BP wellhead efforts hoping for closure
The slick around the Mississippi Barrier Islands in late June. Oil covered waters are silvery in colour. Photo: NASA
Concerns that a new well head cap placed by BP on its leaking well in the Gulf of Mexico could fail continue to delay testing.
BP began testing late yesterday but a leak in a choke valve was detected and full testing will not resume until it is repaired.
The US government delayed the procedure over concerns that a failure could make the situation worse but approved operations following an expert review of BP’s plans. Incident commander Admiral Thad Allen said, ‘There is a tremendous sense of urgency but nobody wants to make an irreversible mistake.’
Once the leak in the choke valve is repaired the integrity of the new capping device will be tested by monitoring seismic, acoustic and temperature changes in the well and surrounding area to ensure oil does not leak from new locations when valves on the new cap are closed.
The new cap, which is expected to catch all the oil escaping from the seabed in the Gulf of Mexico if successful, was put in place by BP on Monday night using remotely operated vehicles (ROVs).
The old LMRP cap was removed on Saturday. The replacement capping stack, the Q4000, is a better fit as it features three closing rams.
The outcome of testing is not guaranteed, considering the possibility the new cap could result in leakage further back in the line. BP delayed tests of the new cap on Tuesday while engineers worked on a seismic survey of the area around the cap, creating a map of the rock under the seafloor to locate potential dangers such as gas pockets. There is concern that closing the cap valves could cause ruptures elsewhere on the seafloor.
BP pointed out that the new sealing cap, the flexible risers and the planned additional containment systems have never before been deployed at such depths or under such conditions, so their capability cannot be completely assured.
This latest attempt could mean the struggle to stem the disaster, which started on 11 April when the Deepwater Horizon rig exploded killing 11 men, will have turned a corner. Snags have dogged earlier efforts. Besides the failure of the first cap and the limited success of the LMRP version, BP's endeavours to capture oil spewing from its blown out well hit yet another problem three weeks ago when an ROV collided with the containment cap, forcing its removal for inspection and temporarily halting the pumping of oil to up to the Discoverer Enterprise.
Work on the first relief well, which started 2 May, continues. A report from BP says a tenth 'ranging' run to determine whether the drilling is on target was completed, and the well reached a measured depth of 17,810 feet this week, just 190 feet short of its target depth.
Operations will start, hopefully in the first half of August, on killing the flow of oil and gas from the reservoir by pumping specialised heavy fluids down the relief well. The second relief well, which started 16 May, is just below 16,000 feet and BP is preparing to cement its casing.
Meanwhile, The Unified Area Command announced Sunday that the skimmer fleet supporting the Deepwater Horizon Response Operations doubled the volume of oil skimmed near the well site on Saturday. The skimmers were able to skim an estimated 25,500 barrels of oily water, doubling the amount collected the previous day. Currently 46 skimmers are operating at the well site, part of a fleet of more than 570 skimmers conducting the largest oil spill response in US history.
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