Measuring and testing – Borehole or drilling – Downhole test
Patent
1982-10-27
1985-10-08
Caldwell, Sr., John W.
Measuring and testing
Borehole or drilling
Downhole test
340853, 367 81, E21B 4900
Patent
active
045452423
ABSTRACT:
A high resolution method and apparatus for measuring the depth of a tool suspended from a cable inside a borehole are described. The tool includes accelerometers for measuring its acceleration and this measurement is combined with a cable depth measurement with which the amount of cable in the borehole is determined. A Kalman filter is employed to continually provide estimates of the velocity and depth of the tool from the accelerometer and cable depth measurements. A filter modifier alters operation of the filter during discontinuous motions of the tool such as when it is stuck and slips. A tool sticking detector senses when the tool is stuck and for how long to correspondingly modify the filter by forcing it to more strongly rely upon accelerometer measurements when the tool is stuck and gradually return to normal filter operation when the tool resumes movement after having been stuck.
REFERENCES:
patent: 3490149 (1970-01-01), Bowers
patent: 3490150 (1970-01-01), Whitfill
patent: 3862499 (1975-01-01), Isham
patent: 3882474 (1975-05-01), Cain
patent: 4348748 (1982-09-01), Clavier et al.
patent: 4362054 (1982-07-01), Ringot
"The High Resolution Dipmeter Tool", by L. A. Allaud and J. Ringot, reprinted from The Log Analyst, May-Jun., 1969.
"Optimal Linear Filtering", reprinted from Applied Optimal Estimation, edited by A. Gelb and published by M.I.T. Press, Cambridge, Mass., 1974.
Borst Stephen
Caldwell Sr. John W.
Carroll David
Harding Ellwood G.
Reens Louis H.
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