Something About the Deepwater Horizon Accident

 

There was an explosion on the semi-submersible Deepwater Horizon on 20th April 2010, which was completing a well for BP, 50 miles from the edge of the Mississippi delta in the Gulf of Mexico. Eleven of the guys on board the rig unfortunately lost their lives. Nine of them were employed by Transocean, the owners of the rig, and two of them by MI-Swaco, a service company. The rest of the crew successfully evacuated by lifeboat and were subsequently recovered to the Tidewater platform ship, Damon B Bankston, and finally landed in Port Fouchon twenty-seven hours after the incident. The rig continued to burn and gradually took on an increasing list, and slipped under the waves on 22nd April.

Today, 17th May, BP have announced that they have stemmed the leak, apparently by means of inserting a flexible tube into the end of the riser and channelling the oil flow to the drill ship Discoverer Enterprise on the surface. The Discoverer Enterprise has on  board the plant required to separate the gas from the oil, and is flaring off the gas, and is storing the oil in its tanks. Apart from anything else, this process will provide everyone with a good indication as to what the actual flow of oil from the well might be, since the storage capacity of the drill ship is known. The possible flow has been estimated as being as little as 1000 barrels per day and as much as 80,000 barrels per day. The upper figure seems to be pretty unlikely however. Today’s announcement should bring some relief to the people on the gulf coast, to the US administration and also to BP. There seems to have been general amazement that the well could not just be turned off, but as everyone in the business knows, that not the way it works.

Over the last few days those of us who are still following this story have seen some witness statements appearing in the press, which, give us the opportunity of finding out just a bit more about what happened, or at least what was going on at the time. Apparently the supply ship Damon B Bankston was attached to the rig by a hose when the blowout occurred and was engaged in the task of backloading mud. Already I realise that I am lapsing into industry speak, so we’ll back track a bit.

It seems that the well that the Deepwater Horizon had been drilling was all over bar the shouting. They would have successfully drilled into the reservoir, maintaining the integrity of the well bore and the rig, by ensuring that the oil and gas down there was kept in the proper place by the column of mud and the pressure of the pumping system. Mud or as it is more correctly known “drilling fluid” is made up of some form of oil ( they used to use diesel oil once) or water, together with chemicals, mainly baryte, which is pumped down the hole using very large pumps. The ones on the Deepwater Horizon were capable of pumping at a pressure of 7500 psi. This fluid is stored in tanks on the rig, and as well as providing a hydrostatic head brings back to the surface the debris produced by the drilling operation. While the well is being drilled the returns are analysed by mud engineers to determine what the formation is like, and whether there is any gas or oil about. Back on the rig the mud is cleaned and then pumped back down the well, and the weight of the mud plus the pressure created by the pumps keeps everybody safe.

So having been through the process of drilling the well, including casing it, which means inserting steel pipe for the whole depth, something will be done with it. If there is no oil down there, or not enough to warrant further work the well will be plugged with cement and the wellhead removed by one means or another. In the old days they always used explosives but it is possible that more scientific techniques are used today. Even if it is intended that the well will be re-entered, as was to be done in this case, it will be plugged with cement and left with just the wellhead sticking out of the seabed. So that’s where they were apparently on the afternoon of 20th April. The well had been plugged with cement, and the Tidewater platform ship Damon B Bankston was attached to take the mud back to base for re-processing. There would probably have been mud in the tanks, or pits as they are known, and also mud in the well and the riser. Eventually it would all be displaced with seawater, because if the well was plugged with cement, and all the work was finished, there were be no need for the hydrostatic head.

At some point during the discharge of the mud from the rig to the ship the blowout took place, and a report by a journalist who had interviewed one of the crew said that a plume of mud and gas could be seen spurting into the air like a geyser. Apparently the ship was then instructed to let go the hose and stand off 500 metres. Within a couple of minutes there was an explosion and fire and all the lights went out.

What then of the blowout preventer, the BOP, you might ask. Well who knows. The first thing to say is that as far as the guys on the rig were concerned, even though it was still there on the seabed, they would probably not be considering it necessary for the maintenance of safety, because the cement plug was doing that. So there would be no-one’s finger hovering over the buttons. And much has been said about BOP testing and BOP failures, and even about the numerous failure modes that there might be in this sort of equipment. Is the poor old drilling industry to be hoist for testing the gear? Those familiar with reliability science would tell you that the availability of equipment is determined by testing, and also that the time for which the equipment is required to be reliable is taken into account. For instance, in calculating the reliability of the equipment used for space flights, they know it only has to last for the duration of the flight. Similarly BOPs only have to last – to remain reliable – for the duration of the well, but if one is to make use of this knowledge you have to test the BOP and correct any failures before attaching it to the end of the riser and lowering it to the seabed. And as I have said before, deep water BOPs are extremely complex beasts. So who knows about the BOP. We have not heard what the actual status of the rams was after accident. Were they all still unfired, unactioned, or were they all closed about the drill pipe, with finally the shear rams almost meeting but held apart by some bits of metal in the wrong place, allowing the pressure in the reservoir to force the oil out. And what were those ROVs actually trying to do with the BOP? We little people on the outside have no idea.

