gas saturation in rocks also depends on rock type.

R you talking about Gas in Shale  or Gas in other rocks (Sst or Lst)

10% gas saturation in Shale means higher pore pressure as compared to 10% gas in sandstone

A rapid increase of fluid compressibility in pores causes the rapid growth in bulk modulus

I'm referring to sandstone.

dear Simon,

You can find the detail answer by doing gassmann fluid substitution. You can play around with gas saturation to analysis bulk mod changes.

Here I want to give some analog.

Let say you have value 10 (analogue for 0 gas saturation or water saturated condition)

Then you add value 1 (analogue for let say 10% gas). You can calculate the average: 10+1 devided by 2 equal to 5.5. You can see, the value dramastically drop from 10 to 5.5.

Lets continue, imagine we add gas saturation per 10% or equal to value 1

10 + 1 + 1 devided by 3 equal to 4

10 + 1 + 1 + 1 devided by 4 equal to 3.25

10 + 1 + 1 + 1 + 1 devided by 5 equal to 2.8

So you can see the first gas adding makes original bulk mod drop dramatically to 5.5. Since the gas is adding more the bulk changes drop slighly become 4, then 3.25 then 2.8.

This is simple analogue why adding gas 10% results significant drop compare to 30% or even 80% of gas. It because there is significant different between bulk for quartz in sandstone filled by water compared to sandstone with gas.

I hope I can answer your question

Hi , Which acids or chemical can dissolve rock. give detail of chemical or rock which can dissolve rock.

A rapid increase of fluid compressibility in pores causes the rapid growth in bulk modulus

Hi Simon,

The bulk modulus of sandstone depends on the probing wave's amplitude. Please check my recent JGR paper: https://www.researchgate.net/publication/339390199_Effective_fluid_bulk_modulus_in_the_partially_saturated_rock_and_the_amplitude_dispersion_effects/citations?latestCitations=PB%3A342919155

If you consider smaller waves amplitudes, it will change with the gas saturation.

Best regards,

Alexander