There were a lot of mistakes made that resulted in the coming "Mess".
The BOP (Blow Out Preventer) was disabled by something. Most likely that something is a drill stem "collar" (the "connection" between 2 sections of drill pipe). The "Blind Ram" on a BOP is designed to shear drill pipe and casing, in a "Blow Out" event. However, the Blind Ram is limited in it's mechanical function-ability. "Brute Force" is used for shearing, but the BOP cannot generate enough brute force to shear through the collars of drill pipe or to shear through "drill collars" (the thickest, heaviest pipe sections, located at the bottom of a drill string).
Drill string - Wikipedia, the free encyclopedia
The Blinds can shear through some casing collars, dependant on the "weight" of those collars. Some extremely heavy casings can not be sheared.
Here is a link to definitions of "terms" being thrown out by various news media types and industry experts.
http://oilgasglossary.com/casing.html
I got to talk with my best friend last night. He was on a unit 45 miles southwest of the Horizon. He rode over on a helicopter that flew off the unit he was working on, and went out to the Horizon to do an aerial survey, mid-day on wednesday after the explosion. His video and still photo's are at corporate offices in Houston. The company he works for was the operator of the "Mud System" on Horizon.
My friend's "conjectures" as to what happened;
First. It is fact that Halliburton had just completed a "Plug Back", in preparation of Horizon being disconnected from the find and repositioned onto another drill site. That is a fact.
Second. This well is a "Discovery" well. BP had no intention of the "Production Volumes" being public knowledge at this time. That is a fact.
Third. The fire was extinguished when the Horizon flipped over and sank. That also is a fact.
Unfortunately.....by flipping and sinking, the shear weight of the entire Horizon unit, caused BOP issues totally separate from whatever issues were in place, at the time of the first and second explosions. This was a "double" explosive event. The second explosion and the resulting fire occurred approximately 3 hours after the first. The eleven people whom died, were working to correct or repair the conditions that caused the first explosion.
Now the "conjectures" come into play.
The main...and most likely conjecture. The rig lost track of the collar locations, as the string was being worked. When rig crews are working a "string", they strap every stand or joint run into the well bore, to maintain an accurate placement of collar location. This is done to prevent a collar being placed in the "Blind Ram" point.
Whether on land or offshore, drill pipe strings are "stood back" in 3 joint sections, as they are pulled out of the "well bore". When those strings are run back into the well bore, they are re-attached in exactly the same pattern that they were stood back. The last string out of the hole is the first string to go back into the hole.
[ Back when I worked in the oilfield, everything that was run, was strapped. Every time. Every few strings, operations were stopped, so that tally books could be compared, and figures could be double checked. The idea was to prevent BOP's being blocked by collars, but also.......to be accurate in the specific placement of the drill bit or other "down hole" tools. Usually tally books were being kept by The "Company Man", the "Tool Pusher" (the man whom was in direct charge of the drill rig), the "Tool Man" (the person whom was in charge of the drill bit or other "down hole tools" such as a "bridge plug", a "packer", casing "floats", etc) and usually either a "Mud Man" or a "Cementer".
That was in the 70's and 80's....when I did this type of work. I was a "Cementer" and a "Safety Man". That ended when I changed jobs 23 years ago.
Things could be done a little differently...but not that differently. They still have to keep track of tools and collar locations. ]
Now.....The main conjecture....as to the "Cause" of the blow out.
First conjecture alludes to the "Bridge Plug" and it's failure. If the bridge plug did not hold it's position or was improperly set, it would not do its job, which is to prevent bottom hole or production zone, fluids and gases leaking by.
Second conjecture alludes to substandard cement being spotted above the bridge plug. "Substandard" could mean anything. The cement itself could have been contaminated in some manner and did not "setup" as it should have. There should have been at least 2 cement plugs set on top of the bridge plug (which is a mechanical device).
Third conjecture alludes to the drilling mud itself, being to thin and unable to control the "kick" when the blow out started. Drilling mud serves three purposes. First it lubricates drill bits. Second, it transports drill shavings. Third...it's density controls "Bottom hole" fluids and pressures from the production zone. In this case the mud may not have been heavy enough to stop a blow out.
The final observation........there was no attention being paid to "returns". Returns are the fluid discharge coming from the well while work is being performed. Regardless of the work being done, there should have been "Static fluid" at the top BOP or "Stack"(yes...there was a BOP directly beneath the drill floor). While working a string, it is imperative that fluid be "static" (fluid that is holding in place, with the exception of annular volume created by removal of pipe and tools) in the well bore.
If the bridge plug and cement plugs had been properly placed and were doing their jobs, the well would have been "static". The only thing the rig crew on duty would have needed to do, to maintain fluid at the top of the stack, was to attach the "Kelly" every so many stands or pipes laid down, and re-circulate the well bore.
If the fluid is being sucked into the well bore, then the well is on a "vacuum" and things are done very quickly to plug the well bore and stop the vacuum. The rig crew would use things such as cellophane chips' cotton seed hulls or crushed walnut shells, to thicken the drilling mud and plug up the formation which is on a vacuum. That was not the case for the Horizon.
In this case.....the fluid was being forced out of the well bore. Those fluid returns should have been immediately noted, and the stack should have been closed in and the Kelly reattached to the drill string, in preparation of controlling the approaching "Kick". In my friends opinion...and in my opinion...this was where the rig crew dropped the ball. They were not paying attention to the monitors and did not see the "kick" coming. Bad mistake.
In the case of this well, the last cement plug would have been a "brittle" plug, set at about 150 to 200 feet below the seafloor BOP, which would have remained in place when the Horizon was moved. A brittle plug would have been set as a precaution to prevent the GOM waters from leaking past the BOP assembly before a production unit was in place. A brittle plug is used at the surface because it drills out easily and there is little risk in a drill bit "sidetracking" out of the well bore at that point.
At the time of the first explosive event, the rig may have been at the point where they were laying down the bottom hole assembly........which would account for the BOP being blocked. To set that last plug, the bottom hole assembly is laid down, then the string needed to set the last plug is run back into the well bore. After the plug was in place, the crew would have then laid down that last string of pipe, in preparation of disconnecting from the stack and moving to the next drill site.
Because every one involved is most likely dead and with the video record of the work being done, also destroyed by the fire and sinking of the unit........BP, Transocean, the Federal government and it's entities.......and all of us..........are left to conjecture.
was I articulate enough in explaining what little I know?
Also! Something that the "Enviromental Lobby" is not going to be bringing to the forefront, as it pertains to this spill and the mess that it will create.
After the Exxon Valdez mess in Alaska, Prince William Sound and the Cook Inlet, as well as the surrounding Kenai Peninsula area, fish, crab and mammal populations rebounded at before unseen rates. The fishing in Prince William Sound and Cook Inlet is better now (and was two years after the spill) than it had been in the previous forty years.
Crude Oil is an organic compound. It is composed of decayed matter such as leaves, grass, trees and mammals(re: dinosaurs). Yes...It is visually unappealing and it is hard to clean off. But in the end..."Crude Oil" is as natural as the water we drink and the air we breath.
As with Prince William Sound, natural will clean herself up and life will go on.
It is what man does with crude oil that is harmful to life. There is nothing any of US did in the past, in the present, or will do in the future, that was not or is not, the result of crude oil and it's uses. The computer that you read this with, is proof of that. :thumbsup:
Oil Spill
Very interesting. :thumbsup:
