Klinkenberg and MICP pressure range question

[vinomarky]

yasiobasio123 sent me a message;

hi vinomarky
happy ne year...
how to calculate the klinkenberg perm?
I have air perm from core plugs and I'm using the J fuction for saturation height modeling from micp data. MICP is upto 60000 psi measured on endtrims. Please let me know, what should be the max Pc to calculate J to plot against Sw for regression constants a and b? Is it all upto 60000psi or is there any limit for that?

Response posted here for everyone;

Klinkenberg Correction
Gas slippage is corrected for by making permeability measurements with gas at multiple pressure differences and constructing a graph of the measured apparent permeability against the reciprocal of the mean pressure in the core. If the input gas pressure is Pi and the output pressure is Po, then the permeability is plotted as a function of 1/Pav = 2/(Pi + Po). The points should now lie on a straight line, which intersects the y-axis at 1/Pav = 0. This value is called the Klinkenberg permeability, and effectively represents the permeability at which the gas (which is near to a perfect gas) is compressed by infinite pressure and becomes a near perfect liquid. It is because of this that the klinkenberg permeability is often given the symbol k_L.

The klinkenberg permeability is very commonly used within the oil industry, and should approximate very well to the permeability of the sample measured with liquid flowing through it. It should be noted that the correction cannot be ignored, especially in tight rocks, as it can lead to corrections of up to 100%. In general, the correction is smaller for higher permeability rocks containing larger pores.

[link Point to another website Only the registered members can access]

MICP Pressure Range
Samples are often taken to Mercury pressures equivalent to unachievable in-situ reservoir pressures. The reason for this is that (a) the additional tests are relatively cheap and (b) by taking all samples you take to the same (high) pressure, it makes it easier to compare samples across different fields and possibly start grouping into correlations with perm etc – a common benchmark if you will.

Just because the samples are taken to those pressures though, does not mean that those higher pressures are at all relevant to your particular modelling exercise.

What pressure range to use for fitting? It depends on your reservoir geometry and quality. If you have a low relief reservoir with poor perm, then characterizing properly the transition zone (and entry pressures) will likely be very important (you may never be out of transition, and some reservoir may not have any charge at all), and as such it may be more important to accurately characterize the entry and curvature than the end points. With high relief and/or better perms the transition zone and entry pressure will be a very small component of your HCIP and as such the end points become very important to get right. I guess at a high level, you should choose your range of pressures to perform your regression in a way that minimizes your overall HCIIP error, while allowing for logical FZI grouping. Generally though, there is not much value in matching pressure ranges significantly above the expected buoyancy pressures expected at the crest of your reservoir.

Don’t forget that the MICP is much different to the insitu pressure – you will need to transform lab data to equivalent in situ pressure before you do your fitting. You can find info on this in my post here -

[link Point to another website Only the registered members can access]
*EDIT** - Just checked that link and realized it was more about sat height functions. The simple math to convert lab pressure to insitu pressure is as follows;

Pc_res = Pc_lab * Sigma_res.Cos(Theta_res) / Sigma_lab.Cos(Theta_lab)

Lab;
Air-Water: Sigma.Cos(Theta) = 72
Oil-Water: Sigma.Cos(Theta) = 42
Air-Hg: Sigma.Cos(Theta) = 367
Air-Oil: Sigma.Cos(Theta) = 24

Reservoir;
Oil-Water: Sigma.Cos(Theta) = 26
Water-Gas*: Sigma.Cos(Theta) = 50

*P/T dependant, reasonable value to depth of 5,000 ft

So if you were modelling an Oil-Water system, your insitu pressures = Lab pressures x 26/367

[yasiobasio123]

many thanks Vinomarky. If you have any template in Excel spreadsheet for J Function, please share that. Many thanks.

[yasiobasio123]

as a function of 1/Pav = 2/(Pi + Po):

how can we get Pi and Po? when we have MICP data

[vinomarky]

I think you need to re-read the post. If you ONLY have MICP data, then you don't have enough data to correct for gas slip - these are corrections that need to be made at the time of perm measurement through the multiple tests as outlined above. Generally RCA data you receive is already gas slip corrected. There is another correction though that is quite important - especially for low perm samples - and that is cross plotting your Klinkenberg corrected K_Air vs K_Brine at Swir. Through this process it is very important that you maintain consistency. If you create a static model based on KAir, then ensure your J-Function is also created relative to KAir and you pair it with initial relative permeability tables that correct for fluid flow characteristics under reservoir saturations (ie Kr for our hydrocarbon will likely be substantially less than 1 - as low as 0.1 or even 0.01 for very low perms even at residual water saturations)

[yasiobasio123]

Thanks vinomaky If you have a excel spreadsheet as template for saturation height modelling, please share. Many thanks for this

[vinomarky]

I have many. I often make then fresh for each situation as they really are very simple. Build one yourself, its the best way to learn

[Born-Different]

I've read that before converting from lab to res conditions, the corresponding mercury pressures have to be converted first to hydrocarbon system, and only then from HClab to HCres. If I'm not mistaken, I read it in Crain's book for PP. Doing that one can get consistent pressure ranges that can be comparable then Pc's and heights at the reservoir conditions.

[vinomarky]

Those conversions are all done at once in the above equations

[yasiobasio123]

thanks vinomarky, I have some issues making J unit less, can you give some hints .... thanks

J=Pc/IFT*cos (theta)*(k/phi)^0.5

[yasiobasio123]

thanks vinomarky, I have some issues making J unit less, can you give some hints .... thanks

J=Pc/IFT*cos (theta)*(k/phi)^0.5