modelling of exposure. further development of the dream …concentrations/stressors in the sediment:...
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Modelling of exposure.Further development of the DREAM model.
Henrik Rye, SINTEF
DREAM Model
DDose-related RRisk and EEffects AAssessment MModel
• Originally: Doses on biota
• Then: Zero discharge policy
• Response: EIF for produced water
• Follow-up: EIF for drilling discharges
Two compartments involved:Water
columnBottom
sediments
Component specific EIFs
Produced Water
Drilling Operations
Model structure:
DREAM model
Dischargedata
Environmentaldata
Modelparameters/databases
Concentrationfields
Risk calculations
Pie charts and time plots
”Ocean currents used in the DREAM model. ”Snapshot”of the surface currentscalculated with the ECOM-3D model. Geographicalresolution 4 km.
Concept
2. Exposure Modeling (PEC)
1. Hazard identification
4. Risk assessment
3. Effect assessment (PNEC/thresholds)
Exposure Modeling (PEC)
PEC = Predicted Environmental Concentration.Concentrations in the recipient calculated with the DREAM model.Concentrations are calculated as a function of x, y, z and time.
PNEC = Predicted No Effect Concentration(Thresholds). The largest concentration of a product or a chemical expected tocause no measurable environmental effects. For offshore chemicals the PNEC value is determined from acute toxicity testing results values divided by an assessment factor.
EIF = Environment Impact Factor.A measure for potential environmental risk, that is, damage on marine organisms from a discharge to sea. EIF is defined as being proportional to the water volume where PEC/PNEC > 1 (or a joint risk probability > 5 %).
Unit EIF for water column: 100m x 100m x 10m (vol.)Unit EIF for the sediment: 100m x 100m (area)
Calculation of produced water concentrations with the DREAM model.
3D and time variable concentration field
Parameters
WindCurrentsBiodegradationEvaporationAdsorption to particulates
1°30'E
1°30'E
1°45'E
1°45'E
2°00'E
2°00'E
2°15'E
2°15'E
2°30'E
2°30'E
2°45'E
2°45'E
60°5
0'N 60°50'N
61°0
0'N 61°00'N
61°1
0'N 61°10'N
61°2
0'N 61°20'N
20 km1°30'E
1°30'E
1°45'E
1°45'E
2°00'E
2°00'E
2°15'E
2°15'E
2°30'E
2°30'E
2°45'E
2°45'E
60°5
0'N 60°50'N
61°0
0'N 61°00'N
61°1
0'N 61°10'N
61°2
0'N 61°20'N
20 km
5:00:00
Calculation of PEC Concentration field for discharge of produced water, calculated with the DREAM model.
The figure shows the sum of all compounds that contribute to potential risk to the environment:
• added chemicals• dispersed oil• PAH’s• phenols• heavy metals
1°30'E
1°30'E
1°45'E
1°45'E
2°00'E
2°00'E
2°15'E
2°15'E
2°30'E
2°30'E
2°45'E
2°45'E
60°5
0'N 60°50'N
61°0
0'N 61°00'N
61°1
0'N 61°10'N
61°2
0'N 61°20'N
20 km1°30'E
1°30'E
1°45'E
1°45'E
2°00'E
2°00'E
2°15'E
2°15'E
2°30'E
2°30'E
2°45'E
2°45'E
60°5
0'N 60°50'N
61°0
0'N 61°00'N
61°1
0'N 61°10'N
61°2
0'N 61°20'N
20 km
5:00:00
Risk Map Time Series
Calculation of EIF
Example of the calculated risk contributions for the concentration field. Red area/volume indicates the water volume where the concentrationsexceed thePNEC level, that is, PEC/PNEC > 1 (or a joint probability of potentialenvironmental damage > 5 %) for the red area/volume.
DischargeDischarge representedrepresented by by particlesparticles((LagrangianLagrangian approachapproach): ):
21°00'E
21°00'E
21°02'E
21°02'E
21°04'E
21°04'E
21°06'E
21°06'E
21°08'E
21°08'E
21°10'E
21°10'E
21°12'E
21°12'E
21°14'E
21°14'E
71°2
8'N
71°28'N
71°2
9'N
71°29'N
71°3
0'N
71°30'N
1 km
21°00'E
21°00'E
21°02'E
21°02'E
21°04'E
21°04'E
21°06'E
21°06'E
21°08'E
21°08'E
21°10'E
21°10'E
21°12'E
21°12'E
21°14'E
21°14'E
71°2
8'N
71°28'N
71°2
9'N
71°29'N
71°3
0'N
71°30'N
1 km
0:23:00
Deposition of particles on the sea floor:
1°42'45"E
1°42'45"E
1°43'00"E
1°43'00"E
1°43'15"E
1°43'15"E
1°43'30"E
1°43'30"E
1°43'45"E
1°43'45"E
1°44'00"E
1°44'00"E
58°2
9'30
"N
58°29'30"N
58°2
9'40
"N
58°29'40"N
58°2
9'50
"N
58°29'50"N
58°3
0'00
"N
58°30'00"N
200 m
1°42'45"E
1°42'45"E
1°43'00"E
1°43'00"E
1°43'15"E
1°43'15"E
1°43'30"E
1°43'30"E
1°43'45"E
1°43'45"E
1°44'00"E
1°44'00"E
58°2
9'30
"N
58°29'30"N
58°2
9'40
"N
58°29'40"N
58°2
9'50
"N
58°29'50"N
58°3
0'00
"N
58°30'00"N
200 m
15:12:00
DREAM: Near field plume, dissolving and non-dissolving chemicals, particle behavior:
Concentrations in the water column:
Chemical stress (toxicity):• Concentrations are calculated as for produced water
(dilution, transport and biodegradation, basically)• Near field plume mixing and descent are included
Particles stress: • Concentrations are calculated as for chemicals (no
biodegradation), except that fall-out of particles are included
• Near field plume mixing and descent are included• Chemicals with large partition coefficient (Pow ≥ 1000) are
”attached” to particles
Concentrations/stressors in thesediment:
Thickness of deposited layer (deposition of particle matter)
Oxygen content over the active bioturbation layer is calculated by means of a set of ”partial differential equations” for diffusion and consumption of pore water oxygen in the sediment
Average concentration of chemical compounds in added mud is calculated over the upper 3 cm of the sediment. Toxicity is basedon pore water concentrations deduced from ”equilibrium partitioning” between pore water and sediment concentrations
Average change of grain size (in terms of median grain sizechange) is calculated over the upper 3 cm of the sediment causedby particle deposition, mainly cuttings.
