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Muddied Waters

A Survey of Offshore Oilfield Drilling Wastes and Disposal Techniques to Reduce the Ecological Impact of Sea Dumping

by Jonathan Wills, M.A., Ph.D., M.Inst.Pet., for Ekologicheskaya Vahkta Sakhalina (Sakhalin Environment Watch); 25th May 2000

Go to Previous Page: Environmental Effects of Produced Waters Discharges continued

Environmental Effects of Drilling Waste Discharges (continued)

The Effects of Discharges of Produced Water (continued)

In his review of progress towards that reassessment, the Russian eco-toxicologist Stanslav Patin (Patin, 1999, op. cit.), mentioned above, appears to disagree with UKOOA, and with the E&P Forum's view that "the environmental aspects of produced water are well understood". Writing 12 years after Neff's 1987 paper, Patin drew attention to the relative lack of data on produced water, compared with the literature on other oilfield wastes:

In contrast with drilling fluids, the eco-toxicological studies of produced waters are rather limited. At the same time, the amounts of produced water discharges can be enormous. Everyday volumes of produced waters discharged from a single platform can reach 2,000-7,000m3 and total hundreds of thousands of tons a year... The oil content in these discharges usually varies within the range of 23-37mg/l (Law, R. J. and Hudson, P. M. 1986. Preliminary Studies of the Dispersion of Oily Water Discharges from the North Sea Oil Production Platforms. ICES C.M.1986/E:15). [p.279]

Patin summarised more recent research on produced water components:

[they may] include solutions of mineral salts along with oil, gas, low-molecular-weight hydrocarbons, organic acids, heavy metals, suspended particles and numerous technological compounds (including biocides and corrosion inhibitors) of changeable and often unknown composition used for well development and production. Prior to discharge, produced waters can be combined with injection water, deck drainage, and ballast and displacement waters that complicates the chemical composition of these discharges even more...

...it is not surprising that the toxicity of these discharges also varies within very wide limits. The values of LC50 in acute experiments range from 10-2% to 30%. The high toxicity of some produced waters is probably explained by the presence of the most toxic substances in their composition, for example heavy metals, biocides and other similar compounds. [p.284]

Patin went on to discuss studies (Described in detail in Gamble, J. C., Davies, J. M., Hay, S. J. and Dow, F. K. 1987. Mesocosm Experiments on the Effect of Produced Waters from Offshore Oil Platforms in the Northern North Sea. Sarsia 72(3-4):383-387) that revealed an increased sensitivity of zooplankton organisms (copepods and others) exposed to produced water. They were "especially vulnerable at the embryonic and larval stages of their development" when lipophilic hydrocarbons could disrupt growth.

He agreed with Neff and the E&P Forum that "field observations of the distribution of produced waters discharged from offshore platforms... reveal the rather rapid dilution... 100m from the point of discharge, produced waters can be diluted 1,000 or more times", but drew a slightly different conclusion:

The rapid dilution of produced waters is usually used as evidence to prove the limited and insignificant environmental impact of these discharges. However, hydrological conditions in different areas and even at the same place at different periods could be extremely diverse and must be taken into account. For example, the rate of dilution in shallow waters or areas with limited water circulation can be lower than the rate... for the open sea. Besides, and this is critically important, the long-term biological effects of low concentrations of produced waters have not been studied yet. Research in this direction may radically change the presently dominating concept about the insignificance of ecological disturbances in the marine environment caused by produced waters. [p.285]

These findings appear to reinforce the idea that the hydrocarbons in produced water may have a greater effect than has sometimes been thought on hydrocarbon levels in the sea near oil platforms. This is of particular relevance to the shallow, biologically productive waters of the Sakhalin Shelf. Only one northern North Sea oilfield is close to the coast (Beatrice (Davies et al. (1984, p.72) discuss the environmental effects of 24 wells drilled at Beatrice from 1978 to 1986, 11 of them with "low-toxicity, oil-based muds" and the rest, presumably, with WBM. They found that biological effects "appeared to be largely caused by organic enrichment, except in the cuttings pile beneath the platform, where physical smothering was responsible for the impoverishment of the fauna". They also reported "lower species diversity" around the platform but, 20 months after drilling ceased, there were "dramatic reductions" in hydrocarbon concentrations close to the platform, "typically of one order of magnitude". This reference also contains a useful table, for the period 1981-1986, on the proportions of discharged oil attributable to North Sea platform oil spills, produced water and oil on cuttings - giving an indication of the extent of contamination that can occur when discharges are lightly regulated. JWGW), 12 miles out in the Moray Firth). Discharges from most UK platforms are diluted and dispersed by winds and currents over about 100 miles of open sea before they can reach sensitive coastlines. This is not the case in eastern Sakhalin.

Table 12: Examples of Effects of Produced Water

(after Patin, 1999: Table 48 - Summarized Results of Toxicological Studies of Produced Waters Discharged in the Sea)

ConcentrationTest durationTest organisms Effects Reference
Dilution to 25 µg/l Hours and days Larvae of Atlantic cod (North Sea) Reduced survival Davies et al., 1981
0.15% with 5-15 µg/l of oil 100 days "Natural zooplankton" (North Sea) Reduced survival at population level "
5% 48 hours Larvae/embryos of oyster Crassostrea gigas (North Sea) 50% mortality Somerville et al., 1987
10% 24 hours Copepod Calanus Finmarchus (North Sea) 50% mortality "
5% 10 days Hydroid Campularia Flexuosa (North Sea) 50% decrease in population growth "
5-6% 15 minutes Luminescent bacteria (North Sea) 50% decrease in photoluminescence intensity "
5-6% 48 hours Daphnia Daphnia magna Immobilization of 50% of test organisms "
10% 24 hours Trout Salmo gaigdneri 50% mortality "
0.1-0.3% 60-130 days Natural communities of plankton in mesocosms (North Sea) Reduced abundance of copepod larvae, disturbances of trophic structure, biochemical changes in fish larvae Gamble et al., 1987
3-30% 96 hours (Gulf of Mexico) Invertebrates and fish 50% mortality Middleditch, 1981
1-10% Chronic tests (California Shelf) Macrophytes Macrocystis pyrifera Reduced ability of zoospores to settle on the bottom Lewis & Reed, 1994
20-70mg/l 1-2 days Fish eggs, fry and larvae (Caspian Sea) Death of juveniles at 60-70mg/l; larvae at 35-40mg/l; eggs at 20-25mg/l. Alekperov, 1989
2-30mg/l "Several days" Invertebrates (Caspian Sea) Death of crustaceans at 30mg/l; reduced survival at 2mg/l. "


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"Muddied Waters":

Contents

Author

List of Abbreviations

Summary of Conclusions

Drilling Waste Streams from Offshore Oil and Gas Installations

The Law on Offshore Wastes Discharges in Different Jurisdictions:

The OSPAR Convention

United Kingdom

Norway

Canada

United States

Inviting Regulation

Environmental Effects of Drilling Waste Discharges

The SBM Controversy

"Non-Water Quality Environmental Impacts"

Additives

Drill Cuttings

Produced Water

Minimising Waste Discharges and Their Effects

Reinjection Offshore

Cleaning Produced Waters

List of Main Sources

Selected References





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