65 comments on An Oil Production Model from Roger Bentley
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65 comments on An Oil Production Model from Roger Bentley
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Interesting post, thanks!
It reminds me what I've tried to do a few years ago:
Convergence of the sum of many oil field productions
I also observed a Gamma distribution:
Some statistical models are also well established in geology such a Lognormal distribution for the distribution of field size. Once the triangle parameters are random variables, the skweness of the resulting production profile almost disappears:
see here for the details.
It's gonna take me some time to digest your article but from a first look it seems that there are no stochastic aspects in your model, the triangle parameters are not random variables, right?
Khebab,
As you probably know log/normal distributions also dominate decline rates for certain reservoir drives. While estimates during the early life stages can be tricky, estimates toward the far end of reserve life become virtually straight lines. Even when secondary recover efforts or additional late life redrilling takes place it usually just represents just an upward vertical shift in the trend with the decline exponent changing very little.
I was actually thinking about the potential of your knowledge base of reservoir dynamics combined with his math skills. It would be interesting to see a stepwise change in his model towards field specific modifications of some of the mega reserves that carrying much of the current output.
If well production profiles is a lot shorter than the total oil production I guess that the shape of the total oil production is almost unaffected by the shape of the production.
The long tail is missing in the production profiles. A simple approximation could be made by making the area of the current production profile a little bit smaller and adding it with a long flat triangle. This a nodal basis and it could be constructed very easy by using two hat functions and a mesh there the points are at the four years [production start, peak, tertiary recovery?, production stop].
From my experience, just getting good info on the value and the time of maximum production per field as well as an estimation of the average decline rate is enough to get a good approximation of the region production profile (see comment on Norway below). Now, you can develop a more sophisticated field model with a production plateau for instance but it does not imporve the result that much and requires much more information per field.
Agree as well. There is something to be said about not overanalyzing a specific region. The macro trends wash out any micro trends as you aggregate these smaller loglet or shocklet functions (loglet is Khebab's idea and I volunteer the shocklet to provide a mnenomic for the oil shock model)
Khebab, I always think of the simplest explanation for a 2nd order Gamma is an exponential damped maturation/reserve growth fuction convolved with a expontial damped extraction function, ala the oil shock model.
I tend to agree. This will likely be the topic of our next TOD press release.
If we're gonna do a press release I'd like to check the math before it goes out.
Deal. As long as I check the spelling.
I agree, it's an elegant and concise solution which has many interpretations.
I do not understand exactly how you and Chris Vernon has done the calculations but I got an idea.
This is the way shold have done it and will if I get enough time:
1. Do an approximation for the distribution of oil field size. Preferably by looking at produced field size in a mature region.
2. Choose a skewed triangle.
3. Let triangle area be equal to field size and delay equal to production year or use the distribution approximation.
4. Sum triangles and plot total production for different triangle skewness.
5. Choose an appropiate skewness (constant or field size or time dependent) and try for other regions.
6. If it works try for world production! and submit result.
I would expect triangle skewness to have effect on total production profile if the quote (field production time)/(region production time) is close to one. It could be a good idea to use well production instead of oil field size because I expect that highly productive well in a new field could be drilled before a low productive well in a mature old field.
The Bentley model has no stochastic aspects. The Michel model has stochastic aspects both in the size of the field and the time production starts, but the shape of the production curve is fixed. Thanks for the link to your work.