BP has given up on efforts to rein in the blown out Macondo well by pumping mud and debris into the well bore and will try to cap the well and collect as much of the flow as possible.
Noah Brenner 30 May 2010 08:36 GMT
The UK supermajor now plans to cut off the riser from the lower marine riser package (LMRP) and attach a collection dome to the top
Failed
BP operations boss Doug Suttles said Saturday that BP determined that the top kill would not work and it was time to move on.
Crews pumped more than 30,000 barrels of mud down the well at rates as high as 80 barrels per minute and used a variety of bridging materials and junk shots.
Those materials, including fibrous pieces of rope and chunks of rubber, were supposed to force more of the mud down the wellbore, but ultimately it did not work.
Around 330 pm local time on Saturday, BP and government officials called a halt to the operation.
Cap
The LMRP cap process that is expected to take four to seven days, Suttles said Saturday.
After cutting the existing riser, the device will be coupled to a flex joint above the LMRP with a sealing grommet to keep water out of the flow and control gas hydrate formation.
The cap also has valves to inject methanol directly into the production stream, while hot water could be circulated between the drilling pipe and the riser, both of which should limit hydrate formation.
BP has already lowered more than one LMRP cap to the seafloor so the UK supermajor can determine which one will work best and deploy it as soon as possible, Suttles said.
The LMRP cap would allow BP to capture a significant amount of the production stream while it works on other options to kill the well, Suttles said.
Suttles said Wednesday that the next option likely would be to add a second BOP on top of the first.
Stopped
BP has stopped drilling one of the relief wells to intercept the blown out Macondo bore so it can ready the rig's blowout preventer (BOP) to go on top of the crippled Macondo BOP.
Transocean boss Steve Newman told analysts Friday that Transocean semi-submersible rig Development Driller II had stopped drilling when BP began top kill operations.
BP spokesman David Nicholas told UpstreamOnline that the rig was stopped so its BOP could be prepped for deployment.
"The (Development Driller II) has temporarily suspended drilling operations in preparation for the possible future deployment of its BOP on top of the (Macondo) BOP," he told UpstreamOnline in an email response.
"This is a possible future option for stopping flow from the well and, as throughout, we are advancing options in parallel."
Flow
Meanwhile, US Secretary of the Interior Ken Salazar told a Congressional inquiry that the government estimates the flow to be between 12,000 barrels per day and 19,000 bpd.
The top end of that new estimate is as much as four times the previous estimate of 5000 bpd, which was endorsed by both BP and the government agencies responding to the spill.
That latest figure was formulated by a team of scientists and subjected to a peer-review process.
Estimates for the flow rate have been controversial since the spill began after a blowout at the well on 20 April.
BP and the US Coast Guard first estimated the flow rate at just 1000 bpd and then later revised that figure to 5000 bpd, but admitted that there was a wide margin of error around that figure.
Academics and outside experts had said they believed the flow could be as high as 70,000 bpd to 100,000 bpd, despite the fact that the record production for a well in the US Gulf is a little bit more than 40,000 barrels per day, according to energy investment bank Tudor, Pickering, Holt & Company.
Drilling
The Transocean semi-submersible rig Development Driller III was continuing downhole at a little more than 12,000 feet below the drilling floor on the first of two relief wells on Saturday.
Suttles said the rig continues to be “slightly ahead of schedule.”
Its sister rig, Development Driller II is still staging its BOP should BP decide to use it to try to cap Macondo.
Both relief wells are planned for casing strings of 36, 28, 22, 18, 16, 13-5/8, 11-7/8 and 9-5/8 inches, the same string as the original Macondo well.
Both rigs spud their wells about 3000 feet from the original Macondo bore.
They will drill vertically to about 10,000 feet before drilling directionally to intercept Macondo at roughly 18,000 feet.
Once either well intercepts the Macondo bore, BP can pump cement and plug the producing zone.
Suttles said the company has no plans to ever produce from the Macondo well because it has been damaged beyond repair.
Casing
Flow from the Macondo well is not travelling up the main well bore, Suttles said Tuesday, a revelation that supports theories that a cement failure played a part in the blowout.
“We actually believe the flow path is between two strings of the casing and not up the main wellbore,” Suttles said.
Suttles said BP could not be certain of the flow path but diagnostic tests on the well seem to indicate the flow is not coming up main bore.
A veteran industry source told UpstreamOnline that the news about the flow path “almost certainly confirms” what many suspected, that problems with the annular cement around the production casing played a part in the blowout.
In its internal investigation, BP also flags up cement problems, adding that the float collar initially did not operate as intended - it appears it took nine attempts with higher than usual pressures to get the float to bump.
It also appears that the float test carried out after cementing may not have been definitive, flagging up concerns that the cement slurry may have been contaminated by drilling mud.
