Artificial Lift
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Artificial lift in oil and gas production.
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What happens when we follow the well … it can flow to the surface through the pressure that exists in that formation, plus the gas that’s in solution in the liquid. It’s just like this. This is CO2 dissolution in the Coke. In oil, we have natural gas dissolution in oil. When we drop the pressure it expands, just like this. That’s what’s flowing the well up through the tubing streak. Go to west Texas.
The reservoir pressure’s very low and the oil’s dead. From the day one they have to put an artificial lift because there’s just not enough energy to flow. A Lot of other reservoirs flowing on light oil, high gas-oil ration, they may flow without an artificial lift for a year, two years, three years, before they finally have no more energy to be able to lift that fluid out of the well.
Same with gas wells. Gas wells should flow to depletion. Usually we think they will, but if gas wells begin making much liquids, condensate, water, then what happens as a reservoir pressure starts to decline, my flow rates are declining because I don’t have very much pressure in the reservoir pushing that fluid up. When the flow rates decline I can’t lift that oil and condensate out of the well. It drop out, builds up and it kills the well. If I want to keep producing gas I’ve got to lift that fluid out of the well, so, even in gas wells, I may use artificial lift.
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With artificial lift, typically, the engineer’s going to choose from four types of artificial lift.
By the way, there’s over 450,000 wells in the US and the Gulf of Mexico on artificial lift.
When we look at the types we have gas lift, we have a rod or beam pump, we have electrical submersible pumps, ESPs, and we have hydraulic pumps. If we look at those 450,000 wells on artificial lift, how does that break out? Typically, with gas lift, we’re producing about 15% of the wells have gas lift. About 80% of the wells have a rod pump or ream pumps, about 2.5% are ESP, and about 2.5% are hydraulic pumps. That’s just roughly the way to break it out. You can see that rod pumps are, by far, the most popular type of pump system that we have in the industry.
When we look at how they work, in your notes, gas lift is really easy to understand. It’s exactly what I was doing here with the bottle. If there’s not enough gas to lift that fluid to the surface, we’ve got gas available to us. One of the things about gas lifts, is that you have to have a gas system or a gas well nearby so you can have gas.
Basically, what we’re going to do with gas lift is simply replace the gas that got depleted from the oil coming into the reservoir. We’re going to supply to gas to be able to lighten the fluid and lift that fluid to the surface, so, it’s just like a flowing well, and we analyze it the same way.
On gas lift then, what we’re going to do is add valves. So there are gas lift valves we’re going to put in the tubing string, like this. When we’re producing the well, only the bottom valve is open. We have to have a source of gas and at the well head … or the facility rather, we got to have a compressor to compress that gas to a high enough pressure that I can push it out through the well. Now we’re going to inject the gas down the annulus. That’s the area between the tubing and the casing. We’re going to force the gas down through there.
Notice I’ve got a packer right here. A packer seals off the well-borer so the fluid below can’t go in the annulus, between the tubing and packer, and the gas coming out of the annulus doesn’t go around the bottom of the tubing string. We force it in through these valves. Now the valve is spring loaded. It has a designed opening in it so that it doesn’t open until we have sufficient pressure.
When we supply sufficient pressure inside a bellows that’s charged with nitrogen, when we increase the pressure it compresses, when it does it opens the valve. Then the gas can go from the annulus into the tubing string. Now the gas can come around the bottom, go through the tubing string and then it lightens all the fluid above that in the tubing. It lightens that fluid to allow the well to go back to flowing again.
The nice things about a valve is I control the opening in the size of the orifice of the valve. I control how much gas I’m putting in the well hole, so I can optimize the gas with a flow rate of oil into the well-borer. I can use that gas very efficiently. Gas lift is really good system. It can operate anywhere from 50 to about 25,000 barrels per day.
At the surface, if you’re on shore, environmentally it’s a really good system because all you see at the surface is a well head. There’s no noise, there’s no moving parts. You can put bushes around it and hide it and nobody even knows it’s there. The flow lines bringing gas out to the well can be buried. The flow lines bringing the gas and the oil back to the separator, those can be buried, so at the well site you don’t see anything. Environmentally, it’s really good.
One of the things I’ve mentioned–
[inaudible 00:05:15]
You’re starting to push gas lift, trying to go higher than that. The problem with that is that you’re getting into bigger tubing sizes. When getting into bigger tubing sizes it’s more difficult to get gas to do a good job of lifting the liquids.
