Gulf Oil Disaster – Beneath the Waves

The sinking of the Deepwater Horizon oil rig in the Gulf of Mexico is an economic disaster and may prove to be an ecological disaster. The graphic below shows the situation in cross-section.


The primary cause of the disaster is yet to be determined. There is speculation that an unexpected pressure surge destroyed, or overcame, the 450-ton blowout preventer. Natural gas separated from the oil and caused an explosion and fire on the rig. There have been suggestions of improper cementing in of the well head, of metallurgical failure of the drill pipes, and of human error, even some speculation of sabotage.

The Deepwater Horizon rig, located 45 miles south of the Louisiana coastline, was attempting to exploit an oil field discovered in 2006, by a consortium of oil companies. The first well in this field, called the Jack well, was drilled in 7,000 feet of water, to a depth of more than 20,000 feet below the sea floor. It found a major field in a geological area called the lower tertiary trend. It is estimated that the formation may hold up to 15 billion barrels of oil, which could boost America’s reserves by 50 percent. The three companies took major geologic risk by targeting the lower tertiary, but they were proved right. The Jack well cost more than $100 million.

When the surface rig sank, the riser pipe kinked and restricted the leakage to about 5,000 barrels (210,000 gallons) per day. However, if there is another pressure surge, that pipe or the well-head could break and result in unrestricted flow of oil into the Gulf. A good well in that region could produce up to 30,000 barrels per day.

A relief well is being drilled, but according to BP, the owner, that effort could take two to three months to stem the flow. When that well intercepts the original well, special heavy fluids can be injected to stem the flow, then the original well can be sealed.

Blowouts such as this one are uncommon in U.S. waters. The last one was in Santa Barbara in 1969. That one was close to shore. There are many natural oil seeps, especially off the California coast. In fact National Geographic has an article about an asphalt volcano developed 10 miles off-shore from Santa Barbara.

The following is taken from “Seis Matters” a blog by an oil industry professional. It discusses what probably happened. The article refers to Transocean the owner of the drilling rig, which was hired by British Petroleum, the company holding the lease on that portion of the oil field and paying for the well.

According to the Transocean veteran, BP had discovered significant quantities of oil and gas at Macondo, the name of the field that the Deepwater Horizon rig was drilling. BP had reached total depth and penetrated the reservoir horizon at 18,000 feet. Halliburton had cemented the last casing string in the well and inserted several cement plugs within it which BP intended to drill out at some future point when they returned to Macondo to begin full-field development.

With the cement plugs in place, Transocean had begun the process of removing the drill string in the well (used during the cementing operation) and had begun to replace the heavier mud in the wellbore with less dense sea water. This is apparently a common practice, as the plugs are designed to contain the reservoir fluids downhole. Effectively, the Deepwater Horizon was hours away from moving off the Macondo location.

At this point, some speculation begins. The leading hypothesis is that the cement plugs failed. The drilling crew wouldn’t be expecting a failure and perhaps weren’t monitoring the systems that detect an influx of fluids into the well, drill string, and drill pipe riser. Unbeknownst to those on the rig, a mixture of gas and water was coming up the drill string and riser to the surface and the deck of the Deepwater Horizon. The volatile mixture of high-pressure hydrocarbons likely ignited quickly and unexpectedly, killing the 11 individuals who were on the drilling floor itself.

Normally, one of these drillers would have hit the “panic button” that closed the blowout preventers (BOP) on the seabed, but likely didn’t have the time to do it. The toolpusher a bit farther away also has access to a panic button, but himself may have been incapacitated in the explosion or, if the electrical switches to the BOP were cut when the riser exploded, may have been unsuccessful in his attempt.

The next line of defense is called a “dead man’s switch” and is supposed to activate the BOP on the sea floor if electrical and hydraulic communications with the rig are lost. If this switch had activated properly, five hydraulic “rams” under thousands of pounds of pressure, including one “shear ram” that acts like a pair of scissors, should have cut the drill string and closed in the well. The shear ram is designed to cut up to 13-3/8 casing, which is far larger than what was in the well at the time.

