**Syntax**

` >> COMPRESSIBILITY`

**Parent Command**

` > PARAMETER`

**Subcommand**

` >>> MATERIAL`

**Description**

This command selects as a parameter the pore space compressibility c (TOUGH2 variable COM(NMAT)) of a certain rock type. It is suggested to estimate the logarithm of c. Under fully liquid-saturated conditions, pore space compressibility estimates c can be converted to a specific storage coefficient S [1/m] as follows:

S_{s} = phi*rho*g*(c_{l} + c)where phi is porosity, rho is density of water, g is gravitational acceleration, and c_{l} = 4.4E-10 [1/Pa] is water compressibility. Similarly, estimation of c for grid blocks representing a well or borehole is useful for the determination of a dimensionless wellbore storage coefficient C_{bh} :

C_{bh} = phi_{bh} *rho*g*V_{bh}*(S_{l}* c_{l} + S_{g} * c_{g} + c)where phi_{bh} and V_{bh} are the porosity and volume of the grid block representing the well, S_{l} and S_{g} are the liquid and gas saturation, and c_{g} is gas compressibility which is approximately 1/p.

**Example**

` > PARAMETER
>> pore space COMPRESSIBILITY
>>> MATERIAL: BOREH
>>>> ANNOTATION: Wellbore storage
>>>> LOGARITHM
>>>> RANGE : -10.00 -7.0
<<<<
>>> MATERIAL: SKIN_ ROCK_ BOUND
>>>> ANNOTATION: Storativity
>>>> LOGARITHM
<<<
<<`

**See Also**

` - `