Klinenberg perm.

[yasiobasio123]

Hello, why Klinenberg correction is applied and what is needed for this correction?, please guide, thanks.

[DAH7542]

It's needed whenever gases are used to measure rock permeability since they exhibit the so called "slipage effect". Fluids (gases and liquids) flowing through porous media during laboratory measurements of rock permeability (or anywhere in the reservoir) are expected to have zero velocity on the surface of the grains and higher velocities towards the center of the pores, this seems to be true for liquids but not for gases. Gases virtually slip on the grain surfaces resulting in overestimattion of rock permeabilities; this is the "Klinkenberg effect". In order to account for this deviation (i.e. Klinkenberg effect correction), lab measurements of rock perm are performed at different confining pressures. Then, you simply plot the perm value from lab test vs the reciprocal of pressure (i.e. 1/P). If you have, lets say, three k measurements at three different pressures using air, you'll come up with three points in your plot kair vs 1/P. A linear regression is drawn and extrapolated to 1/P = 0, this condition is matematically equal to P = infinite. Any gas subject to infinite pressure can be considered a liquid, so theoretically, if you find the perm value corresponding to 1/P=0 by simple extrapolation of the linear regression you'll come up with a rock permeability value measured in lab using a gas (in this example air) but equivalent to a rock perm as if it would have been measured using a liquid. This rock perm value is known as the Klinkenberg permeability and is the one to be used for further charaterization of the reservoir rock.

[yasiobasio123]

Thanks a lot DAH7542 for explaining. Can you please brief a bit what reservoir engineer need from SCAL for modelling? thanks

[DAH7542]

Basic SCAL properties used in reservoir simulation are Kr and Pc. You'll need to define also rock (pore) compressibility, however, other special core analysis including critical velocity, XRD-SEM, mojability tests, and some others are indirectly used for facies definition, data validation, etc.

[yasiobasio123]

Thanks again, any helping material for beginner? suppose if one is asked by Res. engineer then what should one do or look into?

[yasiobasio123]

Hi DAH, How we can QC Kr and Pc of SCAL?

[DAH7542]

I'll try to answer both questions here. From a reservoir engineering and reservoir simulation standpoint, there are some issues you have to take into account to ensure that the SCAL data is ok:

1. Smooth curves: kr data should be as smooth as possible to avoid convergence delays or failures. I order to make sure that your kr data is smooth enough for reservoir simulation, plot the derivative d(kr)/d(sat). You should see derivatives smoothly varying, if not, make proper corrections by using Corey functions.
2. When using hysteresis option, the drainage and imbibition end-points must be consistent.
3. When using three-phase kr data, the relative perm to oil at Swi (krow at swi) must be the same as the relative perm to oil at zero gas saturation (krog at sg=0). Here is the explanation: at gas saturation equals to 0 there are still irreducible amounts of water filling the pore spaces (i.e. water at Swi), so the first value of Kro as defined in an oil/gas kr table would be at Sg = 0, which means, as explained before, irreducible water saturation, this makes that the first Kro value in a gas/oil kr table must be equal to the first line (kro valued) in an oil/water kr table (which starts at Swi).
4. As for capillary pressure (Pc) data, you must know the advantages and limitations of each one of the three methods of measurement (mercury injection, porous plate and cetrifugue). Since mercury inj Pc yields to high displacement pressures I tend to trust more the porous plate and cetrifugue measurements for model initialization under equilibration, although mercury test are very useful to get poro size distribution.