The use and management of drilling fluids and cuttings

There are essentially three main categories of drilling fluids: oil based fluids (OBF’s), synthetic based fluids (SBF’s) and water based fluids (WBF’s). OBF’s have been traditionally been used for their high performance drilling characteristics but tend to have a poor environmental performance in terms of their ecotoxicity and their tendency to persist in cuttings piles on the seafloor. More recently, SBF’s have been developed to provide similar drilling performance as OBF’s but with improved ecotoxicity and biodegradation characteristics. Synthetic based fluids include internal olefins (IO’s), poly-alpha-olefins (PAO’s), linear-alpha-olefins (LAO’s), acetals and ester based fluids (EBF’s). WBF’s, whilst generally not delivering optimal performance in more challenging drilling conditions, provide the best environmental performance in terms of their non-toxic nature and enhanced ability to biodegrade rapidly on the seafloor.