shelburn on May 7, 2010 - 10:12am
This is slightly updated from yesterday’s post but I thought I would post it again for those who might have missed it.
I have been playing with some very rough calculations and trying to develop analogies that are understandable to laymen about what has happened and what is/can be done.
I’m not a downhole expert so I’ll leave that side to Rockman and others with the necessary experience.
I do have some relevant background as I retired a few years ago after almost 40 years in the offshore industry primarily in the underwater service side so I am very familiar with the ROVs, in fact some of the ROV operators currently working on the BOP used to work for me. I also was involved in building an oil capture and recovery dome (actually a pyramid) in much shallower water and was also involved in the Exxon Valdez cleanup and environmental surveys several years after that incident.
First off there is every indication that the BOP was activated and at least partially worked. It is almost a certainty that the “leak” is inside the BOP and as that oil leaks through the BOP it then finds its way through the damaged riser and drill pipe where it will exit out any open end or damaged area.
Therefore trying to repair the leaks in the riser does not decrease the flow but it can reduce the number of places where oil must be captured which is why they capped the end of the leaking drill pipe.
Every deepwater work class ROV has a sector scan sonar. Sonar can pick up oil leaks that the naked eye cannot see. The picture of oil bubbles painted on a sonar screen is like fireworks going off.
There was an ROV survey of the BOP and riser within hours after the rig sank. At that time there was no indication of any oil leakage from the BOP. And everyone breathed an extremely large, and extremely premature, sigh of relief.
Estimates made about leakage are primarily done from aerial surveys and satellite photos and are notoriously inaccurate as is clearly stated in the USCG manual on reporting oil spills. The gravity of the oil, the temperature, weather, currents, time, weathering of the oil and other factors all have a major impact on the size of a slick from a given amount of oil.
For example; if you are on a lake in very still water and pour a gallon - not a barrel, a gallon - of gasoline over the side in a matter of minutes you can have a slick covering a square mile – which will evaporate just a quickly, especially on a hot day. If you do the same with heavy crude like the Exxon Valdez spill it will probably take 500 barrels to cover that same square mile although with the fullness of time it will end up covering an area many times larger, and will take months to dissipate in the absence of heavy weather. This sweet crude is somewhere in between.
It was sometime the night after the sinking that oil leaks started appearing from buckles and holes in the riser. This was stated to be about 1,000 barrels per day. I would read that to mean the leak was between 250 and 3,000 bpd. And a 5,000 bpd leak is probably between 2,000 and 10,000 bpd. Until there is some way to measure the flow like running it through a pipeline it is impossible to have any accurate measurement of the leakage.
Factoid: If you assume that there over 5,000 psi of downhole pressure at the BOP - and everything I have heard indicates it is substantially higher than that - then a 1/4 inch hole is large enough to “leak” 5,000 barrels a day. That “leak” would probably cut off your arm if you passed it in front of it.
There is almost certainly sand in the oil and as that sand passes the leaking portion of the BOP it acts as an extremely high pressure sand blaster eroding away the area around the leak and enlarging it. So there is a perfectly rational explanation why the leak would escalate from 1,000 bpd to 5,000 bpd to ???.
Nobody was lying about the volume. The leak was, and is, getting worse.
How much is 1,000 bpd? It works out to 30 gallons per minute, about the output from 3 garden hoses running wide open, or about enough to fill a smallish backyard swimming pool in 24 hours.
Let talk about the dome a little. It would appear from the photos that the dome is designed to be large enough to encase the BOP if the broken riser were removed. It has mud mats 16 feet off the bottom so obviously the idea is to let it sink into the mud and seal the area around the leak.
It is to be connected to the drillship with a 6-7/8” drill string. I wore out a whole napkin making these calculations but if you assume the specific gravity of the oil at 0.89, the specific gravity of sea water is 1.026, the depth of 5,000 feet (actually this is of little importance in calculating the maximum flow), a freeboard of 33 feet to reach the drill ship deck piping you should be able to get about 24,000 bpd on the ship using the natural buoyancy of the oil. Most of my numbers, especially the specific gravity of the oil, are conservative so the actual output could be greater.
If there is any gas entrained in the leaking oil that will change the whole picture as the gas will expand approximately 150 times going up the drill string and act as a giant airlift so the problem won’t be getting the oil up the pipe but throttling back the flow onboard the drillship. Luckily, about the only place in the world you would expect to find the proper equipment just laying around is on a deepwater drillship.
The expanding gas also has a substantial cooling effect, enough to freeze the water entrained in the stream. So the design of the drill string has been modified t include a warm water jacket and methanol (antifreeze) injection.
