Abstract: A method of identifying the presence, type and extent of internal casing wear and distinguish worn casing from various types of unworn casing. Two inspection instruments are tied together in the combination traverses a section of casing where information on internal wear is desired. The first inspection instrument generates two signals related to the minimum and maximum wall thickness present at each location within the casing section. The second inspection instrument generates a signal related to the degree of phase shift at each location of the casing section.

Abstract: A method of determining the location and dimensions of collars present along a section of casing. An inspection instrument is passed through the casing section generating an electromagnetic wave which permeates the casing. The phase shifted electromagnetic wave is detected by a receiver and a data string comprising the degree of phase shift present at each point along the casing section is created. The data string is processed to identify the location of collars present along the casing section. Upon the identification of a collar, a series of pattern recognition interrogations are used to confirm the collar location and to determine the collar's dimensions.

Abstract: A method of determining the presence of channels in the cement behind a well casing utilizing the temperature profiles of the well. In a first embodiment rate coefficients indicative of the rate of temperature change along a zone of investigation are calculated from the geothermal gradient, flowing temperature profile and at least one shut-in temperature profile. These rate coefficients are plotted versus depth, with inconsistencies in the valves of the rate coefficients being indicative of the presence of channels. In a second embodiment rate coefficients are calculated over a well bonded zone of the well casing and utilized to predict shut-in temperatures along the zone of investigation. Differences in the predicted and actual shut-in temperatures is further indicative of the presence of channels.