A New Experimental Core Analysis Method for Formation Permeability Measurement Under Two-Phase Condition
Bibliographic record
Abstract
Abstract Experimental methods for core plug analysis are widely used to measure formation permeability under steady-state flow or unsteady state flow conditions, which provides important geoscience information on formation properties. However, typical laboratory techniques hardly reproduce the two-phase water and hydrocarbon storage and transport conditions that formation is subject to in reality. Accordingly, we presented an integrated experimental core analysis method for permeability measurement, which better reproduces these two-phase conditions. The proposed experimental method consists of two-phase fluid initialization and production test, during which the gas rate, liquid rate, and inlet/outlet pressure of the core plug are recorded simultaneously. After constructing with uniform distribution of gas and liquid, the core sample is transformed into a two-phase production process under the conditions of variable rate and sealed boundary. Rate transient analysis is performed to estimate formation permeability with the gathered two-phase rate decline and pressure data. A two-phase diagnostic plot and specialty plot are introduced to identify flow regimes and extract permeability from the slope of a straight line during the experimental data analysis. In this paper, commercial software is used to generate synthetic data for the production test of a core plug. The simulation of two-phase fluid initialization and production tests were conducted on core plugs. The simulation results show a unit-slope straight line on the generated diagnostic plot, which indicates a clear boundary-dominated flow (BDF) regime. By performing a straight-line analysis, we calculated the permeability of the core plug with the slope of straight-line period on specialty plot. The good match of the calculated permeability with the reference value confirms the accuracy of the proposed experimental method with the relative error less than 10%. In addition, the proposed two-phase core analysis method can enormously accelerate test-time, as the permeability of selected rock sample can be estimated in less than 10 minutes. Instead of measuring permeability only under the condition of single phase flow, this paper presents a laboratory technique that combines the experiment of small-diameter core production test under two-phase flow with rate transient analysis method. Unlike prior experimental techniques, the proposed method reproduces the more realistic condition of two-phase flow in the formation during permeability measurement. The two-phase core analysis method achieves the objective of accurate and fast characterization of formation permeability, which is a more "apples to apples" comparison between the fluid flow in the actual reservoir and the core plug.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".