See an updated in this report here: Feds provide further evidence that the formation has collapsed around BP’s Macondo well (VIDEO)
Press Briefing by National Incident Commander Thad Allen, August 19, 2010 at 12:00 p.m. EDT:
Well there's some that would tell you that the lack of communication between the annulus and the reservoir might not be cement, it could be just a collapse of the formation around it. We really don't know, all we know is there's no communication. One assumption is that that was cement from the top kill...
We don't know the condition of the bottom of the annulus. It could be that there – that whatever is blocking that wouldn't take much to move it. We don't know, we think that's a low probability but would be a very high consequence outcome. The only thing we don't want is direct communication between that reservoir and the surface.