So, regardless of what was happening down on the seabed, gas and oil made it to the drill floor, and of course a small volume of gas 23,000 feet down will expand quite a bit on its way up. Once more we don’t know what actually happened but a sufficient volume of gas could envelope the rig seeking out any possible ignition sources. We should remember that this rig was dynamically positioned, meaning that its computers were using satellites, and probably beacons on the seabed, to identify the required position and that this information would be being transferred to the thrusters which would be turning and whirring to hold the rig over the well. The thrusters were powered by 6 Wartsila engines developing 58,000 bhp. Of course the engines can provide ignition sources and worse, they can be fuelled by gas so that even if you turn them off they don’t stop. It is possible to fit engines with valves in the air intakes, which overcomes this problem, but in the case of the Deepwater Horizon would they have wanted to stop the engines since they are the means by which the rig is kept in position, or possibly changing the position. Whether those in control on the rig stopped the engines or not, survivors reported that all the power went off and that there was an explosion, possibly not in that order. So now the rig was left, being held in position by the riser, with the product from the well burning on deck. It must have been truly terrifying.

And we can speculate on why the rig sank – but on another day.

Photo of the Damon B Bankston by Oddgeir Refvik

Vic Gibson 17th May 2010.

Ships and Oil News and Views for May 2010

THE DEEPWATER HORIZON ACCIDENT

There was an explosion on the semi-submersible Deepwater Horizon on 20th April 2010, which was completing a well for BP, 50 miles from the edge of the Mississippi delta in the Gulf of Mexico. Eleven of the guys on board the rig unfortunately lost their lives. Nine of them were employed by Transocean, the owners of the rig, and two of them by MI-Swaco, a service company. The rest of the crew successfully evacuated by lifeboat and were subsequently recovered to the Tidewater platform ship, Damon B Bankston, and finally landed in Port Fouchon twenty-seven hours after the incident. The rig continued to burn and gradually took on an increasing list, and slipped under the waves on 22nd April.

Since then the story has migrated from the inside pages of the newspapers to the front pages, as the well which the rig was completing has continued to pump oil into the Gulf of Mexico at a rate which is generally agreed to be 5000 barrels a day. There are 6.3 us barrels of oil to a metric tonne. BP is attempting to stem the flow and to prevent the oil from polluting the beaches on the edge of the gulf and to this end it is mobilising hundreds of small craft to assist. Never-the-less as I write this, the first traces of oil are reaching the edge of the Mississippi delta and the residents and business people on the coast, and the US legislature are becoming more and more angry. They started off being surprised that the well could not be magically turned off, and then have become even more amazed that no matter how much money and expertise is thrown at it, it still can’t be stemmed.

Mt first thought was – does no-one in America read the international news? In 2009 there was a blowout on the  jack-up West Atlas off the east coast of Australia, which took 10 weeks to plug and resulted in the discharge of thousands? hundreds of thousands? a great deal of crude oil, into the sea. But then it should have been the Minerals Management Service alerting the government to any problems in the industry, and as this story unfolds it is becoming evident that there may have been an unhealthily close relationship between the service and commercial interests.

And then I became surprised that this is the first time that this has happened, almost. There was a blowout off California in 1968 which had dramatic results on the coastline and the wildlife, and there have been accidental discharges off Mexico which no-one much has bothered about. Of course many people have died offshore in the Gulf of of Mexico drilling for oil,  but there has not been much effect on the wildlife and so not many people have noticed. Now, as the politicians and the media try to catch up and learn something about what is happening, we are seeing whole swaths of strange comments, which seem ludicrous to those with even a little specialist knowledge.

I was going to carry on with this, but feel it is worth a further article in the features section of the website. I have written a couple already, in which I am hoping I clarify some of the confusion relating to this event. There is a lot of new information now, as to what the actual status of the well was when the blowout occurred, some of it relating to cement. I am not an expert on cement, but I’ll do my best.

