I'm a geologist by trade. In a former life I spent a few years
working oil rigs, a couple of those on offshore rigs. Here's my
analysis and worst fears, based on what I've gleaned from the news
1. To save time/$, they didn't circulate the mud in the borehole
("bottoms up") before they set the liner. Had they done so, they
would have identified the disasterous conditions before the disaster.
2. To save time/$, they "hung" the liner (ran it only from the bottom
of the previous casing, rather than run it all the way up inside the
previous casing to the BOP).
3. To save time/$, they used only 6 liner centralizers rather than the
"recommended" 21 (recommended by whom I don't know). If the hole
deviated at all from vertical (which I'm sure it did), that'd mean
that in places, the liner would be placed up against the borehole
sidewall rather than through the center of the borehole. That'd make
it very hard to get an adequate cement seal of consistent thickness
and strength along the entire length of the liner.
4. To save time/$, they used an inferior cement mix.
5. To save time/$, they didn't run a "cement bond log". To do this,
they run a special tool on a wire line through the recently cemented
interval, and log the qyaulity of the cement bond between the liner
and the formation.
6. To save time/$, they displaced the drilling mud in the riser (above
the BOP up to the drill rig on the surface) with sea water before the
inferior cement had completely set, and without the normal plug in the
casing below the BOP. This would drastically reduce the pressure head
on the formation, and allow formation fluids to enter the borehole.
Now my "worst case" fear:
The bad cement job outside the liner failed; the gas/oil in the
formation, under intense pressure (could be as high as 50,000 psi!)
blew out and eroded the cement and possibly the liner, allowing it to
flow unimpeded and expand quickly due to the pressure release, into
the annular space outside the liner, and possibly into the liner, and
into the previous casing. THE WORST WORST CASE: if they were to cap
the well at the BOP, the pressure would overwhelm the cement-formation
seal at the previous casing (where they hung the liner), and break
down the higher formations and cement, and flow unimpeded outside the
previous casing and BOP to the seafloor surface (cf: the Santa Barbara
spill). If that was the case, there would be NO WAY to control the
flow until the relief wells are completed (in August). Maybe that's
why they "failed" to cap the well at the BOP.
Joe Barton should be hanged.
Sorry, just my $0.02 worth.