Pump Jack Power

Are the motor starts causing the 100 amp jump in load? Is it a varying load on the motors? what is happening?

you sound like an ad for a UPS system to me

With out further explanation this comment is not helpful

tell ya what, when you get my bill just toss it, this one is on me

Many comments made here are not helpful.

It's kinda like the price of admission to the forum.

The motor overload cause should be obvious to even the most casual observer: You need a second mechanical counterweight, or a larger motor/generator.

I know, I know, not very helpful, but people have been dealing with this problem ever since electric pumps have been used on oil wells.

What do the knowledgeable in your industry do?

Yes I know, electric pumps have been used on oil wells for a long time, although not too often powered by a small onsite generator. In response to your last question, the knowledgeable people in the industry struggle with the same thing as myself. Or they just don't bother. To add to that I am looking for answers specifically from knowledgeable people in my industry. I take some offense to most of your comments above lyn, but what do I know, I'm clearly not as bright as an average casual observer. Maybe I should ask one of the knowledgeable people in the condescending industry.

I guess my point is that you will not find many "knowledgeable people in my industry" in an engineering forum that does not specifically cater to the petrochemical extraction, or "down-hole" technology sector.

These pumps and their cyclical power demands are well known and, apparently, tolerated throughout your industry. I'd devise a means to use the idle motor power to energize a spring/flywheel/hydraulic accumulator that would give a mechanical push during the 1/4 cycles when the load is high and the motor needs help.

Good luck.

Thank you for your honest answer. I'm looking for help with a "power" problem - a constantly changing load on a power source that doesn't like that - Kinda right in the electrical engineers wheel house one would think. Not to mention I'm sure there are some engineers in this forum that do work in the "oil and gas" industry. Thanks for the luck

I'm looking for help with a "power" problem - a constantly changing load on a power source that doesn't like that - Kinda right in the electrical engineers wheel house one would think. Not to mention I'm sure there are some engineers in this forum that do work in the "oil and gas" industry.

You are apparently looking for a miracle. One of the few drawbacks of electrical power is the difficulty in storing it. Fredski's suggestion of a UPS is not actually that far off in that it is the only ELECTRICAL solution available, and you came to an ELECTRICAL engineering forum. Other respondents have tried to let you know this is akin to a common issue faced, and accepted, by users in this specific industry for years, yet your attitude seems amazingly defiant. That's actually OK, I get it. Many of the world's best inventions are the result of the defiance of someone refusing to accept the status quo. But my suggestion is to avoid getting so close to belligerence, that's a cliff that once you step off of, you cannot get people to follow you over. OK, chastisement over. Now to your problem.

I too have had some experience in jack pumps and VFDs, including those powered by portable gensets. Here in California, a lot of old well sites that were abandoned when crude was $33/bbl became suddenly interesting again when crude was $120/bbl, so people were scrambling to pump fast before it dropped again. But our utilities, PG&E and SCE, were taking 12-16 months to drop a new service because air quality regulations and a drought had all the farmers forced to replace DGs with electric pumps, and the utilities couldn't keep up. So a lot of jack pump sites had to use portable gensets, even though they were limited to 3000hrs/yr.

But still, I have never seen this problem. So in analyzing why that might be, I come to the conclusion that I have never encountered one where the genset had a turbo boost. I actually have no direct experience with that, but I have to ask, why is there a turbo boost on a genset? My theory is that someone KNEW there was a problem with the cyclical nature of the load, but were attempting to solve it by utilizing a generator that had a steady state output that was barely adequate (likely to keep the cost and size down), then added the turbo boost feature to compensate for the cycling of the peak loading. I'm no ME, but I have friends who race cars. As they explain it to me, turbo boosting a combustion engine is a SHORT TERM strategy to solve OCCASIONAL peak loads, such as passing an opponent, but is well know to cause engine damage. They make a conscious choice to sacrifice engine life in a race in order to win, but they are not in it for the long haul, that's why they rebuild their engines after every race! So my thoughts are that this is a flawed concept from the outset.

So back to what I call "solutioneering". I feel that there is little that can be done from a strictly electrical side of this, short of a UPS, which I'm sure is untenable. But from my experience, a flywheel as mentioned previously is the kind of simplistic and workable mechanical solution that has been used for things like this for ages and ages. The NG genset people may not like it, because it renders their turbo boost as a useless waste of money, but that is not the problem you are trying to solve in my opinion.

