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A P (  2  P 2 )
Q gas s.c.  k per.g.  1 2 , (3.3)
2 g L  P  atm
where Q gas s.c. is the volumetric flow rate of gas under standard

3
conditions (atmospheric pressure and standard temperature), m /s; P
atm
is atmospheric pressure, Pa,  is dynamic viscosity of gas (air), Pаs;

g

P is inlet absolute pressure, Pa; P is outlet absolute pressure, Pa
2
1

(usually P = P );
2 0
,
/
P  P  P (3.4)
1 1 0
/
where P is the manometer (surplus) pressure at the entrance of the

1
core, Pa.

The equation (3.3) is obtained after such transformation as putting

into the equation (3.2) volumetric flow rate of gas reduced to the

-
average pressure in the sample Q (the average flow rate of gas under
gas
conditions of the sample) instead of volumetric flow rate of liquid.

-
The average flow rate of gas under conditions of the rock sample Q
gas
is determined according to Boyle’s law.

So the equation for determining the permeability coefficient of

rock for gas k under condition of gas filtration by the linear law of
рer.g.
filtration (Darcy’s law) after the transformations mentioned above can

be expressed as:

2 Q gas s.c. P  atm  L g
.
k рer.g.  2 2 (3.5)
A P (   P )
1 2
The unit of measurement (dimension) of permeability coefficient

(in SI system) follows from the equation (3.2):

17