Page 191 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

160 Reservoir Engineering

on field observations of porosity versus travel time:

This relationship is valid up to 37% porosity.
The heavy set of lines in Figure 5-89 [199] was derived using the Raymer
et al. [210] transform, and the lighter set represents the Wyllie relationship.
The sonic porosity derived from the Wyllie equation (Equation 5-102) does
not include secondary porosity (vugs and fractures), so it must be cautiously
applied in carbonate rocks.

Density Log. The formation density tool measures the bulk electron density
of the formation and relates it to porosity. It is a pad device with a caliper arm.
The tool is usually run in combinatioh with a neutron log, but it can be run alone.

Porosity Evaluation from Sonic
SVf = 5300 ft/S
English

. . . -. -
- Time Averaoe
.

, PSchlumberger I

n
30 40 50 60 70 80 90 100 110 120 130"
t, Interval Transit Time (ps/ft)

Figure 5-89. Chart for evaluating porosity with a sonic log [199].