| abstract |
Process for using biodegradable drilling muds, characterized in that a biodegradable surface sludge which is stable up to about 100° C., with an adjustable filtrate-reducing power of from 2 to 13 cm<3 >depending on the amount of filtrate-reducing agent used, and with an electrical stability of greater than or equal to 1000 volts, is introduced into the well at the start of drilling, and in that, when the temperature of the terrain passed through reaches 100° C., the surface sludge is replaced with a bottom sludge which is stable at a temperature above 200° C., the volume of the surface sludge representing from 60 to 80% by volume relative to the total volume of sludge used. |