use gas lift pump on BP Macondo blowout? 4

[Windward]

To capture the leaking oil and gas until it has been stopped, would a gas lift pump work? There is about 40% methane by mass in the leak. This high percentage of gas would create a very powerful gas lift.

Direct the leak -that is, after the oil/gas has left the wellhead and is in the water at the 5000 foot depth (in other words, I am not suggesting using gas lift in the well itself) - into the open bottom end of a pipe running down to the leak from a salvage vessel.

Once this flow starts moving up the pipe, the highly pressurized methane will continuously expand because the pressure above the mixture is constantly falling. This will reduce the average density of the mixture in the pipe. At steady state flow, it will be much lower than the density of the seawater outside of the pipe.

It would be a giant chimney but with a much greater driving force than if the fluids were gases only, because of the much greater densities and the much greater difference in those densities. If the average density in the pipe is 4/5 that of seawater, the driving force at the bottom of the pipe would be more than 400 psi.

The oil/gas/water mixture will exit the pipe at high velocity at the salvage vessel, perfect for separating the liquid from the gas in a cyclone.

No outside power needed, equipment far simpler and cheaper than what they have been trying.

I know that word - CLATHRATES. They will plug up the flow! But will they, with 400 psi driving it? And if they are a problem, do what they are doing with tophat and put some methanol into it, or some warm water. Not hard when we are looking at the complete destruction of marine life in the Gulf of Mexico and the consequences of that.

 

[BigInch]

"The claim that the pipe would collapse from steam condensation is just wrong."

Sorry, but that quote is complete rubbish and makes me highly suspect of the rest of the content.


"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[zdas04]

Windward,
When I said "People" don't realize how big a heat sink the ocean is, I meant "people" in the generic sense--as in it is difficult to accept how big the heat sink is.

I didn't work on the project I referenced, one of the Engineers who did work on it related the results of their thermodynamic model over a beer after class. He was a pretty sharp guy with no reason to lie to me. He also had the material specs on the jacketed pipe that they were considering, I don't. My guess is that his analysis was faithfully performed and the results that he reported included a competent review of that data. I'm sure that you know more than he did so I'll withdraw from the discussion.


David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"

 

[Windward]

Big Inch, thanks for the warning. I return the sentiment.

If you would analyze the system, you would see that I am correct. I did prepare an explanation, but it is long and boring and I will not inflict it here. If you want to prepare a long and boring explanation, I will read it to see where you went wrong.

David, I am hoping Big Inch comes through. After all these years, you will have a definitive answer to that classroom problem.

 

[docellen]

Windward, The good stuff is at:

http://www.energy.gov/open/oilspilldata.htm

There are two links at the bottom of that page to PDF files on the LMRP system and device. The second one has some interesting drawings.

There are a bunch of other links to good technical info in the old Wikipedia article, which is now preserved in the original authors sandbox. See the top link on the discussion page for the article "Offshore oil spill prevention".

The problem with the original article seems to be less interest in engineering, and a bunch of folks wanting to push the article in a different direction.

 

[docellen]

It seems to me the explanation for not shutting the vents and reducing the leakage to just what comes out around the jagged edge, can't be right. We know there is positive pressure in the top hat (in spite of the gas lift from the expanding methane). So shutting the vents will only raise that pressure, making it *less* likely that water will get in.

On another topic, has anyone seen or heard of a well with multiple wellheads? That would allow them to relieve the pressure on the main wellhead while fixing the BOP. All it would take is some extra piping, not extra drilling. Too late for the current disaster, but it might help the next time a BOP fails.

 

[BigInch]

This thread just crossed over.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[DrillerNic]

Windward, when we talk about shifting gas like oxygen, volumetric and pressure flows are more useful than mass flows.

