434 



Subsurface Geologic Methods 



Radioactivity well logs are also employed for a variety of specialized 

 applications. One of these is the logging of added radioactive material. 

 In the study of squeeze cement jobs on the Gulf Coast, it has been found 

 desirable to know the vertical travel of the cement and its mass distri- 

 bution behind the casing string. By means of a radioactive tracer such 

 as carnotite mixed with cement, it is possible to determine the direction 

 and extent of the cement travel. The usual procedure is to record a 

 gamma-ray curve of the well under normal conditions. The mixture of 



GAAAMA RAY 

 CURVE 



GAMMA RAY 

 CURVE 



AVERAGING NATURAL 

 RESISTIVITY POTENTIAL 

 CURVE CURVE 



WEIL 3 



Figure 202. Gamma ray-electrical log correlation of section in Long Beach field, 



California. (Lane-Wells.) 



