Sealing Ability of Barrier Materials for P&A Application: Investigation of Casing-Barrier Interface

The bonding properties between a sealant and steel casing are an important component of well barrier. However, there is no consent about how sealing materials should be tested and qualified, and the understandings around the bonding interface and its mechanisms of failure remains uncertain. A custom setup and a systematic interface analysis procedure was established to test the hydraulic bond sealing properties of different sealants, and to investigate their interface with a L80-Cr13 steel casing. The results of hydraulic bond sealability was correlated with macro and microstructural evidence of the bonding interface to understand the behavior and the performance of class G cement and a geopolymer recipes. The geopolymer recipe showed improved sealing performance in relation to class G cement. The interface analysis suggests that, in addition to the mechanical interlocking mechanism, the geopolymer sealant has a strong bond with the coating of the steel casing, as a secondary adhesion mechanism. Understanding the interface and the mechanisms of failure may be the key to further develop current and future sealants, and to reduce risk of leak and to reduce cost with well intervention in P&A operations.