| 摘要 |
In Earth formation measurements, an investigating tool having a first and a second detector at a relatively small spacing from each other and a third detector at a relatively great spacing from the first and second detectors is moved through a borehole having anomalies such as radioactive bullets or casing joints which are relatively uniformly spaced from each other by a distance which is of the order of said great spacing between the third detector and the first and the second detectors. The first and second detectors generate detection signal peaks for the same anomaly within a short time interval, and the third detector generates a detection signal peak for an adjacent anomaly at about the same time. By means of a defined apparatus, electrical signals representing the times of occurrence of the detection signal peaks from the first and second detectors for the same anomaly and the known small spacing between these detectors are used to obtain an electrical signal for the speed of the investigating tool at that time, and at least some of these electrical signals are combined with electrical signals representing the time of occurrence of the detection signal peak from the third detector for an adjacent anomaly and at least one of the known distances between the detectors to thereby obtain an accurate measure of the distance interval between the pair of adjacent anomalies. Provisions are made for detecting the most representative point of a detection signal peak, for accommodating irregularities in the occurrence of detection signal peaks resulting from anomalies which are not uniformly spaced or which do not provide an adequate detection signal peak, and for utilizing, in the last-mentioned combining operation, either the distance between the first and the third detectors or the distance between the second and third detectors, whichever would give a more accurate measurement of the distance between the particular pair of adjacent anomalies. The invented technique can be used to find the actual average speed of the tool within any time interval between the times of detection of any suitable formation anomaly by two spaced-apart detectors.
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