The Effect of Drilling Fluid Base Oil Properties on the Occupational Hygiene and the Marine Environment

Abstract

Abstract Drilling operations can require the usage of oil base drilling fluids (OBM). These fluids are formulated as an emulsion consisting of water emulsified into a continuous oil phase. During the last decade the North Sea drilling industry has moved from using diesel oil to low toxic base oils in OBM. Further development of low toxic base oils has continued on the Norwegian Sector of the North Sea, and resulted in the use of non-aromatic base oils. The current paper describes the results from a field test where the introduction of non-aromatic base oils reduced the hydrocarbon content by more than 50% in head space level in the shale shaker area compared to the use of low toxic base oils. In this test two wells were drilled where the hydrocarbon vapour and mist were collected at the same locations in the shaker area. The first well was drilled with a more traditional low toxic mineral oil based drilling fluid. The second well was drilled in a comparable formation with a drilling fluid based on the non-aromatic base oil. The paper also describes how skin irritation is reduced when using the non-aromatic base oils compared to the use of previous base oils and synthetic base oils. The reduction in skin irritation and hydrocarbon content at head space level has significantly improved the occupational hygiene for personnel exposed to drilling fluids offshore. The paper also discusses biodegradability and toxicity of different base oils. Ecotoxicological test results indicate that use of the non-aromatic base oils may result in less environmental impact compared to use of other mineral oils or synthetic oils if an accidental discharge occurs. Finally, the paper discusses dermal irritation effects from the different drilling fluids. It is shown that use of the non-aromatic base oil reduces the skin irritation index compared to use of other oil or synthetic base oils.