zones of permeability in a well. It was found that the data obtained could be 

 correlated readily with other types of well data, including core analyses, drill- 

 time logs, temperature surveys, and electric logs. 



Thousands of permeability-profile surveys have been made since the com- 

 mercial introduction of the method in 1941. The experience so obtained has 

 been most helpful in perfecting the technique, improving the instruments (figs. 

 20-1 and 20-2), and interpreting the data. 



METHODS The four basic methods of determining the 



comparative permeability of rocks in situ 

 at the bottom of a well are classified as : 



a. Electric or radioactivity logging 



b. Moving-interface surveys 



c. Static-interface surveys 



d. Fluid-velocity surveys 



The moving-interface survey (fig. 20-3) consists of injecting fluid into a 

 well at a given rate, and then following the interface between two dissimilar 

 fluids (fig. 20-4) down the well bore by means of a suitable detection tool 



-WEIGHT INDICATOR 



ELECTRODE 



POWER DRIVEN REEL 



AMMETER ON EXTENSION CORD 



WELL 



vXa 



10 VOLT AC- GENERATOR^ TRANSFORMER 



Figure 20-3. A schematic diagram showing well hookup for conducting a two-fluid perme- 

 ability survey. 



398 



