Graph explaination : Klickenberg Effect

At infinite average or mean pressure, gas molecules will be as closer as liquid,

So gases will behave like liquids at higher mean pressure.

So, high mean pressure means less inverse of mean pressure (1/Pm).

So, at zero inverse pressure, there should be minimum absolute permeability.amd that's callled liquid permeability.

So, according to klinkenberg, it follows straight line rule and we can express it like,

Gas permeability = liquid permeability *(1 + (b/Pm))

Pm is mean pressure.

So, at infinity mean pressure, (zero inverse mean pressure), Gas permeability is equal to liquid permeability.

Now, in lab, we can not go for infinitiy pressue (zero inverse pressure),so we obtain data which are possible (shown in continuous line in graph) and as we know it is straight line, we extrapolate it to zero inverse of mean pressure.

(Intercept of line).

And get liquid or Absolute 

Permeability of that rock.

For low molecular weight gases, it will be easier to slip through pores that's why they have more increase in gas permeability than high molecular gases. (More slippage effect)

So, more the molecular weight, less the klinkenberg effect.

Apart from this, another factor which can have impact on curve position is, initial permeability of rock.

Look at below graph.

So, acording to this above graph, we have done another 3 experiments (with 3 cores) and plotted this graph, extrapolated at zero (1/Pm).

So we found high permeable, intermediate permeable and low permeable core respectively.

*(all Permeability we talked here are absolute permeability and not the relative  permeability).

(And all the graphs are shown at fixed or constant temperature.)

Apart from this all general things, one more thing to be notice is, as we have less liquid permeability, we have less slop of straight line.

It means we have lesser the klickenberg effect, if we have tighten pores or less absolute Permeability.

If they have high abs permeability, then intetcept (that is constant liquid permeability) will be more.

Conclusion of whole discussion.