PIRATES

The saga of the Somali pirates continues, and for the first time there has been successful retaliatory action. Back in February the Slovenian owned, and Barbuda (Barbados?) registered bulk carrier, Ariella, was captured by pirates, but the whole crew made themselves safe and as a consequence Danish special forces from the warship Absalon were able to board the bulker from a helicopter. Apparently all the pirates had made their escape before the troops arrived, but never-the-less it can be chalked up as a success. Then, recently, pirates captured the Russian owned tanker “Moscow University”. This resulted in retaliatory action by a Russian warship which re-captured the tanker. During the action one of the pirates was killed, and apparently the other ten were put back into their small boat and set adrift. According to later information, these ten seem to have died at sea, causing threats of retaliation from pirate leaders against the crews of any further Russian ships captured. This action apparently took place 300 miles from the coast, so one wonders where the mother craft was.

Meanwhile the British registered chemical tanker St James Park has been released on payment of a ransom, but another ship owned by the same company, a car carrier, is still being held, and the unfortunate British yachtsmen the Chandlers are still in captivity, despite noises that they were about to be released in early April. Meanwhile, ashore, an extreme Muslim group seem to have invaded one of the pirate villages causing a mass exodus of polished four wheel drive vehicles and their occupants. This included the Chandlers apparently.

One should remember that even when these ships are released some of them have been swinging at anchor off  a port in the Horn of Africa for months. The St James Park was captured before Christmas, and as a result its crew have been in captivity for more than five months, for doing nothing more than going about their lawful business. 

ACCIDENT INVESTIGATIONS

I am keeping up with the listing of some marine accidents to remind me that we want to know why these vessels sank and as a result what can be done to reduce the risk of further sinkings. The ones I have in mind are the loss of the Demas Victory in June 2009, the capsize of the Danny F II in December 2009 and the loss of the Ocean Lark in January 2010.

The Demas Victory was registered in St Vincent and the Grenadines and sank with the loss of 30 lives outside Doha, the Danny F II was registered in Panama and capsized close to the Lebanese coast with the loss of forty lives and the Ocean Lark was registered in Singapore, and sank under unknown circumstances with the loss of eleven lives. Apparently there is an IMO (international Maritime Organisation) rule that flag states should investigate accidents which are deemed to be sufficiently serious. Surely in all cases, since there was considerable loss of life, investigations are warranted. But the responsibility remains that of the flag state.

I am hopeful that now for the first time News and Views is a blog as well as an article on my website, we might find out more about these accidents, because surely there are people out there who are familiar with these ships and the work they do, and hence might be able to shed some light on the accidents, even if the authorities continue to do nothing.

THE WINDMILLS OF ABERDEEN – AGAIN

I am really pleased to be able to report that some-one seems to have seen sense regarding the placing of the wind turbines in the sea outside Aberdeen Harbour, and as I write this it strikes me how unimportant this seems when one looks at the items above. However, in the greater scheme of things it is extremely beneficial for ports to have anchorages available outside them, otherwise the ships waiting to enter are required to steam back and forth outside until they are able to enter. This increases their use of fuel and also requires increased vigilance on the part of their watch-keepers.

The fuss, for those who have just joined us, was that there were going to be large numbers of wind turbines located just outside the harbour at Aberdeen spread all over the only anchorage for thirty miles in either direction. And to make things worse there were some who though that the windmill had found their way there because of the Donald Trump golf development further up the coast at Balmedie. Now the turbines seem to have been moved just ot the North of the mouth of the River Don, which is more or less the northern limit to the anchorage.  

THE SAUDI ARABIA OF MARINE ENERGY

Back in March the Scottish First Minister Alex Salmond suggested that Scotland was to be the Saudi Arabia of marine energy, and certainly there seems at last to be a move forward, with people intending to spend £4,000,000 on the installation of wave and tide energy harnessing devices.

My former company still makes efforts to market their skills as marine experts to the people in charge of these activities so far with little success, and I did the same when I was in Aberdeen, taking a stand at the renewables exhibition. What were we selling one might ask. The answer is that we were selling our marine expertise, our knowledge of what it is like out there. This seems to be what many of these organisations lack. After all it is logical that where the tides and currents are strongest, that is where one would want to place one’s energy harnessing devices, but it is difficult to believe the force of the water in these places. In the southern North Sea for instance it is only possible to send air divers down for an hour either side of slack water. The prime area up there in the north of Scotland is the Pentland Firth, a stretch of water feared by all sensible mariners. We’ll just have to see how it goes.

Victor Gibson. May 2010.

