Novel Composite Cement for Improved Well Integrity Evaluation

Elshahawi, Hani (Shell International Exploration and Production Inc.) | Huang, Shan (Shell International E&P Inc.) | Pollock, Jacob (Oceanit) | Veedu, Vinod (Oceanit)



For E&P companies, well integrity during the production cycle is of paramount importance for safeguarding health, safety, and the environment (HSE) and for maintaining the license to operate. In this paper, we describe the development of a composite well cement with specific enhanced acoustic signatures that can be detected by traditional sonic logging tools as well as next-generation ultrasonic tools. This new acoustically responsive cement uses specially engineered particle fillers that act as acoustic band-gap filters and contrast agents at specific frequencies. The resultant acoustic signature can thus be analyzed to determine the mechanical integrity of the cement as well as the mechanical stress experienced by the cement.

During the development of this technology, finite-element analysis and simulations were used to determine the acoustic response and guide the design of the new cement. The composite cement was produced on the laboratory scale, and the acoustic band-gap features were confirmed using vibrational measurements. Ultrasonic sensors were then used to determine the acoustic response of subscale composite structures, including under mechanical load and in simulated environmental tests. Finally, shallow buried pipes with cemented annuli and engineered voids were constructed for pilot testing. During that final stage, a slimhole monopole sonic logging tool was used to map the cement location and determine the location and relative degree of mechanical loading.

Stress was applied using a variety of methods and mapped along the wellbore. The results indicated improved acoustic detection using sonic bond-log tools including uniquely identifiable cement placement, enhanced void discrimination, and localization of loaded regions. The acoustically responsive cement allows distinguishing between fluids and lightweight cement, monitoring of formation depletion and reservoir compaction, and increased knowledge of wellbore stresses in the oil field. Furthermore, the material has the potential to be continuously monitored with an acoustic interrogation system for remote, real-time indication of cement stress and integrity on a zone-by-zone basis.