The volume and type of solids in a drilling mud system can adversely affect mud properties, reduce penetration rates, cause damage to drilling equipment, and increase total drilling costs. Efficiency controlling the solids content of the mud system is an important phase of an efficient and cost-effective drilling program. The three basic methods of removing solids are dilution and/or displacement of whole mud, settling and mechanical solids-control equipment.
The fates of drill cuttings from offshore wells, and their effect on the marine environment, have been studied by means of side-scan sonar, scuba and underwater photography. Adverse effects are minimal and short-lived, and in some instances the accumulation of cuttings may be beneficial. Modification of normal mud and cuttings discharge procedures would be needed only in very unusual circumstances.
The rotating separator process is based on a different principle than the shale shaker process. The mud line flow is fed into the slowly rotating separator. The drilling fluid contaminated with drilled cuttings is fed into the centre of a screen coated drum as shown schematically in Fig. 1. The outside of the drum is connected to an under-pressurised ventilation system.