Sunday, August 8, 2010

What happened to the mud and cement ?

Hello all, sorry I haven't been around so much, I have been busy with a new project.


When BP released this photo on their website, the blogosphere was on it, like butter on an English all the nooks and crannies.

Ask yourself this :

Why was the "leg" of mud considered to have "killed" the well...measured from the ship to around 5k' down the well.... , and not from the wellhead down.?
   When they had originally stated the beginning of the base oil injectivity testing, they also stated that the mud pumping operation would probably go on for a little while, the mud was going to be the type that does not clog rock and formation pores too much, ie:, a non-caking mud with small particle size( I am sure after all the press coverage, you know that they use anything and everything to plug cracked formations...sawdust...coconut husks...shredded tires....etc etc..), specifically to allow for the mud to travel further .

  One of the things I noticed, and I'm sure a few others did too, was that the mud pumping operations suddenly proceeded before the estimated original time for the operation to start. If you lok at the chart below, you can see on the right-hand side, the projected ideal gradients for the injectivity parameters, ie: the pump pressures, mud rates of injection, pressures at various points in the system,..the gentle arcs plotted on the right-hand side are the "ideal" plots.....the two thicker lines on the left-hand side of the chart are the actual pressures of the testing done.

PT-3K-2 was the pressure at the gauge monitoring the kill line.
PT-C was the pressure at the gauge monitoring the choke line.
PT_B301 was the pressure at the gauge monitoring the bottom of the old BOP.

(PT stands for pressure transducer, it's what is really used to measure flows in the pipes, the yellow boxes you have seen for weeks with wire frame handles)

Looks like PT-B301 flat-lined at 5841 psi, while PT-3k-2 211 was at 5161 and dropping @ 369.8 bbl of 13.25 ppg mud.

Look at the left side over the guy's head.

" PT-B301 flat-lined at around 5841 psi "

So if the pressure needed from the pumps would steadily decrease as the leg of mud gets established, then we would see an arc plotted. If the pump pressure flat-lined at the same time the mud volume was plotting an arc...would this not indicate a rather large loss...?

Normally , a "static kill: would be considered to be successful when a mud leg is established in the was was from a little ways down the bore...and all the way up to the surface. On top of that, they never did reach true static equilibrium, they were gradually pumping mud the entire time, the rate of loss was determined to be around 1b/minute.

I think that the test itself is what could cause problems..hypothetically speaking,...the leak location was established by the fact that they could not get to a hydrostatic equilibrium,ie: the point where you could saw the entire stack off and nothing would come out....if there were a shallow leak, and fluids were forced through it, this in itself, would make them larger due to erosive qualities of the flow. So really...the only way to see where the oil and gas would vent in the surrounding area would be to shut the well in....but at the same time, by doing so, you could cause larger pathways for the leak. I look at this like stress testing materials. You never stress test something...and then use it in the manufacture of a product, for you destroy what you observe in the course of the test. So I think they might have realized, that by the fact they had to continuously pump mud into the well, without ever reaching equilibrium, that that mud pumped IN , would represent roughly the mud lost, per pore counts and such. So maybe the sudden switch to cementing could be attributed to the "pucker factor" of perhaps causing a larger fluid migration path than before...?

So after the cementing operations they tell us in the briefing that they pump approx 200 bbls into the first formation...just the first....they said they had established a leg of cement reaching 5000', from the seafloor, to the bottom of the leg. So there is a shallow leak that has been identified, it also would explain all the venting we are seeing on the ROV cams, BTW, there are 3 cams on each ROV, we get to only see 1.. 

So let's next look at the reworked diagram from Alex Higgins' blog ( Which I would highly recommend ) so we can get an idea of exactly how far they have really gotten in the overall operation of shutting this well down for good.

                                            , my wild guess, is that they will have to stop cementing from the top. This will leave a long length of wellbore with trapped fluids. They will intersect the wellbore from the bottom and start to slowly squeeze in mud from the bottom, this will, in my mind, produce a rather large amount of fluid and gases to vent from the deeper layers again. If you envision an oil-filled shock absorber with a hole/holes, getting compressed, than you can visualize what happens during this process. The oil in the wellbore has to go somewhere....

I'm thinking about the mud "bubblers" in Yellowstone, and how the bubble would travel up through the fluid, granted THAT mud is a fairly homogeneous blend so travel is smooth, for the most part. Now I think about what is the likely composition of what the ocean floor is made of where we see this little "volcano". Probably mainly silt, some larger particulates, maybe even bone fragments...and microbial mucous, natural polymer precursors ...same snot we see floating around, I think it's refereed to as " marine snow ", and probably a little asphalt. So if it's traveling up through a thick layer of softer materials, then we would tend to see eruptions as these "bubbles" came up through the muck, as opposed to a steady stream of fluids/gas, like what would be coming through a crack in a rock formation. I think it's natural that we will continue to see more fluids coming up, especially when they start squeezing from the bottom. Somebody over at the Drum( a reservoir engineer in the field ) said that the mud they had used indicated a very porous formation of sandstone around 13k' down.

We'll see, but I think anything migrating up through the muck won't create a pathway, the muck will close the channel behind the fluids/gas.

I am keeping my hopes high.