Aged drill cuttings offshore Gabon: new methodology for assessing their impact

Abstract

From the Abstract: “During E&P offshore activities, and in particular during drilling operations, the living conditions of the flora and fauna on the seabed may be disturbed. The paper describes the study made for assessing the actual impact of the discharged cuttings, the regenerating capacity of the ecosystem and the medium and long-term recolonization processes, based on in situ measurements. A previous study undertaken on cuttings recently discharged offshore Congo measured kinetics of space and time restoration of the drilling site. To validate the results we carried out a similar study dedicated on aged cuttings offshore Gabon. Usual process for monitoring biological effects of cuttings includes several approaches such as benthic macrofauna (> 1mm size) studies, physicochemical analysis of sediment and ecotoxicological tests. One of the key features of our study was to add, to this process, a study of the benthic meiofauna (0.1 to 1mm size). Experiments conducted demonstrated: very low concentrations of hydrocarbons stemming out from the cuttings, a very low toxicity of sediment, no benthic macrofauna community alteration, no change in the communities of actual and fossil foraminifera (meiofauna) and, last but not least, that the study of the benthic meiofauna improves the quality of the assessment made.”