Bayesian inference of petrophysical properties with generative spectral induced polarization models
Bibliographic record
Abstract
ABSTRACT Mechanistic induced polarization (IP) models describe the relationships between the physical properties of geomaterials and their frequency-dependent complex conductivity. However, practitioners rarely use mechanistic models to interpret the IP data because the uncertainties associated with estimating petrophysical properties from complex conductivity spectra are still poorly understood. We propose a framework for critically assessing any IP model’s sensitivity and parameter estimation limitations. The framework consists of a conditional variational autoencoder (CVAE), an unsupervised Bayesian neural network specializing in data dimension reduction and generative modeling. We apply the framework in a case study of the “perfectly polarized interfacial polarization” model by training the CVAE on the IP signatures of synthetic mixtures of metallic mineral inclusions hosted in electrolyte-filled geomaterials. First, the CVAE’s Jacobian reveals the relative importance of each petrophysical property for generating the spectral IP data. The most critical parameters are the conductivity of the host, the volume fraction of the inclusions, the characteristic length of the inclusions, and the permittivity of the host. Contrastingly, the inclusions’ diffusion coefficient, permittivity, and conductivity, as well as the host’s diffusion coefficient, have marginal importance. A parameter estimation experiment using various model constraints yields the standardized accuracy of petrophysical properties and corroborates the sensitivity analysis results. Finally, we visualize the effects of data transformations and model constraints on the petrophysical parameter space. We conclude that a common logarithm data transformation yields optimal parameter estimation results and that constraining the electrochemical properties of a geomaterial improves the estimates of the size of its metallic inclusions and vice versa.
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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 | 0.003 | 0.011 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| 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".