Downhole cable length measuring apparatus

Abstract

A wireline cable length measuring apparatus tracks the length and other parameters of a wireline cable in a well bore. The apparatus has three major components: a rotational distance measuring assembly; a rotation-to-length (rotation:length) calibration assembly; and a processor unit. The rotational distance measuring assembly engages the wireline cable in a manner similar to a standard wireline count wheel, typically receiving the cable from a draw works or a wireline service truck. The rotational distance measuring assembly has a rotation sensor which generates a rotation signal in response to the paying-out and reeling-in of the cable over the count wheel. The rotation:length calibration assembly also engages the wireline cable. However, the rotation:length calibration assembly only intermittently engages the wireline cable, and therefore is subject to substantially less wear than the counter wheel. The rotation:length calibration assembly has a length sensor which generates a length calibration signal in response to the length of the cable in passing through the rotation:length calibration assembly. The length calibration signal is used by the processor to convert rotations of the counter wheel into calibrated length measurements. The processor component receives and processes the sensor signals generated by the other components of the apparatus and provides processor output signals relating to the length and other parameters of the cable passing through the apparatus and into the well bore. The processor unit includes a CPU which accomplishes the processing function of the present apparatus.

Dependencies are inferred from the claim text.