II. ENVIRONMENTAL IMPACTS AND RISKS EVALUATION OF OFFSHORE DRILLING
_____________________________________________________________________________
58
Table 6: Definitions and corresponding units of selected impact and damage categories in
CML method
III.3 ANALYSIS RESULTS AND DISCUSSIONS
II.3.1 Calculation of impact scores related to well sections
The overall analysis of the environmental impacts of the different sections of the well shows that
the contribution score of the last section of well drilling (8'' ½) is the most important in several
impact categories. This is due to the fact that OBMs constitute the largest part of the drilling
fluids for difficult technical reasons at this depth level of the well. However, it is section 26
which registers the greatest contribution in the total impact concerning acidification and
eutrophication. As for marine aquatic ecotoxicity and that of marine sediments, the largest
contribution comes from section 36" which, on the other hand, has the lowest scores in all the
other impact categories.
Figure 21: Percentage of impact scores related to well sections
Photochemical
oxidation
Secondary air pollution, formed in the
troposphere caused mainly by the
reaction of sunlight with emissions from
fossil fuel combustion creating other
chemicals (eg ozone).
kg
C2H4
Kg eq CO2/
kg C2H4
Abiotic
Depletion
Reduction in availability of abiotic
natural resources (minerals and fossils)
for human use.
kg Sb
eq
MJ
Primary/kg
Sb eq
Ressources
[MJ Primary]
0
10
20
30
40
50
60
70
80
90
100
A b i o t i c d e p le t i o n
A c id i f i c a t io n
E u t r o p h ic a t i o n
G l o b a l w a r m i n g
O z o n e l a y e r d e p le t io n
H u m a n t o x i c i t y
F r e s h w a t e r a q u a t ic e c o t o x .
M a r i n e a q u a t i c e c o t o x .
T e r r e s t r i a l e c o t o x i c i t y
M a r i n e s e d i m e n t e c o t o x .
F r e s h w a t e r s e d im e n t e c o t o x .
I o n is i n g r a d ia t i o n
P h o t o c h e m ic a l o x i d a t io n
Impact
total
%
Section 36"
Section 26"
Section 17 1/2"
Section 12 1/4"
Section 8 1/2"
_____________________________________________________________________________
58
Table 6: Definitions and corresponding units of selected impact and damage categories in
CML method
III.3 ANALYSIS RESULTS AND DISCUSSIONS
II.3.1 Calculation of impact scores related to well sections
The overall analysis of the environmental impacts of the different sections of the well shows that
the contribution score of the last section of well drilling (8'' ½) is the most important in several
impact categories. This is due to the fact that OBMs constitute the largest part of the drilling
fluids for difficult technical reasons at this depth level of the well. However, it is section 26
which registers the greatest contribution in the total impact concerning acidification and
eutrophication. As for marine aquatic ecotoxicity and that of marine sediments, the largest
contribution comes from section 36" which, on the other hand, has the lowest scores in all the
other impact categories.
Figure 21: Percentage of impact scores related to well sections
Photochemical
oxidation
Secondary air pollution, formed in the
troposphere caused mainly by the
reaction of sunlight with emissions from
fossil fuel combustion creating other
chemicals (eg ozone).
kg
C2H4
Kg eq CO2/
kg C2H4
Abiotic
Depletion
Reduction in availability of abiotic
natural resources (minerals and fossils)
for human use.
kg Sb
eq
MJ
Primary/kg
Sb eq
Ressources
[MJ Primary]
0
10
20
30
40
50
60
70
80
90
100
A b i o t i c d e p le t i o n
A c id i f i c a t io n
E u t r o p h ic a t i o n
G l o b a l w a r m i n g
O z o n e l a y e r d e p le t io n
H u m a n t o x i c i t y
F r e s h w a t e r a q u a t ic e c o t o x .
M a r i n e a q u a t i c e c o t o x .
T e r r e s t r i a l e c o t o x i c i t y
M a r i n e s e d i m e n t e c o t o x .
F r e s h w a t e r s e d im e n t e c o t o x .
I o n is i n g r a d ia t i o n
P h o t o c h e m ic a l o x i d a t io n
Impact
total
%
Section 36"
Section 26"
Section 17 1/2"
Section 12 1/4"
Section 8 1/2"