For reasons not understood, the BOP’s either didn’t activate at all or didn’t do their job as intended. ROV pictures from the seabed show drill pipe extending out of the BOP (which should have been sheared off) and the oil is leaking at this point, as well as at several points above it where a part of the drilling riser remains.

As for liability, it primarily rests with BP according to this panel of experts. Maritime law has a precedent called “the anchored tanker” that says that the owner of the anchored tanker is liable for any damage resulting from it, even if that tanker is hit by another ship that was behaving in a reckless or negligent manner. BP is the owner of the anchored tanker in this case.

Moreover, the typical 100+ page drilling contract specifies that the rig owner (Transocean) is liable only for spills that happen in the course of the drilling operation (such as a tank of diesel rupturing and spilling overboard). In the case of a blowout, all drilling contracts specify that those are the responsibility of the oil company that has contracted the rig (BP in this case) and that most of them even specify that the oil company will “protect and indemnify” the rig owner even if they are shown to be reckless, negligent, or had behaved with gross misconduct.

It would appear that this will be hard for BP to prove, especially since the Deepwater Horizon was the “top performing rig” for BP worldwide, with an unmatched safety and operational performance record and a crew that had been on board more or less continuously since 2001. Net-net, it sounds like BP is going to shoulder the lion’s share of the liability for this accident and clean-up.

As for fall-out, there are three expected ramifications. The first is the “natural resource damage” that will be incurred (presumably by BP) as marine habitat, fisheries, etc. are shut-in and temporarily or permanently damaged. These costs, primarily resulting from jury awards or settlements in commercial litigation, are expected to far outweigh the clean-up costs (which themselves are estimated to be approaching $1 billion).

The second impact will likely be increased government intervention. The participants on the call don’t believe that there will be a blanket ban on offshore drilling (despite some White House commentary suggesting this earlier today) but they do see Congress spending significant time on the holistic topic of offshore drilling in the years ahead. In their opinions, this could actually be a good thing as it might provide a more consistent and stable regulatory regime for E&P operators.

Lastly, they expect higher costs to conduct offshore E&P operations. Similar to Congress mandating double-hulled tankers after the Exxon Valdez spill, they expect a host of regulations to be put in place to add “double and triple redundancy” in offshore operations to prevent incidents like the Deepwater Horizon explosion and the Macondo blowout and spill from repeating in the future.

A truly unfortunate incident in every sense.



  1. Outstanding explanation. I obviously have alot of “fringe” individuals offering me all kinds of conspiracies, but your explanations of the engineering help us to understand what a fragile world we still live in. Nothing of human effort will be perfect. But we still take the risks. I pray that our technology is sufficient to contain, clean-up, and improve.

    1. 30,000 bpd is possilbe but unlikely.  Another scheme they may try is a type of underwater balloon to capture the oil as it leaks.

  2. I have been reading news stories on this blowout for two weeks.  This is by far the best article out there!  Thanks!

  3. I worked as a wellsite geologist/production test engineer for 17 years mostly on off shore drilling facilities.  My sense when hearing about this incident, is that it was a failure with a cement plug.  Someone on the rig though should have noticed  the increase surface flow in the riser as the gas bubble was circulated to the surface. Tranocean would have had their own flow sensor devices  to monitor this flow along with whatever data logging service company whose job would have been to monitor the drilling operations.  Anyone who has spent time working in the oil patch will tell you that drilling for oil is a risky business and accidents will inevitbly happen.

