Influence of the chemical composition of reservoir water on specific electrical resistance

In hydrocarbon reserves evaluation, reservoir rocks are commonly distinguished according to their fluid saturation using a threshold value of reservoir water resistivity. This parameter is usually derived from the chemical composition of formation water recalculated to an equivalent NaCl concentration. However, the existing method introduces significant errors when reservoir water contain elevated concentrations of hydrocarbonate ions (HCO₃⁻). Accordingly, this method cannot be used for hydrocarbon fields in the northern part of the West Siberian Basin, where groundwater often contains high levels of dissolved hydrocarbonate. To study the influence of reservoir water chemical composition on value of electrical resistivity, the authors of this article consider the results of determining the resistivity of reservoir water done in laboratory conditions obtained from 127 water models that closely replicate the composition of natural reservoir water under different temperatures from 20 to 100 °C. As a result of studies, the authors found that to obtain the values of the resistivity of reservoir water at any content of hydrocarbonate ion, it is expedient to use a formula that takes into account mineralization obtained from the dry residue in laboratory conditions. When the hydrocarbon content is below 10% for determining standard method also produces reliable results.

1. Gimatudinov Sh. K. Physics of Oil and Gas Reservoirs. Moscow: Nedra; 1971. 312 p. (In Russ.).

2. Dakhnov, V. N. Interpretation of the results of geophysical studies of well sections. Moscow: Nedra; 1982. 448 p. (In Russ.).

3. Djebbar T., Donaldson E. C. Petrophysics: theory and practice of measuring reservoir rock and fluid transport properties. Elsevier, 2004.

4. Rodivilov D. B., Kokarev P. N., Shay T. A., Sidorova T. N. Study of the effect of low salt content formation waters on geophysical and petrophysical characteristics of the terrigenous rock. Кarotazhnik. 2013;9(231):50–64. (In Russ.).

5. Iselidze O. V., Zhukov V. S., Tsybulsky S. P., Bayanova N. G. Influence of temperature on specific electroresistance of the water-saturated sandstone. Vesti gazovoi nauki. 2014;4(20):184–187. (In Russ.).

6. Latyshova M. G. Practical Guide to the Interpretation of Well Geophysical Studies. Moscow: Nedra; 1991. 219 p. (In Russ.).

7. Guidelines for calculating geological reserves of oil and gas using the volume method. Moscow–Tver: VNIGNI, NTC; 2003.

8. Antropov L. I. Theoretical Electrochemistry. Moscow: Higher School; 1984. 519 p. (In Russ.).

9. Vorobyov N. I. Application of Electrical Conductivity Measurements for Characterizing the Chemical Composition of Natural Waters. Moscow: USSR Academy of Sciences Publishing House; 1963, pp. 24–94. (In Russ.).

10. A Concise Handbook of Physical and Chemical Quantities; edited by A. A. Ravdel and A. M. Ponomaryova. St. Petersburg: Ivan Fedorov; 2003. 240 p. (In Russ.).

11. Kuznetsova A.M., Mamashev V.G., Shkilev V.M. Modeling the electrical resistivity of the ion conductive terrigenous sedimentary rocks to assess the characteristics of application of the Archie-Dahnov equation. In: Geodynamics. Geomechanics and Geophysics: Proceedings of the 19th All-Russian Conference, Novosibirsk, July 22–28, 2019. Novosibirsk: Publishing House of the Institute of Mining, Geology and Geophysics of the Siberian Branch of the Russian Academy of Sciences; 2019:42–44. (In Russ.).

12. Ponomarenko O. M., Istomina K. A., Makasheva L. D., Bolshakov M. N. Experimental exploration of the effect of NaCl and other salts solution mineralization on the electrical resistivity of the solution. Actual Problems of Oil and Gas. 2019;4(27). https://doi.org/10.29222/ipng.2078-5712.2019-27.art7 (In Russ.).

13. Tikhonov I. A. Influence of the ionic composition of water on its electrical conductivity. Sanitation. Heating. Air Conditioning. (S.O.K.). 2021;(2):42–47. (In Russ.).