ABSTRACT

Discharges of rock wastes from the drilling of offshore oil and gas wells often results In the formation of cuttings piles at the seafloor The size, nature and longevity of these piles is dependant on a range of factors, most importantly the formations drilled, mud type used, discharge point, number of wells drilled and local hydrography The primary effects of drill cuttings piles are physical (smothering, creation of topographic relief, alteration of sediment type) chemical, (oil, metal and other constituents/contaminants) and biological (responses to organic enrichment, toxicity, changes to sediment type) Secondary effects may Include Interference with fishing activity and Impact on company and industry reputation The effects of cuttings piles are summarised and considered in the context of other sources of natural and manmade seabed disturbance and recent/impending changes in North Sea drilling practices Attention has recently been focussed on cuttings piles, in part through the Imminent decommissioning of some large platforms The extent and likely duration of primary and secondary effects need to be factored Into plans for decommissioning and cuttings pile intervention projects including defining de Minunis criteria

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