The Casing Inspection Tool — An Instrument for the In-Situ Detection Of External Casing Corrosion in Oil Wells

A surface recording, down hole instrument for the detection of external corrosion in oil wells is described. The tool is a non-contacting, eddy-current instrument which measures and records casing wall thickness. Equations are presented which are useful in describing the tool’s action. Examples of laboratory and down hole logs are shown demonstrating the tool’s response to general thinning, pits, holes, collars, etc. Results of a number of down hole runs representing some 40,000 feet of well logged are discussed. 2.4.2, 8.4.3