In modified form, permeability surveys can be used to control the application 

 of chemicals in selective-acidizing treatments. 



HISTORY The rapid and widespread use of chemicals 



in wells to improve their producing char- 

 acteristics led to the early development of tools and techniques that would assure 

 more efficient and effective use of the chemicals. 



One of the problems solved by researchers in well treating was the de- 

 termination of what part of the exposed section in the well should be treated 

 chemically. This determination led to the development of methods that would 

 insure introduction of the chemicals into the desired zone. One of these methods 

 which utilized a subsurface electrode suspended on an electric cable, indicated 

 at the surface the location of an interface between the treating acid (pumped 

 down the tubing) and oil (pumped down the annulus). 



The success of this technique led to its adaptation to other uses. Not long 

 after, the selective acidizing electrode was being utilized to locate and evaluate 



Figure 20-2. Interior view of electric pilot truck showing control panels and automatic 

 chart recorder. 



397 



