Miscellaneous Subsurface Methods 



669 



are to be taken. Most wells that produce formation water will have reason- 

 ably clear fluid covering the formation. If there is some doubt as to the 

 type of fluid in the hole, a sample can be obtained by running a thief or 

 bottom-hole sampler. If it develops that the hole is filled with oil or water 

 too turbid for good pictures, it will be necessary to replace the well fluid 

 with a relatively clear fluid. This is easily accomplished by spotting the 

 clear fluid, usually salt water, in the well bore through tubing. The tubing 

 is then removed from the well in order to run the camera. 



If the well is flowing, it should be killed before an attempt is made 



Figure 357. Section of casing at 2,361 feet, 8 inches, which contains a collar. 



to operate the camera. By using a clear fluid to kill the well, it is possible 

 in one step both to accomplish this and to condition the bore hole so that 

 optimum conditions exist for taking pictures. 



In wells that have a layer of oil on top of the clear fluid covering the 

 section to be photographed it is necessary to cover the window of the 

 camera with a material that is very soluble in water but insoluble in oil. 

 This is done so that any drops of oil that might cling to the window of the 

 camera will be released when the material dissolves in the water. Thus 



