

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.

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.

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

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

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.

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!

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

Contact Information Robert V Everett Petrophysics Consulting, Teaching, Coaching Address PO Box 271 – 1589 Nurmi Road Merville BC V0R 2M0 Robert: 250-442-9696 / roberteverettsupercomputer@gmail.com Jamie: 403-620-2403 / jamie@everett-energysoftware.com