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Examples shown in Figures 1-3 make use of thermal conductivity and
electrical formation factor data from Asaad (1955). Three different sandstones (labelled B, C, D) were studied by Asaad,
and several different sets of experiments were performed on each.
The Figures show data from experiments B30, C10, C20, and D10.
I plot both the new formation factor bounds (FF) and the
Hashin-Shtrikman bounds (HS) based on volume fraction information.
A selection of the data is displayed in all three cases.
Electrical formation factor measurements were made on all three
samples (*F*_{1}^{B} = 12.0, *F*_{1}^{C} = 23.0, *F*_{1}^{D} = 33.0). Frame
formation factor can be determined from measurements of thermal conductivity
when the pores are evacuated. But a value of effective grain thermal
conductivity must be found. Asaad (1955)
solved this problem --
using an extrapolation method -- assuming that a certain geometric
mean approximation (which is just a straight line on a log-log plot) when
fit to the data would then give an accurate estimate of the point
at which . Results
displayed as they are here on the log-log plots in Figs. 2 and 3
show that Asaad's method
is in fact quite accurate for all these data. Then,
, and I find
*F*_{2}^{B} = 13.5, *F*_{2}^{C} = 15.9, *F*_{2}^{D} = 3.72. Measured
porosity values were , , .

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Stanford Exploration Project

10/23/2004