Page 55 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Basic Principles, Definitions, and Data 43

Hill and Milburn [49] provided data from 450 core samples taken from six
different sandstone formations and four different limestone reservoirs. The
sandstone formations were described as ranging from clean to very shaly. The
formation factor was determined at a water resistivity of 0.01 ohm-m since, at
that value, the apparent formation factor approached the true formation factor
when the rock contained low-resistivity water. From their data, the following
equation was provided:

F~ I: 1.44-1.7a (5-50)
An expression was also provided for the case in which the constant, a, in
Equation 5-49 is taken as unity:
FR (5-51)

Using 981 core samples (793. sandstone and 188 carbonate), Carothers [52]
established a relationship for sands:
FR = 1.45@-'." (5-52)

and for limestones:

FR 0.85$-p.14 (5-53)
As shown in Figure 5-30, a relationship was suggested for calcareous sands:
FR = '1.45$-i33 (5-54)

and for shaly sands:

FR = 1.651$--'.~~ (5-55)
Using these data, the nomograph in Figure 5-51 was constructed to solve the
modified Archie expression (Equation 5-49) when it is desired to vary both
constants.
Using 1,575 formation factors from California Pliocene well logs, Porter and
Carothers [59] presented an in-situ relation:

FR = 2.45$-'.08 (5-56)
and a similar relation for 720 formation factors from Texas-Louisiana Gulf
Coast logs:

FR = 1.97$-'.49 (5-57)
This investigation used well log data from sandstone formations known to have
water saturations of 100%.
From an analysis of over 1,800 sandstone samples, Timur et al. [54] presented
the following expression:
F~ = 1.159-1.73 (5-58)

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