12 tonnes/ hr of O2? What's that is terms of volume? Well, 1 mole of O2 is 16g so 12 tonnes is 750,000mole, molar volume of an ideal gas is 24.46litres (Google is your friend!) so so that's 18,345,000litres / hr (18,345m3/hr or about 250,000scf/ hr of oxygen that needs to be compressed to about 2,200psi .... I'm sure there's a pipeliner on this boards that can help me out, but those look like quite large numbers, and I'm guessing you don't get a compressor capable of 20,000m3/ hr rated at 150bar in less than 6 months lead time!!!!

 

[zdas04]

A mole of O₁ is 16g, a mole of O₂ is 32g. You need to double all your numbers.

Also, you either need an air plant to extract 500 MCF/hr of oxygen from air or you need to inject air. The lead time on an air plant is years, so plan on injecting air. Multiply the doubled value by 5.

Now you either have to have REALLY big pipe or accept that friction is going to eat a lot of your pressure at that sort of flow rate and assume that the surface pressure is 3500 psi. That requires a 4 stage recip compressor (or more likely a 6 stage centrifugal or axial) and around 600 hp/MMCF.

So to move 60 MMSCF/day of air to the sea floor would require something like 36,000 hp. Not a small compressor station. The air permit alone would require 2 years under normal circumstances. Which isn't a problem because compression hp that specialized and that big would take 2-4 years to acquire anyway.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"It is always a poor idea to ask your Bridge Club for medical advice or a collection of geek engineers for legal advice"

 

[Windward]

Good points, DrillerNic and David, although I believe the objection concerning lead time for equipment should not be a concern, as I will explain.

Suppose we start with liquid oxygen. Many plants already in existence could supply twelve tons per day, and a tank could carry that much on a service vessel.

At the leak site, use the heat from the flare to expand the LOX into the injection pipe. This would eliminate the compressor, but it would require a pump for the LOX to generate the injection pressure. Is there such a pump? It would be like the feed pump in a Rankine plant.

Suppose it would be better to use a compressor after the LOX has been vaporized. In this emergency, perhaps one could be found right away. In my time with Rolls Royce, we sold a lot of RB211 compressor units of at least 36000hp, but I was in the engine division and don't have much knowledge of compressor capacities. David, some of these units were for sending raw gas ashore for processing. They were high pressure drum types. The centrifugals for pipeline service would have too low a pressure ratio for this job. Would a drum type produce the pressure and flow?

This is all supposing. Probably none of us have the time, much less the resources, to determine whether this idea would work. I appreciate your input and hope you will stay with it for awhile. If the idea is worth a try, it would take some equipment, but look at what they are deploying now to capture only some of the oil, and the situation looks like it could get a lot worse. What do we do then?

docellen, thanks for the links, I will be looking at them.

Big Inch, I like the graphic. Can we overlook the recent unpleasantness and have your expert opinions here?

 

[waross]

From the latest accounts we may have multiple wellheads. Unfortunately they don't have any hardware on them.
Windward. The great problem with solving the problem is finding out what the problem is. I believed that it may be possible to completely close the BOP. It possibly is, but bp didn't tell anyone in a timely fashion that they suspected a bad casing. Knowing that, it may be safer for sub sea bed conditions to increase the flow of the BOP. Given the latest postings, it may be too late.
Re the gas lift. I have trouble understanding the need for a gass lift. There is ample pressure in the well to move the oil to the surface.
In a shallow leak, and low pressure oil, a gas lift may raise the oil from the sea level to the deck of a collection ship.
Hydrates are a problem when water is present.
We don't know if there is water in the oil or not. Given that the production from the latest kludge seems stable, I doubt that there is much included water.

