Gulf of Mexico oil rig accident

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Gulf of Mexico oil rig accident

#1  Postby chippy » May 16, 2010 3:08 pm

I've been out of College for too long to remember my basic Chemistry. I remember PV= NRT and was curious why the "box" they placed over the spill, failed?

I mean, the hydrocarbons(?) that are alleged to be responsible for forming ice crystals due to the depth. But, I would think the pressure at 5000+ feet would be so great to prevent the solidification of almost any liquid. What is the freezing point of these hydrocarbons(?) at sea level? If they aren't crystallizing inside the oil pipe, I imagine they are real close to the FP. If so, isn't it possible to stop the flow by introducing liquid nitrogen into the equation some how?

Thanks
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Re: Gulf of Mexico oil rig accident

#2  Postby piscator » May 16, 2010 7:33 pm

not a chemist, but i found this from USGS, which may help answer your questions about the response of methane hydrates to the Ideal Gas Law at subsea T/Ps


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"Gas Hydrate Stability Curve...a curve representing the stability of Gas Hydrate in sea water. Pressure and temperature are two of the major factors controlling where the hydrate(solid) or methane gas will be stable. Whether or not gas hydrate actually forms depends on the amount of gas available."


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"Gas Hydrate Stability in Ocean Sediments...shows where the same stability curve above crosses the temperatures of ocean sediments."


Capacity to Trap Gas

Hydrate forms as cement in the pore spaces of sediment as well as in layers and nodules of pure hydrate. Hydrates also seem to have the capacity to fill sediment pore space and reduce permeability, so that hydrate-cemented sediments act as seals for gas traps.

Gas hydrates are stable at the temperatures and pressures that occur in ocean-floor sediments at water depths greater than about 500 meters, and at these pressures they are stable at temperatures above those for ice stability. Gas hydrates also are stable in association with permafrost in the polar regions, both in offshore and onshore sediments. Gas hydrates bind immense amounts of methane in sea-floor sediments. Hydrate is a gas concentrator; the breakdown of a unit volume of methane hydrate at a pressure of one atmosphere produces about 160 unit volumes of gas. The worldwide amount of methane in gas hydrates is considered to contain at least 1x104 gigatons of carbon in a very conservative estimate). This is about twice the amount of carbon held in all fossil fuels on earth.

Gas hydrate concentration occurs at depocenters, probably because most gas in hydrate is from biogenic methane, and therefore it is concentrated where there is a rapid accumulation of organic detritus (from which bacteria generate methane) and also where there is a rapid accumulation of sediments (which protect detritus from oxidation).




as to the LN, where would you introduce it to the oil/gas flow? at what quantity?

like i said, i'm not a chemist, and i think i should note that my responses to This Thread should not be limited to methane hydrates, but to methane, heptane, and other liquefied gas deposits
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Re: Gulf of Mexico oil rig accident

#3  Postby chippy » May 16, 2010 9:07 pm

@piscator

Thanks. That's what I was looking for.

Not exactly sure how to introduce the ln (or some other chemical that would perform at those depths). Just seemed reasonable that if the hydrates (thanks for the clarification) are that close to where they're ice one instant and gas or liquid the next that maybe it wouldn't take much to kick them into their solid state. Perhaps some kind of heat exchanger could be affixed to the exterior of the pipe? May be a silly idea.
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Re: Gulf of Mexico oil rig accident

#4  Postby JaxonCO » May 22, 2010 4:39 pm

THe gas hydrates issue is well explained in the material shown. However, it should be pointed out that the hydrate formation process can be mitigated via the introduction of heat, or of salts (NaCl, KCl, CaCl2, etc), of methanol, and of certain glycol compounds (aka "anti-freeze) into the water component of the reaction. I used to design and run drilling fluids for deepwater operations in the Gulf of Mexico. Our solution of choice at the time was a combination of salt (KCl) and glycol.
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Re: Gulf of Mexico oil rig accident

#5  Postby JaxonCO » May 22, 2010 4:53 pm

Further to the liquid nitrogen concept, it is routinely used for the purpose you describe. The problem here is the inability to introduce the LN into the outflow at sufficient depth into the well bore to generate an ice plug of sufficient length to withstand the well pressure which will begin to build the instant the ice plug is put in place. Further, the LN-induced ice plug would likely transient.

