Page 483 - Petrophysics

RADIAL LAMINAR FLOW OF GAS 45 1

For other well locations inside closed (or bounded) drainage area
shapes (f = 0), the general form of Equation 7.105 is:

WP2 - P$)
qsc = (7.107)
1,422pgzT[ln(rG/r,) + SI

where r is given by Equation 7.64~.

EXAMPLE

A well is producing 275 MSCFD from a gas reservoir under the
influence of a partial water drive with an index of 0.5. Calculate
the wellbore pressure and the pressure at the drainage boundary. The
following reservoir and fluid properties are known:

pg = 0.035 CP k=5mD Swi = 17%
z = 0.95 h=35ft @= 12%
T = 130°F re = 2,640 ft

p = 2,720 psia r, = 0.5 ft
s=o

SOLUTION

The wellbore pressure can be obtained from Equation 7.105:
pw = [p' - m(Ln (') - 0.75 + 0.25f)l 0.5

r,

where:

m= qscPgZT
0.702 x lO-3kh

Substituting the values of the fluid and reservoir properties gives:

(275)(0.035)(0.95)(460 + 130)
m= = 43,895
(0.702 x 10-3)(5)(35)

and:
( ('I:)
2,720' - (43,895) In - - - + 0.25)]0.5 - = 2,655 psia
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