Pipe-trenching

[known100]

This work is not that old and quite elaborate.
Too little I know about the intricacies and put these queries to the Forum.
What holds the 'A-to-Z' of pipe-trenching?
From selecting the site (landfall); survey; precautions, etc. such as:
The most versatile equipment (available) on land and for underwater part of the job.
The trench to be up to 1000 meters seaward from chartdatum (MLWS).
Direction; cutting; base preparation; pipe laying; covering; backfilling and monitoring in the years to come.
Pipes are either for gas or for oil (from production platform). To be ready as well from a SMB (singlemooring buoy) installation.
Anything, guidance or advice / links on choice of gas- oil-pipes, manufacturers, is really welcomed.
Thanks so much.

 

[StephenA]

This is a huge question, but here are some pointers.

Selection of landfall.

This will depend on the following (amongst others)

Ground conditions.
Wave action.
Available access from land.
Distance from nearest safe haven for marine craft.

In general trench above MLWS would be by land based equipment and below MLWS by marine craft but this will depend on ground conditions. Is it mud, silt sand, rock etc.? It will also depend on tidal range.

The depth of the trench required will depend on the following (amongst others):

Pipe size
Design wave size and direction
Seabed material
Armouring required.
Future seabed level changes
Future sea level changes

The equipment to be used for the land based and marine based trenches will also depend on the above conditions and well as an economic one. (For example you may not want to mobilise a cutter suction dredger from the other side of the world).

For a 1000m pipeline, a standard method would be to fabricate the pipeline in strings parallel to the centreline on dry land and pull them into the trench, welding the following one behind those already pulled. The PLEM (Pipe Line End Manifold) could be towed out as the pullnose.

I have just completed a brief installation method description for a similar pipeline which ran to 16 pages (too long for this forum).

With more information further assistance is possible.

Best regards

StephenA

 

[known100]

To: StephenA

I will sit on your "pointers" and use them to have a good starter! If then, there are further queries, I will certainly not hesitate to post them here again.
Many thanks for this 'booster'.

 

[elbow1]

thanks,StephenA,
you also give me some direction about this topic, Could you please send me your 16 pages description to meixi2001@yahoo.com.sg?

thanks alot.

 

[evilkudos]

Hi StephenA,

I am extremely interested in your 16-page explaination. Could you please send me a copy too? I'm currently doing my internship in a offshore pipelines company and I believe your invaluable information would do wonders in helping me understand this field of work (I major in structural, but choose my internship in pipelines coz it looks extremely attractive. No more boring buildings for me!!!)Kindly send it to: zephyranthes_fb@hotmail.com

I'm facing the same problem, as I'm supposed to do a report on new/advances equipment for all aspects of offshore pipelines related work (speaking of which, do you know of any?), and all the jargon is killing me!

Many thanks for your help!

Regards,
Evilkudos

 

[StephenA]

The 16 pages was for a particular pipeline and unfortunately is priveleged information. I only mentioned it to demonstrate the size of the subject.

I have been trying to find a publication on submarine pipelines which describes all the aspects of pipelines that cross the shoreline. One of the authors was a Peter Neville-Jones. If I can locate it or a similar publication I will post the link.

Our website

http://www.landandmarine.com

describes the work that we do.

I hope this helps.

StephenA