METHOD FOR MULTI-SENSOR ELECTROMAGNETIC DEFECTOSCOPY OF WELL CASINGS AND DEVICE THEREFOR

摘要

A group of inventions relates to geophysical well logging, in particular to magnetic imaging defectoscopy of well casings including magnetised ones, that can be used to identify and classify defects in production and intermediate casing and tubing strings in oil and gas wells. An electromagnetic multi-sensor defectoscope for surveying casing pipes contains a source of the electromagnetic field in the form of a central exciter coil designed to transmit current pulses from a current pulse generator, a system of measuring elements placed on bow springs to be forced against the inner surface of a casing pipe, and a unit for signal recording, control and data processing connected to the system of measuring elements through communication lines, wherein the system of measuring elements designed to record signals proportional to the longitudinal component of the electromagnetic field consists of at least three compensated sensors, each placed on the inner side of a bow spring and being equidistant from one another along the circumference of the cross-section of a casing pipe to ensure reliable detection of defects within its surveyed section. A method of multi-sensor electromagnetic defectoscopy for surveying casing pipes, in which an electromagnetic field is generated within the surveyed section of a casing pipe by current pulses, and mainly response signals of the secondary electromagnetic field are measured in the intervals between excitation pulses using a system of measuring elements, while most response signals of the primary electromagnetic field are compensated, and the signals are then transmitted into a signal recording, control and data processing unit recording the time dependence of the output EMF of the signal of the system of measuring elements.