FEATURES
 

DEEPWATER HORIZON

Deepwater Horizon - What Have we Done to Deserve This
Deepwater Horizon - After the BP Report
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


ACCIDENTS
The Costa Concordia Grounding
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
Safety Case Development
The ALARP Demonstration
PFEER, DCR and Verification
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

THE DEEPWATER HORIZON ACCIDENT - LATER

By today, 28th May 2010 everyone in the western world must be aware that things have not been going well for BP in the Gulf of Mexico, nor have they been going well for the American Government, the President and the Chief Executive of the Minerals Management Service, the authority which has up to today controlled the issuing of licences to drill, the collection of revenues and the management of safety in US offshore waters. Apart from what's happening out there at sea, in the choppy waters of the political ocean President Obama has attempted to create a lee by banned further deepwater drilling for six months and demanding the suspension of operations on 33 wells in the Gulf. Also the chief executive of the MMS has either been sacked or resigned, depending on which paper you read.

The well which had been being drilled by the Deepwater Horizon has continued to release oil into the Gulf, although BP had  achieved some success with the tube inserted into the end of the riser connected to the Discoverer Enterprise, which was collecting a proportion of the discharge. As things stand today the blowout preventer is still attached to the wellhead, and the riser, a 21 inch pipe, itself still attached to the top of the BOP, is lying like a strand of partly cooked spaghetti on the seabed. Most of the pictures seen so far have been of the end of the riser, from which the drill pipe protrudes, and from which oil can be seen belching out. The position of the rig itself which sank on 22nd April still burning furiously, is probably known to some-one,  but this has not been revealed to the general public. It is worth remembering now, in the rising tide of public indignation over the threats to the environment, that eleven guys died in the explosion on the rig on 20th April, and the more cynical of us would be wondering whether the event would still be news, and whether anyone would still be interested, if the rig had remained afloat, and the well had ceased to flow.

So today there apparently is progress as BP initiate a "top kill", pumping heavy mud into the well through the choke and kill lines. This is known in the industry as "bullheading". They have been doing this for about 24 hours and have stopped pumping recently to see whether the well is still flowing, and now have resumed this operation. There are loads of pictures and diagrams available of what is happening, and on the BP site there are graphics of the BOP with the manifold and pipework and the drillpipe from the rig, the Q4000. Indeed many of the vessel involved have been named. Because some of the mud is is not going down the well, but is rising through the BOP and can be seen exiting the end of the riser, the company has large quantities of mud on site in the large all aft Hornbeck support vessels the HOS Centreline and the HOS Strongline. Each of these vessels is capable of carrying over 30,000 barrels (4700 m3) of mud as well as much else. These ships are Hornbeck conversions, and when I updated the Hornbeck page on my website I left them out because I thought they would never be any use to anyone. It just shows how wrong you can be. There are also other well stimulation vessels hovering about in case they are needed, and the distinctive Ulstein SX 121, the Viking Poseidon, can be seen in many of the pictures probably providing ROV services, as is the DOF construction ship Skandi Navica.

This is the top of a riser at what is known "the slipjoint". The wires leading upwards are the riser tensioners, supporting some of the weight of the riser. They are part of the complex system which allows the rig itself to move while the connection to the well is maintained. The flexibles connecting the rig to the choke and kill lines can be seen on either side.

But back to the choke and kill lines, which no-one actually bothers to explain. The choke and kill lines are connected to the BOP and, as shown in the diagrams, are piped in between or beneath the rams, so as to give the rig the maximum flexibility in their operations. These lines run up the sides of the riser and, under the drill floor of the rig, they are piped to something called the standpipe manifold, which itself is connected to the mud pumps and often the cement unit pump as well because of the higher pressures which this pump can usually achieve. What all this stuff can do is control a kick, an excess of pressure in the well. If everything works out, the pressure is detected and some of the rams in the BOP will be closed so that the overpressure is contained. From this point the choke lines and valves can be used to bleed off the pressure and the kill lines can be used to inject heavier mud into the well to control the problem. Once equilibrium is achieved the job can continue. From the initial report of the congressional investigation it seems that the drill crew on the Deepwater Horizon may have done exactly this more than once  during the hours before the disaster.

Now it seems that the ROVs (Remotely Operated Vehicles) have managed to make these lines available at the BOP and have connected up flexible pipes to them from a manifold which must have been constructed to allow the team to control the flow to the various entry points between the rams. This in itself is something of an achievement since the BOPs are not built to be ROV operable, no matter what recent reports may say. And to digress for a moment, there is a difference between wellhead manifolds, which are intended to remain permanently in position on the seabed, and BOPs, which although they are also positioned on top of the wells being drilled, are deployed from the rig and recovered at the end of the job. The wellhead manifolds are now always constructed so that their valves can be operated by ROV - hot stabs as they are known - but as I said, not so the BOPs.

Although the oil industry has spent time trying the dispel the wildcat image which it used to have, there is no getting away from it, they have always worked at the edge of what was technically possible, particularly at sea. And most of the accidents in years gone by, which have resulted in major loss of life have been as a result of marine failures. These include the Sea Gem in UK, the Ocean Ranger in Canada and the Alexander Keilland in Norway. Of course the Piper Alpha accident in UK waters was due to a processing failure. It was oil stuff, not marine stuff, and it resulted in a complete change to the way that offshore safety was dealt with in the UK. There are today the first signs that the loss of the Deepwater Horizon will initiate a similar change in the Gulf of Mexico.

Vic Gibson 28th May 2010.

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