Tuesday, November 9, 2010

The BP Deepwater Horizon Oil Spill and Offshore Drilling Commission

Courtesy of MoonofA, I am able to tell you that this past weekend the final act in the closing of the Deepwater Horizon well was the placing of a steel cap on top of the well, after the top plugs had been put in place, and the well was ready to be abandoned.



And on Monday the Oil Spill Commission began two days of public hearings.

As part of this, the Oil Spill Commission has issued its preliminary conclusions which are:
Flow path was exclusively through shoe track and up through casing.
• Cement (potentially contaminated or displaced by other materials) in shoe track and in some portion of annular space failed to isolate hydrocarbons.
• Pre-job laboratory data should have prompted redesign of cement slurry.
• Cement evaluation tools might have identified cementing failure, but most operators would not have run tools at that time. They would have relied on the negative pressure test.
• Negative pressure test repeatedly showed that primary cement job had not isolated hydrocarbons.
• Despite those results, BP and TO personnel treated negative pressure test as a complete success.
• BP’s temporary abandonment procedures introduced additional risk.
• Number of simultaneous activities and nature of flow monitoring equipment made kick detection more difficult during riser displacement.
• Nevertheless, kick indications were clear enough that if observed would have allowed the rig crew to have responded earlier.
• Once the rig crew recognized the influx, there were several options that might have prevented or delayed the explosion and/or shut in the well.
• Diverting overboard might have prevented or delayed the explosion. Triggering the EDS prior to the explosion might have shut in the well and limited the impact of any explosion and/or the blowout.
• Technical conclusions regarding BOP should await results of forensic BOP examination and testing.
• No evidence at this time to suggest that there was a conscious decision to sacrifice safety concerns to save money.

Needless to say these conclusions have not all been met with complete agreement, even the first has been challenged by Halliburton. The report on the test of the cement is revealing:
We asked Halliburton to supply us samples of materials like those actually used at the Macondo well so that we could investigate issues surrounding the cement failure. Halliburton provided us off-the-shelf cement and additive materials used at the Macondo well from their stock. Although these materials did not come from the specific batches used at the Macondo well, they are in all other ways identical in composition to the slurry used there. Chevron agreed as a public service to test the cement slurry on behalf of the Commission. Chevron employs some of the industry’s most respected cement experts, and it maintains a state-of-the art cement testing facility in Houston, Texas. Halliburton agreed that the Chevron lab was highly qualified for this work.

We attach Chevron’s report of its laboratory tests, and we have invited one of its experts to discuss that report with you at the public hearing on November 9.

Chevron’s report states, among other things, that its lab personnel were unable to generate stable foam cement in the laboratory using the materials provided by Halliburton and available design information regarding the slurry used at the Macondo well. Although laboratory foam stability tests cannot replicate field conditions perfectly, these data strongly suggest that the foam cement used at Macondo was unstable. This may have contributed to the blowout.

Halliburton has stated publicly that it tested the Macondo cement before pumping it on April 19th and 20th, and that its tests indicated the cement would be stable. When Chevron informed us of the preliminary results of its tests, we asked Halliburton to give us all of the data from all tests it had run on the Macondo cement slurry.

The documents provided to us by Halliburton show, among other things, that its personnel conducted at least four foam stability tests relevant to the Macondo cement slurry. The first two tests were conducted in February 2010 using different well design parameters and a slightly different slurry recipe than was finally used. Both tests indicated that this foam slurry design was unstable.

Halliburton provided data from one of the two February tests to BP in an email dated March 8, 2010. The data appeared in a technical report along with other information. There is no indication that Halliburton highlighted to BP the significance of the foam stability data or that BP personnel raised any questions about it. There is no indication that Halliburton provided the data from the other February test to BP.

Halliburton conducted two additional foam stability tests in April, this time using the actual recipe and design poured at the Macondo well. We believe that its personnel conducted the first of these two tests on or about April 13, seven days before the blowout. Lab personnel used slightly different lab protocols than they had used in February. Although there are some indications that lab personnel may have conducted this test improperly, it once again indicated that the foam slurry design was unstable. The results of this test were reported internally within Halliburton by at least April 17, though it appears that Halliburton never provided the data to BP.


As was brought out in the hearing, the resulting protocol that was implemented for the abandonment of the well at that time also put additional pressure on the cement.
BP’s temporary abandonment procedures at Macondo could have introduced additional risks, such as putting more pressure on Halliburton Co.’s cement job by removing mud and replacing it with seawater, setting the surface cement plug 3,000 ft deep, or deciding not to run a cement bond log test immediately, he continued. 