Here, as information comes out in little bits and drabs, the limiting problems now seem to be:
1> The casing is compromized below the sea bed. More flow through the BOP is better than less flow.
2> bp believed their own estimates and do not have enough surface facility to handle any more oil than they are presently collecting.
3> I can't see wasting time and equipment to bring any more oil to the surface when they don't have a pot to hiss in. Well, it may be better floating on the surface than drifting in a cloud below the surface, but you get my point.
When they get enough surface capacity to handle the flow, I am sure that they will be able to collect almost 100% of the oil that is leaking from the BOP. If they are able to increase the flow so as to reduce presure on the compromised casing they will probably do that as well.
Now if they reclaim the concrete mausoleum and fill in the side holes to prevent the ingress of sea water and open the top a little, they may be able to drop it over one of the seaps to collect that oil. A gas lift may be useful there. Adding a LOX burner to clear any hydrate buildup may be useful. I surmise that clearing any hydrates resulting from entrained water will be much less burden than clearing hydrate buildups resulting from the ingress of sea water.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Windward]

waross, roger on the multiple wellheads without BOPs, and what do we do then? The only thing we can do is capture the oil after it is in the water. Do we capture it immediately, or let it spread out and kill the GOM for an even longer time?

I know this thread is long and previous posts forgotten. I proposed this gas lift idea for catching the oil after it is in the water. If they can cap the BOP and direct the oil to the surface, the pressure in the reservoir will provide the driving force as you say, aided by the gas lift that also occurs in that case. The gas lift I am proposing would be for the oil and gas that escapes into the water, where the well pressure is useless.

There is probably very little if any produced water, from what I have read. The oil that is still leaking into the water does prevent any seawater from entering the flow up the riser, which would probably clog with hydrates otherwise.

If BP does not have enough lightering capacity yet, shame on them, but now they have permission to burn the oil that comes up. It seems to me that the best way to get all of the oil up, especially when there is no hardware below to latch on to, is to install a gas lift pump. Got to deal with the hydrate problem in that case. The controlled fire is the best thing I can think of, and I do not know if it would work. It seems possible, since it works with oxy-acetylene torches under water. Thanks for a good post.

 

[DrillerNic]

zdas04: "A mole of O1 is 16g, a mole of O2 is 32g. You need to double all your numbers."

ooops... well I just make holes in the ground... I'm not a process engineer!

Windward- I know about RB211 compressors (the last offshore platform I was on had three of them for gas lift and two enormous John Brown frame 7s for the gas export line to shore)... but you don't get them off the shelf do you?

It would be very hard to put multiple wellheads on a single well- the wellhead has to hold and seal the casing and there's only one set of casing strings per well...

One of the questions about this blowout is the failure of the BOP system. The Deepwater Horizon's BOP had two annular preventers, three pipe rams with variable bore rams, a casing ram with 7" rams a blind/ test ram and a Shear/ blind ram. None seemed to close (or close fully) when the ESD switch was actuated from the bridge. Neither did the LMRP disconnect from the top of the BOP when the ESD switch was hit (imagine if at least the LMRP had worked- a lot of oil spilling into the sea until another rig arrives, run a new riser & LMRP onto the BOP, engage, and breath a sigh of relief.....) and then the automatic deadman switch, that should work if the BOP looses electrical, command and hydraulic communications with topsides should close the shears and the annuluars. That doesn't seem to have worked either.

So why not?

 

[Windward]

DrillerNic, I would like to know the answer to the BOP failure also. Some posters on the Oil Drum argue that no driller should rely on the BOP. They should just follow best drilling practice to avoid the need to shut the hole. BOPs have a failure rate of about 25%, and it is not even common in the industry to test them as the regs require. So I read anyway.

On the multiple wellhead point, I believe waross was referring to the speculation, and some evidence, that oil and gas have started to come up through the seafloor at some locations away from the BOP, because of damage to the overlying layers of the reservoir or failure of the DW casing below the seafloor.

I think that if BP needed a compressor, usual lead time one year, they could get one in a few days from some rig somewhere in the world. BP certainly has a few. Their competitors should also be interested in stopping this blowout. One of them would probably provide a compressor in this emergency. If they have to shut down production to do it, they would be well paid for it.

Can you give us some details about the RB211 gaslift operation? What was the pressure and mass flow of the gas, what other equipment was needed, just a general explanation of the operation would be very interesting.

 

[Windward]

I should have mentioned that a compressor designed for natural gas may not work for oxygen. I will ask the compressor expert at RR about it.

