Lufkin Sucker Rod Pump Speed

[denniskb]

I need to determine the maximum rod lift speed of a sucker rod pump as a client has wells which trip on restart while pumping 100% liquid. I believe it may be the friction in the flowline when filled with liquid that is causing the trips. On normal operation they are fine as there is gas in the production.
I believe that the rod motion is probably sinusoidal and that I can find the velocity directly from the stroke and period i.e Max Velocity = Stroke / (2 x Period).
From this I will find the maximum flow as Max Flowrate = Max Velocity x Annulus Area.
I need to be very sure that I have determined the correct velocity and flowrate and would like to confirm my assumption that the motion is sinusoidal.
Are there any other known causes of re-start trips that I should check out?

 

your proposed solution is interesting.

motion is almost sinusoidal at surface, allowance for friction of rod string on tbg, rod stretch, and other factors also are necessary.

also, you don't mention composition of 100% liquid phase on start up, i.e. what percentage is h20?, what is gravity of oil?

unless you're dealing with a really big pumping unit or microscopically small piping fluid friction is not a significant factor.

 

[denniskb]

I was too quick writing the original query.

The formula for rod velocity is found from
Angular Velocity = 2 x Pi / Period
and
Max Velocity = Angular Velocity x Stroke / 2
therefore
Max Velocity = Pi x Stroke / Period.

I now have information from Lufkin which confirms the movement is very close to sinusoidal.

mppeca:
Your comments are significant if I was trying to find the loads on the pump. I am working on the wellhead pressures during operation which will directly reflect the flowline losses and discharge pressure. Dennis Kirk Engineering

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