20 40 60 80 

 RELATIVE RATE OF FLOW 



100 



Figure 20-9. The "hot-wire" tool detects rate of fluid movement by measuring change in 

 resistance of a heated wire, as a result of cooling effect of external fluid; degree of 

 cooling is proportional to rate of flow. 



medium and its heat conductivity. Any movement of the fluid surrounding the 

 heated wire results in an immediate increase in the rate of heat loss. This 

 increase is a function of the rate of flow of the fluid past the heated wire. Thus, 

 by measuring the rate of heat dissipation from the wire, one can obtain an 

 accurate and extremely sensitive measure of the velocity of the surrounding 

 fluid. 



INTERPRETATION Comparative permeability profiles are made 



OF DATA to determine the thickness of the various 



permeable sections in the bore hole, the vertical position of these zones in the 

 bore hole, and the relative capacities of the various zones. Also, data obtained 

 from the permeability surveys may be used to calculate three different indices 

 that pertain to the volume of fluid injected into the various permeable zones. 

 The nomenclature for these various indices has been set up to correspond with 

 the various productivity indices except that they are a measure of injected fluid 

 rather than produced fluid. 



In normal production practices, the term "productivity index" usually 

 refers to the barrels of fluid produced each day, for each pound per square 

 inch of differential pressure. In permeability surveying, the injected fluid is 

 measured to get a term equivalent to the productivity index, except that the 

 term represents injected fluid rather than produced fluid. 



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