gas well deliquification using PCPs 1

[koma72]

Gents,
we have a gas field with a quite active aquifer. Currently we try to produce out of it using PCP. Unfortunately we failed twice. The first time the PCP broke after 2 weeks operation and the second time after 4 hours. The first time, the explanation that we got from the vendor, was that the elastomer and the rotor were selected wrongly. This time I don’t know what is going to be their excuse. Dose anybody know a proper vendor with big experience in gas well deliquification using PCPs preferable in Europe

 

[yimc]

Koma72, please advise a couple of parameters on the well. Is it producing water with any oil? Generally oil in conjunction with water will make the pumps last longer as the oil tends to lubricate the elastomer.

How much gas does it make? We have found that, if it is 100% water, the amount of gas produced with a PCP is reduced significantly, as there is little cooling effect on the elastomer from the water. Our rule of thumb is less than 4E3m3/day however we have had some success running with a greater gas volume if the pump is run slowly enough.

When you say that the PCP broke, do you mean that the elastomer failed, or that the rotor broke/got stuck?

How fast are you rotating the PCP? Again, higher rotational energy translates into higher temperatures to the elastomer. Perhaps look at a larger size PCP and slow the rotation down a bit.

I don't know who your vendor is, but they need to be asking some questions about gas composition and water analysis. If the gas is primarily methane (say 85% or more mf), you may be OK, however, if there is acid gases present, then elastomer selection becomes more critical. H2S and CO2 in an aqueous environment tend to be "more polar" and this results in a greater degree of swell in the elastomer as it more closely mimics the behaviour of water - and since your elastomer is most likely hydrophillic, this can exacerbate your elastomer swell and resulting excessive friction.

Lastly, this is not a plug for a product, but A VERY GOOD resource is the technical resources group (Lonnie) in Edmonton, Alberta, Canada. You can contact them at (780) 417-4800.

 

[ppata]

Dear sir,

From my point of view a better way to solve your water problem it will be to use a foaming agent and the gas will lift easier that new formed foam.
The usage of PCP in this case might be unfortunate because you must have a verry good control of your dinamic fluid level in the borehole, and through the a contiouus calculation of the dinamic pressure gradient to set the PCP rotation level.
If you need other detail contact me.


Best regards,
Andrei

 

[zdas04]

One clarification on the above. Water does a reasonable job of cooling a PCP, the problem is that water is very poor at capturing gas. Oil is very good at capturing gas an a large quantity of gas will be disolved in the oil, lowering the pump backpressure and making things work well. The same amount of gas in a water system will turn your pump into a compressor (with all the attendent heat of compression that cokes elastomers very quickly).

Foamers only work when there is enough flow energy at the BHA to activate it. I see a lot of problems caused by foamers that never become foam. Activation is the one issue that causes the most problems with foamers in gas-well deliquification scenarios.



David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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