Actually Vast is lying again, "the fact that Halliburton is one of the main contributors to this crisis", isn't quite a fact. They have concerns about the cementing process and it will be the focus of scrutiny, doesn't mean that the cement was a factor in the explosion.
Haliburton was in fact handling the cementing process, whether it contributed to the explosion has not been determined.
Correct, and a mea culpa from me. They were involved and no one knows the exact sequence of events andwhat caused it.
I doubt the cement was a contributing factor, my guess is the drilling mud wasn't circulating back throught the well, which is needed to form a sort of plug to keep oil and gases from leaking through and consequently the mud not being able to plug the hole and contain the reservoir pressure it allowed the oil which can be at temperatures exceeding 400 degrees to erupt up and out the well hole. Althought there are many things that can cause a blowout it's hard to pinpoint the exact cause at this point. Just for grins here's four ways a rig can suffer a blowout.
Blowout No. 1
A kick up the drill string fish during fishing operations can lead to an underground blowout. With the top of fish up in the casing, flow can come up the drill string and back down the annulus to the casing shoe or out through a casing rupture.
The flow path up the parted drill string has been common to many sustained blowouts. Bridging is less likely as flowing pressure is high and limited formation exposure to the flow path. Drill string restrictions and fracture pressure at the flow exit depth control flowing pressure. Similar blowouts have occurred in the past onshore and offshore, but not as of yet in ultra-deepwater. The key is always plugging the bottomhole assembly prior to a drill string back-off. Blowouts are possible when cement is over-displaced out the bit in an attempt to plug only a limited portion of the drill string. The operator mistakenly treats well as if drill string is plugged. One solution is to inject materials that would plug the bit with cement or place a wiper plug behind the cement that sets up on some restricted ID to control cement over-displacement.
Blowout No. 2
A bridged underground blowout can result in a severe drill pipe kick. A surface pressure chart of an deep high temperature, high pressure (HTHP) underground blowout can be seen. Note that 408 bbl of 17.4 ppg oil mud were pumped into the drill pipe at zero pressure when the well was flowing underground. After the well bridged in about 230 minutes, drill pipe pressure suddenly increased by over 4,000 psi in seven minutes and ultimately to a recorded maximum of 6,300 psi while blowing out the mud pump pop-off valve. The drill pipe kick experienced in this well is not uncommon in drill string blowouts. The kick and drill pipe blowout are caused by the following circumstances:
•Drill string hydrostatic pressure balances with underground flowing bottom hole pressure which drops mud level in drill pipe.
•Well bridges shutting off underground flow.
•Bottomhole pressure at the bit builds-up to the pore pressure of the zone at the bit that originally kicked. The drill pipe then kicks. The greater the differential between flowing and static bottomhole pressure, the worse the drill pipe kick.
•Successfully closing surface safety valves and/or standpipe gate valves in near sonic high density mud flow fails. The kelly cock valves cannot be closed in high flow. Valve seats cut-out from high velocity mud solids. The kelly hose fails. Leaks in the pressure-isolated top drive can occur at elevated pressure.
•In some circumstances, severe hydraulic hammer occurs at surface when the column of mud that remained in the drill pipe is rapidly pushed to surface by the kick.
•In the example well blowout, the upper and lower kelly cock valves and standpipe gate valves either could not be closed or cut-out.
Blowout No. 3
A sheared drill pipe blowout may result in a follow-on blowout. The drill pipe may drop or may still be landed within the subsea blowout preventers (BOP). Flow can sustain up the drillstring and then down to rupture casing or the casing shoe. With sheared drill string in the subsea BOP, flow can continue through closed lower pipe rams. These floating rams seal pressure only from below. BOP erosion can occur at the top of the sheared drill pipe, followed by dropping pipe through eroded rams. Annulus pressure builds up, then the casing or shoe fails. A costly North Sea subsea blowout resulted after shearing drill pipe (multiple casing ruptures).
Blowout No. 4
A drill pipe blowout is the most likely flow path of a sustained blowout while drilling. Based on US Gulf of Mexico continental shelf and onshore examples, this is the most common of all surface drilling blowouts. Flow is through the bit and bottom hole assembly to surface.
The well does not bridge as easily, since the bit may be within the reservoir and flowing pressure is high. Pressure drops through the bit nozzles, and the bottom hole assembly and drill string limit formation draw-down. High shut-in pressures and rapid pressure build-up could lead to pipe rupture. Drill pipe does not seal against gas very well and leaks could lead to quick pipe failure. It can be impossible to close a valve against high velocity dense mud flow (the valve jams partially open or cuts out). Kelly hose can fail, if the well was isolated at the standpipe. The kelly hose or standpipe can rupture, or the well can blow out at the mud pump pop-off valve. All of these failures have occurred recently in onshore and offshore shelf water blowouts. Nothing is so unique about ultra-deepwater that would reduce this risk. The common answer is "that is why we have shear rams." Though this may solve an immediate problem, an even larger one now is at hand.
Eh?
