664 Subsurface Geologic Methods 



DEEP-WELL CAMERA 



0. E. BARSTOW and C. M. BRYANT 



The optical system and general principle of operation of the deep- 

 well camera are shown schematically in figure 355. For clarity, the di- 

 mensional proportions of the figure have been somewhat distorted. In the 

 figure are a cut-away drawing more nearly to scale, giving a better idea 

 of how some of the parts are constructed and arranged, and a photo- 

 graph of the exterior of the assembled apparatus. 



The camera is run into the well on an electric cable, which serves to 

 transmit the power required by the apparatus and to provide remote con- 

 trol of the camera from the surface. As shown in figure 355, the apparatus 

 consists of two main parts, a camera chamber and a water chamber. The 

 camera chamber contains air at atmospheric pressure and houses the 

 camera, including the lens, the film, and the film-drive mechanism. It must 

 be strong enough to withstand the external pressure of several thousand 

 pounds to the square inch encountered in deep wells. 



The water chamber, which is filled with clear water, is used merely to 

 provide a badi of clear liquid between the lens and the rock formation 

 being photographed, an idea originally proposed by Reinhold. The water 

 chamber houses a light to illuminate the subject and an inclined mirror, 

 which permits the camera to view the wall of the well horizontally through 

 the cylindrical picture windows in the side of the water chamber. The 

 bellows shown in figure 355 serves to equalize the internal and external 

 pressures on the water chamber, so that the picture window can be rela- 

 tively large without encountering difficulties due to high pressure. In the 

 bulkhead at the top of the water chamber is a pressure window immediately 

 below the camera lens. The window must withstand full well pressure, but 

 this is a comparatively simple matter because the window diameter can be 

 small. 



Attached to the outside of the case is a spring which pushes the pic- 

 ture window against the well wall, thus minimizing the thickness of turbid 

 well fluid through which the picture must be taken. This spring also assists 

 in keeping the camera stationary during exposures. The importance of 

 pushing the camera close against the formation is illustrated in figure 355. 

 Here, one end of a shallow glass baking dish has been blocked up about 

 two inches above the table, and the dish filled with water made turbid by 

 the addition of a little aquagel. A scale on the bottom of the dish is nearly 

 invisible at one end but becomes progressively more distinct as the water 

 depth decreases from two inches to zero. The scale figures denote actual 

 immersion depth. In this case, water which would be murky enough to blot 

 out the picture completely at a distance of two inches from the picture win- 

 dow would permit reasonably clear photographs to be made at distances of 

 one-fourth or one-half inch. By pushing the picture windows against the 

 formation, satisfactory pictures have actually been made in water so turbid 



