Formation Evaluation Through Casing - Cased-Hole Log Analysis and Reservoir Performance Monitoring - page 155

Fig. 11.18 Ratio curve response to gas. Courtesy Schlumberger
Near and Far Count-Rate Display
In Track 3, the near and far count rates are displayed as an overlay. Figure 11.19 illus-
trates this presentation. When the correct scales are chosen for the near ( N 1 ) and far ( F 1 )
count-rate displays, a useful quick-look log results, with the following properties:
• In 100 % water (section A), F 1 = N 1
• In gas (section C), F 1 > N 1 (dotted line is left of solid)
• In shales (at the top of the log), F 1 < N 1 (dotted line right of solid)
Question # 11.2
Refer to Fig. 11.19
(a) Color code the gas-bearing intervals on the near/far count-rate display using red
or pink.
(b) Color code the shale zone at the top of the log green.
(c) Why do you think the oil-water contact is marked where it is (i.e., at 4,535 ft)?
(d) Read the average value of ʣ in the water-bearing zone.