Correlations between TDS and electrical conductivity for high-salinity formation brines characteristic of South Atlantic pre-salt basins

Abstract

Total dissolved solids (TDS) is an important property in the characterization of natural waters for diversified applications, such as in geochemistry and the petroleum industry. Under appropriate circumstances, the determination of this parameter through correlations with the electrical conductivity (EC) of aqueous systems yields considerable advantages over the gravimetric method. However, the development of empirical equations correlating TDS and EC is still required due to the physical-chemical complexity of charge transport in multicomponent natural waters. Most existing correlations were built considering systems in the lower or medium salinity range. In this context, this research aims to provide experimental correlations between TDS and EC in a broad concentration range for high salinity formation brines characteristic of the pre-salt reservoirs. It contributes to filling a gap in the literature for geochemical systems of this nature. Moreover, correlations were also obtained for a concentrated desulphated seawater and an aqueous sodium chloride solution in the same salinity range. For all aqueous solutions, the polynomial fittings of degree greater than one fit the experimental data better compared to both linear and exponential equations. In addition, the solutions with higher concentration of divalent ions had lower EC than the solutions dominated by monovalent ions with the same ionic strength. This evidences the effect of ion pairing on the EC, particularly in solutions of high ionic strength. Therefore, the use of a general correlation to represent solutions with dramatic variations in chemical composition carries substantial error, particularly in the high salinity range. Thus, a specific correlation must be developed to represent brines with similar composition.

The Effects of Some Physical and Chemical Factors on Apparent Resistivity of Surface Soil in the University of Mosul, Mosul City, Northern Iraq

“…Salinity is defined by the presence of the main dissolved inorganic solutes (primarily Na +1 , Mg +2 , Ca +2 , K +1 , Cl -1 , SO4 -2 , HCO -3 , NO3 -1 and CO3 -2 ) in aqueous samples. Most of laboratory studies performed to establish the relationship between salinity and clay soil resistivity revealed that the two have a strong relationship [8,14]. This relationship came from the fact that the separation and movement of positive and negative ions, while applying an electric potential to the solution, greatly helps in the transfer of electrical charge (current flow).…”

The irrigation suitability potential of an effluent treated by a pseudo‐natural wetland

“…Also, a very strong correlation can be observed between TDS and EC; it has to be noted that TDS and EC are quality parameters used to describe salinity levels in the water. In the literature, these two parameters have also been observed to be highly correlating (Rebello, Siepman, & Drexler, 2020; Thirumalini & Joseph, 2009) and usually, one can be estimated from the other using the expression in Equation () (Chang et al, 1983). But the process of determining TDS from water is more complex compared to TDS.…”

Compositions and Interior Structures of the Large Moons of Uranus and Implications for Future Spacecraft Observations

“…Extrapolation of the temperature dependence of NaCl solubility suggests only a slight increase of this value at subzero temperatures (e.g., about 10% increase from 273 to 233 K; Cong et al., 2019 ). Brines saturated in sodium chloride are common on Earth and have conductivities of about 23 S/m for a reference temperature of 298 K (e.g., Rebello et al., 2020 ).…”