Risk informed integrity management of sub-surface well production tubings subject to combined scale and corrosion degradations

The progressive loss of integrity of production tubing results from time- and space- variant degradation processes, mainly scale and corrosion. Due to the potential disastrous consequences of failure, it is necessary and required to manage the integrity of production tubing systems by means of inspections, monitoring and maintenance. However, there are substantial uncertainties associated with the degradation processes and it is prudent to account for these in the optimal planning of integrity management. To this end risk informed approaches taking basis in the Bayesian pre-posterior decision analysis and methods of structural reliability, introduced already 3–4 decades ago for integrity management of offshore structures, comprise a strong basis. With such an approach an optimal trade-off between the cost of inspections/maintenance and the benefits due to increased production and reduced risk to personnel and environment can be determined. This paper presents such a framework and demonstrates its implementation on a selected example. The novelty of the framework is the risk informed Bayesian decision framework and the joint consideration of the two common failure modes of the tubing: tubing clogging and leaking due to scale and pitting corrosion respectively.