Research Predicts Improved Cement Bond Evaluations With Acoustic Logs

Abstract

Laboratory investigations and test-well oscilloscope pictures were made to determine the application of acoustic signals for evaluating the effectiveness of casing cementing. This work indicated the possibilities of measuring the amplitude of acoustic signals from the pipe and from the formation, both in open and cased hole, to indicate the bonding to pipe and to formation. Field tests have shown the applicability of the system, but experience and further model tests have shown that a number of variables affect the interpretation. Some of these variables-such as type of cement, quantity of admixes, sheath thickness and time of logging after cementing-are being investigated , and the results to date are included. These results indicate that it will be possible to evaluate the effectiveness of cementing under most conditions. Introdnction When production tests do not agree with log, core-analysis or other formation evaluation data, the effectiveness of casing cementing is usually questioned. Even in wells which have been produced for some time and then begin to produce water or excess gas, the isolation by cement behind the casing has been found to be incomplete by a squeeze and reperforation. The answers to these questions in the past have been quite expensive and often damaging to formation productivity during the process of repair.