An oil reservoir dipping at 20 degrees has a flow area of 1 MM square ft and a total fluid flow of 2,830 barrels per day. The oil has a permeability, relative permeability, viscosity, and specific gravity of 40 md, 0.4 md, 1.5 cp, 0.8, respectively. The water has a relative permeability of 0.02 md, with a water/oil viscosity ratio is 0.1. Assuming standard water density and specific gravity, and that the formation permeability averages 100 md, the fractional flow of water is closest to: (A) 0.2 (B) 0.3 (C) 0.4 (D) 0.5.
This problem is nearly the same as the Guidebook example on 14 WLF 2; only the flow area has doubled. The computation then changes to (1-0.4)/(1+2) = 0.6/3 = 0.2, or (A).
To better understand fractional flow in a dipping reservoir, see page 158 of TS8 (Towler). Slider has some good practice problems as well. These problems are not common, but being directly from SPE Textbook Series reservoir text, it's fair game.
For this one, the viscosities are different than in the guidebook also, right? (oil visc=1.5 and water is .15? or am i interpreting that wrong?) The answer I came up with was 0.29
ReplyDeleteI'm not getting you. Oil viscosity = 1.5 cp in the problem and GB. The water/oil viscosity is used in the problem as this ratio so you don't need to back calc water vis. It should be exactly like the GB problem, with the water oil ratio is 0.1/1. Make sense?
DeleteYes! thanks. didn't think about not backing out water vis. Second question. Why is 1.05 used for SGw instead of 1?
DeleteSalt/minerals make it heavier than fresh water...SPE TS of uses 1.05 (I think Slider does too). But should generally be given IMO...or the answer have a broad enough range it don't matter. I don't know if I did that here?
DeleteYep, comes out to .22 so works. Thanks!
DeleteWe cant take the book to the exam. In Ali Ghalambour the equat is (1+(.....))/(1+1/M)
ReplyDeleteI strongly doubt there will be many straight "plug-and-chug" problems. So knowing where the equation resides in provided Ghalambour or the Handbook will be the least of one's worries. Rather, questions will be asked that test one's understanding and/or speed of understanding, due to complicated wording and/or inputs.
DeleteAlso remember anything can be provided in the problem itself. Thus, and SPE reference (like Towler here) one should be prepared for. In fact, differences between Ghalambour and other SPE references would be excellent word problems to trap the tester who is trying to rely on his provided resources. It's a great way to test "understanding" versus equation-hunting.
Having said that. What would the problem solution look like if only using the provided text from Ali Ghalambor?
DeleteAgain, I would not attempt to outsmart the exam here. The test writer can add anything they want, including word problems. I would just focus on understanding problems regardless of the text. These problems, even if they won't show up exact on the exam, do help give understanding that can translate to whatever problem they spring.
DeleteWithout a given capillary pressure this equation is not solvable with the 2020 reference guide. The key take away would be understanding how to convert relative perm to effective perm (pg 20). Calculating densities (density = SG because formula is asking in g/cm3 and density of water is 1)
ReplyDeleteAgain, the exam can give anything it needed. I would never use the 2020 guide as an indication to what will be on the exam. Rather, I would use the SPE Handbook and Textbook series, including any and all charts. These can be easily copied and inserted into the exam for every specific problem that needs them.
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