Bottom sediment fate calculations:
CC QCKzCD
ztC
+−⎟⎟⎠
⎞⎜⎜⎝
⎛∂∂
∂∂
=∂∂
Where ….
Use of the “diagenetic” equations:
Change of property
Diffusion term
Source/sink terms
Z is the vertical co-ordinatet is timeD is a diffusion coefficientC is the property consideredK and Q are reaction constants
Impact on water column:
Water columnSediment
Chemicals with Pow < 1000
Chemicals with Pow ≥ 1000
Heavy metals in barite
Particles in mud
Cuttings
Chemical stress
Particle stress
Discharge compound: Impact:
Impact on sediment: Water column
Sediment
Chemicals with Pow < 1000
Chemicals with Pow ≥ 1000
Heavy metals in barite
Particles in mud
Cuttings
Chemical stress
Grain size changeand burial
Discharge compound: Impact:
Oxygen depletion
Restitution time of the sediment:Toxicant concentrations, oxygen changes, grain size changes and burial all change over time
EIF sediment over time
0
20
40
60
80
100
120
140
160
0 2 4 6 8 10 12 14 16 18
time in months
EIF
(are
a m
2 )
burial
oxygen
toxicants
grainsize
integrated
Stressors (and corresponding risks) arecalculated for each grid cell:
1°40'E
1°40'E
1°45'E
1°45'E
58°2
8'N 58°28'N
58°3
0'N 58°30'N
2 km1°40'E
1°40'E
1°45'E
1°45'E
58°2
8'N 58°28'N
58°3
0'N 58°30'N
2 km
1:06:00
Drilling discharges included:
CuttingsParticles in mud (barite, bentonite, other …)Non-particle type chemicals in the mudDifferent types of discharges:• Discharges over “shaker” and batch discharges• Both WBM, SBM and OBM types of mud• Both exploration and production drilling• Top hole sections and deeper well sections
Example calculation:Discharges from an exploration drilling, using Water Based Mud (WBM):• Cuttings• Barite as weight material• Water soluble drilling fluid• Discharges go directly to the sea floor (upper drilling
sections) and from the drilling rig (lower drilling sections)
Deposition on the sea floor:
Risks for the sediment layer due to burial. (PNEC = 6.5 mm)9°52'00"E
9°52'00"E
9°52'20"E
9°52'20"E
9°52'40"E
9°52'40"E
9°53'00"E
9°53'00"E
9°53'20"E
9°53'20"E
9°53'40"E
9°53'40"E
66°4
1'00
"N
66°41'00"N
66°4
1'10
"N
66°41'10"N
66°4
1'20
"N
66°41'20"N
66°4
1'30
"N
66°41'30"N
200 m
10:00:00
Sediment Risk Map: Effective thickness
Publications: The use of the diagenetic equations to predict impact on sediment due to discharges of drill cuttings and mud.
Henrik Rye, Mark Reed, Ismail Durgut and May Kristin Ditlevsen, SINTEFPresented at the International Marine Environmental Modeling Seminar, Rio, 9 – 11 October 2006. Also submitted.
Development of a numerical model for calculation of exposure to toxic and non-toxic stressors in water column and sediment from drilling discharges.
Henrik Rye, Mark Reed, Tone Karin Frost (Statoil), Mathijs G.D. Smit(presently IRIS/Statoil), Ismail Durgut, Øistein Johansen and May Kristin Ditlevsen, SINTEF.Accepted for publication in the SETAC – IEAM Integrated EnvironmentalAssessment and Management Journal.
Acknowledgement
The oil companies financing the ERMS program are acknowledged for financial support as well as scientific input during the program.
Contractors in the program have been: Akvaplan-niva, Battelle, MUST, RF-Akvamiljø, SINTEF, TNO and University of Oslo, with SINTEF as the co-ordinator of the program.