On Sun, 2 May 2010 21:44:44 -0700, "Steve B"
wrote:
snip
How would one run a BOP so far down when a BOP must be hooked to hydraulic
lines at all times in order to function? I am not familiar with the deep
water drilling techniques.

Steve
======
If I understand correctly, the "normal" position of the BOP
is closed, with very considerable force, designed to shear
the normal "string" of drill pipe. The hydraulic
lines/pressure force/hold the BOP open, thus if all the junk
on the oil platform did slide off and cut the lines, the BOP
should have slammed shut. There is the possibility that the
junk falling from the capsizing oil platform crushed the
control lines trapping the pressure and holding the BOP
open, but from the somewhat ambagious media reports it
appears one of the remote submersibles managed to trip the
emergency dump valve on the hydraulic lines at the BOP, and
trip one of the emergency cutoff valves with no effect on
the flow.

Two other items that may have contributed/be contributing to
the problem:

There are several media report that the BOP was modified by
the drilling contractor, but these modifications were not
approved by or even known to the BOP manufacturer until they
say the underwater photos of the BOP.

Halliburton had just finished cementing the well about 20
hours before the blowout. Halliburton was a pioneer in the
cementing of deep sea wells, but as the depth increased over
the last few years [c. 5,000 feet] so did their problems,
indicating that their procedures/materials may have exceeded
their limits. Again according to the media, cementing is
one of the most dangerous phases of bringing a deep sea well
into production, with almost 1/2 of blowouts and other
serious blow-outs over the last few years occurring at that
time. Another factor according to several posters that
appear to know was the use by Halliburton of a new and
slightly less expensive cement formulation.

If the oil flow is indeed around the outside of the well
casing this is very critical and highly dangerous problem as
the flow will scour a larger and larger channel increasing
the flow rate, and in many cases has been known to blow the
casing and its contents [drill stem, drill, cement plug] out
of the well, and the emergency cutoff and BOP valves out of
the way.

--
-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).