IAGC is pleased to announce the completion and publication of an Environmental Impact Assessment (EIA) of electromagnetic (EM) techniques used for oil and gas exploration and production in the marine environment. The EM EIA was funded by the member companies of the IAGC EM Subcommittee and prepared by LGL Limited environmental research associates.
Electromagnetic (EM) survey techniques can identify differences in the resistivity of subsurface rocks that may be related to the presence of hydrocarbons. This information, when combined with measurements from other techniques such as seismic surveys, can help oil and gas companies reduce exploration risk and improve drilling success rates.
EM survey technologies currently in use offshore use an electric dipole antenna (source) towed behind a vessel. The electric and magnetic fields - either natural or subsequently induced in the subsurface - are measured and recorded by an array of receivers. To date, these receivers have usually been deployed on the seafloor then retrieved to process the measurements. Tests are currently being conducted to commercialize a system that tows the receivers underwater behind the vessel, similar to the method used in most marine seismic surveys.
The goal of the EIA was to provide a comprehensive resource summarizing available literature and potential effects of EM technologies on marine life. Designed for a broad audience, the document provides a basic description of EM survey technologies, naturally-occurring EM fields, and the potential use of these fields by diverse animal groups.
The assessment focuses on survey activities considered to have at least some potential to affect marine animals, such as EM, noise, light emissions, and accidental events.
The EIA concluded that EM sources as presently used have no potential for significant effects on animal groups such as fish, seabirds, sea turtles, and marine mammals. In addition, cumulative effects from EM surveys are negligible compared to natural EM anomalies, induced fields from natural water currents, and anthropogenic EM sources such as those originating from undersea equipment.
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