Acoustic cementation logging tools have been run in a full-scale cement flow loop and the logs compared to a physical examination of the cement in the annulus. In the flow loop the complete cycle of cementing operations — mud and spacer circulation, and cement placement — was carried out. The flow loop included artificial formation and double string sections.
Three tools were used in the flow loop: a sonic tool and two ultrasonic pulse-echo tools. The sonic tool measures the attenuation of sonic waves along the casing and is sensitive to shear coupling between casing and cement. The ultrasonic tools measure the damping of a thickness-mode resonance and the acoustic impedance. One ultrasonic tool samples every 45 degrees in azimuth; the other provides complete coverage using a rotating probe.
Conditions such as channeling, good and contaminated cement, mud and water were created in the flow loop. The logs were consistent with the subsequent physical examination, within the resolution limits of each tool. Very thin annulus and highly contaminated cement posed interpretation problems. Of the tools investigated, the rotating ultrasonic tool provided the most accurate predictions of cement distribution and quality.
The results illustrate the advantages and limitations of the different types of tools, and will be a useful aid in the interpretation of cementation logs.