By the way, could capacitors help? Maybe, but only if you had a cap bank the size of a school bus (if even that size) for each pump. Your VFDs already have capacitors by the way, and adding caps to VFDs is very tricky. But caps can only store a limited amount of ENERGY, defined as power through time, and they release that power essentially all at once. There are ways to overcome that, but batteries are a cheaper and smaller solution, which is where the UPS concept came from. You would not actually need a UPS, because that is an inverter and batteries, but the VFD is already an inverter. So you can, in theory, hook up a large battery bank to the DC bus of the VFD to make this happen. This by the way has been tried in your industry, but for the purpose of braking screw pumps (longer story). The thing is, it was totally impractical, nobody would maintain batteries in an oil field application. They want to install it and never look at it again until it stops pumping, then get mad at everyone because the cash flow stopped. But you probably already know that.

Thank you very much for your honest and helpful post. I know I was bordering rude to some replies, but only the ones that felt like a personal shot. I was excited to find this forum as I thought it would be very educational. Some of the ideas people offer may not make sense but I appreciate all who offer them.

That being said, I was being honest with fredski and welcomed some more info on the ups, just not sure why I sounded like an add.

As for you Sir, you are basically spot on with all of your comments. I believe there was no real care or consideration put into the purchase of these gensets other than the cost and the nameplate rating. I personally would have killed the idea of purchasing 50 gas engines with turbos that are to be use on continuous duty (with varying loads). I beleive that if we had natually aspirated engines they would atleast prove more reliable. As you can see from the above "50", I am now stuck with solutioneering.

So I had the same thoughts about the caps releasing energy too quickly, and I think that due to the long stroke cycle they may actually make the problem worse.

And I feel the flywheel may face the same challenges.

Have to go but thank you again for the helpful insight.

Who's VFD are you using? The reason I ask is that some VFD mfrs, especially thosed used in oilfields a lot, have adapted "macros" in their firmware that are specifically for highly cyclical loads, in fact some mfrs, such as Allen Bradley, even call them their "Pump Jack feature". The purpose is actually to solve a different problem, that of the down stroke of the counterweight causing regeneration in the VFD that causes the DC bus voltage to build up and trip on High DC Bus Voltage. What it does is to modulate the torque producing elements of their vector algorithm within each load cycle, so that it only produces the exact amount of torque in any point in the curve, but also anticipates the carryover effect of the counterweight and reduces torque producing current just before the apex. Like I said, it's a solution for a different problem, but I am wondering if it might have value here as well, by maybe "softening" the cycle a bit through a reduction of the amplitude of the peaks of the load on the genset. Just a wild thought, but might be worth buying one as an experiment.

The varying load is caused by the changing positions of the counterweights on the pumpjack. When the weights are near vertical there is not much power required to turn the jack. When the pumpjack is lifting the weights or the rod it pulls hard on the generator.

Sounds like you need to run them with larger generators. Right now you are cycling them from zero load to near 100% every 5 seconds. No gen set is going to like that sort of long term loading work.

The NG fueled gen sets I have seen around the Bakken wells here in ND were running 180 - 200 kw or larger gen sets on the larger pumps with the 50 -75 HP electric motors which I suspect has to do with the highly variable load cycling issues you are seeing.

Some well sites run the pumps directly off of NG fueled engines skipping the generator - VFD - electric motor concept all together in the very remote locations.

Just my thoughts and observations.

Thank you for your help Tcmtech. The problem I see with larger generators is that we are on the low end of total loading as it is. It is just the majority of no load followed by brief moments of high load during the lifting of the weights that is the issue. The other problem is that the load varies over time due to changing fluid levels and waxing on the rod string making it nearly impossible to keep balance. As for the old gas engine prime mover, I like them, but oil companies need to optimize everything these days.

check wethear genset is protected with all possible faults..

I suspect it's that peak load point issue for why the gen sets I have seen around here being considerably over sized for what work they were doing.

I don't recall ever seeing any NG powered units having turbos though but every one had large 100 gallon plus auxiliary oil tanks and automatic oil level control systems on them which makes sense when they are being ran 24/7 off of the well gas as a fuel source.

As far as the direct engine drive systems go well they are alive and well here in our oil fields! I have seen a few semi loads of brand new well pump engines going through town in the last few years. All of them look like the massive 1920's and 30's Fairbanks Morse and Atlas single cylinder hit and miss engine designs. Simple, rugged, reliable, efficient, and apparently very low maintenance. (Yea I want one.)

Did you try a flywheel?.

Is this standard practice to run a VFD controlled motor on a pump jack? Is the VFD there to control speed? Which maybe the problem. Since it was more likely design to run off the grid sharing power on a distributed load. Which maybe an option for you larger Gen Set running multiple Jacks.

You have a motor which draws a steady load thru the rotation of the pump jack except at two points when the counter balance is top or bottom.

I would also look at the possibility of changing the gearing. Since you can change motor speed. It maybe able to cut the duration that the motor draws 0 amps so the Gen Set doesn't have time to react.

