I Drilling in sensitive areas I DNV SERVING THE OIL AND GAS Industry I 19
Suggested applicable monitoring methods for each of the identified sources with potential of influencing coral communities.
SAMPLE/ANALYSES
DESCRIPTION
PURPOSE
Sediment traps
Vertical cylinders “trapping� sinking particles in the
Collect particles to be analysed for grain size distribution, barium and other
water column.
metals. Increased levels will indicate spreading of drill cuttings.
Core samples which can be cut in various depth
Samples to be analysed for drill cutting constituents, thus mapping the spread
intervals, e.g. surface sediments and deeper
of drill cuttings.
Sediment samples
sediments. ROV inspection
Use camera on ROV.
Visual evaluation of the particle dispersion in water and at the seabed. Observe excessive sedimentation. Used in sediment sampling and deployment of equipment.
Turbidity
Sensors measuring the transparency of the water,
Indicate particle concentrations in the water to reveal spreading of drill
thus indicating particle concentrations. The data are cuttings. stored in the sensor. Water currents
Sensors measuring water currents (velocity and
Gives the main current direction and velocity at certain depths for a period of
direction). Can be of profiling type (measuring in
time. Main parameter regarding expected direction of dispersion, and when
the whole water column) or single depth
deciding where to place the measuring equipment/sampling stations.
measurements. Detects increased consecrations of metals and can be used to monitor the
Passive samplers
Diffuse Gradients in Thin-film (DGT) Passively
(DGT etc)
measures dissolved and particularly bound metals in discharge of metals from drilling operations. the water over time.
Hydrophones/ geophones
Sensors measuring sound waves and vibrations.
Obtains data on possible noise pollution and impact from tremors and vibrations through the seabed.