Vessel Utilisation – Part 1: The analysis of on hire times


Marine operations often require multiple vessels which are assigned specific tasks to perform.  Often the tasks performed by the vessels are independent of each other (i.e. the vessels work alone) but are linked in such a way that one vessel is dependent on the other completing work.  In this series of posts we are going to consider cable lay and trenching operations using two assets.  We’ll also look at the consideration of the simulation results both in Mermaid and as part of a bespoke analysis outside Mermaid. Read more >

Analysing Wind Farm Foundation Installation – Part 7: Two Vessels – The Division of Labour

In the last post we arrived at a strategy which we like, this being:

  • Start our operations sometime in March.
  • Use two vessels, unfortunately we can get the two we’d like though, so we’re using a slight cheaper, slightly less capable vessel as our second.
  • Modify the capable vessel so it can carry more foundation units per trip (3).

However, we saw that the division of labour we’d set wasn’t optimal and that we off hired one of our vessels early and lost some of the advantage gained by this strategy. Read more >

Analysing Wind Farm Foundation Installation – Part 6: Work Faster – Two Vessels On Hire

As we’ve moved through this analysis process and applied Mermaid to the consideration of how we can baseline and improve our performance two main objectives have repeatedly arisen:

  • Work entirely in the spring and summer to reduce winter downtime.
  • Maximise the time spent performing offshore operations when favourable conditions occur by reducing the number of transits required.

Here we are going to perform two simulations which it is hope will improve our performance.

The Simulations

There are two scenarios under consideration here:

  • Two vessels operating, both vessels can carry a set of foundations at a time, one vessel is from the base case, the other is a different, slightly less capable vessel (i.e.
Read more >

Analysing Wind Farm Foundation Installation – Part 5: Reduce Transits to Improve Performance – Offshore Resupplies

In this post we’re going to look at bringing the foundations to the installation vessel at site.  It’s thought that, as with carrying more components, we can increase the working time by transiting less.  If another vessel (a barge and tugs) brings components to the main vessel the transit requirements are reduced, although it’s worth noting that offshore transfers of this type are quite strictly limited; the trade-off between transit reduction and sensitive operations is the main concern here.

The Simulation

Our base case simulation includes the transfer of installation components to the installation vessel from a storage barge in the port.  Read more >

Limiting the maximum suspension time for tasks which are allowed to suspend

Indefinite suspensions

For a long time it has been possible to allow tasks and groups of work in Mermaid to suspend, meaning that work is allowed to stop once it has started but before it is complete.  There are two cases for this, Fully Suspendable which allows the vessel to come and go as it pleases, and If Holding Station which requires the vessel(s) to remain at the working location throughout the suspension.  In both cases the length of time for which work can stop has been unlimited.   Read more >

Analysing Wind Farm Foundation Installation – Part 4: Improve Performance – Split Installation

In the last post in this series we identified that even with a larger carrying capacity, our work force was still unable to fully exploit the preferable summer weather and that all start options performed at least some work during the winter.  In this post we’re looking at splitting our installation process into two halves.

The Simulation

To see if we can gain a performance improvement by better exploiting the summer season we are going to install the foundations in two batches of 36.  Read more >

Analysing Wind Farm Foundation Installation – Part 3: First Attempts to Improve Performance – Larger Carry

Continuing the series of posts on the analysis of offshore wind turbine installation methods, this post looks at the improvements, if any, which can be gained by increasing the carrying capacity of the installation vessel.  It is thought that time spent transiting between the vessels home port and the wind farm could be better spent on performing the installation operations, particularly in the summer months when favourable weather occurs.  To do this we’re looking at increasing the on station time by allowing the vessel to carry more monopiles and transition pieces. Read more >

Analysing Wind Farm Foundation Installation – Part 2: Initial Results

We’re looking at ways in which we can install the foundations for a North Sea offshore wind farm and using Mermaid to make decisions on the vessels and the strategy which best suit our needs.  In the previous post in this series we discussed the base case for this analysis process, this being our first look at how we might perform the work.

In this post we’re going to take a look at the results of the analysis we ran last time and we’ll try to work out how, and indeed if, we can improve things. Read more >

Modelling Unexpected Breakdown

So, as we said in the first blog post of the series, we also not only have a mechanism for modelling expected breakdowns, but can use this mechanism with a systematic philosophy of failure management for modelling unexpected breakdown on short operations.

Before we get into it, let’s consider the question we want to ask. On the face of it, we might want to know the P50 of the duration of the operation, with all risk taken into account. Read more >

Modelling Expected Breakdown

In yesterday’s entry about modelling breakdown, I introduced the idea that from next week, Mermaid enables the modelling and analysis of technical breakdown. The new feature that we’re releasing is called “Occasional Tasks”.

An Occasional task or group is one that only happens for certain repeats of its parent group. So, take this very simple task diagram for a survey job to start with:

We’ve got 60 survey lines to complete, and each one takes an hour and a half. Our “Survey One Line” group is repeated 60 times to show this. Read more >