Page 88 - Basic Well Log Analysis for Geologist

POROSITY LOGS

“igure 27... Chart used for converting interval transit time (At) values to sonic porosity, using values picked from a sonic log.
Courtesy, Schlumberger Well Services.
Copyright 1977, Schlumberger.
Given:
V na = 26.000 f/see where V .,, is the sonic velocity of the matrix (in this case dolomite; sce
Table 6). At (from log) = 63 psec/ft at a depth of 9,310 tt (see Fig. 26).
Procedure:
|. Find an interval transit time value (At) taken from the sonic Jog in Figure 26 (in this example 63 fasce/ft) on the
scale at the bottom of the chart.
2. Follow the value (63) vertically until it intersects the diagonal line representing 26,000 ft/sce (dolomite, in this
case),
3. From that point, follow the value horizontally to the left. and read the porosity value froin the porosity scale. In
this case, the value is 16.5% (6 = 16.5%).

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