DEEP WELLS 



Diamond-drill holes. 



107 



Advantages. 



Disadvantages. 



Gives complete core of rocks penetrated. 

 Can be drilled at any angle. 



Other advantages similar to those of other 

 drilled wells. 



Adapted only to hard rocks. 



Requires costly outfit and materials, skilled labor, steam 



power, etc. 

 Cost greater than drilled wells. 



Other disadvantages similar to those of drilled wells. 



Wells sunk by calyx and steel-shot method. 



Outfit and cost of sinking less than in diamond- 

 drill holes. 



Readily used in connection with hydraulic- 

 rotary rig when hard rocks are encountered. 



Other advantages similar to those of drilled 

 wells. 



Both outfit and cost of operation more than in drilled wells. 



Slower than diamond drilling. 



Other disadvantages similar to those of drilled wells. 



Wells sunk by hydraulic process. 



Rapid in soft materials. 



Can be used where soft and hard beds alternate, 

 but works best in uniform materials. Pene- 

 trates hard beds by fall of drill. 



Operation nearly continuous. 



Affords good records. 



Other advantages similar to those of drilled 

 wells. 



Usually limited to relatively small diameters. 

 Requires previous supply of water for drilling process. 



Other disadvantages similar to those of drilled wells. 



Wells sunk by hydraulic rotary process. 



Very rapid in soft materials. 



Applicable to alternations of soft and hard mate- 

 rial. 



Operations are relatively continuous; little lost 

 time. 



Can penetrate hard beds by use of calyx appli- 

 ance and chilled-steel shot. 



Other advantages similar to those of drilled 

 wells. 



Satisfactory only where the materials are prevailingly soft. 



Small water seams not readily recognized; shut off by pud- 

 dling by thick sludge. 



Requires previous supply of water for process of sinking 

 well. 



Affords unsatisfactory records. 



Possible for polluting matter to penetrate by passage 



through loosened zone along casing. 

 Other disadvantages similar to those of drilled wells. 



Stovepipe or California wells. 



Utilization of all horizons of water. 



Cheapness of casings as compared with large- 

 sized driven or drilled wells. 



Shortness of sections, permitting use of steady 

 pressure by hydraulic jacks. 



Adaptability to conditions where driving is 



impossible. 



Plush outer casings and absence of screw joints. 

 Ready adjustment to strains. 

 Avoidance of clogging of perforations. 

 Exclusion of sources of pollution. 

 Affords fair records of materials and water beds 



encountered. 



Limitation to soft materials. 



Lack of strength of casing; distortion by lateral pressure; 



pulled with difficulty if distorted. 

 Thinness of casing and shortness of life where waters are 



corrosive. 

 Expensive; requires elaborate outfit available in only a few 



sections of country: skilled labor, etc. 

 Cleaned with difficulty. 



Slight storage capacity. 



Taste of water due to solution of iron by corrosive waters. 



Short life under some conditions. 



