how to calculate derivative of WGR as shown in Chan's Water control diagnostic plots.

[Malvika015.upes]

hi all,
can anyone tell me how to prepare WGR derivative plot without using a software.
i have seen chans log log plot in which derivative of WGR is indicates cause of water cut.(coning ,channeling etc).

Regards,
Malvika

[vinomarky]

Derivative is just the slope - calculating the slope between some points is trivial with Excel

The key with these sorts of plots though is that the base data is normally so noisy that the derivative is almost meaningless - I was on an injection well profile modification job with KS Chan once in the early 90's when he was just formulating this work, in the years since I think he has perhaps lost a bit of the optimism about applicability - mainly due to the data noise seen in most data sets. Try sensitizing on the aperture of data (ie number of data points to calculate slope over) used to calculate the slope over in order to smooth out much of the noise while leaving the underlying signature unaffected.

[reservoir_ff]

send me an e-mail to share an excel spreadsheet with Chan plots

[bayan]

Could u please share us also please
thank you in advance

[darcyoil]

Very simple. I did this in excel 10 years ago. Just take the standard equation for the derivative and set the cycle to a suitable limit so that you are masking the noise without masking the response. Make sure you've got all the negative values blocked, and plot up on a chart. I must say, the Chan plots seemed at the time like a very, very powerful diagnostic tool, but surprisingly, very little work has been done since. I ran some plots on my wells and did get interesting results. The problem for me was that I was unable to quantify. Perhaps if a bright one among us (not me!!) could push these into the analytical realm, oh then we'd have a whole new section in performance analysis going.

PS. Looked for the excel sheets...couldn't find them. Sorry.

[Malvika015.upes]

Thanks Darcyoil...
i'll try this....
Can u pls tell me that whether Chan's plot can be used for Horizontal Oil Wells...

[darcyoil]

No idea. Like I said, it was a long time ago, and I didn't spent much time on this. It was interesting though........