Page 224 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Formation Evaluation 193

Apparent Water Salinity Determination
from GST" Gamma Spectrometry Log-Inelastic Mode

CIM, Chlorine-Hydrogen Salinity Ratio
Figure 5-11 6. Chart for finding apparent water salinity from chlorine-hydrogen
ratio and borehole fluid salinity from a GST log (in elastic mode) [199].

Cased-Hole Completion Tools. These tools examine cement bond and casing
quality They assure that no leakage or intercommunication will occur between
producing horizons, or between water-bearing horizons and producing horizons.
The most common completion tools include:
1. Cement bond logs (CBL).
2. Multifingered caliper logs.
3. Electromagnetic inspection logs.
4. Electrical potential logs.
5. Borehole televiewers.

Cement bond logs (CBL-VDL). Cement bond logs are used to check cement bond
quality behind the casing and to estimate compressive strength of the cement.
It can also be used to locate channeling in the cement or eccentered pipe and
to check for microannulus.
Theory. The cement bond tool is the same as a conventional sonic tool except
that the receiver spacings are much larger. It consists of a transmitter and two
receivers. The near receiver is 3 ft below the transmitter and is used to find At
for the casing. The far receiver is 5 ft below the transmitter and is used for the
variable density log (VDL) sonic-waveform output. The operation is the same
as a conventional sonic except that the transmit time (one way) is measured.
The transmitter is fired and a timer is triggered in both receivers. The wave