[inaudible 00:05:27]
That’s a percent, yeah. Gases, well … artificial wells … All the wells on artificial lift in the US and Gulf of Mexico is about 450,000. That’s the break out. About 80 to 85% are on beam. 10% or so … 10 to 15% are on gas lift and then the rest are split between ESP and hydraulic.
Now, the other thing I did mention, off-shore. When we go off-shore, what are first are … are the wells off-shore on artificial lift? The answer’s, “Sure.” Same problem. I don’t have enough pressure, I don’t have enough gas. They stop flowing. Off-shore, we don’t have enough room on the platform. Off-shore, about 97% of the wells are gas lift and about 3% are ESP.
The first one is gas lift, relatively inexpensive to install. Now, it’s expensive if you only have one well on gas lift, because I need a compressor to bring the gas out to the well and compressors are expensive. If I have 6 or 10 wells, then it’s a very economical system. I buy one bigger compressor, allocate the cost of 6 or 8 wells, and then I can distribute the gas out to those wells. The two things is I’ve got to have is, usually you want to treat multiple wells and I’ve got to have gas available for this to work.
It’s a good system, it works really well, only one drawback to it. Notice that I have gas and liquid all the way from bottom hole all the way to the surface. Lets say I’m at 10,000 feet. A liquid gradient for oil is about .3 psi per foot of depth. I’m going to add a lot of gas to it though, so, let’s say that the gradient, the gradient is how much that liquid pressure, how much hydrostatic pressure that liquid is creating.
Let’s say that I’m only at … I had enough gas so I get that to .25 psi per foot. Well, notice down here in the perforations, that’s 2,500 psi. That’s the pressure at the bottom of that fluid column. That’s the pressure right here. When the reservoir pressure’s 4,000, no problem, I’m flowing. But what happens when the pressure get to 2,500 psi. You’re done. At 2,500 psi you’ve left a lot of oil and gas back in the reservoir.
That’s one of the reasons we don’t see gas lifts as any more popular than it is. Typically, when you go into a typical field, particularly on shore, you’ll start off flowing. It might flow for a year and then you’ll put it on gas lift for 3 to 5 years. Then you put it on beam pump for 10 years to take it all the way to depletion.
How does a beam pump work then, when working with a beam pump?
It’s just a rod or a beam pump. The way this works is very similar to a syringe and a needle. You ever had a syringe where you want to put medicine in it? You push the plunger all the way down, put the needle in the medicine, pull up on the plunger, you’re pulling medicine up into the syringe. Same thing with a beam pump. When you look at a beam pump … This creates reciprocal action.
The pump is actually at the bottom of the hole attached to the rods that you see coming out of the well. The rods then are attached to the pump, and right here’s a pump barrel and then this is a plunger right in here. That’s a plunger. Just like a plunger and a syringe.
When you see the horse’s head going down, inside that pump barrel, at the bottom of the tubing string, the plunger’s going down and there’s no production. Now, when the horse’s head is starting up, then the plunger’s coming up. As the plunger’s coming up, and the horse’s head, it’s doing two things. One is, the tubing is full of oil. As it’s coming up, it’s lifting all that oil up the tubing, down the flow line and into the separator. At that same time, in the pump barrel below the plunger, just like that syringe, when the plunger comes up it’s creating a very low pressure and it’s sucking oil up into the pump.
There’s a check valve on bottom. It opens up, lets the oil come in, horse’s head starts down, the check valve on the bottom of the pump barrels closes, the check valve on the plunger opens, so the plunger can go down to the fluid, and do it again. When you drive by and the horse’s head is doing this, no production. This, production. No production, production. No production, production. Ever go by with that? That’s no production, that’s not good.
One of the nice things about beam pumping, though, is … I set it on a clock or a timer, so that, now, if I’m making 8 barrels a day … Well, 8 barrels a day, that pump doesn’t have to go like this. It’s a very [inaudible 10:09]. I can set it on a timer, it may pump for an hour, it’s got all the fluid out, and then it shuts it down for 8 hours. The fluid build back up in, kicks it back on again. It’s a very efficient way to do that.
Primary advantage to the rod pump is that it doesn’t create a suction, but it gets the pressure in the well borer opposite the perforations, down to between 50 and 80 psi. Now at the bottom of the hole, I don’t have 2,500 psi, I have 50 psi. That reservoir pressure at 2,500 psi, I’m back on production again. I can take with a rod pump, I can take the reservoir pressure all the way down to 2, 300 psi. I can still get the pressure lower in the well borer so the well won’t flow to the well-borer.
