I. LITERATURE REVIEW OF OFFSHORE OIL AND GAS DRILLING
33
I.4.3.3
Behaviour of drilling emissions in the marine environment
Exposure to marine pollution linked to offshore drilling activities concerns various targets
depending on the levels of pollutants and their behaviour: aquatic species living in different
levels of the water column; aquatic species living near marine sediments or in their interstitial
waters; humans through the consumption of contaminated seafood.
Drilling fluids, particularly oil-based (WBM) fluids with a high hydrocarbon content, have a
complex chemical fate that depends on the physico-chemical and bathymetric conditions of the
marine environment.
Several processes characterize this fate, such as surface evaporation of light hydrocarbon
fractions, dispersion in the water column, persistence of emulsions formed with seawater and the
possibility of being transformed into polymers that are difficult to degrade.
Some research is taking a more ecosystem-based approach to measuring the effects of chronic
contamination from offshore drilling. This research is increasingly revealing the existence of
cumulative and long-term consequences. New evidence indicates that the composition of species
of marine microorganisms can change dramatically; bacteria that feed on hydrocarbons develop
particularly rapidly, to the detriment of other microorganisms (Kloff and al.2004; Al-Hadhrami
and al., 1995; Vik and al., 1996).
Other studies show high mortality and morphological abnormalities for fish eggs and larvae
(NERC, 1994; MacGarvin, 1995). A Norwegian study has recently shown that exposing fish to
very small amounts of polycyclic aromatic hydrocarbons (HAPs), present in production waters,
results in the feminization of male fish, this significantly reduces fertility and delays the
spawning period by several weeks (Meier and al., 2002). Cancers in fish and especially in
benthic organisms have been directly related to pollution from offshore production facilities
(Anderson, 1990; Klekowski and al., 1994).
The degradation of organic molecules in drilling wastes by microorganisms can lead to anoxic
zones that are problematic for local communities. In this respect, the risk arises from the
combination of an anoxic zone and the inherent toxicity of the drilling waste and possibly the
degradation products.
On other hand, metals can also be found in concentrations of concern in drilling waste due to the
chemical composition of diesel fuel as well as that of certain additives and reagents. For
example, the worrying concentrations of lead, barium and other metals in drilling effluents as
well as rock cuttings are due to the initial high levels in the chemical composition of gas oil and
barite produced in Algeria (Ghazi M.2010).
33
I.4.3.3
Behaviour of drilling emissions in the marine environment
Exposure to marine pollution linked to offshore drilling activities concerns various targets
depending on the levels of pollutants and their behaviour: aquatic species living in different
levels of the water column; aquatic species living near marine sediments or in their interstitial
waters; humans through the consumption of contaminated seafood.
Drilling fluids, particularly oil-based (WBM) fluids with a high hydrocarbon content, have a
complex chemical fate that depends on the physico-chemical and bathymetric conditions of the
marine environment.
Several processes characterize this fate, such as surface evaporation of light hydrocarbon
fractions, dispersion in the water column, persistence of emulsions formed with seawater and the
possibility of being transformed into polymers that are difficult to degrade.
Some research is taking a more ecosystem-based approach to measuring the effects of chronic
contamination from offshore drilling. This research is increasingly revealing the existence of
cumulative and long-term consequences. New evidence indicates that the composition of species
of marine microorganisms can change dramatically; bacteria that feed on hydrocarbons develop
particularly rapidly, to the detriment of other microorganisms (Kloff and al.2004; Al-Hadhrami
and al., 1995; Vik and al., 1996).
Other studies show high mortality and morphological abnormalities for fish eggs and larvae
(NERC, 1994; MacGarvin, 1995). A Norwegian study has recently shown that exposing fish to
very small amounts of polycyclic aromatic hydrocarbons (HAPs), present in production waters,
results in the feminization of male fish, this significantly reduces fertility and delays the
spawning period by several weeks (Meier and al., 2002). Cancers in fish and especially in
benthic organisms have been directly related to pollution from offshore production facilities
(Anderson, 1990; Klekowski and al., 1994).
The degradation of organic molecules in drilling wastes by microorganisms can lead to anoxic
zones that are problematic for local communities. In this respect, the risk arises from the
combination of an anoxic zone and the inherent toxicity of the drilling waste and possibly the
degradation products.
On other hand, metals can also be found in concentrations of concern in drilling waste due to the
chemical composition of diesel fuel as well as that of certain additives and reagents. For
example, the worrying concentrations of lead, barium and other metals in drilling effluents as
well as rock cuttings are due to the initial high levels in the chemical composition of gas oil and
barite produced in Algeria (Ghazi M.2010).