World's OFFSHORE VESSELS

[Clipper]

The GA of the Stril Orion can be found here. ;-)

Thanks Matthias,

I hadn't guessed these vessels have so much bulk/liquid storage capacity down below the main deck. From outside views it looks as if A-Deck itself is the only carrying space, but that's only part of the story.

Anybody, what is meant by "mud"? I know the normal English dictionary definition but assume the word has a special "offshore" meaning.

Clipper

[Ginnick]

Anybody, what is meant by "mud"? I know the normal English dictionary definition but assume the word has a special "offshore" meaning.
[/B]

The simple answer is that it is the liquid that is pumped down the drill pipe when drilling a well. It cools the drill bit and brings cuttings (the broken up bits of rock "cut" by the bit) back to the surface. The Mud is then processed to clean all the cuttings, etc out and then circulated back down the well again.

The weight of the Mud in the well also balances the pressure of oil or gas in a well. Because of this the weight (density) of the Mud needs to be adjusted depending on the conditions in the well. Get this wrong and the oil or gas will come up to the surface, this is called a "Blowout" and can cause fire or explosion on the rig.

Have a look at the following link for more detail:
http://oilgasglossary.com/mud.html

The Mud also has other functions, it gets complicated quickly! I am not an expert, so if anyone wants to correct errors in the above please feel free!

From the boat operating side we get asked to carry different grades and weights of Mud. Traditionally it was Oil Based but lately it has been Water Based or Synthetic Mud as these cause less issues with pollution from the well. This is more relevant in places like the North Sea where Environmental Regulations are well enforced (unlike West Africa).
The boat will have a number of Mud Tanks; these are specially designed to deal with the weight of the Mud and to be easy to clean. There will also be tanks for Brine and Base Oil and a system for carrying Barite or Bentonite. The last two are heavy powders that are mixed with liquid (Base Oil) to make up Mud. The Bulk Handling System uses compressed air to "blow" cargo in powder form up to tanks on the drilling rig. It can also be used to carry Cement.

When you add in other products required by rigs and platforms (Potable Water, Drill Water, Fuel Oil and Methanol for FSPO's) you can see why you need a good bulk/liquid capacity on an offshore boat.
PSV's like the Stril Orion will have a much greater capacity for this type of cargo than an AHTS, but AHTS's still need a decent capacity so they can run supplies to the rig when they are not Anchor Handling.

[Clipper]

Thanks Ginnick, so that's what "mud" is. It had to be important given that all the GAs referenced above show "MUD" tanks.

Getting a bit deeper (in the mud), I wonder what control systems they employ to measure and adjust mud density in a wellbore. And what are the time constants - long I guess - days/weeks rather than hours/minutes. I started my career with a control systems company (a famous name that most people have heard of). That experience still makes me think about control issues even though I have not worked in the industry for nearly 40 years now.

Thanks also for the http://oilgasglossary.com/ link. It's is a great site and now finds itself in Clipper's "Hurigrutgen" bookmark folder.

Clipper

[Ginnick]

I wonder what control systems they employ to measure and adjust mud density in a wellbore.

I am far from an expert in this; it is just what i have picked up 'along the way'. It is useful when we are working boats alongside rigs to have an idea of the operations onboard, as it helps make sense of some of the stranger requests. So I will attempt to give you an answer that makes sense! Any questions about driving AHTS's or PSV's and that i can answer!

The control of Mud Density would come under the heading of Well Control. The driller needs to keep very close eye on the weight of mud in the well, as too much weight can be as bad as too little. http://en.wikipedia.org/wiki/Well_co...ntial_pressure - http://www.lib.lsu.edu/ref/oilspill/wc_manual.pdf

The mud is used to balance the pressures found at depth in a well. Any oil, gas or water in a reservoir will be pressurised because of the weight of rock above them. The deeper you go the higher the pressure.
If this pressure is not matched by the pressure of the mud used in the well then water, gas, or oil will start to flow from the reservoir into the well. This gain in volume is known as a “kick”. If it is not controlled then this kick can get out of control, if you imagine high pressure gas flowing into the well at depth it will start to rise up the well and expand as it rises. The Driller has to be able to recognise this is happening and use a set of control valves he has to “shut in” the well. If he fails to do this the kick can reach the surface (or rig) as a “blow-out”, this is an uncontrolled release of gas. Blow-outs have many dangers, fire/explosion (as in the Deep Water Horizon and the Jack-up rig off Nigeria last year) and also loss of stability for floating rigs. http://www.youtube.com/watch?v=rhZKUYVXM78

