In domestic practice of calculating and recalculating reserves, the assessment of water saturation of rocks is carried out using the Dakhnov – Archie model. Its parameters can be adjusted only for one constant value of mineralization. This model works well in pure non-clayey sandstones, but for clayey sandstone, it is necessary to use complex models of electrical conductivity based on measuring electrical conductivity at different mineralization, taking into account the effect of additional conductivity arising at the boundary of the liquid and solid phase. Using experimental data on the electrical conductivity of core samples at different mineralizations in the full and partial water saturation mode, three models of electrical conductivity were considered: B.Yu. Wendelshtein, Waksman – Smits,, Double Water. A number of assumptions, including the effect of double electric layer (DEL) on the saturation parameter and the need to normalize additional electrical conductivity to the current water saturation to account for the increase in the effect of the DEL with a decrease in water saturation, required verification on core samples. The influence of mineralization on the cementation coefficient was confirmed; the influence of the saturation parameter on the rock remains the same regardless of mineralization. New data do not confirm the need to take into account the influence of the DEL on the saturation coefficient and normalize the additional electrical conductivity to the current water saturation with a decrease in the total water saturation. The modification of the models was performed, which resulted in simplification and improvement of the convergence of the calculated electrical conductivities with experimental data.
References
1. Archie G.E., The electrical resistivity log as an aid in determining some reservoir characteristics, Transactions of the AIME, 1942, V. 146, pp. 54-62,
DOI: http://doi.org/10.2118/942054-G
2. Dakhnov V.N., Interpretatsiya karotazhnykh diagramm (Interpretation of well logs), Moscow-Leningrad: Gostoptekhizdat, 1941, 496 p.
3. Dakhnov V.N., Geofizicheskie metody opredeleniya kollektorskikh svoystv i neftegazonasyshcheniya gornykh porod (Geophysical methods for the determination of reservoir properties and oil and gas saturation of rocks), Moscow: Nedra Publ., 1985, 310 p.
4. Ellanskiy M.M., Petrofizicheskie svyazi i kompleksnaya interpretatsiya dannykh promyslovoy geofiziki (Petrophysical relationships and complex interpretation of production geophysics data), Moscow: Nedra, 1978, 215 p.
5. Ellanskiy M.M., Ispol'zovanie sovremennykh dostizheniy petrofiziki i fiziki plasta pri reshenii zadach neftegazovoy geologii po skvazhinnym dannym (Using modern achievements of petrophysics and reservoir physics in solving problems of oil and gas geology based on well data), Moscow: Publ. of Gubkin University, 1999, 111 p.
6. Vendel'shteyn B.Yu., On the relationship between the porosity parameter, surface conductivity coefficient, diffusion-adsorption activity and adsorption causes of terrigenous rocks (In Russ.), Proceedings of MINKhiGP, 1960, V. 31, pp. 16–30.
7. Clavier C, Coates G, Dumanoir J., Theoretical and experimental bases for the Dual-Water model for interpretation of ShalySands, SPE-6859-PA, 1984,
DOI: http://doi.org/10.2118/6859-PA
8. Waxman M.H., M. Smits L.J., Electrical conductivities in oil-bearing shaly sands, Society of Petroleum Engineers Journal, 1968, DOI: https://doi.org/10.2118/1863-A
9. Simandoux P., Dielectric measurements in porous media and application to shaly formation, Revue del’Institut Francais du Petrole, 1963, pp. 193–215 (Translated text in SPWLA Reprint Volume Shaly Sand, July 1982).
10. Poupon A., Leveaux J., Evaluation of water saturation in shaly formations, Trans. SPWLA 12th Annual Logging Symposium, 1971, pp. 1–2.
11. Dakhnov V.N., Promyslovaya geofizika (Industrial geophysics), Moscow: Gostoptekhizdat Publ., 1959, 423 p.
