Fluid cannot be compressed, but the wellpipe isn’t sealed, and the pressure is due to methane gas which can be compressed.
They did have to “increase” pressure slightly, to pump the oil into the well. a 5 gallon flow hardly increased the presssure though, and would almost immediately start dropping the pressure as heavier mud pushed oil back into the deposit.
Technically, they could do this without increasing pressure at all (not practically though). Mud at 1-psi higher pressure than the well would flow into the well, and start dropping the wellhead pressure.
My previous post was in response to the Matt Simmons post that said they’d have to increase pressure by thousands of psi to get the mud in, and the wellhead would blow up.
I also didn’t see any indication of a “blow out” of a new leak. Just a little more seepage, and I wonder if they didn’t open something up just a bit to help get the mud into the pipe to start.
Of course, I guess I’m more tolerant of these little tiny leaks, as most of my plumbing seems to do that from time to time.