Measurements of the Relationship Between Microstructure, pH, and the Streaming and Zeta Potentials of Sandstones
Bibliographic record
Abstract
A large number (1253) of high-quality streaming potential coefficient ( $$C_\mathrm{sp})$$ C sp ) measurements have been carried out on Berea, Boise, Fontainebleau, and Lochaline sandstones (the latter two including both detrital and authigenic overgrowth forms), as a function of pore fluid salinity ( $$C_\mathrm{f})$$ C f ) and rock microstructure. All samples were saturated with fully equilibrated aqueous solutions of NaCl (10 $$^{-5}$$ - 5 and 4.5 mol/dm $$^{3})$$ 3 ) upon which accurate measurements of their electrical conductivity and pH were taken. These $$C_\mathrm{sp}$$ C sp measurements represent about a fivefold increase in streaming potential data available in the literature, are consistent with the pre-existing 266 measurements, and have lower experimental uncertainties. The $$C_\mathrm{sp}$$ C sp measurements follow a pH-sensitive power law behaviour with respect to $$C_\mathrm{f}$$ C f at medium salinities ( $$C_\mathrm{sp} =-\,1.44\times 10^{-9} C_\mathrm{f}^{-\,1.127} $$ C sp = - 1.44 × 10 - 9 C f - 1.127 , units: V/Pa and mol/dm $$^{3})$$ 3 ) and show the effect of rock microstructure on the low salinity $$C_\mathrm{sp}$$ C sp clearly, producing a smaller decrease in $$C_\mathrm{sp}$$ C sp per decade reduction in $$C_\mathrm{f}$$ C f for samples with (i) lower porosity, (ii) larger cementation exponents, (iii) smaller grain sizes (and hence pore and pore throat sizes), and (iv) larger surface conduction. The $$C_\mathrm{sp}$$ C sp measurements include 313 made at $$C_\mathrm{f} > 1$$ C f > 1 mol/dm $$^{3}$$ 3 , which confirm the limiting high salinity $$C_\mathrm{sp}$$ C sp behaviour noted by Vinogradov et al., which has been ascribed to the attainment of maximum charge density in the electrical double layer occurring when the Debye length approximates to the size of the hydrated metal ion. The zeta potential ( $$\zeta $$ ζ ) was calculated from each $$C_\mathrm{sp}$$ C sp measurement. It was found that $$\zeta $$ ζ is highly sensitive to pH but not sensitive to rock microstructure. It exhibits a pH-dependent logarithmic behaviour with respect to $$C_\mathrm{f}$$ C f at low to medium salinities ( $$\zeta =0.01133 \log _{10} \left( {C_\mathrm{f} } \right) +0.003505$$ ζ = 0.01133 log 10 C f + 0.003505 , units: V and mol/dm $$^{3})$$ 3 ) and a limiting zeta potential (zeta potential offset) at high salinities of $${\zeta }_\mathrm{o} = -\,17.36\pm 5.11$$ ζ o = - 17.36 ± 5.11 mV in the pH range 6–8, which is also pH dependent. The sensitivity of both $$C_\mathrm{sp}$$ C sp and $$\zeta $$ ζ to pH and of $$C_\mathrm{sp}$$ C sp to rock microstructure indicates that $$C_\mathrm{sp}$$ C sp and $$\zeta $$ ζ measurements can only be interpreted together with accurate and equilibrated measurements of pore fluid conductivity and pH and supporting microstructural and surface conduction measurements for each sample.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".