Method and system for measurement of internal tube dimensions within a wellbore

摘要

A caliper logging sonde is provided having a plurality of sensing fingers each of which is pivotally mounted to the sonde and movable with respect to the sonde in response to variations in the internal dimensions of a wellbore tube through which the sonde passes. An electrical signal which is proportional to variations in the internal dimensions of a wellbore tube is determined at regular time intervals at a series of points around the circumference of the wellbore tube. A maximum and minimum dimension for each point around the circumference of the wellbore tube during a selected time interval is temporarily stored and thereafter transmitted to the surface at regular intervals. A high density array of sensors is provided by utilizing a transducer plate having a large number of cylindrical apertures disposed around the circumference thereof. Thimble members, each having an internal chamber and an elongate body narrower than the cylindrical aperture are fixedly inserted into one end of each of the detector plate apertures while an associated electrical coil is inserted into each aperture from the other end, surrounding the elongate body. Movable magnetic rods within the internal chamber of each thimble are then variably positioned in response to movement of the sensing fingers and the variable inductance of each electrical coil is then utilized to produce an electrical signal proportional to variations in the internal dimensions of the tube under measurement.