Reliability Availability and Maintainability Analysis of New Offshore Platform

As part of the design development of a new offshore platform in the North Sea, MACH10 was asked to conduct an integrated Reliability, Availability, and Maintainability (RAM) analysis of the subsea and topside portions of the asset.

The task was performed using best-in-class RAM analysis software to model the process and assess the product export system, the maintenance plans, and the staff composition to predict the asset’s up-time and production efficiency. In addition, the Customer’s plan was to use the findings of this analysis as one element of the overall maintenance strategy development.

For the topside and certain subsea equipment, an Exponential type failure distribution was used, as is common in such RAM studies. However, because the failure rate of certain subsea equipment increases over time, due to ageing and wear out, a Weibull type distribution is more appropriate.

The asset production efficiency stood initially at approximately 90% and had an average value of approximately 87%, during the first four years. After this period, it varies from year to year but, over time, declines to less than 80% , at the end of the 15-year lifecycle ,primarily due to the subsea system.

As would be expected, there is a noticeable drop in production efficiency in the years when periodic maintenance is conducted. The overall average lifecycle oil production efficiency for the integrated asset is approximately 86.6%.

It should be noted that:

• nearly 2.8% of the 3.8% overall average subsea losses are due to the DSV and Drilling Rig mobilisation time. Over the life of the asset, 15 years, around 30 repairs will be completed by the DSV and about 2, by the Drilling Rig;
• on-board staffing resources, with shift restrictions and external resource mobilization time combined, contribute 3.3% to the overall efficiency loss;
• the single export gas compressor contribution to production loss due to failures and scheduled maintenance is 1.7%;
• the planned maintenance turnarounds occurring in the fifth year and recurring every two years thereafter, contribute to approximately 0.8% of the loss ;
• around 4-5 times per year, two of the three GT power generators are also down at the same time and, consequently, contribute to a production shutdown resulting in 1.3% loss.

The use of a single software and an integrated model including all the asset components (mechanical, electrical, instrumentation of topside and subsea part) and strategies (supply chain, product export, maintenance philosophy) created a powerful tool for testing different scenarios over the expected production timeframe. The enormous amount of data produced during the design phase by different software and models, has been uploaded to our model, to make results available ,when required for crucial decisions about sustainable operations.