Concern over the environmental impact of drilling operations – in particular the disposal of whole mud and contaminated cuttings – is leading to a major reappraisal of acceptable mud types and the way in which they are used. Strict control over the use and discharge of fluids is exercised in, for example, the USA, the North Sea, the Adriatic and the CIS. Government agencies in almost every area of the world are conscious of the potential damage caused by drilling mud and cuttings discharges and are legislating accordingly.

In addition to these legislative pressures, increasing demands are placed on fluids as the industry drills more extended reach, horizontal and high temperature/high pressure wells. These new challenges are in addition to existing ones – such as the need to control reactive shales, provide good fluid loss control and minimise formation damage – which remain critically important to the success of a well.

Given these requirements asked of the fluid, many operators are convinced of the benefits of continuing to use oil based mud (OBM). Hence the industry, including companies such as BP, is committing considerable resources to developing ways of using OBM which comply with good environmental practices. These methods, such as cuttings cleaning and cuttings injection, are discussed by Minton, 1992 and Minton, Begby et. al., 1991.

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