What is conceptually required is a method to first staunch the outflow of oil, gas and water from the well; secondly to place a "platform" of some form of viscous material well into the well-bore upon which to stand a column of cement; thirdly introduction of a cement slurry of sufficient volume to guarantee an effective cement plug, when set up; fourthly the cement slurry must possess appropriate chemistry to set up within a rather short time interval (due to the well building pressure upon stoppage of outflow), attaining sufficient compressive strength to withstand the final well-bore pressure, likely in the neighborhood of 15.0 lbs/gal *0.052*18,000', or about 14,000 psi. Due to the rate of outflow and the depth of the well, I would guess that you would have about 2 3 hours in which to complete this process.
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Re: Gulf of Mexico oil rig accident

#6  Postby chippy » May 22, 2010 6:55 pm

JaxonCO wrote:Further to the liquid nitrogen concept, it is routinely used for the purpose you describe. The problem here is the inability to introduce the LN into the outflow at sufficient depth into the well bore to generate an ice plug of sufficient length to withstand the well pressure which will begin to build the instant the ice plug is put in place. Further, the LN-induced ice plug would likely transient.

What is conceptually required is a method to first staunch the outflow of oil, gas and water from the well; secondly to place a "platform" of some form of viscous material well into the well-bore upon which to stand a column of cement; thirdly introduction of a cement slurry of sufficient volume to guarantee an effective cement plug, when set up; fourthly the cement slurry must possess appropriate chemistry to set up within a rather short time interval (due to the well building pressure upon stoppage of outflow), attaining sufficient compressive strength to withstand the final well-bore pressure, likely in the neighborhood of 15.0 lbs/gal *0.052*18,000', or about 14,000 psi. Due to the rate of outflow and the depth of the well, I would guess that you would have about 2 3 hours in which to complete this process.


Wow! Thanks Jack. Very informative. 14,000 psi is way more than I would have imagined. I assume that's the pressure delta at the well head, 5000 feet below sea level?
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Re: Gulf of Mexico oil rig accident

#7  Postby piscator » May 22, 2010 9:11 pm

JaxonCO wrote:Further to the liquid nitrogen concept, it is routinely used for the purpose you describe. The problem here is the inability to introduce the LN into the outflow at sufficient depth into the well bore to generate an ice plug of sufficient length to withstand the well pressure which will begin to build the instant the ice plug is put in place. Further, the LN-induced ice plug would likely transient.

What is conceptually required is a method to first staunch the outflow of oil, gas and water from the well; secondly to place a "platform" of some form of viscous material well into the well-bore upon which to stand a column of cement; thirdly introduction of a cement slurry of sufficient volume to guarantee an effective cement plug, when set up; fourthly the cement slurry must possess appropriate chemistry to set up within a rather short time interval (due to the well building pressure upon stoppage of outflow), attaining sufficient compressive strength to withstand the final well-bore pressure, likely in the neighborhood of 15.0 lbs/gal *0.052*18,000', or about 14,000 psi. Due to the rate of outflow and the depth of the well, I would guess that you would have about 2 3 hours in which to complete this process.


thanks Jax, for the great info


with an LN injection, there's also the issue of thermo stress to the metal of the casing, which is likely close to its burst pressure in some of the larger diameter sections of the tapered string

since i don't think it would do a lot of good to inject LN into the riser above the BOP and take advantage of the adiabatic cooling of the oil, we are talking about injecting a supercold liquid into hot oil/gas coming up the hole at something like 230C, and we are talking about doing it at something close to reservoir pressures

if you drop the casing temperature to -50C by pumping in LN @ ~-200C, it could well shatter what's probably stainless steel under the pressure/temperature stresses
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Re: Gulf of Mexico oil rig accident

#8  Postby Dudely » Jun 17, 2010 5:09 pm

They knew it wouldn't work, but they had it lying around so they thought they'd try it anyway.
This is what hydrogen atoms do given 15 billion years of evolution- Carl Sagan

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