No, I don't think it is standard practice for the generator VFD setup. I think if it was, manufacturers would have more answers to our questions. The reason for this set up is to have the capability to monitor and control these pump jacks from basicaly anywhere in the world. So now corporate can have a look from the comfort of their office in the city. The other factor that compounds our problem is winter temps down to minus 40c. This makes it very hard on an engine running a partially loaded as it can not get up to proper operating temp. I will be trying to gear one down and speed up the VFD tomorrow. Hopefully it responds surprisingly. Thank you

let us know if it worked

This is and old post that I am answering.

When running a pump jack with a vfd from shore power or generator set.

Overhauling loads are a big issue there are a couple of workarounds that you can do .

First one is go to the next bigger size vfd in the motor type set it at svc.

Then set you max frequency to 73 hertz. The second thing you could do is purchase a Schneider electric atv71 series this unit has electrical network adaptability. When this feature is active it will decelerate the load to keep the current draw even on the generator set. Installing a vfd on a pumping unit is not a plug and play installation.

I just got back from a well that is pulling 36 amp on the pull stroke and .5 amps on down stroke. It currently has altivar 61 rate for 40hp and motor load is 25 horsepower.

Remove the mother of all problem ..................'Counter weight'

Removing the counterweight would simply leave you fighting the weight of the rod string and fluid weight.

Not the answer to your question... but change to progressive cavity pump? the workover may be cost prohibitive tho

Would that be a down hole pump. We pump our water up using electric submersible pumps and it think they work very well. I've asked a few of the old guys in the industry why we need to have 10 tons of steel above ground to lift oil, and the answer that shines through, whether they say it or not, is usability. I will be doing some more research in that direction, as I think the technology has come a long way. Could you explain the progressive cavity pump a little more? Thanks

I work for a small oil company in Alberta. We have many remote sites that require us to use Natural gas Generators to power our VFD controlled electric motors to drive our pump jacks. The problem we have is a large variance in load. Over the course of one 10 second stroke we may see up to 100 amp draw then to zero then back to 100 amp then zero. This causes us great issues with our generators burning oil, taking out turbos, and overall be very unreliable. I need some suggestions on how to stabilize the draw on the generators. We have 480v, 125kva gensets driving 75hp motor depending on loading. Would capacitors help at all. I've considered a resistive load bank but worry that it may overload the generators and I would rather not spend money just to heat the outside air. I appreciate any help.

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Response: I am not sure if you ever received a satisfactory answer to your question, but there are VFDs available with software that levels out the pumpjack load that the generator "sees". The speed during every cycle is varied so that the load is leveled out. You set the average SPM (strokes per minute) to what you want (say 4) and then the VFD during any stroke will vary from zero speed up to say 10SPM instantaneous to level out the load. You set the maximum speed so as not to over stress the rods or put them into compression.

Dear something clever and terry, I have recently been exposed to the same issue that BP is struggling with. Seeking a potential market entry point for our novel generator design, I assume that the power cycling dilemma has not found satisfactory solutions. VFDs are bandaids but don't address the core problem yet add complexity and reliability issues. Capacitors are technically feasible, excellent to extend the life-time of batteries, but not a reliable solution for harsh, high-voltage environments and critical power. I propose for a couple interested parties to co-fund a solution we have on the drawing board that can deliver a solution on multiple challenges: a) store and release full-power between 5 and 30 seconds without batteries or capacitors. b) output 3-phase 480-V grid-synchronized power without inverters. c) utilize multi-fuel, potentially co-generating, micro-turbines that work with dirty gas. Our high-speed generator design is combining the most reliable, ocean-rated aircraft generator architecture with the most powerful motor design used for military rail guns, integrating motor, generator, and flywheel energy storage functionality. Consequently, there is little technology risk. If you look up our team (former Sundstrand, Honeywell, and Texas Instruments) you will realize the caliber of our team. We already working with a micro-turbine partner, and the smallest possible design is 15-kW, scalable to 100, 200, possibly 500-kW with minor design changes. A few pieces of information would be helpful for finalizing the solution: a) what does the actual power envelop look like? Is it sinusoidal or distorted? b) what is the maximum peak power it has to deliver, particularly during start-up? c) what common sizes (i.e. 75HP prime mover, 125kW generator, etc) are currently being used and d) how many generators are used per well, or well-site? For this exciting business opportunity at a timely point when oil prices put operating cost pressure on higher-cost producers, we also need a business dev/marketing exec to guide our channel strategy and a few strategic investors. Easy to find us when you google my username. Send me an e-mail to further discuss offline.

dear frnd,

the solution of your problem is sector gearbox. this gear provides constant load on motor and motor power also converted into power fluctuation then provide to pumpjack, as suction and discharge stroke requires. this is a new technology patented recently in this year.if u required this gearbox contact us.my company makes this type of gearboxes.

thanks

himanshu poonia

himanshupoonia257@gmail.com

+917665719449