Independent risk assessment : an innovative approach of qualitative risk mitigation measures-prioritization for well integrity assurance

Abstract

Degradation of original well barrier elements might occur after some time in operations. Due to huge number of wells and increasing matured field issues, the key challenge faced is to prioritize the remedial measures and pro-active health checks based on well risk level, barrier status and available resources to ensure that wells operate in safe operating envelope. Knowledge of well integrity status at all times enables company to take the right actions in a proactive manner to prevent incidents. In 2015, management has undertook this project with the goal of understanding and minimizing risk of well barriers failure. The operations include 5 fields, 7 platforms, for a total of 135 active wells. This project present a study in which well integrity was evaluated by independent reviewer as approach for an efficient visualization and description of interrupted well barriers. Then, the responsible parties involved can take action more accurately according to the type of failure that has been revealed to verify and reinstate barrier integrity of the wells. Well integrity risk assessment operational methodology approach includes comparison between measured leakage rate/pressure with maximum allowable limit to estimate how close each well is losing its barriers safety condition. Total of 6 case studies have been performed, which are packer leak, tubing leak and SCSSV passing for primary barrier, while cement failure, high annulus pressure and Christmas Tree valves passing for secondary barrier. Result shows that SCSSV (75%) and Christmas Tree valves (65%) passing are the highest barrier failures which contributes to 53% of high (H) risk ranking. Only 35% of serious (S) risk ranking reported which requires immediate intervention or else shut-in until further approval. In future study, strong focus should be on development of site-specific performance standard in order to demonstrate compliance and ensure well integrity. Operators can benefit by efficiently identifying the critical wells among the thousands being operated so that limited resources can be applied to gain most benefit.