What I believe is going on is that BP is running a series of "junk shots" with the Nat Lab "junk", and after they run one they fill the well with mud to see if it has changed anything. To date, while there are changes (you stop doing this when there aren't) they haven't been enough. But after each time that they fill the well with mud, they switch the pumps off while they go and regroup. That allows the gas and oil to push the mud back out of the way (one of these tries, perhaps, it won't and we will know that it has worked). Much more under the fold, including video. (Click "there's more").

"The (Development Driller II) has temporarily suspended drilling operations in preparation for the possible future deployment of its BOP on top of the (Macondo) BOP," he told UpstreamOnline in an email response.

But when the oil and gas get through the constriction of the BOP there is a drop in pressure and an expansion, and this gives that little bit of excitement that we see. After a while, not so exciting, though this time one of the cameras went off air, so maybe there was something else going on as well?? Oh, and BP has decided to halt, for a while, the second drilling of a relief well, so that they can prepare for plan B . One has to remember that these drilling rigs are at a premium, and there is an opportunity cost with just about every decision.: 10:53 pm. It appears that they are pumping mud again, so another test may be under way. (I am judging this on texture and jet structure) . There is one interesting thing to note, and you have to be familiar with the patterns to see it. So I am going to repeat a picture from 3:45 am yesterday (which has been my standard base reference for mud, rather than oil flows.

3:45 pm 5/26/2010

Now look at the current flow:

10:59 pm 5/28/2010

Notice the changes in the flow pattern, and particularly that the crack to the right of the central paint removed line, which had a piece of rubber jammed in it . By adding more NL junk they have just about totally bridged that crack and stopped the flow - which illustrates that what they are trying to do at the BOP is at least partially working - as I explained in an earlier post I am almost tempted to note that the flow seems at a little less pressure, judged again by jet structure, and which would indicate more bridging in the BOP, but I grow more cautious as the process extends.And one last point - you should not expect the majority of the cracks at the riser (the ones we are looking at) to get closed until almost the end of the injections since their width is much smaller than the one that they are trying to block in the BOP, but as it grows smaller, so they should come into the range of the NL "junk." Unfortunately they don't seem to have got the main flow bridged effectively yet, and it may be that the gap is wider than the thickest piece of tire they have tried so far. Which now gets into tricky territory as there are absolute limits on how big they can make the pieces. But this is a problem where a tenth of an inch can make a big difference.