First Application of Innovative Dual-String Barrier Evaluation Tool for Annular Cement Validation in UAE

Abstract Evaluation of the annular barrier is an integral part of well construction, integrity, and reentry scope. The current industry practice is to run sonic and ultrasonic tools to evaluate the barrier quality across a single string. However, many wells require the evaluation of the barrier behind a second string, for which today, the inner string must be pulled out to log the outer string. The dual-string technology allows the simultaneous evaluation of both string annuli without having to remove the inner string. An innovative technology using a combination of multimodality ultrasonic imaging and multimode advanced array sonic measurements has been developed to evaluate the barrier quality in the second string annulus. With consideration of the underlying measurement physics, this work explored the implications of well geometry, the impact of pipe-to-pipe standoff, the correction, and the validation scheme. A verification method for the actual pipe-to-pipe standoff versus estimated standoff provides an accurate approach for the evaluation of cement slurry placement and practices. Formation compressional and shear measurements were also enabled via dual-string logging simultaneously. The dual-string barrier evaluation technology was deployed in an offshore well in Abu Dhabi. Data were initially recorded in a 13 3/8-in. single string using sonic and ultrasonic tools; afterward, data were recorded with both 9 5/8-in. and 13 3/8-in. dual-string configurations. Data interpretation and benchmarking provided insights on the qualitative barrier state and demonstrated dual-string measurement robustness and accuracy. Further insights were drawn in the evaluation of formation acoustic properties using compressional and shear measurements acquired across two strings and its use for other subsurface geoscience applications. Dual-string barrier evaluation technology demonstrated the potential CAPEX saving in heavy-casing design by providing insights to the first- and second-string annuli simultaneously. Additionally, this technology provides a new solution to assess zonal isolation for the surface casing. This is particularly important as the quality of cement behind this surface casing is usually not evaluated, which creates a gap in proving the required zonal isolation information. Without the information about the top of cement, the isolation between the Simsima formation (the flowing formation) and the aquifer is not proved.