Symposia
Alternative Technologies to Seismic Airgun Surveys for Oil and Gas Exploration and their Potential for Reducing Impacts on Marine Mammals
A diverse group of biologists, physicists, engineers, and government representatives met in Monterey, California, in late summer 2009, to review the various technologies available and under development for finding and measuring oil and gas deposits. The goal was to find more benign alternatives to the presently used seismic airgun surveys, which are thought to impact marine mammals and other marine life.
Participants considered how airguns could be made safer, or how airgun surveys could be reduced or even replaced by quieter alternatives. Technical information presented on various technologies at the workshop was combined with the biological details to determine the potential strengths and weaknesses of each technology. It is clear that not all technologies can be used at all stages of oil and gas exploration and extraction, nor in all conditions, and that most are not presently able to replace airguns.
However, workshop panelists identified several ways in which noise in the ocean from seismic airguns might be significantly mitigated with little or no effect on the quality of data acquired. A possibly substantial fraction of the airgun sound that impacts marine mammals (either physically or behaviourally) likely comes from "waste sound" that is either too high frequency and filtered out before recording, or propagates laterally away from receivers and is also never recorded. In addition to eliminating waste sound, peak sound levels required for exploration might be significantly reduced by increasing receiver density and sensitivity (some of which is already being done), spreading the source energy out over time, and moving sources and/or receivers closer to the seafloor.
Panelists also discussed promising new technologies that are completely silent but can still lessen the amount of seismic data required to reduce the economic risk of hydrocarbon recovery, i.e. controlled source electromagnetic, and passive seismic techniques.
Thus, some technologies that are coming into commercial use at this time and/or will be commercially available in the next few years showed particular promise for reducing total airgun usage and/or source levels. Similarly, a slight change in the order that current survey technologies are used at the moment may also reduce the overall use of airguns.