CHANNELLING THE OIL LEAK

Amidst further comment and speculation about the progress of the intervention by BP into the reservoir blowout in the Gulf of Mexico we get almost hourly updates on what is happening. The senior BP management continue to say it is not their fault, but of course those who understand something about the way these activities are undertaken, will know that the oil company, even though they may not own the equipment being used, can be responsible for the problem. A major component of the continued safety of the operation is the well plan, and no matter what other stuff is involved, the well plan must be correctly designed, taking into consideration any identified downhole problems and the reservoir structure. The BOP is the last ditch stand. So, unless something new has happened in this business, when some stuff comes bubbling up onto the drill floor several barriers will have already failed, but the driller can reach behind him and press the button to activate the BOP, or at least part of it.

And if this activation is unsuccessful – failing to shut off the well flow – and if the rams activated were the shear rams, what on earth will any additional means of operating the BOP do? The Norwegians require acoustic means of BOP operation to be available, so that some-one in a lifeboat can dangle a transmitter over the side and operate the BOP. All one can say is that the Norwegians, earnest about safety as they are, tend to go for the ambulance at the bottom of the hill rather than the fence at the top. I hope this analogy is clear. And of course all this extra clobber on the BOP is likely to make it less reliable. Deep water BOPs are already complex bits of kit, because of the differences in pressure between the surface and the seabed. But as I have already said, they are the last barrier in the prevention of a blowout, not the first barrier.

But to get back to the current efforts  to stem the flow, today it has been announced that an ROV (Remotely Operated Vehicle) known throughout the BP press releases so far as a “submarine”, has been successful in stemming one of the leaks. What this means of course is that a little more oil is going to come out of the other two leaks, but never mind. All will be well they hope, or at least better when the containment device is lowered over one of the remaining leaks. Apparently the Discoverer Enterprise is to be used to recover the oil and process it, and in fact store quite a bit of it. The obvious means of deployment would be for the dome to be loaded onto the drill ship, for it to be connected up to the drill string and for it then to be lowered towards the seabed. The drill ship will certainly be provided with a means of moving this object, large as it is, underneath the drill floor. The drill string could then be connected to the top and it could be lowered towards the seabed. What seems to militate against this is the fact that the cranes on the ship are not rated for 90 tonnes, apparently the weight of the structure. Like the Deepwater Horizon was, the Discover Enterprise is dynamically positioned so it does not need any moorings.

I note that there are two apertures on the sides of the structure to be lowered, one labelled riser, and one labelled drill string and I assume that there will be a choice as to which one is used depending on how far the drill string is sticking out of the end of the riser. Either the box will be lowered over the end of the pipe, or the end of the riser, and it will sink into the mud – they hope – until the horizontal bits which are attached half way down get to the seabed. If the drill pipe is not used to lower the box, it will be lowered on a wire from a support vessel, and what-ever way it happens an ROV will be used to observe its position. When it is above the leak it will be lowered away into the correct position. An ROV would be used to disconnect the wire and assist with the connection of the drill pipe – if that is what is needed.

Well fluids can then make their way up the drill string. They are lighter than water, and doubtless there will be a valve at the top so the flow can be stopped if necessary. It sounds as if the intention is to process the oil and then store it in the tanks on the ship. A barge has also been mentioned so one assumes that once the ship is full, the barge will be moored alongside and then filled up.

In the past I have been involved in risk assessments to assist in the recovery of offshore mobile units from emergency situations, and one hopes that this intended process has been suitably reviewed. As well as making it more likely that everyone will remain safe, often a degree of reality can be injected into a plan which may be a bit over optimistic.

Below is a diagram of what the set-up might look like when the Discoverer Enterprise is in position.

Update on 7th May – the US Coastguard have published pictures of the containment device being lowered into the sea using a crane on the DP rig Q4000. Once it gets into position, assuming this is successful ROVs will be used to disconnect the lifting gear from the device and in some way a pipe will be connected to the top.

A picture of the Q4000 by Oddgeir Refvik follows:

Preventing Fires and Explosions on Offshore Installations

The explosion and fire on the semi-submersible drilling rig “Deepwater Horizon” on Tuesday 20th April 2010, with the loss of 11 lives, and its subsequent capsize and sinking, has prompted me to write something about the manner in which jobs of this sort are usually carried out, and how the related risks are minimised. Of course we have no idea what went wrong on the rig, but almost certainly there was a leak of hydrocarbons from the well which ignited at deck level What follows is not intended to suggest what might have gone wrong on the rig. It just provides some information for those who have an interest, but who do not have detailed knowledge of the work.

 Those who have followed the content of my website, www.shipsandoil.com over the years will be aware that in a previous life I was a safety consultant and technical author with a marine background, and part of what I used to do was to assist my clients to develop safety cases for mobile drilling units. I started doing this work in 1993, five years after Piper Alpha, and have only recently given it up, but of course I have retained much of what I have learnt.