Suttles also said that BP believes the greatest restriction on the flow of the well is coming from obstructions downhole from things like cement chunks.
“In that space would be cement, would be the rocks from the formations we drilled through and other bits of restrictions,” he said.
BP has been able to measure the pressure on the lower portion of the well’s BOP and found that it was “considerably lower” than would be expected if the flow was rushing unimpeded to the surface, he said.
Suttles said the obstructions in the well itself are the “most significant” restrictions to the flow rate, but that BP also believed that “some” rams on the BOP have closed but they are obviously not shutting off the flow.
The obstructions in the BOP and the well itself will not hinder the top kill, Suttles said.
Mistake
BP told congressional investigators that pressure tests on a drill pipe hours before the deadly explosion that caused the Gulf of Mexico oil leak flagged up a "fundamental mistake", a memo released by congressmen Henry Waxman and Bart Stupak said.
Representatives Waxman and Stupak were briefed by BP about the progress of its internal investigation.
The error the BP official referred to concerned the results of a negative pressure test.
The BP investigator said that two hours before the explosion, as preparations were being made on the Transocean semi-submersible Deepwater Horizon to start negative pressure testing of the wellbore, the system gained 15 barrels of liquid rather than the five that were expected, indicating there may have been influx from the well.
A cementer witness was quoted as saying. "The well continued to flow and spurted."
The investigator said the pressure test was then moved to the kill line, where a volume of fluid came out when the line was opened. It was then closed.
Pressure
At this time, pressure began to build in the system to 1400 pounds per square inch. The line was opened and pressure on the kill line was bled to 0 psi, while pressure on the drill pipe remained at 1400 psi.
The BP investigator said this indicated a "fundamental mistake" may have been made here as this was an "indicator of a very large abnormality".
However, once the pressure was bled off, work continued as normal - the line was monitored and by 7.55pm the rig team were apparently satisfied the test had been successful and started displacing the remaining downhole fluids with seawater.
The memo, released late yesterday, did not indicate who made decisions after the problem was found. BP and rig owner Transocean both had supervisors on the rig when it exploded.
BP would not comment on the memo. It had earlier stressed the report is preliminary and further work was needed.
However, a Transocean spokesman appeared to blame BP for the disaster, telling Reuters: "A well is constructed and completed the same way a house is built - at the direction of the owner and the architect. And in this case, that's BP."
Leaks
Details of events leading up to the blowout come as new information from the leaking well seems to confirm widely held suspicions within industry that problems with cementing played a key role in the 20 April blowout.
The congressional memo said BP data showed that several problems were experienced with production equipment aboard the rig.
Nearly five hours before the explosion, an unexpected loss of fluid was observed in the well's riser pipe. That suggests "there were leaks in the annular preventer", a rubber gasket in the BOP, the memo said.
Waxman and Stupak together lead the House Energy & Commerce Committee's investigative subcommittee, which has reviewed over 105,000 pages of internal documents from BP, Transocean, cementing contractor Halliburton and BOP manufacturer Cameron.
The memo said the BP investigation has also raised concerns about the maintenance history, modification, and inspection of the BOP.
Officials from BP and Transocean are scheduled to testify before congressional panels tomorrow.
The BP officials testified that unwanted flow in the well starting 51 minutes before the explosion. About 18 minutes before the explosion, abnormal pressure leaks of drilling mud were observed and the pump was shut down.
"The data suggests that the crew may have attempted mechanical interventions at that point to control the pressure, but soon after, the flow out and pressure increased dramatically and the explosion took place," the memo said.
Tragedy
The Macondo well - a discovery well which was to be temporarily abandoned ahead of later completion as a subsea producer - had been drilled to 18,000 feet by the Deepwater Horizon. An explosion late on 20 April rocked the semi-sub before the rig was engulfed in flames.
The rig sank on 22 April, extinguishing the blaze.
Eleven of the 126 crew on board the Deepwater Horizon at the time of the explosion are missing, presumed dead.
Relatives of the 11 held a private memorial service in Jackson, Mississippi Tuesday.
Drilling giant Transocean has confirmed nine of its employees were among the missing. Two worked for services outfit Smith International and Schlumberger's M-I Swaco joint venture.
BP has a 65% stake in Mississippi Canyon Block 252. Anadarko has 25% and Japanese player Mitsui the remaining 10%. All are liable for costs on a proportionate basis.
On Friday, BP lifted the total bill for the clean-up to $930 million, up from a $760 million estimate on 24 May.
Analyst forecasts for the clean-up costs and compensation for the spill off the coast of Louisiana have ranged to as much as $12 billion.
Additional information sourced from news wires.
Published: 30 May 2010 08:36 GMT | Last updated: 30 May 2010 08:36 GMT
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