Canadian Applications of Cement Bond Logging

For a long time the Oil Industry has been looking for a logging tool which can determine the quality of the cement job behind casing. Older methods such as Temperature Surveys and Radioactivity Surveys might detect the presence of cement behind the casing, but short of production tests, it was impossible to tell that the producing zones were adequately sealed off from adjacent zones. A new logging method, which is called the •Cement Bond Log, operates on the principle that a sonic pulse transmitted by the casing is greatly attenuated when the casing is strongly bonded to an outer annulus such as cement. The down-hole tool consists of a source of sonic energy which is detected by a receiver situated a few feet away from the source. The amplitude of the detected energy is measured and the resulting signal transmitted to the surface where it is recorded versus depth. Amplitude is a function of attenuation and thus the log is readily interpreted. Laboratory studies have shown that there are straightforward relationships between attenuation and per cent of circumference bonded. They have shown that cement which is not set or which is not bonded has small attenuating effect. Field examples show variations in cementation quality, increase of bonding with time, and bonding attained by squeeze jobs. The detection of poor bonding has been confirmed by production tests and formation test results. The method should have a wide application in evaluation of cementation and thus in the solution of many production problems
Keywords: amplitude, cement bond log, cementation, gas oil ratio, Attenuation, Bonding, Cement, Cementation, Logging, Logs, Pipe, quality, test, Tests
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