 Maybe the first thing is to identify different types of offshore installation. There are platforms are nailed to the seabed and which stand up on their legs above the waves, there are jack-ups which are used for drilling the holes and which stand above the waves on legs, but which can be lowered into the sea until they float and then moved from one place to another. And then there are semi-submersibles which float on pontoons. The pontoons can be submerged when they are drilling, to provide a stable platform, so that the vertical columns and the decks on top of them are visible, which prompts many journalists to describe them as if they are some-how standing on the seabed. Semi-submersibles can be anchored or dynamically positioned, using thrusters. There are also drill ships which look like large tankers which are also usually dynamically positioned. It is conventional for the dynamically positioned vessels to drill in deep water, although rigs have been anchored in water depths of 3000 metres (Nearly 10,000 ft).

 Strangely these exploration rigs have the task of probing the earth’s crust in the hope of locating a sufficiently large deposit of hydrocarbons, oil, gas or a mixture of the two, to make it worthwhile  bringing it to the surface. But oil and gas under pressure is dangerous stuff, so they have to be able to drill into a reservoir while at the same time keeping it under control. I’m sure we have all seen film, either real or fictitious, of a wooden drilling rig being engulfed in a fountain of oil and people rushing about throwing their hats in to the air. They had found oil, but had as yet not found a way of containing it. There are also pockets of gas near the surface which should be avoided as far as possible, and ideally this is done by carrying out surveys to locate them, and then putting the rig at a distance from them.

 It is also necessary to emphasise the difference between drilling rigs and production platforms. Production platforms are usually collecting points for the hydrocarbons from a number of wells. The oil is processed and then pumped on, either to the shore or to some other storage facility. Of course on a production platform there is always a quantity of hydrocarbons, the inventory, being processed and there is therefore the possibility of a leak in the pipework or in some form of containment. This was the case in Piper Alpha. On a drilling rig, in ideal circumstances, the only time there are hydrocarbons (well fluids) at deck level is during well testing.

 Without going into too much detail, the rig is connected to the seabed by a large diameter pipe, known as the riser, and at the bottom of this is the blowout preventer. The well is drilled through this, and the resulting hole, and the riser is filled with  drilling fluid which is known in the business as “mud”. The mud is the first line in defence against the pressure in the reservoir. The fluid is a mixture of chemicals, based on water or a form of oil and is weighted with the mineral baryte. The whole business of dealing with mud is a science in itself and the weight must be just right, heavy enough to keep the oil down there, but not so heavy that it fractures the formation and disappears into the ground.

 Of course it is possible that the pressure in the reservoir will exceed the hydrostatic head provided by the mud and so the drillers may find the mud coming back up the hole. That or some other sign, often known as a “kick” will result in the activation of the blowout preventer (BOP). You will remember that the BOP is installed at the seabed on the top of the well, and at the bottom of the riser. The BOP is an enormous lump of steel about fifty feet high and weighing up to 150 tonnes. It contains a number of rams of different sorts which can either encircle the pipe passing through, or else in extremis cut the pipe.  

 In the first case the pipe can be encircled and the well isolated, but work can still be done on the well. Heavier mud can be pumped down the drill string and control be regained. However if it seems that control will be lost the pipe can be cut and the well completely isolated. Of course once this is done, getting things sorted out is a complex operation, but everyone remains safe.

This is a description in the simplest possible terms, and there are other circumstances where gas or oil can get to the surface during the drilling operation, and in order to minimise the possibility of this being ignited much of the equipment on the deck of the rig is constructed in a way which will minimise the possibility of ignition. There are gas detectors positioned in all the most important areas and these are usually monitored from the control room. If gas is detected then things can be done, and finally if it seems that all control will be lost it is possible to get everyone into the lifeboats and to evacuate the rig.

There have been many blowouts over the years all over the world, but only a few of them have been investigated in a way which has resulted in the findings being available in the public domain. Hence those helping with the development of emergency procedures, and providing guidance for the guys out there, have only a limited amount of information available, and it may be that there are still new situations which are unaddressed. It is also true that different legislations have different approaches to the whole business.

 After Piper Alpha and the resulting public enquiry, the whole process of offshore safety in the UK was put in the hands of the Health and Safety Executive, with the requirement that all offshore installations including drilling rigs be provided with a safety case. There is no doubt that Lord Cullen’s intent in recommending the safety case regime was well intentioned, with the idea of making complex structures and activities more transparent, but even after 15 years it is still a work in progress.

 So, keeping people safe offshore is still a difficult business. The guys out there are at sea, and have lots of other stuff to contend with. For me just being at sea was difficult enough.