Where is NickatNite?

LACamper said:

Ahhh but they're pumping a mix of drilling mud and concrete down that pipe now to do the topkill. I don't know the specific gravity of the mix but its got to be higher than oil.
and, yes, my head hurts also.

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Barney88pdc said:

Weight up from 9.6 to a 16.0 WOW that would be one hell of a pressure graident.

Sir I need to get a few more sacks of Barite coming.

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themcfarland said:

is it possible , that during the pullout.. they swapped water for the mud as they were gearing up to move ? Swapping out sea water for the mud would be to what advantage? I just heard someone say it and I think he is full of it , but I dont know..

that could explain the blow out though.. it cant be that simple..

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Barney88pdc said:

Going from a 9.6 to a 16.0 all at once would be one hell of a weight up. I would hope to have offset data. And I probably would keep my keys and wallet in my pocket. Mud pushing into the formation sure. If you drilled the previous hole section with 9.6 you would probably be asking alot from the shoe. Possible but that might be a bit cowboyish. You might what another intermediate string for a stronger shoe before hitting your 16.0 required zone. And drilling with a 16.0 just for the hell of it when only a 10ish would be required would be quite expensive. Not only for the additional mud properties but also the bits you would burn up being that overbalanced.

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shoalsfugro said:

Does this make sense?

Water pressure at 5000 feet is a little over a ton per square inch
About 2165 psi IIRC.

If the crude oil has a specific gravity of 0.82 (and different crudes have varying spedific gravities) then the pressure at the bottom of a 5000' pipe filled with crude would be 0.82 x 2165 or 1775 psi.

Suppose however that the oil is at the bottom of a hole 8000 feet below sea level under 3000 more feet of rock with a specific gravity of 2.5. Now the total pressure of sea water plus rock overburden at the bottom of the hole could be:
2165 + (3/5)*2.5*2165 = 5412 PSI

However, the oil in the 8000 foot well would have a pressure of 8/5 * 1775 = 2840 PSI.

So there is a pressure differential of up to 5412 - 2840 = 2572 PSI available to push the oil up the well. Hence the blowout.

Now the above is not exact, since the pressure of the oil flowing out of the sand at the bottom of the well is not as much as the simple calculation would suggest, given that the rock is stiff and there is resistance to flow through the sand or rock to reach the well.

But that is the general idea.

During drilling, the well is supposed to be filled with a dense "drilling mud" in order to overcome the pressure of the oil under the weight of the rock.

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Sigforty said:

It mostly has to do with unknown conditions until the well is drilled and logged. It helps to be safe. Of course on the flip side, if you use a heavy mud when it is not needed you can lose circulation as the mud pushes into the formation.

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Ritten said:

What he meant was the well started at 9.6 and TD'd with a 16.0ppg. Of course they had a weight up schedule as they drilled the well.

Sigforty...we can build mud weights higher than 20ppg, but it's rarely seen over 17ppg in the gulf. Above a 19.0 it's much better to use Ferox instead of Barite. Most land jobs that we're drilling down here start out with 9-10ppg but will end much higher depending on depth.

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Sigforty said:

You pretty much show my point though at how the mud changes based on pressure needs and well requirements.

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shoalsfugro said:

Does this make sense?

Water pressure at 5000 feet is a little over a ton per square inch
About 2165 psi IIRC.

If the crude oil has a specific gravity of 0.82 (and different crudes have varying spedific gravities) then the pressure at the bottom of a 5000' pipe filled with crude would be 0.82 x 2165 or 1775 psi.

Suppose however that the oil is at the bottom of a hole 8000 feet below sea level under 3000 more feet of rock with a specific gravity of 2.5. Now the total pressure of sea water plus rock overburden at the bottom of the hole could be:
2165 + (3/5)*2.5*2165 = 5412 PSI

However, the oil in the 8000 foot well would have a pressure of 8/5 * 1775 = 2840 PSI.

So there is a pressure differential of up to 5412 - 2840 = 2572 PSI available to push the oil up the well. Hence the blowout.

Now the above is not exact, since the pressure of the oil flowing out of the sand at the bottom of the well is not as much as the simple calculation would suggest, given that the rock is stiff and there is resistance to flow through the sand or rock to reach the well.

But that is the general idea.

During drilling, the well is supposed to be filled with a dense "drilling mud" in order to overcome the pressure of the oil under the weight of the rock.

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Ritten said:

There, fixed it for ya.

Ferox (Hematite) will increase wear in seals, pumps, and other equipment, but it doesn't mean it's not used. Barite (Barium Sulfate) is not as abrasive but there is still a degree of elevated wear and tear compared to pumping straight water. It's used for fluids where possible for that reason. When it comes to mud choices usually the well needs come first though. Maintenance schedules just have to be updated to accommodate what's used.

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Sigforty said:

Interesting! I thought stuff much higher than 20 would cause issues with the pumping equipment.

You pretty much show my point though at how the mud changes based on depths.

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