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US 4,594,691 AGranted
Sonic well logging
AssigneeSchlumberger Technology Corporation
InventorsChristopher V. Kimball, Thomas L. Marzetta
Life of this patent
Estimating the term…
Abstract
Disclosed is sonic well logging which gives good results both in open and in cased boreholes. New use is made of the energy content output from a multireceiver tool to find a coherence measure for the received sonic energy and to find the peaks of that coherence measure at each depth level so as to produce a number of new logs of parameters of those peaks. Examples are a slowness/time coherence log for those peaks, as well as new logs related to the arrival times of the coherent energy associated with the peaks and the energy attenuation for those arrival times.
Claims39
A well logging method comprising:
- deriving logs of the respective receiver outputs of a multi-receiver sonic tool for a selected borehole interval;
- stacking moveout-corrected receiver outputs by depth level and identifying selected peaks of a coherence measure of the result without reliance on first motion detection;
- and
- producing logs of sonic properties of the formations versus borehole depth on the basis of selected parameters of said peaks.
1 more element
A well logging method comprising the following machine-implemented steps:
- deriving sonic logs as respective functions of the receipt of sonic signals by sonic receivers which are carried by a tool moved through successive depth levels in a borehole and are spaced along the length of the tool from each other and from at least one transmitter of said signals carried by the same tool;
- converting the sonic logs into a slowness log which varies with depth in the borehole as a function of a coherence measure related to the ratio of moveout-corrected coherent to total energy received by the respective receivers;
- and
- producing a tangible representation of said slowness log.
1 more element
A well logging method comprising the following machine-implemented steps;
- passing a multi-receiver sonic tool through a borehole to derive therefrom sonic logs as respective functions of the receipt of sonic signals by receivers which are spaced along the length of the tool from each other and from at least one transmitter of said signals carried by the tool;
- converting the sonic logs into a slowness log which varies with depth in the borehole as a function of the respective peaks of a coherence measure of the energies in said sonic logs which does not rely on first motion detection;
- and
- producing a tangible representation of said slowness log.
1 more element
A well logging system comprising:
- means for deriving sonic logs of the receipt of sonic signals by sonic receivers which are carried by a tool moved through successive depth levels in a borehole and are spaced along the length of the tool from each other and from at least one transmitter of said signals carried by the same tool;
- and
- means for converting the sonic logs into a slowness log which varies with depth in the borehole as a function of a distribution of a coherence measure of the energies in said sonic logs but does not rely on first motion detection and for producing a tangible representation of said slowness log.
A well logging method comprising:
- deriving sonic logs based on sonic signals received by sonic receivers which are carried by a tool moved through successive depth levels in a borehole and are spaced along the length of the tool from each other and from at least one transmitter of said signals carried by the same tools;
- seeking for each depth level at least one peak of a coherence measure of the energies in said sonic logs which is different from the results of correlation of cross-products, and identifying any found peak as corresponding to a respective compressional or other sonic wave component;
- and
- producing a tangible representation of a selected parameter corresponding to said peak versus depth in the borehole to thereby produce a new log.
1 more element
A well logging system comprising:
- means for deriving sonic logs of the receipt, at successive borehole depth levels, of sonic signals by sonic receivers which are spaced from each other along the borehole but are at respective fixed distances to an origin of the sonic signals;
- and
- means for finding for each respective borehole depth at least one peak of a coherence measure of the energies in said sonic logs which is different from the results of correlation or cross-products and for producing a tangible representation of selected parameters of said peaks.
A well logging method comprising the following machine-implemented steps:
- deriving logs of the sonic energy received at sonic receivers spaced from each other and from a sonic transmitter along a tool moved through a borehole;
- for each of a succession of selected depths in the borehole, and for each of a multiplicity of time-slowness or time-velocity combinations which form a grid in time-slowness or time-velocity space, finding a measure of the coherent energy received by said receivers;
- for each of said depths, finding any peaks of said measure of energy which meet selected criteria;
- and
- producing a tangible representation of the variation with borehole depth of selected borehole characteristics related to said peaks.
2 more elements
A well logging method comprising:
- deriving respective logs of the outputs of acoustic receivers spaced from each other and from an acoustic transmitter along a tool moved through a borehole;
- for each of a succession of depth levels in the borehole, selecting a multiplicity of pairs of values of (i) time and (ii) an acoustic characteristic of the medium through which acoustic signals propagate from the transmitter to the respective receivers for the respective depth level in the borehole, and for each pair combining with each other the logged portions of the respective receiver outputs which correspond to said pair of values to derive a respective combined measure, and finding any pairs of values at which said measure is at a peak meeting selected criteria of a coherence measure;
- and
- producing a tangible representation of the variation with borehole depth of one or more selected borehole characteristics which correspond to said peaks.
1 more element
A well logging method comprising:
- producing logs of the respective acoustic signals detected at receivers spaced from each other and from an acoustic transducer along a tool moved through a borehole;
- combining the logs, with moveout correction but without first motion detection, to produce a processed log of the variation with depth in the borehole of the acoustic velocity or slowness of the surrounding medium as determined by selected peaks of a coherent measure and
- producing a tangible representation of said processed log.
Dependencies are inferred from the claim text.