 |
| Titel |
Steady-state streaming potential coefficient measurements and modelling of sandstones as a function of pore fluid salinity and pH |
| VerfasserIn |
Emilie Walker, Paul W. J. Glover |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074155
|
|
|
|
|
|
| Zusammenfassung |
| The last twenty years has seen the steady increase in the quality and quantity of streaming
potential coefficient and zeta potential determinations in the laboratory. More recently
(Glover et al., 2012), a model has been developed that allows both the zeta potential and
streaming potential coefficient of a porous rock to be calculated theoretically. We have carried
out high quality streaming potential coupling coefficient measurements using a newly
designed cell with both a steady-state methodology and a new pressure transient approach.
We have shown the pressure transient approach to be particularly good in providing high
quality streaming potential coefficient measurements as it allows thousands of measurements
to be made at different pressures to which a good linear regression can be fitted. Nevertheless,
the method is approximately five times as fast as the conventional measurement approaches.
Measurements of streaming potential coefficient have been carried out on seven samples of
Berea, Boise and Lochaline sandstones as a function of salinity (approximately 18
salinities between 10-5 M and 2 M) and pH (approximately 11 pHs between 8
and 2). The data have been inverted to obtain the zeta potential. The streaming
potential coefficient becomes greater (more negative) for fluids with lower salinities
and higher pHs, which is consistent with the corpus of existing measurements.
Our measurements are also consistent with the high salinity streaming potential
coefficient measurements made by Vinogradov et al. (2010). The streaming potential
and zeta potential tend to zero as the pH approaches the point of zero net surface
charge for quartz (approximately 3), which was 2.8±0.2 in our measurements. Both
the streaming potential coefficient and the zeta potential have also been modelled
using the theoretical approach of Glover et al. (2012). This modelling allows the
microstructural, electro-chemical and fluid properties of the saturated rock to be taken into
account in order that the theoretical model provides a relationship that is unique to the
particular rock sample. In all cases, we found that the experimental data was a
good match to the theoretical models, but only if we used the actual salinity and
pH of the fluid in the rock rather than that of the bulk fluid, as might be expected. |
|
|
|
|
|
|