Development of Downtime Cost Calculator for Offloading Operations Influenced by Parametric Rolling

Round 1

Reviewer 1 Report

The authors present a study about downtime cost analysis of offloading operations influenced by parametric rolling. The main aim of the study is to co-relate the problem of vessel behavior under wave load to the global loss in revenue of oil production.

They developed a Graphical User Interface (GUI) able to give to users (e.g. oil operators companies): the unstable wave conditions, the parametric roll due to resonance and ABS criteria, the range of frequencies prone to parametric resonance, the downtime charts and other information.

They present an application of the GUI using a generic model of a shuttle tanker for two water depths and three Malaysian locations.

I think that the topic could be of interest to the JMSE readers.

However, some clarifications have to be discussed. After making these additions and clarifications I may recommend the paper for publication.

General comments:

Authors declare that the GUI could be useful to operator companies. However, the GUI needs to input some information about the shuttle tanker. This requires an expert user. The authors should clarify this point.

Authors tested the GUI with three different locations using 50 years of hindcast data. Is there any validation of the results obtained using the GUI? The computed downtime costs, match the real one? Without other information, it is not possible to understand the real reliability of the proposed tool.

Did the calculator consider the effect of the mooring system?  Are there any possibilities to use this GUI in real-time?

Minor comments:

Line 173: there is a typo, chance “wae” in “waves”.

Line 209: the number of the figure is missing.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

It is a well written paper; the approach is sound and the development of the arguments clear. My only point of concern is the lack of any novelty. The authors apply widely accepted methodologies and rules and deliver an useful application. Apparently, they could use more sophisticated techniques for the estimation of the probabilities, but this is an issue of 'taste' and availability of data. Yet all remarks of that sort are basically 'subjective'. Therefore the authors should 'somewhere' in their text highlight the novelty of their research and illustrate the importance of their work to their peers.  

Author Response

Point 1 - It is a well written paper; the approach is sound and the development of the arguments clear. My only point of concern is the lack of any novelty. The authors apply widely accepted methodologies and rules and deliver an useful application. Apparently, they could use more sophisticated techniques for the estimation of the probabilities, but this is an issue of 'taste' and availability of data. Yet all remarks of that sort are basically 'subjective'. Therefore the authors should 'somewhere' in their text highlight the novelty of their research and illustrate the importance of their work to their peers.  

Reply 1 -Thank you for your comments.

This research paper achieves the main objective of connecting motion response (like parametric rolling) which are potential threats to offloading and production operations. There have been previously lots of work done in the domain of hydrodynamic interaction, parametric rolling and likewise related researches but an existing gap prevails in connecting these responses to OPEX and downtime cost. Additionally, the overall objective is to present a graphical interface for field operators or potential operators to have a near estimate of probable downtime cost for locations of interest. As far as the probabilities are concerned, it is obtained from processed sea fine data of wave scatter obtained from Offshore Engineering Center in Univeriti Teknologi PETRONAS (OEC, Perak, Malaysia).

Finally, it can be said that this paper is proposing a calculating tool for field operators and novelty of linking response to cost was successfully achieved. The novelty and significance was added in the paper and paper was revised

Round 2

Reviewer 1 Report

The authors answer all my doubts or questions. I recommend the paper for publication.