Abstract
A risk based inspection and equipment strategy program was developed for mature down-hole tubulars in Bass Strait oil and gas wells. This paper outlines the major features of the program including identifying components, describing degradation mechanisms, assigning a credible failure scenario, defining the probability and consequence of failure, development of strategies to mitigate "unacceptable" risk and finally assigning a mitigated risk.
The strategy development is applicable for caliper and proactive work-over candidate selection, work-over rig plans, reservoir depletion strategies, downhole corrosion management and platform life end plans.
A key feature of strategies is determining the probability and consequence of tubing failure. The consequence of failure determined in these reviews is based on financial criteria given that Safety, Health and Environment (SHE) risk is low due to completion design. The basis for obtaining these will be described. Corrosion rate and failure prediction are based on Bass Strait field data and are used in determining probability. Consequence is based on reservoir remaining reserves and when combined with probability is plotted on a risk matrix. A multi-functional team develops strategies to mitigate risks that are determined to be "unacceptable". Strategies include "do nothing", inhibition, patch tubing, coil tubing, work-over, proactive work-over, utilise corrosion resistant alloy, caliper and continue to monitor. The team measures success by determining the resultant mitigated risk.
The paper describes a process that enhances the tubing life cycle management process. Using this tool cost saving can be obtained through proactive preventative programs and utilisation of failure prediction to provide for improved planning and budget management.
