842 



GEOPHYSICAL WELL TESTING 



[Chap. 11 



Several containers may be arranged in tandem with the T joint. The 

 open containers are applied in dry, open holes. In wells filled with water, 

 drilling fluid, or oil, the use of the closed containers (A-C) prevents the 

 pressure of the liquid from reaching the thermometers and altering the 

 reading. Thermometers in European equipment are enclosed in cotton- 

 packed and capped steel cylinders, which are arranged in tandem in a tube 

 of larger diameter. Leather diaphragms are provided around the ends of 

 the large tube to reduce circulation. 



The thermometers may be lowered into the well on the end of the sand 

 line, inside or outside the bailer, or on a separate line, using an apparatus 

 developed especially for this purpose, illustrated in Fig. 11-17. This ma- 



1^ 



y4' 



Fig. 11-16. Holders and containers for maximum-thermometers (after Van 



Orstrand). 



chine holds 9000 feet of No. 19 or No. 20 piano wire and is equipped 

 Avith a spooling and depth indicating mechanism. 



The use of nf»aximum thermometers requires that the well be in tempera- 

 ture equilibrium and that jars and other sources of error be carefully 

 avoided. Since this technique is intended for structural correlations, dis- 

 turbances arising from an influx of oil, water, and gas into the well are 

 considered sources of error and are carefully avoided if possible. Drilling 

 with a standard rig should be discontinued for at least twenty-four hours 

 before a test is begun. For a rotary outfit the time required for tempera- 

 ture equilibrium is much greater and may be several days. When meas- 

 urements between 100-1000 feet are taken with maximum thermometers, 

 outside temperatures may be higher than the well temperatures, and the 



