This paper discusses the drilling related complexities of the Greater Ekofisk basin which have demanded innovative shale stabilizing mud systems. The innovative mud systems discussed include "pseudo and synthetic" oil emulsion fluids; and cationic water based fluids. Phillips Petroleum Company Norway (PPCoN) has improved drilling fluids standards and drilling/wellbore performance with environment awareness.

The environmental evaluations of the innovative drilling fluids have involved a series of studies including Acute toxicity; Bio-degradability; and Bio-accumulation. In addition, marine seabed surveys have included studies to trace drilling fluids in the sea bottom sediments. The studies have revealed weaknesses in some test procedures. Through cooperation with external research laboratories, alternative test methods have been developed and evaluated.

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