II. ENVIRONMENTAL IMPACTS AND RISKS EVALUATION OF OFFSHORE DRILLING
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62
Thus, the latter is assessed, in the case of human toxicity, by taking into account the fraction
ingested by humans, via contaminated food (such as fish) or drinking water or even following
inhalation of polluted air. The high scores of the substances identified therefore depend both on
their concentrations (variable according to their mass in the fluids losses) but also on their
toxicity thresholds.
The graph in figure 24 below shows also that total emissions to water (TEW) and total emissions
to all environmental compartments (TEC) which are exposed during the life cycle of the system.
It can indeed be seen that emissions due to drilling losses to water (marine waters and marine
sediments) are greater than all emissions occurring during the other stages of the system's life
cycle.
Figure 25: Human toxicity scores of toxic substances emitted from drilling fluid losses
0.00E+00
5.00E+04
1.00E+05
1.50E+05
2.00E+05
2.50E+05
DALY/Kg
1,4-DB
eq
Section 36" 2.09E+047.04E+03 2.21E+031.03E+02 9.17E+013.21E+011.63E+01 4.76E+003.37E+00 1.52E+003.61E-01 2.09E-01 1.14E-01 1.09E-01 6.71E-02 6.30E-02 3.04E+04 7.09E+04
Section 26" 5.86E+045.89E+02 1.26E+041.20E+02 4.66E+011.13E+015.74E+00 1.69E+003.46E+00 5.33E-01 2.88E-01 5.88E-01 4.31E-02 3.64E-03 1.72E-01 2.29E-02 7.21E+04 1.45E+05
Section 17 1/2" 7.30E+049.83E+02 1.74E+037.21E+01 4.15E+011.85E+019.44E+00 2.77E+004.63E+00 8.79E-01 3.99E-01 7.32E-01 6.63E-02 2.26E-02 2.15E-01 3.77E-02 7.59E+04 1.44E+05
Section 12 1/4" 1.03E+051.09E+03 1.58E+036.46E+01 2.98E+011.17E+015.94E+00 1.75E+005.44E+00 5.53E-01 4.26E-01 1.04E+00 4.24E-02 2.33E-02 3.01E-01 2.38E-02 1.06E+05 1.86E+05
Section 8 1/2" 1.25E+051.32E+03 3.16E+023.18E+02 1.44E+024.70E+012.40E+01 7.05E+009.10E+00 2.23E+008.27E-01 1.26E+00 1.73E-01 4.37E-02 3.72E-01 9.58E-02 1.28E+05 2.21E+05
PAH
Ba
As Barite Benzene Se
V
Mo
Ni
Co
Pb
To
Cr
Zn
Cd
Sb
TEC TEW
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62
Thus, the latter is assessed, in the case of human toxicity, by taking into account the fraction
ingested by humans, via contaminated food (such as fish) or drinking water or even following
inhalation of polluted air. The high scores of the substances identified therefore depend both on
their concentrations (variable according to their mass in the fluids losses) but also on their
toxicity thresholds.
The graph in figure 24 below shows also that total emissions to water (TEW) and total emissions
to all environmental compartments (TEC) which are exposed during the life cycle of the system.
It can indeed be seen that emissions due to drilling losses to water (marine waters and marine
sediments) are greater than all emissions occurring during the other stages of the system's life
cycle.
Figure 25: Human toxicity scores of toxic substances emitted from drilling fluid losses
0.00E+00
5.00E+04
1.00E+05
1.50E+05
2.00E+05
2.50E+05
DALY/Kg
1,4-DB
eq
Section 36" 2.09E+047.04E+03 2.21E+031.03E+02 9.17E+013.21E+011.63E+01 4.76E+003.37E+00 1.52E+003.61E-01 2.09E-01 1.14E-01 1.09E-01 6.71E-02 6.30E-02 3.04E+04 7.09E+04
Section 26" 5.86E+045.89E+02 1.26E+041.20E+02 4.66E+011.13E+015.74E+00 1.69E+003.46E+00 5.33E-01 2.88E-01 5.88E-01 4.31E-02 3.64E-03 1.72E-01 2.29E-02 7.21E+04 1.45E+05
Section 17 1/2" 7.30E+049.83E+02 1.74E+037.21E+01 4.15E+011.85E+019.44E+00 2.77E+004.63E+00 8.79E-01 3.99E-01 7.32E-01 6.63E-02 2.26E-02 2.15E-01 3.77E-02 7.59E+04 1.44E+05
Section 12 1/4" 1.03E+051.09E+03 1.58E+036.46E+01 2.98E+011.17E+015.94E+00 1.75E+005.44E+00 5.53E-01 4.26E-01 1.04E+00 4.24E-02 2.33E-02 3.01E-01 2.38E-02 1.06E+05 1.86E+05
Section 8 1/2" 1.25E+051.32E+03 3.16E+023.18E+02 1.44E+024.70E+012.40E+01 7.05E+009.10E+00 2.23E+008.27E-01 1.26E+00 1.73E-01 4.37E-02 3.72E-01 9.58E-02 1.28E+05 2.21E+05
PAH
Ba
As Barite Benzene Se
V
Mo
Ni
Co
Pb
To
Cr
Zn
Cd
Sb
TEC TEW