The Oil Drum

Wow.

Thanks for all your posts, BTW. Fascinating stuff.

On your prompting I had come to the conclusion that the high level of water saturation was inconsistent with what we know from Croft about the general nature of Uthmaniyah.

I thought this might be a x-section of a particular part of highly impermeable low-porosity rock, but that seems impossible given the level of water saturation depicted for the lower levels.

Next I wndered how a super-K zone (as described by Simmons) might look. This could be the answer but surely then there would be a greater co-mingling of oil and water rather than the relatively black and white (or indeed pink and blue) picture we see above.

Question is why would the SPE fabricate such a picture or alternatively allow the publication of such an article. Is there no peer review? Who was the author?

I agree it seems strange. It would be interesting to perform some simulations that show water/oil flow using wells placed in different locations. Would it be possible to have this profile if water injection occurred in the lower left and collection occurred in the abrupt peak of the reservoir (center of cross section diagram)? I know there would be multiple injection/collection points, but I'm just trying to think of scenarios that would lead to the above profile.

Looks like they could be injecting water in the upper left-hand (in this view) portion of the reservoir to flush out oil that would otherwise be trapped up there. That could cause the water-oil interface to have a relatively vertical slope. Take a look at this diagram of Ain Dar also from Stuart's paper:

That shows a fairly steep oil-water interface in 1990. Do you think that's a fabrication too?

FF-

These graphs are described as simulations. Simulation data are generated on a computer rather than by empirical measurements, so you can call them "fabrications", but that does not mean they are necessarily wrong.

The pronounced streaking in the graph strongly suggests that the permeability underlying these simulations was assumed to be highly anisotropic, i.e., flow was assumed to be much more facile along the strata than in the perpendicular direction. This would then explain the 200 foot "wall of water".

You are probably in a better position to judge how realistic such a high degree of anisotropy really is. My guess would be that the authors of the SPE paper didn't just pluck their anisotropic permeability tensor out of thin air, but based it on actual measurements on rock samples from the reservoir.

some on here have dismissed out of hand the effectiveness of gravity segregation of the oil and water in these sa reservoirs. i am not convinced. i calculate (using major assumptions) that the ratio of oil/gas density (about 6.3)and water/oil density (about 1.7). in other words the ratio of oil/gas density is 3.5 to 4 times that for water/oil. looking at your x-section (realizing that the vertical scale is exagerated), i would guess that yes there could be gravity segregation . and i am not saying that it is the case, however i think gravity segregation could account for the 60 % or so recovery efficiency in this zone (95-15)/1.34 i.e. (sof-soi)/fvf. i would appreciate your comments.