Current cement evaluation technologies (both sonic and ultrasonic) have, to a large extent, been proven to struggle when evaluating light weight and/or contaminated cements. Light weight cement blends are widespread in the industry and slurry contamination to various degrees is more prevalent than commonly known. The evaluation of the cement bond becomes complicated because of the difficulty of distinguishing between liquid and solid mainly in these cases.
This paper describes the recent trials conducted using the latest generation of ultrasonic cement evaluation technologies, which combines both the traditional pulse-echo cement evaluation technique with a newly developed flexural waveform imaging technique.
The new technique yields a superior characterization of the annulus between the casing and the formation, or the outer casing in case of double casing strings. The end product is an SLG (Solid, Liquid or Gas) map that describes decisively the nature of the material behind the casing wall regardless of its density and/or contamination degree. It also estimates the radial extent or thickness of that material, which is achieved using a newly developed technique called Third Interface Echo (TIE) imaging. This technique also allows the casing centralization to be imaged. When combined, all components of the new tool can yield a 3-dimensional, virtual reality reproduction of the casing and cement sheath, all the way out to the formation or second casing wall.