Page 561 - Petrophysics

528 PETROPHYSICS: RESERVOIR ROCK PROPERTIES

Substituting Equation 8.58b in 3.10 (where r = ~hf) yields:

(8.59)

The fracture permeability in this equation is in cm2, porosity is a fraction,
and fracture height and width are in cm. If fracture width, wf, and
fracture porosity, &, are determined from core analysis and permeability
is determined from well testing, fracture height can be determined from
Equation 8.59. Another application of Equation 8.59 is to decide what
radius a horizontal well has to have in order to get the same benefit of a
hydraulic fracture of width wf and height hf.

EXAMPLE

Core analysis, well logs and pressure data yielded the following data:

$f = 0.027 wf = 0.015 cm kf = 51.3 Darcies

Estimate:

(a) Fracture height and
(b) Hydraulic radius of the fractures.

SOLUTION

(a) Equation 8.59 can be rearranged for fracture height as follows:

(8.60)

Since 1 Darcy = 9.87 x lo-’ cm2, therefore 51.3 Darcies =
(51.3)(9.87 x lo-’) = 5.06 x cm’.

hf = ( 5.06 x 10-5 )2 1 = 314 cm = 10.3 ft
0.05758 (0.027) (0.015)3