Interested from my understanding, the original dome was intended to basically place a funnel over the leak and allow the oil to be a controlled evacuation. That failed. To inject the kill mud, they have been drilling a separate well who's sole purpose is to inject the mud and hopefully seal the two leaks, but until they could complete the new wells they also pursued containment - which has been like bailing a 20 foot leaky rowboat with a soup can.

Lee Thomas I have a post at my site on the basics of the Deepwater Horizon. But let me try to explain what happened here. BP had just struck a 100,000,000 bbl oil find and were in the process of putting casing into the well to seal it up until they could figure out how to best develop the field. The deepwater horizon is a well drilling vessel. It is not a oil field producing vessel. During the day in question the BOP or blow out preventer was tested repeatedly during the day leading up to the event. It seemed to have failed its pressure tests. A BOP is a device that weights in this case about 400,000 lbs. It has 4 dual pistions that are horizontal to the shaft coming out of the ground. When activated a piston will slide into place sealing the shaft and prevent any oil from escaping to the surface. If their is a severe problem and this one does not seat properly then a second set of pistons will slam shut with incredible force. This large piston will sever the pipe and seal the shaft and prevent the oil or gas from rising up the tube. In this case the Deepwater Horizon was drilling in 5000 feet of water with 5000 feet of 21 inch riser pipes reaching from the surface and connected to the BOP on the ocean floor sitting on top of the drilling hole into the sea bed. Each of these risers are tested to 3.5 million pounds of load bearing capacity and are bolted together with bolts the size of paint cans. They are lowered down and another 90 foot section is bolted into place until they reach the BOP on the surface floor. Now in the case of the Deepwater Horizon......the testing that was taking place just prior to the Blow out was most likely now to blame for the accident. The pistons were failing to seat and so they had a test piston in place that was designed to find out why the piston was not sealing. They had apparently reduced the mud in the tube....mud and water is the sole means for preventing a blow back......this reduction in mud was designed to test the seal on the BOP to make sure that it was working properly. As they reduced the mud it put more and more pressure on the seal and test piston that was in place for testing. The BOP failed and the resulting rise of methane roared up the riser. As the methane rose up the rise forcing mud and water back onto the drilling deck the engineer on duty would have seen the mud flowing back out of the drilling hole and realized immediately that the BOP had to be activated. I have no doubt that the enigneer flipped what amounted to a hydraulic switch to activate the BOP on the sea bed before. The problem is that by flipping the switch the BOP did not activate. That of course is the question on everyones mind. WHY...did it not activate. This Cameron designed BOP was not equipted with an acoustic switch and all BOP's are designed with a deadmans switch that as a last resort if everyones dead or unable to flip the hydraulic BOP that it will flip itself as it reads immense pressures in the riser and works on its own. It all failed. Why is the question. It now appears that the BOP might have been improperly installed and though testing in the past showed it would work properly when tested, the deeper they drilled and the higher the pressures encountered they were starting to have troubles with getting the test piston to seal when tested. Hope this helps you to understand. This is light crude. It biodegrades. This is not the same type of oil that the Exxon Valdez had let loose. Most of this oil will never be cleaned up and in fact will biodegrade on its own. A real plus for this crisis. Additionally something to keep in mind...........this is not the first event like this in the GULF. A blowout on the Ixtoc I rig in 1979 off the coast of Mexico spilled 33,000 barrels of oil a day, threatened the coast of Texas, and took nine months to contain. Technologies and techniques for containing oil spills have improved since then, but challenges have also increased. We survived just fine folks because this IS light sweet crude which biodegrades.