The Active Line Source Temperature Logging Technique and Its Application in Fractured Rock Hydrogeology
Bibliographic record
Abstract
Abstract We present a technique for placing a borehole into thermal dis-equilibrium, and thereby interpreting groundwater flow through fractures where it may have been previously undetected. Denoted as Active Line Source (ALS) logging, the method consists of temperature logging while a borehole is heated by the cable and/or during cooling after the heating. With two or more logs collected during either heating or cooling, an estimate of thermal conductivity is obtained. The basic theory, widely used for such things as thermal conductivity probes, is shown to fit the recorded data well. The mechanics of ALS logging are described, and the practical challenges are outlined. In the absence of groundwater flow in or around the borehole, variations in the thermal conductivity of the rock are largely due to variable water content and the ALS log provides a reasonable surrogate for the neutron log. When groundwater flow dominates the dissipation of thermal energy from the borehole, however, the apparent thermal conductivity is increased. In open boreholes this flow can be both ambient (within the formation itself) and connecting (vertical flow between fractures intersected by the borehole). In cased or lined holes with no connecting flow, ALS logs are particularly useful as detectors of ambient groundwater flow. Alternative methods for flow detection, such as chemical dilution or flow-meters, require an open borehole and either have poor vertical resolution or require multiple stationary measurements, often with packers to minimize the effects of connecting flow. The ALS technique is a comparatively simple tool, useful in both open and cased or lined boreholes, run continuously down the length of the borehole, with fracture resolution on the order of a few centimeters. We describe ALS logging of a 75-meter section of a borehole through fractured dolomite which has been lined with a FLUTe sleeve. The ALS results are compared to the geologic units encountered, conventional geophysical logging techniques, time-lapse passive temperature logging, heat pulse flowmeter data and packer testing.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".