E FIXED CONSTRUCTIONS
E21 EARTH OR ROCK DRILLING; MINING
E21B EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
E21B2200/00 Special features related to earth drilling for obtaining oil, gas or water
E21B2200/20 Computer models or simulations, e.g. for reservoirs under production, drill bits