Decision support system for produced water discharges in offshore operations

Chowdhury, Md. Shakhawat Hossain (2004) Decision support system for produced water discharges in offshore operations. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (5MB)

Abstract

Offshore Oil and Gas producing platforms discharge produced water into the sea during production operations. This water contains toxic contaminants that are harmful to the marine environment. Produced water is treated before its discharge into the sea to reduce risks to the environment. Despite treatment, produced water contains a certain amount of contaminants that are not feasible to treat before discharge and can cause environmental concern. -- The main objective of this study is to develop decision support software with an application to characterize risk of produced water released from offshore platforms during operation. The specific objectives are: (1) development of a database for produced water contaminants; (2) integration of a chemical database with selected initial dilution and subsequent dispersion models; (3) development of a probabilistic fish growth model; ( 4) development of human health cancer and non-cancer risk assessment methodologies using probabilistic concepts; (5) development of a methodology to estimate the distribution of chemicals in the bones/shell/skeleton and flesh of a fish; and (6) application of the methodologies to a hypothetical case study. A chemical specific approach rather than total toxicity approach was employed to predict exposure concentration. Both deterministic and probabilistic hydrodynamic initial dilution models were used in this research. Monte Carlo simulations were performed in the probabilistic analysis. -- The database on chemicals was integrated into the initial dilution and dispersion models for predicting available concentration in the marine environment. This predicted environmental concentration (PEC) was converted to exposure concentration (EC) by incorporating probability of exposure and bioavailability. The concentration of contaminants in fish tissue was predicted through integrating a fish growth model and is presented in a modular form in the software. -- The risk of produced water to human health was based on the methodology of contaminated seafood ingestion. The hazard quotient (HQ) for non-carcinogens was predicted through dividing the chronic daily intake (CDI) by the reference dose (RfD). The cancer risk was predicted through multiplying the CDI by the slope factor (SF). The deterministic and probabilistic analyses for risk assessment were integrated into the software. Risk from radionuclides in produced water was performed in a separate module and integrated with the main database. -- This study has introduced a concept of chemical distribution within a fish's body and variability in the lipid contents in the fish. The change in edible parts during the exposure period has been predicted through a probabilistic fish growth model and integrated with the human health risk assessment methodologies.

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