Vital BP oil well test back on course after setback

Adm Thad Allen: "When BP is ready, we will start to increase the pressure in the capping stack"

BP has fixed a problem with the cap on the leaking Gulf of Mexico oil well, which delayed a crucial test.

Work on starting the test, which was due to begin on Tuesday, has resumed.

The oil giant needs to shut all the valves on the new cap in order to test the well's integrity.

If the test is successful the flow of oil could be halted until relief wells can stop the leak permanently.

The government's incident commander Thad Allen said "hopefully" the test would begin later on Thursday.

The test will take 48 hours, he said, and even if it was successful, the well would be reopened and oil captured by ships on the surface would restart while a seismic test was done.

"We can go back then and put the system under pressure again. Once we are convinced we can certainly consider shutting in the well that is always possible and we would certainly look to do that."

Steps in the test

  1. The middle ram valve regulating the oil flow on top of the cap is closed
  2. The kill valve is closed off
  3. The choke is closed; this takes a couple of hours and once it starts the pressure test can be said to have begun
  4. Once the well is shut in, BP and government experts will assess progress every six hours
  5. But if low pressure is detected they will open the well up instantly
  6. Other precautions include extra monitoring, such as by remote vehicles on the seabed

But he emphasised that the option of shutting in the well was a "side benefit" of the new capping stack. The priority had always been to increase the amount of oil being captured and piped to the surface.

The latest setback to the pressure test was a leak on a line on the choke valve of the new cap.

The test had already been delayed while additional safety monitoring measures were put in place.

BP took another choke valve to the sea floor and attached it to the cap.

During the test, the three valves on the new cap will be shut. At the moment, just two - the large valve on top and the choke - are closed. Oil, mixed with dispersant, is billowing out of the kill valve.

Once the test is under way, and the flow of oil stopped, the pressure within the cap will be tested. If it remains high, it is safe to keep the flow of oil halted.

If the pressure drops, the well must be reopened immediately, as it could be an indication that there are other leaks beneath the surface.

The test was delayed by fears from the authorities about the test making things worse by causing a rupture inside the well.

It is going ahead after BP and government experts agreed on increased monitoring and a review of progress every six hours.

Meanwhile, BP continues to face political pressure in the US.

A Congressional committee has agreed measures that would ban the firm from new offshore drilling for seven years.

And in a separate move, Secretary of State Hillary Clinton has said she will look into a request by four senators to investigate allegations that BP lobbied for the release of Lockerbie bomber Abdelbaset al-Megrahi while attempting to finalise an oil deal with Libya.

The 1988 bombing of Pan Am flight 103 killed 270 people - most of them were American.

Megrahi, who has terminal prostate cancer, was freed by Scottish Justice Secretary Kenny MacAskill on compassionate grounds in August 2009 after serving eight years.

In a statement on Thursday, BP admitted it had expressed concern to the UK government about the slow progress of a prisoner transfer agreement between the two countries.

But the firm said it had taken no part in discussions on the decision to free Megrahi.

NEW CAP FOR LEAKING OIL WELL
In June, BP placed a cap, known as an LMRP cap, over the top of the Deepwater Horizon well so oil could be collected at the surface. However, this continued to leak oil and has now been replaced with a better fitting device.
NEW CAP FOR LEAKING OIL WELL
When engineers removed the LMRP cap on 10 July, oil began to freely flow from the top of the blowout preventer once more. However, the Q4000 containment system continued to take some oil to the surface.
NEW CAP FOR LEAKING OIL WELL
Engineers then bolted on a new capping stack onto the blowout preventer (BOP). This allowed them to conduct a series of tests to see if the flow of oil could be stopped using the newly installed equipment.
NEW CAP FOR LEAKING OIL WELL
During the test the three ram capping stack has been closed and all sub-sea containment systems collecting the oil temporarily suspended, effectively blocking the flow of oil from the well.
NEW CAP FOR LEAKING OIL WELL
Once the tests have been successfully completed, BP will resume collecting oil. The Helix Producer ship was recently connected to the BOP to provide another collection route in addition to the Q4000 rig.
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