  4. Very good article Johnathan. Please let me add a little to your explanation in order to clarify a bit further… First as a driller with more than 30 years experience in this industry I will say though that 100% of ALL accidents are preventable. There is absolutely no “inevitability’s”  in our business or any business for that matter…None whatsoever… I will also say that the likelihood of a unstimulated  “surge” in pressure within the well bore is highly unlikely… Formation pressures simply do not surge without the stimulation to do so, meaning that this situation was likely created when the casing was initionally set and cemented. High pressure/ high weight cementing activities are notorious for providing the stimulation necessary to cause a blowout and I submit that this maybe the root cause for this situation. I don’t have knowledge of the drilling/casing program that was used for this well, but I would say that when the casing was set and cemented is when their problems began. The cement job may not have have been 100% which would allow channeling, giving a path to allow the gas/oil influx.  If the cement plugs were being set in a horizontal section of the well, then again heavier cement under lighter or contaminated mud could allow the influx to channel through. And lastly, and I don’t want to point the finger at our fallen comrades, but if the crew was “pulling pipe” too fast, or not filling the hole properly while pulling the drill pipe out of the hole, then the “swab” effect could literally “suck” any influx up the hole with them, until it surfaces. Of course in this situation we must keep in mind that there is 5000 feet of space between the Blow Out Preventer’s or Sub Sea Stack and the Drill Floor and that the reaction will take time. It sounds to me that by the time that the crew noticed they had “flow” coming from the well bore, the bubble had already rounded the corner and was headed up the hole in a hurry, where it will expand exponentially as it travels upward. I am not ruling out that there was a mechanical failure with the Sub Sea Stack, and in fact I personally I feel this is very likely understanding that the ROV’s could not manually close the preventer’s In conclusion, I would agree with your assessment, that there should have been many indicators that would have gave warning to the impending disaster in time enough to prevent it. However we don’t know for certain what actually happened and we won’t for several more months after the industry makes a full investigation. I will say though that the answers for “why” this disaster happened won’t be found in Washington DC and method for how to prevent this from occurring again in the future won’t come from the White House or any other politician for that matter… It will come from within our own American Oil & Gas Drilling Industry, the one which leads the rest of the world in health, safety, and environmental accident prevention. And it will come from hard working, dedicated individuals, just like those Transocean employees that were lost, whose safety record prior to this event exemplifies their personal deep concern and comitment for doing the job safely or not at all…  Bob J. Theis

    1. Bob, thanks for your explanation.  My drilling experience is confined to hard-rock drilling for minerals so such blowouts are very rare  — except for that one time we hit a high-pressure artesian water source which shot the drill stem up through the drilling tower.

      1. Thank you Jonathon and I can appreciate your experiance as you have just pointed out another indicator that something was going wrong. As the bubble moes towards the surface, the drill string weight would begin to fluctuate. Pump pressure, circulating volumes, total pit volumes would also begin to fluctuate or gain sounding alarms.  As well there should have been indicators from total gas-in-mud levels that would begin to increase sounding alarms before becoming explosive. It is intirely possible that the eleven individuals who lost there lives weren’t taken by surprise, but instead were acting heroicly trying to stem the flow and prevent the impending disaster from occuring . But as I said, 5000 feet is a lot of space between the rig floor and the BOP’s. And once the bubble passed the BOP’s there is nothing at surface which would contain nor divert the flow in a safe direction. Our prayers should be with their families and for those who are engaged in keeping the spill from reaching the coast. Thanks again, Bob J. Theis

  5. In other words, no body will know until a full investigation is completed, if the investigation is transparent. I cannot help but assume that if the Federal Government is not intimately involved in the investigation process there will little industry wide nuance changes made toward safety.
    Right off the bat there should be restrictions put on legal manuvers and legal options the responsible parties can take to restrict investigator access to oil and oil service company records.
    Being that this is a National Security matter beyond the oil industry’s scope of operations, which makes this cases oversight the US governments role of responsibility. And, even then, there must be oversight on the oversight as there is tremedous political capital assets waiting to be exploited or politized between the major parties of Congress, The White House and the Courts.

