Gulf oil disaster

Plugging Macondo, the story of how the runaway Deepwater Horizon oil well was finally brought under control

Last May I wrote about the oil drilling disaster in the Gulf of Mexico. This year I can report on the final killing of the runaway well. The story appears in the Spring issue of Mines Magazine, the magazine of the Colorado School of Mines Alumni association. The story appeared there because the two engineers in charge of the operation, Donal Fitterer and Bill McEduff, are graduates of “Mines.” You can read their story here.


The well was plugged at the top, but top plugs are often temporary solutions. What was really needed was a relief well to intersect the hole just above the oil reservoir, the so-called “bottom kill.” All they had to do was hit a basketball-sized target buried under 5,000 feet of water and 13,000 feet of rock while drilling from a randomly moving floating platform. Sounds like a high-pressure assignment, but Fitterer said, “The number one thing I learned at Mines was the ability to focus on exactly what needs to happen to get the job done. They are very big on giving you too much to do, so you have to make a decision as to what is most important.”

The technique they used was to drill the relief well, using standard directional drilling, to get close to the well at a depth. Once there, they used a ranging vector magnetometer to close in on the target which involves drilling a little, putting the instrument down the hole, then adjusting and drilling some more. The goal was to get the relief well parallel to and near the original well, then intersect the runaway well at a depth near 18,000 feet, which is just above the oil reservoir.

Positioning is achieved using a 300-foot-long assembly, which includes a 30-foot-long cylindrical beryllium copper tool equipped with a transmitter and receiver on opposite ends. Invented by Vector Magnetics, the device emits a current that sets up an electromagnetic field when conducted by the well casing. By interpreting data on the electromagnetic field picked up by the receiver, Fitterer can calculate the precise distance and direction to the blown-out well.

It only takes him two or three hours to collect these measurements, but they must be taken every 30 to 60 feet, and getting the equipment into place at the extreme depths at which they were operating was a very time-consuming process: 24 hours to withdraw the drill bit; 12 hours to lower the ranging tools, take measurements, and retrieve the equipment; and another 24 hours to lower the drill bit back into place. As a result, in the final approach, progress moved at a rate of 30 feet every 2 ½ days.

Once the original well is intersected, they could pump in heavy mud to permanently seal the well. You can watch an explanatory video of the technique here.

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What happened to the oil in the Gulf of Mexico?

There is controversy over how much of the approximately 4.9 million barrels of oil spilled from the Deepwater Horizon well remain in the Gulf of Mexico.

A team from the National Incident Command, the Department of the Interior, and the National Oceanic and Atmospheric Administration (NOAA) calculated an “oil budget” for the spill. “The oil budget calculations are based on direct measurements wherever possible and the best available scientific estimates where measurements were not possible.” The report is without any documentation. The results are shown in the graphic below.


The Administration announced that much of the oil was eaten by bacteria. A report in Science disagrees with the government estimates:

“Oceanographers from the Woods Hole Oceanographic Institution (WHOI) in Massachusetts surveyed the gulf around the BP well from the research ship Endeavor from 19 to 28 June, a period of heavy flow. Led by oceanographer Richard Camilli, the team deployed an array of instruments on both a cable-lowered water sampler and an autonomous underwater vehicle. All told, the instrumentation made more than 57,000 separate chemical analyses of a plume southwest of the well.

“The first thing that the researchers noticed was that the plume wasn’t quite as massive as many news reports had made out. The plume surveyed by Endeavor was only 200 meters thick and about 2 kilometers wide. Although plenty of oil was flowing from the ruptured well, it didn’t look much like an underwater oil slick. The team’s camera picked up a yellowish fog half a kilometer from the well, and water samples farther from the well did not look or smell like oil. “The plume was not a river of Hershey’s syrup,” says marine geochemist Christopher Reddy of the WHOI group.

“The plume did, however, contain more than 50 micrograms per liter (about 0.05 parts per million) of a group of particularly toxic petroleum compounds that includes benzene, the team reports online today in Science. That amount of benzene-related petroleum compounds is roughly consistent with the 1 to 2 parts per million of total oil reported in plumes by some other researchers.

“On the microbe front, the WHOI team also found differences. A report released last week by a group of federal agencies led by the National Oceanic and Atmospheric Administration stated—without documentation—that early signs show the oil is “biodegrading quickly.” Not so in the southwest plume in late June, the WHOI researchers found. Their measurements of oxygen dissolved in seawater, which bacteria consume as they feed, showed that microbes had not appreciably degraded the oil during its first 5 days out of the well.”

The New York Times opines “So far, scientific information about the gulf has emerged largely from government reports and statements issued by scientists. Many additional research papers are in the works, and it could be months before a clear scientific picture emerges.

“The slow breakdown of deep oil that Dr. Camilli’s group found had a silver lining: it meant that the bacteria trying to eat the oil did not appear to have consumed an excessive amount of oxygen in the vicinity of the spill, alleviating concerns that the oxygen might have declined so much that it threatened sea life. On this point, Dr. Camilli’s research backs statements that the government has been making for weeks.”

More disagreement with government estimates comes from University of Georgia researchers. They claim that as much as 79% of the oil spilled from the Deepwater Horizon well could in fact remain at large in the Gulf of Mexico, where it still poses a threat to the marine ecosystem. The graphic below shows their oil budget.


Only time and more research will tell who’s estimate is closer to reality.

The Gulf oil spill is estimated at 4.9 million barrels (about 206 million gallons). Let’s put that in perspective.

“A 2003 research paper by Kvenvolden and Cooper in Geo-Marine Letters estimated that natural seeps dump 140,000 metric tons of crude oil into the Gulf of Mexico each year –over one million barrels of crude per year. In fact, the authors estimate that 47% of all the petroleum found in the sea is from natural seeps – the largest single source, ahead of airborne pollution, ground runoff and drilling/shipping accidents,” says the Energy Tribune.

The Woods Hole Oceanographic Institution says there is an oil spill every day at Coal Oil Point, the natural seeps off Santa Barbara, California, where 20-25 tons of oil (about 7,500 gallons) have leaked from the sea floor each day for the last several hundred thousand years (at least 800 billion gallons). The Woods Hole scientist say that some oil is degraded by microorganisms and some evaporates, but most of it winds up in the ocean sediments. Could a similar process have produced the Canadian tar sands?

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.