EMULSIONS 



OIL IN WATER WATER IN OIL 



D - WATER BASE OIL BASE" 



TREATED 

 SALT 

 GYPSUM 

 LIME 



GAS IN WATER GAS IN OIL 



\ / 



WATER IN GAS OIL IN GAS 



GAS 



METHANE 

 AIR 



Figure 35-1. Types of rotary drilling fluids. 



for the proper drilling fluid vary widely. Fresh-water-clay drilling fluid meets 

 requirements in many drilling conditions but is unsuitable in others were salt 

 contamination is excessive. 



The following summary lists some of the more important types and names 

 of available drilling fluids. 



Water-Base 



Water 



Water, either fresh or saline, is used in some areas where only firm, 

 relatively tight formations are exposed. The drilling water is clarified in a 

 special settling pit or by chemical coagulants. Oil emulsifiers, special clay floc- 

 culants, and surface-active compounds are sometimes used with the water to 

 retard corrosion and wear on bits, to speed drilling rates, and to aid in recovery 

 of cuttings suitable for geological purposes. 



Water may also be used to spud in wells in some locations, and then it 

 may be used to accumulate fine solids and become natural drilling mud. 



723 



