Influence of Salt Concentration and Type on Dielectric Permittivity of Rocks
Downtown Houston
Speaker:
Seminar Date: Feb 06 2025
Registration Opens: Feb 03 2025 - Feb 07 2025
Time: 12:00 PM - 01:00 PM (US CDT)
Admission/Registration Link: None
Donation Link: None
Meeting/Webinar Link: https://register.gotowebinar.com/register/1179018858175046494
Contact: Artur Posenato Garcia (VP Downtown, SPWLA Houston Chapter)
Corresponding: vpdowntown@spwla-houston.org
Fees: FREENOTES:
Speaker: Zulkuf Azizoglu
Location: Chevron building
1400 Louisiana St
Houston – TX - 77002
Parking: Hyatt Regency Garage
611 Clay St.
Houston, TX 77002
This seminar will be held both in person and virtually. The event is free, but no lunch will be provided.

ABSTRACT:
Ionic properties and concentration significantly influence the response of brine-saturated rock samples to electromagnetic disturbance. However, the dielectric permittivity response of rock samples under different ionic conditions is poorly described. This significantly limits the potential information that could be gained from dielectric permittivity measurements about the pore geometry and fluid content. Therefore, the influence of salt concentration and type on broadband dielectric permittivity must be quantified in the pore- and core-scale domains to develop analytical dielectric permittivity models. The objectives of this paper are to (a) investigate the influence of salt type and concentration on dielectric permittivity via experimental measurements and pore-scale simulations and (b) identify the limitations of current effective medium theories in the interpretation of dielectric permittivity measurements in samples with different ionic conditions. We investigate the influence of salt concentration and type on the dielectric permittivity of pore- and core-scale Berea sandstone samples. First, we perform frequency-domain dielectric permittivity simulations to quantify the response of the porescale models to electric field excitation. The frequency-domain dielectric permittivity simulator solves Maxwell’s equations under quasi-static conditions at discrete frequencies. We simulate the dielectric permittivity in the frequency range of 20 MHz to 3 GHz. We run the simulations in samples saturated with NaCl, KCl, and MgCl2 brines. The salt concentration of the brine solutions ranges between 2 to 100 PPT. For the core-scale analysis, we fully saturate the samples with different brine solutions at varying salt concentrations. In the core-scale domain, we use the exact brine solutions and salt concentrations defined for the pore-scale analysis. The dielectric permittivity measurements were conducted using a network analyzer with a hightemperature coaxial probe setup in the frequency range of 200 MHz to 3 GHz. We observed that relative permittivity at 1 GHz decreases with increasing salt concentration, irrespective of the brine type. However, the type of salt significantly controls the magnitude of the decrease in relative permittivity. After increasing the salt concentration from 10,000 to 100,000 PPM, relative permittivity at 1 GHz decreased by 7% and 11% when the samples were saturated with KCl and NaCl brine solutions, respectively. Furthermore, this behavior was enhanced as the frequency decreased. The impact of salt type on relative permittivity was negligible in samples saturated with 10,000 PPM brine solutions. Finally, we examined the potential errors that could arise from assuming an inaccurate salt type in the interpretation of dielectric permittivity measurements. We observed that incorrect assumptions about the brine type could result in up to 20% relative errors in water saturation assessment via dielectric permittivity measurements. Therefore, taking the influence of salt concentration and type into account is critical for a reliable interpretation of dielectric permittivity. The outcomes of this work will be helpful in the interpretation of dielectric permittivity measurements in formations with variable salt concentrations of formation water. Additionally, in the cases where the salinity of the formation water is unreliable, this work will illuminate the extent to which the dielectric permittivity measurements can be used for petrophysical analysis.