They have a potentially dangerous situation separating the oil, gas and water but since the Discoverer Enterprise has processing equipment on board they should be able to handle that safely. The Enterprise also has dual draw works and drill floor so they are equipped to handle the drill string to a second dome.
This is obviously a disaster and it is quite possible that a human error or series of errors, coupled with possible equipment failure are to blame.
Does BP have culpability due to trying to move too fast? At over $500 a minute they certainly have the incentive to move fast. We don’t know - yet.
Is Transocean to blame for some sort of negligence in not properly monitoring the mud return or some other aspect of cementing process? We don’t know - yet.
Was Halliburton’s cement job faulty? We don’t know - yet.
Did Cameron International’s BOP fail due to manufacturing or design fault? We don’t know - yet.
Is a combination of one or more of the above? We don’t know - yet.
There are unsubstantiated reports that the kick registered over 30,000 psi. If the BOP stack saw that kind of pressure it could be a important factor, both in determining what happened and how to prevent it from happening again.
For those who are appalled that BP had no contingency plans in case of a spill I guess you think the skimmer vessels, the miles and miles of boom and the couple hundred trained oil spill control personnel that you see on TV just materialized out of thin air. In fact they have been on standby for a couple decades. They train, work on small spills and prepare for this type of disaster. As Rockman says; think of them as a fire department, paid for by the oil companies, under duress provided by the US government.
For those who are appalled by the lack of government response consider that the US Coast Guard was underway in minutes after the blow out and their spill response personnel as well as the teams and equipment from the oil industry were already on site standing by before the rig sank.
For a week after the initial incident, from the blowout April 20 until April 28 things weren't going well with the BOP still leaking and the weather slowing recovery operations but it is fair to say that the incident was reasonably "under control". There was no need for Obama to get directly involved, mobilize the Dept of Defense, etc.
On April 29 everything started going to hell, a true worst case scenario. That morning it was obvious the leakage from the BOP had increased dramatically. Even worse the weather changed and strong offshore winds start moving the oil directly towards some of the most sensitive barrier islands in Louisiana. Not only did the wind change direction but by evening it also increased to the point it effectively shut down all skimming and recovery operations and most boom deployments.
The media, which had only superficial coverage up to this point, got heavily involved and disseminated a great deal of information that was technically just plain incorrect.
There is a certainly an expectation that there may be someone to blame for the uncontrolled blow out with its loss of life and potential for extreme environmental and economic damage. But, it is my opinion, with some understanding of the complexities and technical and operational challenges involved, that both the oil industry and the government operational people have responded to the incident quickly and professionally. I wish I could say the same for the media, the politicians and the bloggers.
The only operation after the blow out that I might question was the decision to keep pumping water into the rig. Would it have been better to let it float and let the oil burn? But with the rigs engines and thrusters dead the only thing holding it in position was the riser so the potential of it further damaging the BOP probably played into that decision. It is always easy to Monday morning quarterback, especially if you don’t understand the technical or operational problems, but they have some of the best and most experienced people in the world working the problem.
BP has stated they will pay for the cleanup and environmental damage (as required by law) and will pay any legitimate claims for economic damage. This is a reasonable requirement. During the Exxon Valdez disaster we saw numerous outlandish claims from “fishermen” who couldn’t tell you the difference between the bow and the stern and “landowners” and “tourist industry people” who had never been to Alaska until after the spill.
There is a lot of press about a $75 million cap on BP’s liability. This has been taken out of context as it does not apply to the cleanup or environmental damage – there BP’s liability is unlimited. The $75 million is in reference to economic damage and BP has stated they will not hide behind that limit. Time will tell but at this time I take them at their word.
I’m sure this will require some effort on the part of people filing claims. For instance if you are a charter boat owner or fisherman I expect BP will require you to submit business records proving you are really in that business and substantiating the amount of business you had before and after the event. It is fair and reasonable for BP to protect themselves from scams just as it is fair that those who have been economically damaged by this event be given reasonable compensation.
I have a much greater problem understanding why the 200+ lawyers currently meeting to decide how to split up the pie should be entitled to the hundreds of millions of dollars in fees they will eventually receive.
We are lucky that this happened to one of the very few companies in the world that has the financial resources to pay the billions of dollars this will cost. This is similar to the Exxon Valdez where Exxon, despite their overwhelming arrogance, did pay all the cost of the cleanup but fought paying many of the economic damage claims I thought were valid and all of the punitive damages.
If either spill had happened to a foreign tanker firm or an independent oil company, the taxpayers would have ended up footing the cleanup bill, the people economically affect would have been out of luck and the companies would have already declared bankruptcy.
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