FEATURES
 

DEEPWATER HORIZON
Deepwater Horizon - The Investigation
The Deepwater Horizon and the Late MMS.
The Deepwater Horizon - PR and Politics
The Deepwater Horizon - Forces at Work
The Deepwater Horizon - Where Are We Now?
ROVs, Risers and Mud
The Deepwater Horizon - Later
Something about the Deepwater Horizon Accident
Channelling the Oil Leak
Preventing Fires and Explosions on Offshore Installations

OTHER ACCIDENTS
The Loss of the Normand Rough
The Bourbon Dolphin Accident
The Loss of the Stevns Power
Another Marine Disaster
Something About the P36
The Cormorant Alpha Accident
The Loss of the Ocean Express

OPERATIONS
The Life of the Oil Mariner
Offshore Technology and the Kursk
The Sovereign Explorer and the Black Marlin

SAFETY
PFEER and the Dacon Scoop
Human Error and Heavy Weather Damage
Lifeboats & Offshore Installations
More about PFEER
The Offshore Safety Regime - Fit for the Next Decade
The Safety Case and its Future
Jigsaw
Collision Risk Management
Shuttle Tanker Collisions
A Good Prospect of Recovery

TECHNICAL
The History of the UT 704
The Peterhead Connection
Goodbye Kiss
Uses for New Ships
Supporting Deepwater Drilling
Jack-up Moving - An Overview
Seismic Surveying
Breaking the Ice
Tank Cleaning and the Environment
More about Mud Tank Cleaning
Datatrac
Tank Cleaning in 2004
Glossary of Terms

CREATIVE WRITING
An Unusual Investigation
Gaia and Oil Pollution
The True Price of Oil
Icebergs and Anchor-Handlers
Atlantic SOS
The Greatest Influence
How It Used to Be
Homemade Pizza
Goodbye Far Turbot
The Ship Manager
Running Aground
A Cook's Tale
Navigating the Channel
The Captain's Letter

GENERAL INTEREST
The Sealaunch Project
Ghost Ships of Hartlepool
Beam Him Up Scotty
Q790
The Bilbao OSV Conference

ROVs, RISERS AND MUD

It is now Friday 4th June, and as I think that the drama for BP, and the US Administration is over I am proved wrong. The fateful hours before the loss of the Deepwater Horizon on 20th April and eleven members of its crew are gradually being made known to the public at large from a variety of sources. Transocean are still saying nothing, but BP themselves and the US government investigators are beginning to reveal a little of what they have learnt. One expert has questioned the displacement of the drilling fluid (mud), with seawater, saying that this was the final straw in a catalogue of errors. Whether this was so or not, there at least appear to have been signs before the event that all was not well.

The other day I was talking to a small group of people about seafaring, and in the questions about the oil spill I realised that no-one really knew what "mud" was. And despite the many superb graphics provided by both the operator (I realise that I am also using oil industry speak - Operator, the person who is in charge of the well) and others, they have still failed to explain what mud is, how it relates to a "junk shot" and actually what these "robots" are. And of course there is the riser, or more commonly in the media, the pipe which the robots have been cutting before the latest "cap" has been put in position.

In my last article I described the riser as appearing to be a string of partially cooked spagetti  lying on the seabed. In its operational state the riser is a set of lengths of 21" pipe bolted together, and it appears that as the rig sank the riser broke off, so that it was still connected to the top of the BOP (Blowout preventer) which in turn was still connected to the wellhead. The riser had originally be 5000 ft long (the distance from the seabed to the underside of the Deepwater Horizon drill floor), but the length up to the break which had previously been the subject of BP's attentions was not revealed. You may remember that they had attempted to recover oil from the end of the riser with only moderate success, and that then they had tried this "top kill" using the choke and kill lines of the BOP. This second effort was actually pretty ingenious and must have tested the ROV pilots to the limits of their capabilities. At the end of it they had managed to install a manifold which allowed them to use different parts of the BOP pipework, and through which they were able to pump "mud". And here I realised that mud to the people I was talking to in Madrid was sort of stirred up earth and water, and that this view seemed to be supported by the fact that BP were also considering a "junk shot", which was described by them as a possible combination of human hair, golf balls and bits of rubber tyres.

Their idea was that they were going to pump mud, which is a combination of oil of some sort and chemicals, mainly baryte,  into the well and eventually to create a hydrostatic head which would tame the discharge. The second string in this particular campaign was to be the junk shot, which I summise would have been intended to close the gap in the BOP which is letting all that stuff out towards the surface. If they tried it, it did not work, so the ROVs (Remotely Operated Vehicles) were sent in again with big saws to cut the riser off just above the BOP.

Apparently the live feed from the ROVs was fascinating viewing. This is a new world we can watch dramas as they are happening, because everything is being recorded or at least presented on a screen somewhere. The ROVs are not robots in any sense of the word. They are small neutrally buoyant devices which can be manoeuvred by means of their small thrusters, and which are provided with tools on their little arms. Without the ROV the offshore oil industry could never have made it beyond the maximum  depth which can be achieved by live divers.

This is a work ROV about to be launched. The whole set will take it down to its working depth, and then the bottom bit, known in the media as the robot will be able to move away from the top hat bit. This saves a lot of time. This one is fitted with a device for doing something to vertical tubulars. Photo: Derek MacKay.

So the ROVs managed to cut the riser off above the BOP, and then a connection was achieved with a set-up lowered from the Discoverer Enterprise. We should not lose sight of the fact that this is not just a matter of connecting one pipe to another and then collecting the oil on the surface. If a good connection is made with the well then the Discoverer Enterprise is exposed to the same risks as was the Deepwater Horizon, hence there is what they call an LMRP, Lower Marine Riser Package, above this connection. The description indicates that within this structure there is a "bag preventer" which is capable of expanding and therefore restricting or cutting off the oil flow.

What can one say. The relief wells are being drilled. The US President is, this day, on the coast showing how concerned he is. The Managing Director of BP has not left America since the the media storm commenced, and I hope that I am contributing in a small way towards an understanding of an event which may change the face of offshore drilling in the US Gulf for good.

Vic Gibson 4th June 2010.

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