“What is of additional concern for us is that the procedures for temporary abandonment were changing up until the very last minute,” said Grimsley. “It is not clear to us why decisions on these procedures were changing in the days before the blowout. You have to make choices on the fly when conditions are changing offshore, but this apparently was not the case here.” There also was no indication that anyone at the rig called to shore in the three hours after the negative pressure test ended and the well blew out and said that test readings were odd, he indicated. 



Bartlit said BP’s decision to halt drilling nearly 2,000 ft short of the well’s original intended depth may have been based on concern that it had to keep mud and cement from leaking into adjacent formations, which could have fractured from unusually high pressure in the well. “They stopped because they were interested in well integrity and safety,” he said. Surprises in the reservoir can cause you to make changes which can affect what happens later. As near as we can tell, talking to experts, BP did the right thing here.”

Halliburton have issued a comment on the testing of the cement.
Halliburton has only recently received and is continuing to review the results, which it believes raises a number of questions. Halliburton is issuing this press release to provide information about the content and its preliminary views regarding Chevron’s cement testing report and the letter.

Halliburton believes that significant differences between its internal cement tests and the Commission’s test results may be due to differences in the cement materials tested. The Commission tested off-the-shelf cement and additives, whereas Halliburton tested the unique blend of cement and additives that existed on the rig at the time Halliburton’s tests were conducted. Halliburton also noted that it has been unable to provide the Commission with cement, additives and water from the rig because it is subject to a Federal Court preservation order but that these materials will soon be released to the Marine Board of Investigation. Halliburton believes further comment on Chevron’s tests is premature and should await careful study and understanding of the tests by Halliburton and other industry experts.

With respect to Halliburton’s internal tests, the letter concludes that “only one of the four tests” showed a stable slurry. Halliburton noted that two of those tests were conducted in February and were preliminary, pilot tests. As noted in the letter, those tests did not include the same slurry mixture and design as that actually used on the Macondo well because final well conditions were not known at that time. Contrary to the letter, however, the slurry tested in February was not “a very similar foam slurry design to the one actually pumped at the Macondo well….” Additionally, there are a number of significant differences in testing parameters, including depth, pressure, temperature and additive changes, between Halliburton’s February tests and two subsequent tests Halliburton conducted in April. Halliburton believes the first test conducted in April is irrelevant because the laboratory did not use the correct amount of cement blend. Furthermore, contrary to the assertion in the letter, BP was made aware of the issues with that test. The second test conducted in April was run on the originally agreed upon slurry formulation, which included eight gallons of retarder per 100 sacks of cement, and showed a stable foam.

BP subsequently instructed Halliburton to increase the amount of retarder in the slurry formulation from eight gallons per 100 sacks of cement to nine gallons per 100 sacks of cement. Tests, including thickening time and compressive strength, were performed on the nine gallon formulation (the cement formulation actually pumped) and were shared with BP before the cementing job had begun. A foam stability test was not conducted on the nine gallon formulation.
Their release concludes:
Well logs and rig personnel confirm that the well was not flowing after the cement job. BP and/or others, following the misinterpreted negative tests conducted after the cement job, proceeded to displace mud in the production casing and riser with lighter seawater, allowing the well to flow. Given these numerous intervening causes, Halliburton does not believe that the foam cement design used on the Macondo well was the cause of the incident.

The Commission web site has some beautifully rendered animations of the drilling process, among others. However, apart from taking over an hour for me to download, the drilling animation, among other things, shows the drilling bits creating holes larger than they are, and at the same size beyond the cased section as the well had before the casing was inserted. This does not happen, the well continues at the bit diameter, which is itself smaller than the internal diameter of the casing inserted into the hole over the interval.

And one other note, it appears that even though the moratorium on drilling has been lifted, no permits are available.
Ensco Offshore claims that since the ban was lifted Oct. 12, the government has not issued a single permit that would allow the resumption of any previously suspended drilling activities.

The government doesn't seem to dispute that allegation, saying in a late Monday filing that it must ensure applications meet regulations toughened after the Gulf of Mexico oil spill.

10 comments:

  1. In other forums, drilling engineers have pointed out that the cement which presumably failed to seal the casing shoe was a simple neat cement chaser -- completely different from the nitrified cement pumped into the annulus.

    In other words, the Oil Spill Commission has been wasting time testing the wrong cement.

    Generally, the Commission is off to a poor start, creating the appearance that partisan attorneys are trying to stick it to Cheney's Halliburton. And that is a real pity. The industry needs an unimpeachable inquiry.

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