Help in calculating pump dynacard from surface data.

[Nilesh]

Working on calculating pump dynacard from surface data by solving wave equation using finite difference method. (Sandia Data is used). I have calculated damping factor considering net stroke length and number of iterations (10) is decided on the considered rod element length (271ft) and the total sucker rod assembly length (2710ft). I have considered a uniform rod string. My final pump dynacard obtained is distorted and does not resemble with expected dynacard. Please advise where I have gone wrong and if the calculations are right. I am attaching link to my calculation file for your reference. Also if anyone have idea about Gibbs Method, please share your insights. Link to my calculation of pump dynacard from surface data. https://drive.google.com/open?id=1Pf2ib ... zkyN6RNGzZ

[bebopetro47]

Hi Nilesh! I am also working on a similar spreadsheet but still couldn't work it out. By looking at yours, i found a mistake on formula column T, as it uses the incorrect nodes for the calculation. Still, with the correction in place, it didn't solve the issue.

I don't know about your dataset, but you need it to be evenly time-spaced. If that is not your case, then you need to create an evenly-spaced time PR position dataset and interpolate loads on the PR from your dataset. You can consult the works by Svinos (SPE-12201) to prepare this dataset.

Let me know if you finally make it work!

[Nilesh]

I have rectified that mistake and also tried to find the solution with different number of iterations (satisfying the stability criteria) but the calculated pump card is still not satisfactory. I am already using Sandia data which gives evenly spaced PR position and load data. Also working to find a solution using Gibbs Method, but haven't achieved any success yet.

Thanks for replying and do let me know if you find the correct solution.

[bebopetro47]

Hi Nilesh! I finally found the solution to with the Everitt-Jennings method. Here are some pointers that might help you:

1- remember to invert surface position (after all, PU kinematic and wave propagation use opposite reference system). Just multiply by -1.
2- I made a lot of timesteps/nodes: 720 timesteps / 100 nodes. I'm sure this can be optimised, but still working on it
3- Once yo have the pump loads, you have to correct the value by subtracting the weight of the rods in fluid (considering you haven't done already)
4- to chart pump card, re-invert the position vector (again, multiply by -1)

I have been testing with some field data; also with the sandia data; and it's working quite good. Still have to program the iteration on dampening factor though.

Hope it helps!