The report indicates that a bad cement seal on the oil well allowed gas and other liquids to flow up the production pipe.

Engineers had spent days pumping heavy drilling fluid into the leaking well head on the ocean floor in a high-pressure bid to smother the gushing crude and ultimately seal the well with cement.

If a stable column of mud has been set up in the well, keeping the oil at bay through its sheer weight, the next step would be to set cement in the well and seal it off permanently.