Miscellaneous Subsurface Methods 



671 



After the well-bore conditions have been determined and corrected if 

 necessary, the camera is loaded with the film and attached to the cable. 

 Each roll of film is identified by taking a photograph of a card contain- 

 ing the roll number, date, well name, and other pertinent data. This is 

 done before the camera is lowered into the well and serves also as a check 

 on the electrical circuit and the operation of the camera and lights. 



The camera is lowered into the well at a rate of approximately 50 

 feet a minute. When the camera reaches the well section to be photo- 



FiGURE 359. Well-developed porous zone on right side of picture. This cavity may be 

 due to enlargement of a fracture by leaching. Entire section shows considerable 

 amount of porosity as shown by small openings appearing all through picture. 

 There is one small stylolite traversing picture, beginning in upper part on right 

 and extending across to join another small fracture on left (2,528 feet) . 



graphed, it is stopped and an exposure made by operating the surface 

 controls. The correct exposure time depends on the lens-stop setting and 

 the type of film being used and generally amounts to a few seconds. With 

 the present cameras the exposure time is controlled from the truck by the 

 length of time that voltage is applied to the cable. This can be done with 

 a manually operated switch or with an automatic time switch. 



