Leveraging Zonal Isolation Index: A Data-Driven Go/No Go Decision for Cement Remediation Based on Cement Evaluation Log Analysis

Abstract This paper presents a comprehensive methodology that integrates the Index of Zonal Isolation (IZI) with Cement Evaluation Log analysis for enhanced well integrity management. The methodology aims to establish a structured, data-driven Go/No Go decision framework for cement remediation, reducing reliance on individual engineering judgment and enhancing the structural stability and operational efficiency of wellbores. By leveraging cement evaluation log interpretations alongside reservoir characteristics, pressure, fluid contents, and operational risks associated with cement remediation, the approach ensures a thorough assessment. Given that zonal isolation is paramount in the annulus cement, particularly in the reservoir section of a well, this paper will conceptually explore the derivation of the Index of Zonal Isolation (IZI). The discussion will highlight how the IZI incorporates reservoir properties to assess annulus cement's primary function—zonal isolation—especially when anomalies such as channels or micro-annuli are detected through various radial cement evaluation logs. The methodology will be exemplified through a case study of a water injector well drilled and completed into an oil pool, situated directly beneath a sequence of different oil reservoirs where zonal isolation is a critical requirement as mandated by the reservoir management team.