Dispersion and fate of oiled drill cuttings discharged from two exploration wells near Sable Island, Canada

Abstract

Sediment samples were collected to study the dispersion and fate of mineral oil hydrocarbons from the above-water discharge of oiled drill cuttings at two exploration well sites. At the shallow water (16 m), exposed location, the primary method of dispersion was wave action. Aliphatic hydrocarbon samples at times showed substantial weathering and concentrations decreased to ten times background at approximately 200 m from the wellhead. The oiled cuttings pile under the drill rig was observed to disappear within three months.

At the deeper water (70 m) location, the dispersal mechanism was ocean (tidal) currents and the oiled cuttings appeared to be much more persistent. Hydrocarbon samples showed no significant weathering and aliphatic concentrations remained more than an order of magnitude above background 1500 m from the wellhead in the primary current direction. Concentrations three orders of magnitude above background were confined within 400 m, and four orders within 200 m. Aromatic hydrocarbon profiles at both well sites indicated a source other than the base oil.