Oil and gas are the main sources of energy for economic activity.
Drilling of oil and gas wells are effected by drills in condition of drilling mud. The drilling mud is required for
cooling, lubricant of the drill, elevation of drilling sludge and till not fixing of the casing pipe. The space between
the rock and the casing (or between the casing pipes) is consistently treated by circulating, spacer fluids. Then they
are squeezed out by grouting mortar. After hardening of the mortar the durable cement ring is formed around the
casing pipe.
When drilling oil and gas wells a lot of drilling sludge is formed. Such sludge is elevated to the surface of the
Earth together with drilling mud. Then the drilling mud is separated. Sludge is passed through the separator,
centrifuged, removed and throwed out into pits and dumps. Such operations may be performed in another sequence.
Dups of drilling sludge make up millions of tons and occupy large territories. This harms the environment,