 

[docellen]

DrillerNic, Maybe "multiple wellheads" is the wrong terminology for what I have in mind. We need some redundancy in the design of these wells, something to fall back on when the BOP fails. Surely there is something less expensive than having relief wells just in case.

Let me try again. I'm thinking of something like a TEE that is used in common plumbing, but of course, much bigger. Run a pipe off to the side, add a 90 degree elbow facing upwards, another short section of pipe, and a cap that can be quickly removed to install an emergency riser. Everything but the cap should be underground, to minimize the possibility of sabotage.

I share your astonishment that everything seems to have failed in the BOP, although it is not surprising that the shear rams failed. As I understand it, they are not rated for deepwater pressures.

Question: Why don't they have some kind of quick connection so they can apply external hydraulic pressure, and close the rams when all the high-tech stuff fails?

 

[DrillerNic]

docellen- one of the failures on the BOP was the Emergency Disonnect- which is supposed to release the riser, leaving the hydraulic connect at the top of the BOP nice and clean ready for a new BOP or riser to be run and nippled up.

If the disconnect has worked, the initial spill rates would have been terrible, but the action would have been: Discoverer Enterprise runs it's BOP and Riser over the existing BOP, latches on, energises the seal, and then either flows oil to surface up the riser or closes the new BOP. Drill the relief well to kill Macondo, and everyone goes home.

A Tee as you suggest wouldm't really work, as the flow would take the path of least resistance and continue up the broken pipe.

The issue about the shear rams isn't the water depth, but that shear rams anywhere, onshore, shallow water, deep water, are designed to cut the drill pipe tube, and not the extra thick walled bits of drill pipe at each end- the tool joints. On a 30ft piece of drill pipe, tool joints are 12- 18" long at each end- so 7- 10% of the drill pipe can't be cut with the shear rams.

I think this may change very soon...

 

[waross]

Hello Nic.
A question concerning rupture disks. I have seen and worked with several types of small rupture disks used for various reasons in surface applications.
There has been speculation that a rupture disk may have failed 1000 ft. below the sea floor. Can you explain to us the arrangement and purpose of this disk?
Thanks
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[docellen]

DrillerNic, Thanks for your excellent information on the BOP Emergency Disconnect. The best I am able to find on the Internet is a drawing of the BOP linked at

http://energy.gov/open/oilspilldata.htm.

I'm surprised that BP doesn't make more of this info public.

So I'm guessing what happened is that nobody had time to hit the Big Red Button when the fit hit the shan, and their backup plan was trashed in a pile of twisted metal. What I'm thinking of is something that will work even in that circumstance. No doubt you can think of even better ideas, but here are my suggestions:
1) Separate quick-connect nipples on the side of the BOP that go directly to every actuator in the system.
2) Clamps instead of bolts on all flanges. These should be easily operable by ROVs. The clamps should also have a well-calibrated breaking strength, so we never have to worry about extreme forces breaking something not designed to break.
3) Multiple wellheads. I'm still not convinced that this won't work. With an extra outlet to relieve the pressure, it won't take much to hold off whatever is coming straight up. You might even put the normal riser on the side connection, allowing emergency access straight down the center pipe.

If they had all this in the current situation, the action would have been: Pop the BOP, grab the drill pipe, and blow some mud as far down as it will reach. If that just blows mud in your face, pull the broken drill pipe and insert a pipe with some kind of plugs that grab the inside of the well casing, maybe one every 500 feet through the zone where the gas and oil is flowing in.

Question: How much force, worst-case does the casing and cement have to hold back? I've heard the pressure at the wellhead could be as high as 15,000 psi. On a 36" diameter wellhead, that could produce enough lift to make those steel pipes stretch like taffy, ripping loose from the cement in a thin zone moving quickly down the entire length of the pipe.

 

[BigInch]

No problem, when it gets to China, they just pipe it to the nearest power plant or build one on the spot.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[Windward]

docellen, I believe you might get a better response on your topic by starting a new thread. The design of the BOP is not related to this thread. Maybe Big Inch will have more to say there. His comments are always interesting.