DEPTH 

 IN FT 



2300- 

 CASING SEAT 2365 



5!^" -14* CASING 

 200 RPM 



65 RPM IN OPEN 



Iwn I OSS- HOLE EQUIVALEN1 

 | INU LUoi , jo 200 RPM IN 

 CASING 



• 15 RPM LOSS 

 •20 RPM LOSS 

 [-20 RPM LOSS 

 25 RPM LOSS 

 ' 5 RPM LOSS 



Figure 20-8. The "spinner" tool measures fluid velocity at various depths; relative injectivity 

 of each subsurface zone is proportional to fluid lost into that zone. 



are correlated with the depths at which they occurred, and the comparative 

 permeability of the formation throughout the well bore is thus obtained. A 

 number of different tools have been developed for use as subsurface flowmeters. 

 The most commonly used instrument (fig. 20-8), usually referred to as the 

 "spinner", consists of a metal guard cage in which a small, plastic impeller blade 

 is mounted. When the instrument is suspended in the well bore, fluids passing 

 through the cage in either direction cause the impeller blade to rotate. The speed 

 with which the blade turns changes with the velocity of the fluid passing through 

 the cage and is measured electrically. These data can be calibrated readily to 

 yield fluid velocity in terms of feet per minute, which in turn can be converted 

 into gallons per minute. By traversing the well with the spinner instrument and 

 recording fluid velocity versus depth, one can readily determine the comparative 

 permeability profile. 



Another instrument (fig. 20-9) that has been utilized experimentally as a 

 subsurface flowmeter is the so-called "hot-wire" tool, which operates on the 

 principle of heat transference. A heated wire immersed in fluid will dissipate 

 heat continuously into the surrounding fluid. The amount of heat lost per 

 given time interval will depend on such factors as the temperature of the fluid 



403 



