So much for BP’s plans to cut off the flow of oil with its newly-installed cap on Tuesday.
It appears that the US administration, in the form of energy secretary Steven Chu and USGS director Marcia McNutt, has stepped in and demanded more analysis before the valves are shut off.
From incident commander Admiral Thad Allen:
“Today I met with Secretary Chu, Marcia McNutt and other scientists and geologists as well as officials from BP and other industry representatives as we continue to prepare and review protocols for the well integrity test – including the seismic mapping run that was made around the well site this morning. As a result of these discussions, we decided that the process may benefit from additional analysis that will be performed tonight and tomorrow.”
So what could Chu and McNutt et al’s concern be?
The plan was to shut the valves off for between six and 48 hours, giving BP time to monitor well pressure. Consistently high pressure, of about 8,000 – 9,000 pounds per square inch, would indicate the well casing was intact. Lower or inconsistent pressure might mean that oil and gas were escaping from other places below the sea bed; the cap risked further rupturing the well in ways that would be very difficult to fix.
In otherwords, the cap is being tested to see if it’s safe to use again in the future.
So perhaps the fear from the administration it is that shutting the valves off completely, even for a test of several hours, would actually threaten the well casing.
Energy investment bank Tudor, Pickering & Holt seems to think this could be a risk. Via Houston Chronicle:
Shutting in the well at the seafloor LMRP cap will result in pressure build up inside the well/BOP (10,000psi+). With the 9 7/8″ production casing compromised (very likely not sealing at the surface) due to flow up the back-side (uncemented annular space behind the 9 7/8″ casing), the high pressure would be exerted on the 22″, 28″ and 36″ casing strings. The burst rating on these larger casing strings is probably much less than 10,000psi. Therefore, if the Macondo well is shut-in at the LMRP cap, there is significant risk that the larger casing would rupture near the surface of the well, resulting is an “underground blowout”. In that bad, bad, bad scenario, oil and gas would crossflow from the Macondo reservoir, up the well and out into the shallow formations.
And how likely is it that the cap would be used to permanently stop the flow until the relief well is drilled, anyway? Although it’s been suggested that a successful test could see the cap being left in place, this BP statement indicates that it was only ever seen as measure that would be deployed temporarily:
The measurements that will be taken during this test will provide valuable information about the condition of the well below the sea level and help determine if it is possible to shut the well for a period of time, such as during a hurricane or bad weather, between now and when the relief well successfully plugs the well.
Which means, collecting the oil is still seen as the default option, until the relief wells are successfully completed.