Page 40 - Basic Well Log Analysis for Geologist

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BASIC RELATIONSHIPS OF WELL LOG INTERPRETATION

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figure 8. Chart for estimating formation temperature (T;) with depth (linear gradient assumed).
Courtesy, Dresser Industries.
Copyright 1975, Dresser Atlas.

Given: .
Surface temperature = 80° fc
Bottom hole temperature (BHT) = 180°
Total depth (TD) = 10.000 feet
Formation depth = 6,000 feet
Procedure:
1. Locate BHT (180°F) on the 80 scale (bottom of the chart: surface temperature = 80°F).
2. Follow BHT (180°) vertically up until it intersects 10,000 ft (TD) line. This intersection defines the
temperature gradient.
3. Follow the temperature gradient line up to 6,000 ft (formation depth).
4. Formation temperature (140°) is read on the bottom scale vertically down from the point where the 6,000 ft line
intersects the temperature gradient.
NOTE: In the United States (as an example) 80° is used commonly as the mean surface temperature in the Southern States,
and 60° is used commonly in the Northern States. However, a person can calculate his own mean surface temperature if
such precision ts desired.