Adequate cement evaluation means running the right tools at the right time under the right conditions. An integrated interpretation of the data will reduce well cost by avoiding unnecessary operational measures (squeeze jobs, sidetracks) or hardware additions (tie-back packers) and by confirming well integrity.The authors will present case studies in which a combination of cement bond log and variable density log (CBL-VDL) logs together with ultrasonic logs were run and where an effort was made to confirm assumptions around cement bond log interpretations by re-running logs at a later time or under different conditions to obtain proof of:1 Incorrect historic data2 Insufficient cement setting time3 Over displacement of cement4 Identification of micro-annulus through ultrasonic log along with conventional CBL-VDL data5 Pseudo-bond signal from lost circulation material mud remnants in the annulusThe learning from above case studies translates into the following best practices:1 If bump plug pressure is not observed displacement volumes after the theoretical bump plug volume need to be limited to avoid over displacement2 A cleanout trip should be run prior to cement bond logging3 Cement setting times determined from laboratory tests might be too short forrunning cement bond logs, cement quality increases even after the given laboratory setting time.4 Historic cement bond log evaluations might not be representative any more. When re-entering existing wells casing integrity and cement bond logs should be re-run to establish the current status5 A low acoustic impedance wellbore fluid improves ultrasonic data quality6 In liquid filled micro annuli a combination of CBL-VDL and ultrasonic logs can determine the presence of micro-annulus
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