#  > Petroleum Industry Zone >  > Reservoir >  >  >  Decline Rate, %??

## petengr

In decline analysis, I used to get the decline rate like (number/year). Can some one tell me how to get in Percentage, like (%/year).



Thanks!See More: Decline Rate, %??

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## Yengineer

If your production is Q and the decline from year to year is dQ then dQ/Q*100 is your decline in percentage.
This is how I recall from quite some time ago, get it with coution.

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## i-anuar

just a reminder to change from nominal (exponential DCA) to effective decline

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## petengr

thank you Yengineer!

I'm using equation like D= ln(q1/q2) / t, where D is what called as "Nominal or continuous" decline rate. now, is multiplying the output(D) by (100) will result in Decline rate expressed in percentage, giving that t(years).

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## petengr

Thank you i-anuar for the reminder! I came across this equation [D = -ln(1-d) ) ] where: D is nominal decline, and d is the effective decline. Does that translate your reminder?

Thanks!

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## i-anuar

Hi Petengr, yes that is what i meant. [d = 1-e^(D)], where: D is nominal decline, and d is the effective decline (both either annual or monthly). Good luck!

ps. attached file i compiled from few sources on DCA

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## REGI_MAX

Boys, theory is good the real data much better;-) take a look on your CumProd data last two years dQ/Qj-Q(j-1), then you already know where the trend is going. DCA was done for the really big fields!!! where you have long production time.... for the small fields I recommend to take a look on the last two years, then take decision for the next year. It is more realistic. :Encouragement: 

 I am not reserves seller ;-) :Mask: 
Regi

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## REGI_MAX

Boys, theory is good the real data much better;-) take a look on your CumProd data last two years dQ/Qj-Q(j-1), then you already know where the trend is going. DCA was done for the really big fields!!! where you have long production time.... for the small fields I recommend to take a look on the last two years, then take decision for the next year. It is more realistic. :Encouragement: 

 I am not reserves seller ;-) :Mask: 
Regi

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## petengr

Thanks All!

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