An accurate estimation of offshore jacket platform performance during its service life is essential. A significant amount of research has been carried out over the past two decades to understand the effect of ageing and the associated degradation of offshore jacket-type platforms. However, there is still scarcity of published literature in modeling residual service life based on inspection records. Offshore platform maintenance systems are dependent on deterioration models to predict the future performance of structural elements. The input for these models is based on the visual inspection records and the current condition of the platform elements.This paper presents deterioration models for maintenance planning based on two methods: i) stochastic Markov-chain based model and ii) stochastic- mechanistic deterioration models based on corrosion rates of steel. The Markov chain model requires the estimation of transition probability matrix (TPM), which is typically derived from the inspection data. The TPM characterizes the conditional probability of transitioning to a deteriorating condition state for a particular structural element. The matrix is then utilized to develop deterioration models based on the current condition of the jacket steel members. This method is suitable to model deterioration based on inspection records of a network of offshore platforms. In the stochastic-mechanistic deterioration modeling, established corrosion wastage models are utilized to estimate the time-dependent deterioration of jacket legs, horizontal and diagonal bracings in various zones- atmospheric, splash, tidal and immersion zones. Monte Carlo simulations are performed to estimate the expected value of deterioration and the associated uncertainty. This method is suitable when there is information about the condition of a particular platform based on visual inspection and non-destructive testing. Based on the proposed modeling approaches, the residual service life of the jacket elements is predicted. This information could be further utilized in developing appropriate planning and implementation of maintenance actions. This will help to reduce the deterioration rate and optimize the total operational costs.Keywords: Offshore Jacket platform; Stochastic deterioration model; Markov chain model, Mechanistic modeling; Monte Carlo simulations.

Stochastic Time-Dependent Deterioration Models for Estimating Residual Service Life of Offshore Jacket-Type Platforms

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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