Where does the flow go: BP testing Macondo well integrity.
BP worries about Macondo integrity
BP and US officials are confident that a new containment cap on the Macondo well can efficiently funnel production to the service but say they are unsure of the condition of the wellbore.
Thad Allen, head of the US oil spill response told reporters today that the well integrity was “the biggest unknown” right now as BP tries to corral more of the oil from the blown-out well.
Allen said the bore could have been damaged during the blowout or have been degraded afterwards during the failed top kill attempt and subsequent flow out of the producing zone.
BP is preparing to attempt to shut in Macondo starting around mid-day today to test for well integrity, which if successful could mean the end of any more oil flow.
“If we can shut in the well, we will shut in the well,” said BP executive Kent Wells during a morning briefing.
That test was supposed to begin aout mid-day on 13 July but seemed to have been slightly delayed.
The shut-in is possible because of the new three-ram containment cap which was landed on top of the spool assembly at 6:20 pm Houston time on 12 July.
Currently there are five flow paths for production from the well; the choke and kill lines on the original blowout preventer, the choke and kill lines on the new cap, and the main bore.
BP will begin the test by closing the choke and kill lines on the crippled blowout preventer.
Then it will being actuating a ram that will close the main bore, followed by one that will close the kill line on the new cap.
Finally, BP will begin to close the choke line on the new cap, which is the only valve that can be closed incrementally.
At each juncture, crews will monitor pressure inside the cap.
Those pressure readings will tell the UK supermajor if the casing and cement in Macondo can withstand the full pressure of the well.
Ideally, BP would like to see pressure increase to between 8000 pounds per square inch and 9000 psi, Allen said.
If pressure builds to that level, it would indicate that all of the production is flowing up the wellbore.
The more quickly and the higher the pressure builds, the better, Wells said, explaining that it would indicate the well construction is intact and all production is flowing up the bore.
A pressure reading lower about 6000 psi that would likely mean that hydrocarbons are leaking out of the bore at some point between the mudline and the producing reservoir, Wells said during an afternoon briefing.
Readings between 6000 psi and 8000 psi would lead to BP have to make “tough decisions” about how to proceed.
The process will take anywhere from six to 48 hours to complete, because BP will stall at intervals to make sure the well can sustain the pressure, Allen said, calling it "a very consequential 24 hours."
Prior to starting the pressure tests, BP wrapped a seismic survey of the region to better understand the shallower horizons of the field and give “baseline” data that will be needed if the bore proves to be ruptured at some point.
WesternGeco’s seismic vessel Geco Topaz completed a 2.5-mile north to south shoot of the location using a streamer and will begin processing the data, Allen said.
During the survey, all vessels needed to be moved off location, Allen said today.
If BP deems it necessary – as a result of the integrity tests – Macondo will be opened back up and oil collection at HPI and Q4000 will restart.
Afterwards, well test vessel Toisa Pisces will be brought in to connect to the second freestanding riser.
The Discoverer Enterprise could also return.
“We have a lot of optionality going forward in terms of our collection capability,” said Wells.
The pressure readings also should help provide the best estimate yet of the flow rate of oil at Macondo.
“At this point we don’t have the ability to measure the flow in it,” he said.
The ultimate end to Macondo will be delivered by the relief well, which is now 17,840 feet deep and a little more than 4 feet away from the original bore.
Wells said another ranging survey is being run to confirm distance and inclination from the Macondo well bore to make sure the relief well is lined up for the final 30 feet of casing run, scheduled for 18 July.
In total, the well has about 100 to 150 feet to go before it will intercept the Macondo bore, Wells said in an afternoon briefing.
“We’re on track” Wells said for the Macondo well bore entry around the end of July. Once penetrated, the much anticipated kill operation can begin, a process that could take anywhere from a few days to a couple weeks, Wells said.
The second relief well, being drilled by Transocean’s semi-sub rig Development Driller II, will likely halt operations when the relief well begins to penetrate Macondo. The rig will stand by in case it is needed.
