Sample Analysis Specification: Abandonment

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Sample Analysis Specification: Abandonment

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There are several different ways in which you could define a pipeline abandonment scenario. The following simplified sequence is used here to illustrate the Analysis component capabilities.

 

Initial Set-up

Typically, for an abandonment analysis, you would define a model containing a pipeline with both pipe and cable components, as well as perhaps a pullhead. The cable, at the vessel end, could be of zero or some nominally short length initially. Choose your model on the Analysis component Properties tab.

 

Defining Stages

In this simplified scenario it is proposed to look at the effect of increasing the cable length while simultaneously decreasing the length of the pipe component. So for the Installation Stages tab it is a matter of deciding over how many steps you want to examine this. In the figure below, there are 15 stages defined.

Abandonment Installation Stages

Abandonment Installation Stages

 

Defining Installation Parameters

For the second and subsequent stages it is proposed that you increase the cable length by a certain amount, say, 50m, while simultaneously reducing the pipe length by the same amount.

To specify this requires two additions per stage on the Parameters tab. Firstly, decreasing the pipe length requires you to (i) nominate the Parameter Type to be a Pipe Section; (ii) use Component Name to select the pipe section of interest; and (iii) press Define and specify the new pipe length (which is the original length minus 50m). The figure below shows how the Parameters tab might look after this operation.

First Parameter Change for Stage 2

First Parameter Change for Stage 2

 

Increasing the cable length works in the same way, except in this case (i) you nominate Parameter Type to be a Cable, (ii) choose the cable of interest with Component Name, and (iii) specify the increase in cable length with Define. Now the Parameters tab might look like the figure below.

Second Parameter Change for Stage 2

Second Parameter Change for Stage 2

 

 

The figure below shows how the tab might look after all 15 stages are added. Note that there is no requirement to specify this data for the stages in strict order from Stage 2 to Stage 15. PipeLay will sort the values into ascending order if you choose not to.

Parameters Tab for All Stages

Parameters Tab for All Stages

 

The only other way in which this example differs from the normal lay earlier in the previous article is that you would typically want to likewise define criteria for each stage. The procedure is quite similar to the above. The figure below shows how an example specification might look. Here the criterion to satisfy is the maximum bending stress in the pipeline sagbend, and it is to be satisfied by iterating on the position of LayVessel(1). When iterating, the vessel is to be moved in the direction defined by the component Vector. This is only an example of the use of this tab, in reality more meaningful values would be defined.

Criteria Tab for All Stages

Criteria Tab for All Stages

 

That completes the two illustrative examples on the use of the Analysis component.