An enhancement of the formation factor parameters ‘a’ and ‘m’
Walid M. Mabrouk 1 2 Khalid S. Soliman 1 Mohamed A. Tawfic 11 Geophysics Department, Faculty of Science, Cairo University, Giza, Egypt.
2 Corresponding author. Email: walid_mabrouk@yahoo.com
Exploration Geophysics 43(2) 87-94 https://doi.org/10.1071/EG10015
Submitted: 7 May 2010 Accepted: 6 March 2012 Published: 23 April 2012
Abstract
The use of incorrect values of the formation constants a, tortuosity factor,and m, cementation exponent, in Archie’s water saturation equation, can result in the overlooking of potential producible zones. Usually, assumptions are made to approximate a and m where often m is 2, while a may be 0.81 or 1.0, depending on the type of lithology. When core is available, accepted laboratory practices exist to calculate a and m, however, these laboratory steps are generally not considered routine analysis and, in order to save time and money, may not be conducted.
Core analysis for a and m require saturating to 100% multiple plugs of varying porosity with water of known resistivity. The resistivity of each water saturated core is graphed on a log-log graph with porosity to determine a and m.
This work illustrates a simple method of calculating a and m that is dependent on sonic transit time and bulk density, and on knowing one cementation exponent value from core measurements.
The method is tested and applied on a large number of samples to ensure its ability to determine formation factor parameters a and m.
Key words: cementation exponent, formation factor parameters, formation resistivity factor, tortuosity.
References
Archie, G. E., 1942, The electrical resistivity log as an aid in determining some reservoir characteristics: Transactions of the American Institute of Mechanical Engineers, 146, 54–62Asquith, G. B., and Gibson, C., 1982, Basic well log analysis for geologists: AAPG.
Bassiouni, Z., 1994, Theory, measurements, and interpretation of well logs: The Society of Petroleum Engineering Inc.
Carothers, J. E., 1968, A statistical study of the formation factor relation to porosity: The Log Analyst, 9, 38–52
Dewan, J. T., 1983, Essentials of modern open-hole log interpretation: PennWell Publ. Co.
Kamel, M. H., Mabrouk, W. M., and Bayoumi, A. I., 2002, Porosity estimation using a combination of Wyllie-Clemenceau equation in clean sand formation from acoustic logs: Journal of Petroleum Science Engineering, 33, 241–251
| Porosity estimation using a combination of Wyllie-Clemenceau equation in clean sand formation from acoustic logs:Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XivVans7w%3D&md5=5276c47c843a22a05066b38eb8c2e5aeCAS |
Paillet, F. L., 1981, Predicting the frequency content of acoustic waves in boreholes: 22nd annual logging symposium, Transactions of S.P.W.L.A., Mexico City, Mexico.
Porter, C. R., and Carothers, J. E., 1970, Formation factor-porosity relation from well log data: Soc. Professional Well Log Analysts, 11th Ann. Logging Symp., Trans., Paper D.
Ransom, R. C., 1974, The bulk volume water concept of resistivity well-log interpretation: a theory based on a new reservoir rock resistivity model: The Log Analyst, 14, No. 1
Schlumberger, Inc., 1972, Log interpretation. Volume I – Principles, 2nd edition: Schlumberger Ltd.
Schlumberger, Inc., 1979, Log interpretation charts: Schlumberger Ltd.
Sen, P. N., Straly, C., Kenyon, W. E., and Whittingham, M. S., 1990, Surface-to-volume ratio, charge density, nuclear magnetic relaxation, and permeability in clay-bearing sandstones: Geophysics, 55, 61–69
| Surface-to-volume ratio, charge density, nuclear magnetic relaxation, and permeability in clay-bearing sandstones:Crossref | GoogleScholarGoogle Scholar |
Sethi, D. K., 1979, Some considerations about the formation resistivity factor-porosity relationships: Soc. Professional Well Log Analysts, 20th Ann. Logging Symp., Trans., Paper L.
Sprunt, E. S., Henset, W. M., York, C. E., and Honarpour, M. M., 1988, Compilation of electrical resistivity measurements performed by twenty-five laboratories: The Log Analyst, 29, 13–39
Timur, A., Hempkins, W. B., and Worthington, A. E., 1972, Porosity and pressure dependence of formation resistivity factor for sandstones: Trans., Cdn. Well Logging Soc., 4, paper D.
Winsauer, W. O., Shearin, H. M., Masson, P. H., and Williams, M., 1952, Resistivity of brine-saturated sands in relation to pore geometry: Bulletin of the American Association of Petroleum Geologists, 36, 253–277
| 1:CAS:528:DyaG38Xis1ejtg%3D%3D&md5=35f96936608eb759a95cad81c02cb65eCAS |
Worthington, P. F., 1985, The evaluation of shaly-sand concepts in reservoir evaluation: The Log Analyst, 24, 23–26
Wyllie, M. R. J., and Gregory, A. R., 1953, Formation factors of unconsolidated porous medium: influence of practical shale and effect of cementation: Transactions of the American Institute of Mechanical Engineers, 198, 103–110