A transient method for measuring the DC streaming potential coefficient of porous and fractured rocks

Abstract

High-quality streaming potential coupling coefficient measurements have been carried out using a newly designed cell with both a steady state methodology and a new pressure transient approach. The pressure transient approach has shown itself to be particularly good at providing high-quality streaming potential coefficient measurements as each transient increase or decrease allows thousands of measurements to be made at different pressures to which a good linear regression can be fitted. Nevertheless, the transient method can be up to 5 times as fast as the conventional measurement approaches because data from all flow rates are taken in the same transient measurement rather than separately. Test measurements have been made on samples of Berea and Boise sandstone as a function of salinity (approximately 18 salinities between 10 À5 mol/dm 3 and 2 mol/dm 3 ). The data have also been inverted to obtain the zeta potential. The streaming potential coefficient becomes greater (more negative) for fluids with lower salinities, which is consistent with existing measurements. Our measurements are also consistent with the high-salinity streaming potential coefficient measurements made by Vinogradov et al. (2010). Both the streaming potential coefficient and the zeta potential have also been modeled using the theoretical approach of . This modeling allows the microstructural, electrochemical, and fluid properties of the saturated rock to be taken into account in order to provide a relationship that is unique to each particular rock sample. In all cases, we found that the experimental data were a good match to the theoretical model.

Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones

“…The experimental cell and measurement set-up is described in Walker et al (2014). The pore fluids were made up to approximately the correct salinity using distilled, deionized water that had been previously degassed.…”

“…The streaming potential coefficient was then calculated from the gradient of the plot. This procedure was described in Walker et al (2014), where such a plot can be found as their Fig. 2.…”

“…Zeta potentials have been calculated from each streaming potential coefficient measurement using the Helmholtz-Smoluchowski law (Glover 2015a) with Overbeek's correction (Jouniaux and Pozzi 1995;Walker et al 2014), together with experimentally measured supporting data and empirical models. This calculation requires the knowledge of the electrical conductivity (σ f ), permittivity (ε f ), and viscosity (η f ) of the equilibrated pore fluid as well as the formation factor of the rock both at high salinities (F o ) and at each of the salinities used in the measurement (F i ).…”

“…Some of this spread is almost certainly due to experimental uncertainties, perhaps with the measurement itself, but most of the scatter is likely to be associated with the lack of pore fluid equilibration or knowledge of the real electrical conductivity, salinity, and pH of the fluid in the sample at the time of the measurement (Walker et al 2014).…”

Measurement of Streaming Potential in Downhole Application: An Insight for Enhanced Oil Recovery Monitoring

“…Jaafar et al (2013) found the point of zero charge (pzc) of two types of core samples (sandstone and carbonate), where the voltage difference was measured at different pH of solution, but there were no further study on the effect of the degree of alkalinity to the streaming potential [9]. In 2014, Walker et al applied new pressure transient approach as a faster approach than the conventional measurement methods, where the measured streaming potential coupling coefficients and zeta potential were aligned with the findings by Vinogradov et al (2010) at high salinity [10,11]. Results obtained by Esmaeili et al (2016) agreed with the published experimental data, and much lower scattering in the data points was achieved for different saline injecting water [12].…”