That’s why we see so many beam pumps. Remember, we said 85% or 80% are rod pumps, because the average production rate of a well in the US is only 10 barrels a day. That’s the only system that works efficiently at 10 barrels a day, is the rod pump. That’s why we want to use that. Rod pumps can work from all the way down to, probably, 8 or 10,000 feet. At 10,000 feet you’re pushing it and deeper than that it’s not going to work very well at all. This can produce anywhere from one to, probably, about 2,500 barrels per day.
That’s only in vertical wells, though, right?
Horizontal wells, also.
Oh really?
The key there is, when we run a horizontal wells, and this is the most popular system in a horizontal well, you can’t run it in a horizontal section. You have to run it in the vertical section.
On a horizontal well, the well’s coming down and turning like this, I can run the rod pump, but it has to sit up here. It can’t get down here. It depends, then, on how steep that turn is. That’s a very gentle turn and I’m going from vertical to horizontal over a 1,000 feet, that means I’ve got a 1,000 feet of fluid sitting below and .25, that’s 200 feet of psi. I can’t get the bottom hole pressure down to 50, now the best I can do is maybe 3 or 4 degree psi. I have to look at, now if that’s a fairly sharp turn, then that’s okay. I’m not giving up very much to do that. Actually, although this isn’t the greatest application because I can get the pressure so low with a rod pump, that’s the most popular system in the [barnet 12:25], in the [eagleford 12:26] and the [inaudible 12:28] shale. We still can’t use it, we just have to stay up in the vertical section.
…More popular in the Middle East where they are…
Yes, yeah. Gas lift and ESP. ESPs are also a very high rate pumping system, they work very well in that application. A lot of it would be the availability of gas, and can I use the gas for something else in which case maybe I want to go to the ESP and save my gas to sell or something like that. Or if gas isn’t readily available, then the ESP would be better.
Picture of the ESP
The ESP can also get to the bottom pressure down lower. Yeah.
The down hole pump, even with the rod pump, would it be used in this situation…
To get the rod pump down to here?
Down hole pump. They’re sold as a system with a rod lift pump.
It’s a rod pump.
The Quinn, well, I would sell the rod pump and the control manager and the down hole pump with the rod pump as a system so that Quinn pump, which I know a lot less about it than I do a rod pump, it goes down in the hole and [inaudible 13:44] helping, something, so I’m thinking, is this what the Quinn pump does? Does it help push the Coke…
Is the Quinn pump ESP?
No. It’s not ESP. Two check valves.
Two check valves in it. Okay. If it’s got two check valves, it may be, it could be extended on the bottom, I apologize, I haven’t seen the Quinn pump, but it might be extended onto the bottom so you can extend it down further.
We sell systems and the system would have this other pump that would push further up so I’m wondering if it might be able to help when you’ve got this horizontal…
To help the system. Could be. It depends on how that pump is working. I have to go and look that up and see what the Quinn pump is. I haven’t run one so I’m not sure exactly how they work but…I haven’t seen one so I’m not sure what they were talking about here but if we could get something down in here it might be, and force the fluid up to the rod pump intake, that would be better.
The Quinn pump, which is in the rod, simply having a hole in the bottom and a ball, so when it’s pushing down, the ball starts to float and then when it starts with the down motion, the ball drops down in the hole and then it’s lifting the …
Gotcha. Gotcha.
That’s the motion and then the valve opens on the top and when it goes down it closes. It’s actually, it’s not sucking like in the syringe but it’s pushing down on the oil and the ball flows up and pressure, and when it stops the ball drops down to the bottom. It’s just a metal ball.
That’s the same thing it’s doing. That’s the same thing as we’re talking about, but it’s not to supplement.
…So it wouldn’t help you any with horizontal?
No.
It will not actually work with horizontal because of the pressure, the ball cannot be on the side…
It’s a gravity…
Yeah.
What I’m wondering, is I’ll bet you that’s to overcome gas logging, because what happens is if I suck gas into that pump, and I’m pumping up and down like this, when I pull up, the gas, it pulls that ball on the bottom. It can’t open to let fluid in and then when I come back down again, it compresses the gas.
Then when I come back up, and the gas expands, it holds the ball in the seat. If the ball comes off the seat and comes up with the gas, then fluid can enter and then the ball drops back down again and seats and now I’ve got the pump full of fluid. What it is, is in high gas oil ratio wells, it’s to help me overcome the gas that is coming to the pump that makes the pump operate more efficiently, that’s what it’s for.
