Research Document - 2002/120

Modelling Oceanic Fates of Oil, Drilling Muds and Produced Water from the Offshore Oil and Gas Industry, with Application to the Queen Charlotte Basin.

By Crawford, W., Cretney, W., Cherniawsky, J., Hannah, C.

Abstract

This manuscript describes the fate of oil, produced water and drilling muds that may be introduced into the ocean by offshore oil exploration and production, and also discusses models of these fates. Oil releases are generally accidental, whereas produced water and drilling muds enter as a normal part of oil exploration and production.

Efforts to model the oceanic fates of contaminants from the offshore oil and gas industry require both generic models and site-specific models. Generic models, which simulate the behaviour of contaminants in the ocean, have been developed over a period of several decades, and include the cumulative knowledge of laboratory and field experiments, theoretical studies, and experience with acute and chronic releases of contaminants, assembled to provide the industry and regulatory agencies with guidelines for safe, environmentally benign operations. Oil spreading on the ocean, oil advection over the ocean by winds, and oil evaporation are examples of such processes.

The role of combining these individual processes into a computer application that will provide reasonable accounting of the risks and impacts of contaminants, is filled by integrated computer models. In the past decade several commercial products have been developed to fill this requirement, along with a few additional products developed by government and non-profit agencies. These integrated models address two issues. First, the contaminant spread and drift through the ocean must be simulated prior to exploration to answer questions such as:

Second, if hydrocarbon exploration proceeds, integrated models must be available to predict the motion of any contaminant released, to enable clean-up and protection operations.

It is expected that integrated models will be available to provide the means to address issues such as these for release of floating contaminants. In the case of drilling muds and produced water, which might be released into the ocean at reasonably small rates over the entire life of an oil and gas production region, the computer applications may require additional development. All integrated models require site-specific information. Processes such as oil evaporation, spreading, and emulsification depend on features of local oil. Processes such as drift, emulsification, and shoreline adhesion require knowledge of shoreline slope and material, ocean currents, tidal currents, wind and wave regime, usually at each site in the basin, at each season of the year.

Funding was provided until 1996 by the Panel for Energy Research and Development (PERD) and by Fisheries and Oceans Canada to examine the physical oceanography of the Queen Charlotte Basin, with concentration of effort for seasons between late spring and early autumn. These studies provided information on the general oceanographic properties of this region, as presented by Cretney et al. (2003), and began the development of numerical hydrodynamical models of ocean currents for input to the integrated computer models. The faster computers and cheaper memory and disk storage now available will enable the required improvement of these numerical models.

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