Top kill/static kill
OK, do I understand this right?
Fill the well bore with mud. The weight of the column of mud creates pressure and counteracts the pressure of the oil in the reservoir, reducing the pressure at the top of the well bore.
I think this is basic petroleum engineering 101.
I've always assumed on most land wells, that when you fill the well bore with mud, the pressure at the top of the well bore drops to zero. i.e. When the bore is full of mud, wouldn't you normally be able to chop the well off at the surface and not have anything flow out of the well? When you're drilling, pulling pipe, etc, isn't the top of the well bore basically open, allowing mud to basically flow freely out the top of the pipe? Isn't the weight of mud the thing that allows you to drill into a pressurized reservoir in the first place?
What I wonder is will the mud produce enough pressure that the gauge pressure at the top of the well bore on the Macondo well is zero, or does it just reduce the pressure? Is the weight of 10,000 feet of mud enough to counteract the reservoir pressure of 7000+ PSI?
Fill the well bore with mud. The weight of the column of mud creates pressure and counteracts the pressure of the oil in the reservoir, reducing the pressure at the top of the well bore.
I think this is basic petroleum engineering 101.
I've always assumed on most land wells, that when you fill the well bore with mud, the pressure at the top of the well bore drops to zero. i.e. When the bore is full of mud, wouldn't you normally be able to chop the well off at the surface and not have anything flow out of the well? When you're drilling, pulling pipe, etc, isn't the top of the well bore basically open, allowing mud to basically flow freely out the top of the pipe? Isn't the weight of mud the thing that allows you to drill into a pressurized reservoir in the first place?
What I wonder is will the mud produce enough pressure that the gauge pressure at the top of the well bore on the Macondo well is zero, or does it just reduce the pressure? Is the weight of 10,000 feet of mud enough to counteract the reservoir pressure of 7000+ PSI?
Tags: Top, kill, kill/static
Views: 129
Replies to This Discussion
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Permalink Reply by Bill johnson on
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if it is heavy enough. 15ppg
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Permalink Reply by The_Baron on -
Is the weight of 10,000 feet of mud enough to counteract the reservoir pressure of 7000+ PSI?
Imagine a column of mud 10,000 feet high, with the weight of another 5000' of mud or seawater stacked on it... it will exert quite a force... simple fluid dynamics..
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Permalink Reply by Mac Davis on
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You do get into the question of gauge vs. absolute pressure. When they say the well pressure is 7,000 PSI, I'm guessing they mean it's 7,000 PSI relative to the water pressure at the seafloor, but I'm not sure. If you stuck a gauge on the BOP, it's probably going to read relative pressure, not absolute pressure.
At 5000 feet below the surface, the absolute pressure of the water would be about 2500 PSI. If the mud weighs 15 lbs per gallon, 10,000 feet would give you about 9,000 more PSI.
For that matter, if you're reading 7,000 PSI gauge at the BOP, the pressure in the reservoir would be higher by the weight of the oil/gas mixture in the 10,000 feet of well bore.
My rough calculations seem to indicate that it's borderline whether even the heavy mud would drop the pressure all the way to zero.
I'm basing this on the fact that a 2 foot column of water gives you 1 PSI, and weighs 8 lbs per gallon.
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Permalink Reply by Spring Branch,mineral owner on
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You can weight up the mud more than 15 ppg if need be.
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Permalink Reply by Jack Blake on
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hhhhhmmmmmmmmmmm said Jack Blake. Jack does not have much faith in BP or their engineers. Maybe some of the other majors who are helping double checked BP's figures hoped Jack Blake.
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Permalink Reply by Mac Davis on
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I'm sure the BP engineers have the pressures and weights figured out. Unfortunately, I don't have access to them to ask them if the mud will weigh enough reduce the pressure at the BOP to zero. Even if it doesn't drop all the way to zero, it's probably still a good thing to reduce it as far as you can.
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Permalink Reply by TPFH on
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Mud 15.00 ppg x .052 x 10000 = 7800psi hp
Seawater app. 8.6ppg x.052x 5000 = 2236psi hp
Total of the two will be 10036psi
I think that the mud wt when they finished drillng was 14.4ppg at that 14.4 mud would have been
to the shaker on the Rig. 14.4ppg x .052 x 18000tvd = 13478 psi hp
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Permalink Reply by Mac Davis on
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Thanks for the info, everyone. Good info.
I have my doubts you can add in the pressure of the water. It depends on whether they are using absolute pressure or gauge pressure when they say 7000 psi.
When they quote "7000" psi as the well pressure, I'd bet that's gauge pressure at the well head. i.e. the amount of pressure difference between the well bore and the water outside. That's the pressure that is acting on the well equipment. For instance, when they cement the well bore, will they say the pressure drops to zero, or will they say it dropped to 2236 psi?
I could be wrong. They could be using absolute pressure measurements, i.e. pressure relative to a vacuum.
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Permalink Reply by P.G. on
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Does the mud being referred to here always remain in a liquid state or will it eventually become a solid like concrete?
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Permalink Reply by Mac Davis on
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The BP diagrams show just the bottom part of the well ending up filled with cement, but that doesn't mean that they won't fill the rest with cement once the stuff in the bottom sets up and everything is tested.
What do they normally do when they plug and abandon a well? Fill the entire bore with cement, fill the top and bottom with cement, leave parts filled with mud, water, tapioca, or what?
By the way, does mud ever separate out into solids and water if you let it sit for too long?
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