Once the well is shut in, then more mud has to be added to increase the weight of mud in the well and stop any more fluid flowing in when the well is re-opened. I is all done very slowly and carefully. There would probably be a quantity of heavy mud on standby in storage when drilling, the density of this would have been calculated to be effective at the depth and pressures being drilled this is called “Kill Mud”

Having too much weight of mud in the well will cause the rock to fracture and the mud will then be lost into the reservoir. This can cause a lot of problems for the driller as he will need to add a lot of mud to keep the volume in the well. I was working off Cameroon last year and the rig we were supplying had this problem as the rock they were drilling was very difficult. They were always sending us back into Douala for more Mud, Base Oil and Barite.

So to finally answer your question, it will be a combination of pre-calculating mud-weights needed (or expected) and careful monitoring of the pressures and flow in (and out) of the well that lets the driller keep track of the Mud Density. Modern Rigs have a lot more control and monitoring systems than older ones, but it still comes down to the skill and instinct of the driller when things go wrong.

A bit like with us on the boats. We now have very good Dynamic Positioning systems that will keep the boat in position alongside the rig, within 2 meters of the desired position. Some systems will even keep position alongside a moving target Eg. a FPSO swinging on her turret. This is very nice equipment, but you still need the basic ‘driving’ skills to be able to take over when it all goes wrong. There is no time to think, you just need to act.

Apologies for the long (mostly) off topic post!

[ombugge]

Some offshore vessels seen in Labuan F.T, Malaysia yesterday.
At Sabah Shipyard:


At Asia Supply Base:

[ombugge]

Anchored in Victoria Harbour:

[ombugge]

Large new utility vessel:


Outside the harbour:

[ombugge]

My target for the day, PSV Bourbon Hamos:

[pilotdane]

Holly cow! Look at the first photo of #1086. It looks like the garden where they grow offshore service ships.

[Clipper]

I am far from an expert in this; it is just what i have picked up 'along the way'. .....

Thanks again Ginnick. That is all very helpful and now I know who to ask when I have questions about driving AHTSs/PSVs.

Although I am not at all knowledgeable, I'm sure I must have offshore somewhere in my blood.

Clipper

[Sterkoder]

Thank you, 'ombugge' for giving us pictures from your part of the world.
It's a clear diffenence in the design of norwegian and non-norwegian offshore vessels.

Today, "Normand Subsea" was moored at Storkaia in Kristiansund.
Seabed anchors for some subsea installation on deck.

(Lense: Tamron 18-200mm)

[Sterkoder]

Nice day for a new lense, so to speak. A new vessel arrived Kristiansund this Monday morning, and at 08:00 I drove down to the docks at Vestbase to fire away.
This is standby-vessel "Ocen Alden" owned by Sartor Offshore, built at Wison (Nantong) Heavy Industry Co., Ltd in China and delivered in October/November 2011.



A little more details

[pilotdane]

So, were the Ocen Alden photos taken with your new lens?

[antias]

Interesting Ship. Look here how it was build. ;-)

Matthias

[Sterkoder]

So, were the Ocen Alden photos taken with your new lens?

Yes, new lense, new ship...., a great start to a new week.

[Sterkoder]

"Ocean Alden" left Kristiansund today. She will have her base in Florø, but came to Vestbase to pick up her oil spill response equipment.
Wanted to take her picture from dock #2 at Vestbase, but there was "Normand Subsea" in the way, so I had to settle for the famous view.




"Havila Borg" waited for a place alongside a quay, and in the strong wind, she was dead steady on DP.

[pakarang]

Very impressive perspective of a ship!

[albatros]

Here are some new photos from The Port Of Bergen and CCB Ågotnes.



DEEPSEA ATLANTIC – CCB Aagotnes, June 2009



HAVILA FORESIGHT – CCB Aagotnes, March 2012



NORMAND PROSPER & SKANDI VEGA & KL SANDEFJORD – Port Of Bergen, March 2012



NORMAND PROSPER – Port Of Bergen, March 2012





SONGA DEE – CCB Aagotnes, March 2012

[Traktor]

Havila Venus passing Bergen, March 2012

[Tommi]

Nice additions.

By the way, what is the bridge on Deepsea Atlantic (#1098/1) used for? I thought these platforms were always towed.