The way these are set up on a beam pump, the pump intake is below the perforations, so the idea is the oil enters through the first, has to go down to get into the pump, when it goes down, the gas can break up and go up the annulus, so the gas is going up the annulus there. Then I bring the liquid in through the pump.
Again, the gas carried in, those gas bubbles get in the pump, at the surface you’re doing this and there’s no production because that gas bubble inside’s expanding and compressing, expanding and compressing. That would get around that. That would bring the ball off and let the fluid enter. That’s what that’s for. Good, we got that out of the way. That’s a beam pump, you get the pressure very low.
The third system is an ESP. This is an ESP pump. It has a long skinny electric motor at the bottom of the pump. Inside the pump, there’s a rotor and a stater and the way it works is kind of like a screw, as the fluid ends up, what the electric motor is doing is turning a shaft or turning this screw and as the fluid enters in these plates, baffles take the fluid and they spin it.
As they take the fluid, it’s like a plate, and they spin up to the next stage. When they spin the fluid up by centrifugal force, I’m adding pressure to the fluids. The pressure might enter the bottom of the pump at 5,000 barrels a day and 500 psi when it goes into the first stage. First intake, then spins it up to the second stage. It comes out of the first stage at 5,000 barrels per day at 520 psi when it goes into the second stage.
Then it goes up into the third stage at 5,000 barrels and 540 psi until finally it comes out of the top of the pump and I can have 200 stages in that pump which are basically like plates that are spinning, forcing the fluid up into the thing. It will go in at 500 psi, 5,000 barrels a day, it’ll come out of the top of the pump at 1,500 psi at 5,000 barrels a day so you can think of it basically as a down hole fluid compressor.
Bringing it in in a certain way, adding enough pressure to it so when it comes out, it can overcome the hydrostatic head of the fluid and the friction up the tubing to be able to force that fluid through the well bore. Again, no packer. I want the gas to go up the annulus. If the gas comes into the tubing, or into the pump, it’s going to lock up the pump and it’s not going to work very well. We need to have a gas separator down hole to separate the gas from the liquid so it will work efficiently.
When I go to a submersible pump, good rates on the submersible pump are anywhere from about 300 gallons a day to 50,000 barrels a day. ESP can go from 300 to maybe 50,000 barrels per day. We can take them down to about 8 to 9,000 feet. They claim they can work deeper than that, 10-11,000 feet, you’re pushing it. The problem there is the heat is high enough that the stater gets damaged on that.
The mature elastomers we have on the stater are damaged and it doesn’t work very well and it will overheat. With ESPs also, they’re very much rate restricted. What I mean by that is if you design it to handle 50,000 barrels a day, you better be producing 1,500 barrels a days, I said 50, 1,500 barrels a day plus or minus maybe 15, max 20%. If you’re less than that, if I’m only producing 1,000 barrels a day and I designed an ESP for 1,500 barrels a day, you’re going to burn it up, because it’s designed so that there’s enough fluid at that rate moving by the motor to cool the motor and allow you to continue to produce.
If the rate is too low, I’m not cooling the motor sufficiently and very quickly you’ll burn up and you’ll get a life on that ESP. The biggest drawback on the ESP is the electrical power, it costs a lot of electrical power and you burn out the motor so the life of the pump isn’t very long and they’re expensive pumps to replace, but if they’re designed properly, meaning they’re sized properly, that pump will last 2, 3, 4 years before you have to replace it.
If they’re over sized, the amount of fluid, and I’ve seen this happen, 3 to 6 months is all the life you get out of them before you have to replace those pumps. It’s really important to design that pump properly and the ESP. The advantage of an ESP over gas lift is I can get the bottom hole pressure down to 500 psi, with an ESP, remember with gas lift, we said this was 2,500. With an ESP, I can go to 500, bottom hole. It’s a big advantage over gas lift because of that fluid column.
What about the horizontal wells?
Great. I can put the ESP all the way here. I can operate it in the lateral portion of the flat if that’s something that I want to do. We could put it anywhere in there. We can actually put it in the curve also. We just have to make sure if you put it in the curve, that when you’re drilling that curve, this section is straight enough that I have room for the pump to come in here on the straight portion. I can put it in the curve, I can put it horizontal. Sometimes that’s useful to you.
What I find generally is it’s probably not gaining much by putting it out here on the horizontal section, you’re probably better off to have it up here someplace. You can use it anywhere, again, there’s no rods connecting it to the bottom hole, it’s being operated by electric current going down to the pump and it’s spinning the pump motor, so there’s nothing to worry about from that…
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