TY - JOUR
T1 - Erosion of cuttings pile sediments
T2 - A laboratory flume study
AU - Black, Kevin Steven
AU - Paterson, David Maxwell
AU - Davidson, Irvine
PY - 2002/7
Y1 - 2002/7
N2 - The best practical option for remediation of drill cuttings piles is directly contingent on a firm understanding of the properties and attributes of these sediments. Whilst there is an increasing literature on the geochemical characteristics of cuttings piles, comparatively little is known regarding the transport by tidal currents and waves. This paper reports some laboratory flume experiments conducted to ascertain the threshold entrainment shear stress (tau(crit)) of drill spoil sediments from two locations (near to the drilling axis and outside the rig periphery) on the NW Hutton platform. tau(crit) varies between 0.12-1.52 Nm(-2) and statistical analysis shows a difference in sediment mobility wherein sediments farthest from the drilling axis are comparatively more stable. Specialised low-temperature scanning electron microscopy (LTSEM) and compositional analysis of sediments (particle size, metal and organic content, inhabitant macrobenthos) are used to provide some insight into the differences between sites. Swelling attributable to the greater clay content of sediment close to the drilling axis may, in part, explain the observations. Comparison of the measured entrainment thresholds with both tidal and wave-induced bed stresses (separately) predicted using numerical models indicates that the sediments are unlikely to be moved by the prevailing tidal currents, but may be moved or agitated by extreme winter storms (wave height similar to9-10 m). However, observations made during the flume experiments suggest a winnowing of the fine particles from the sediment matrix under sub-threshold stress, which may be important if these particles are geochemically reactive.
AB - The best practical option for remediation of drill cuttings piles is directly contingent on a firm understanding of the properties and attributes of these sediments. Whilst there is an increasing literature on the geochemical characteristics of cuttings piles, comparatively little is known regarding the transport by tidal currents and waves. This paper reports some laboratory flume experiments conducted to ascertain the threshold entrainment shear stress (tau(crit)) of drill spoil sediments from two locations (near to the drilling axis and outside the rig periphery) on the NW Hutton platform. tau(crit) varies between 0.12-1.52 Nm(-2) and statistical analysis shows a difference in sediment mobility wherein sediments farthest from the drilling axis are comparatively more stable. Specialised low-temperature scanning electron microscopy (LTSEM) and compositional analysis of sediments (particle size, metal and organic content, inhabitant macrobenthos) are used to provide some insight into the differences between sites. Swelling attributable to the greater clay content of sediment close to the drilling axis may, in part, explain the observations. Comparison of the measured entrainment thresholds with both tidal and wave-induced bed stresses (separately) predicted using numerical models indicates that the sediments are unlikely to be moved by the prevailing tidal currents, but may be moved or agitated by extreme winter storms (wave height similar to9-10 m). However, observations made during the flume experiments suggest a winnowing of the fine particles from the sediment matrix under sub-threshold stress, which may be important if these particles are geochemically reactive.
KW - SCANNING-ELECTRON-MICROSCOPY
KW - DRILL CUTTINGS
KW - NORTH-SEA
KW - OIL
KW - SHELF
KW - COMMUNITIES
KW - STABILITY
KW - WASTE
KW - MUDS
UR - http://www.scopus.com/inward/record.url?scp=0036623880&partnerID=8YFLogxK
UR - http://dx.doi.org/10.3723/175605402783219208
U2 - 10.3723/175605402783219208
DO - 10.3723/175605402783219208
M3 - Article
SN - 1756-0543
VL - 25
SP - 51
EP - 60
JO - Underwater Technology
JF - Underwater Technology
IS - 2
ER -