^5iCSG. 



6020 



6030 



6040 



6050 



6060 



6070 



6080 



F.P.M.CIOG.P.M.O 



-3F.P.M. 



W/A^OXt /A 



5 10 



TIME, MINUTES 



Figure 20-5. By following water-oil interface with the electrode while injecting fluid at a 

 constant rate, one can determine relative percentage of fluid accepted by each zone. 



fluids. In this instance, a differential interface is obtained between a noncon- 

 ducting fluid (kerosene, crude oil, etc.) and an electrically conductive fluid 

 (brine, inhibited acid, or fresh water conditioned by dissolved electrolyte). In 

 conducting this type of survey, the well is first filled with the conducting fluid 

 to a point several hundred feet above the casing seat. The nonconducting fluid 

 is then injected at a constant rate, and the location of the interface is established 

 at predetermined intervals, by means of an electrode unit suspended on an in- 

 sulated, electrically conductive cable attached to control and measurement 

 instruments at the surface. The electrode tool is designed so that it will indicate 

 whether it is immersed in conductive fluid or nonconductive fluid, or whether it 

 is partially immersed in each. 



A more recent modification of this method consists of utilizing the interface 

 between a clear fluid (transparent or translucent) and an opaque fluid (usually 

 produced by the addition of a soluble dye). In this instance, the interface 

 detection tool consists of a photoelectric cell assembly which measures the light- 

 transmission properties of the fluid in which it is suspended (fig. 20-6). The 

 surveying procedure is similar to the electrode method described above. The 

 well is filled with clear fluid (usually water), and a section is conditioned with 

 dye, by means of a remote-controlled bailer. Fluid injection is started at the 



400 



