Acoustic measurements are used throughout the lifetime of a well, from seismic to production. Logging While Drilling (LWD) sonic is traditionally used to log formation slowness in the open hole. In this case study we show that both, measuring formation slowness and evaluating the success of a cementing operation can be obtained with the latest generation of LWD sonic tools while drilling, thus saving rig time, simplifying operations, and adding safety to well integrity solutions. Both, formation slowness and well integrity are often an essential criterion for the decision whether to drill ahead or to take additional measures to assure well integrity.
In this case study we have demonstrated that there is additional approach wherein formation slowness can also be recorded/captured in cased hole with LWD tools when the cement bonding is sufficient to allow good coupling. Continuous formation compressional and shear slowness was recorded and extracted for most of the interval below Top of Cement (TOC) and some short intervals above TOC. This advanced technique of logging formation slowness through casing with LWD can complement or even save an additional logging run in some cases and therefore result in significant savings to the operator.
Where azimuthal cement evaluation is not a strict requirement, knowing the top-of-cement (TOC) from LWD can help to confirm well integrity without adding rig-time. Should the measured TOC be lower than required, then more advanced analysis can be run for additional investigation.