  6. Well Dyke…. The obvious bi-line here is that the situation is already being politicized, as your comment about the probability of this  incident impacting our National Security clearly exemplifies… I would caution anyone believing that any bureaucratic intervention has ever prevented the repeat of any disaster anywhere, that simply doesn’t happen. The fact of the matter is the economic strain stemming from the loss of eleven lives, the loss of an 800 million dollar rig, the loss of a 30 million dollar well, the cost of current intervention techniques and relief well, the cost of a Gulf area wide clean up effort, and the cost of the damage sustained to local industries and economies, all certainly carries more weight than can be generated by any White House or Congressional interference in the matter. Typically, our society wants to find the villain, and then use the government as our whipping stick, just like our society villainized Exxon after the Valdez ran aground while exiting Prince William Sound. But I would remind everyone that although the politicians would like everyone to believe that they came to the rescue then by enacting the double hull tanker laws, the facts of the matter are that the industry itself came up with a myriad of changes needed to make tanker traffic safer, worldwide, and the Federal Govt as well as the State of Alaska simply adopted those ideas in the form of future mandate. It is important to remember that these corporations are comprised of individuals, not villains… And these individuals, like all Americans, take a great deal of pride in their work. And like yourself and all Americans everywhere, we all share a heightened  environmental awareness and are very committed to keeping our lands and waters clean and safe. After all this place is in their back yard, its where their families live, where their children play… Individuals make a difference, not politicians. My father used to tell me,”There are three types of people in the world. First there are the doers, and 90% of the worlds weight is carried upon their shoulders. Then there are those who teach, and they are teaching the next generation of doers, then there are those who can’t do, and can’t teach… These are the politicians who simply criticise the rest and they find their way through life being supported onthe backs of others”  Let me ask you a question Dyke, could any politician with no prior training or any prior background, come in and intelligently tell you how to do your job? Our American Oil & Gas  Industry leads the rest of the world in safety and technology and the fact that we can even drill in these deep water depths  is a technological marvel that we as Americans should all be extremely proud of. Yes, this situation is a huge disaster, but we should be mindful of the individuals involved and not try to vilify them or the amazing companies they work for. Bob J. Theis

  7. Oil spill diaster
    Jim Kirwan published on Rense on May 3 that an engineer with 25 years  of experience with big machines (in the oil industry?) has the impression BP probably never can cap the broken drilling hole and in that case all the toxic ocean water in the world will destroy wildlife.
    I reallize that this is not imginary because BP drilled on the edge of what human technology can do.
    This is not drilling a well and then pumping-up the oil. On the sea bottom which is 5000 feet below sea level the pressure by the water is already 150 bar. To spuw oil in it, is must have a pressure of at least 150 Bar or 2200 psi. This is comparable with the pressure in an oxygen cilinder for welding. If the valve of a compressed air cylinder is broken or sheared off, the released pressure will cause the cylinder of 190 lbs to act like a rocket, shooting away quickly.
    But at the point where the drill hit the oil 30,000 feet under the bottom of the sea then one has to add another column of 30,000 feet oil representing about 13000 psi totalling about 15000 psi. At least this should be the pressure in the well to push the oil up just to the level of the rig.
    But because the safety valves blew out and even destroyed the rig, there was way more extra pressure over 15000 psi in that well. It looks impossible to cap the hole 5000 feet below sea level for BP now tries to position a dome over the hole to catch the oil by sucking it up for 85%. But the oil is squirting immensely into the water pulling and mixing water with it in turbulance. If it works to catch 85% of the oil, which is highly questionable, at least 30000 barrels a day continues spuwing into the sea going in circulation around the earth with the Gulfstream a little later. BP doesn’t expect to release the pressure but after 3 months. That will be 3 million barrels anyway or 20 million if the dome not works..
    Addition of poisonous metanol will poison all wildlife and surface active agents will make an emulsion of the oil in water, moving it downwards in super fine particles which are ingested by all wildlife from the surface till the bottom. Now they can swim under the oil and are not affected that much.
    Bob S

  8. damage exceeds BP’s 137 billion dollar market cap(and falling) confiscate all global assets and get them the f— out of here.Obama should love this commi tactic

  9. Message sent to Rolls Royce "Energy Business" Sector, a short time ago:

    "To Rolls Royce Energy Team Webform E-Mail, 6/21/10, ~19:15
    With ref. to your line of higher capacity gas compressors, would they work with air/air enriched with O2, or pure O2?
    I write in reference to information contained in the following links, concerning the Gulf Oil Disaster (GOD):
    Please take the trouble to read these links, you’ll get the picture. I have used the tinyurl "preview" feature to give you more confidence.
    Pls. pass this message on to you technical people for further evaluation.
    Thanks in anticipation of your prompt response.
    All the Best,
    Dennis Revell.  (Ph: 001? – from USA, anyway) — — —-"

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