Sound and the preservation of marine life

Seismic exploration and marine life

Sound has been an integral part of offshore oil and gas exploration for the last five decades. In the process of 3-D seismic mapping, sound wave reflections are used to map geologic formations below the sea-floor. The energy industry uses these 3-D images to help determine where to drill, reducing the number of wells needed to produce oil and gas resources.

Meanwhile, sounds generated from dolphins and whales, undersea volcanoes and earthquakes, commercial shipping, offshore wind turbine construction and, significantly, the weather, all contribute to a far from quiet ocean ecosystem to which marine animals are well-adjusted.

Seismic surveys are designed to produce low-frequency sounds to map geological formations. Based on peer-reviewed scientific research and almost 50 years of operational experience, there is no evidence to suggest that the sound produced during an oil and gas industry seismic air-gun survey has resulted in physical or auditory injury to marine mammals. Nor is there evidence to suggest that the use of air-guns in seismic surveys has had a population-level impact on marine mammals.

However, ExxonMobil still takes numerous precautionary measures in all its seismic operations to minimize impacts on marine life.  We support and participate in a range of academic research programs to advance our collective understanding of marine life and aquatic ecosystems.

Years of peer-reviewed and published scientific research have shown that oil and gas industry seismic air-gun surveys pose a minor risk to marine mammals. This is supported by the following governmental regulatory agencies and non-governmental scientific organizations:

The U.S. Department of Commerce’s National Marine Fisheries Service (NMFS)

With regard to mitigated offshore oil and gas seismic activity in the Arctic, the agency has stated:

1. “There is no specific evidence that exposure to pulses of air-gun sound can cause PTS [Permanent Threshold Shift in hearing; i.e., auditory injury] in any marine mammal, even with large arrays of air-guns.”
2. “To date, there is no evidence that serious injury, death, or stranding by marine mammals can occur from exposure to air-gun pulses, even in the case of large air-gun arrays.”
3. “Thus, the proposed activity is not expected to have any habitat-related effects on prey species that could cause significant or long-term consequences for individual marine mammals or their populations.”

The U.S. Department of the Interior’s Bureau of Energy Management (BOEM)

In 2015, the department issued a Final Supplemental Environmental Impact Statement for a Gulf of Mexico Offshore Continental Shelf Oil and Gas Lease Sale. It concluded that, despite more than 50 years of oil and gas exploration, “there are no data to suggest that activities from the preexisting OCS [oil and gas] Program are significantly impacting marine mammal populations.”

The U.S. National Academy of Sciences’ National Research Council

The Ocean Studies Board of the National Research Council, an authority on this topic, released a report that found:

“No scientific studies have conclusively demonstrated a link between exposure to sound and adverse effects on a marine mammal population.”

Additional information resources: Bureau of Ocean Energy Management Science Notes, August 2017 and April 2018.

Safe and responsible operations

ExxonMobil is committed to excellence in safety, security, health and environmental performance. The foundation for these standards is a disciplined management framework called the Operations Integrity Management System (OIMS). It establishes common worldwide expectations for addressing risks inherent in our business

Although there have been no instances of sound produced from oil and gas exploration hurting marine mammals, ExxonMobil still takes numerous mitigation measures in its seismic operations to minimize potential adverse impacts on physical safety, feeding, breeding and nursing life functions. Seismic exploration is also carefully regulated by federal governments and managed by operators to avoid impacting marine animals.

We have exploration procedures in place to ensure that we operate responsibly everywhere we do business. The offshore oil and gas industry, along with the geophysical contractors, conducts environmental studies and risk assessments prior to operations, and mitigation measures are carefully designed and implemented to address site-specific environmental conditions of each operation.

Key study types and mitigation measures include the following:

• Environmental assessment: This includes knowledge of species expected to be present in the habitat in question during any given season and an identification of species that could potentially be affected by marine sound.
• Temporal and spatial studies: Environmental information is evaluated ahead of seismic acquisition activities, primarily to identify sensitive times and regions, such as breeding and calving times, and feeding grounds.
• Development of risk scenarios: Possible risk scenarios are determined based on the data and information collected on species that could potentially be affected by sounds.
• Sound source and sound propagation modeling: This includes knowing the introduced sound levels and frequencies that various animals can hear and how sound levels diminish away from its source. Models are specific to the site and to the sound sources used.
• Risk assessment: For all projects, we assess the significance of risks posed by the proposed project, considering potential consequences and the probabilities. The risk assessment helps us design the proper mitigations so that we reduce potential adverse effects.
• Marine Mammal Observers: Marine Mammal Observers or Protected Species Observers are trained and certified professionals who are deployed offshore during activities where sound is produced. Their duties include conducting visual and acoustic monitoring for nearby marine species and advising the seismic crew on how to conduct operations in compliance with environmental regulations.
• Exclusion zones: This describes the zones around a seismic source array kept free of marine mammals. Operations will be delayed or shut down if specific species are detected inside an exclusion zone by a Marine Mammal Observer. The size of the exclusion zone is based on sound modeling and local regulations. 
• Soft starts: This defines the gradual ramp-up in sound designed to allow marine mammals time to move before the source reaches normal operating levels.
• Passive acoustic monitoring (PAM): Hydrophones and on-board software are used to locate vocalizing marine mammals. This is used in concert with visual observations as an additional safeguard measure.

Example species research findings

Gray whales

In an environmental assessment of the Northwest Atlantic Ocean conducted by Rice University and the National Science Foundation, researchers found that:

“Gray whales have continued to migrate annually along the west coast of North America despite intermittent seismic exploration (and much ship traffic) in that area for decades (Appendix A in Malme et al. 1984; Richardson et al. 1995), and there has been a substantial increase in the population over recent decades (Allen and Angliss 2010). The western Pacific gray whale population did not seem affected by a seismic survey in its feeding ground during a prior year (Johnson et al. 2007).”

Bowhead whales

In the same environmental assessment, researchers found that:

“Similarly, bowhead whales have continued to travel to the eastern Beaufort Sea each summer despite seismic exploration in their summer and autumn range for many years (Richardson et al. 1987), and their numbers have increased notably (Allen and Angliss 2010). Bowheads also have been observed over periods of days or weeks in areas ensonified repeatedly by seismic pulses (Richardson et al. 1987; Harris et al. 2007).”

Bottlenose dolphins

A study published in The Journal of the Acoustical Society of America documented that no injury took place and no significant behavioral reaction was observed when bottlenose dolphins were exposed to impulses from seismic air-guns. Dolphins may show little reaction to air-gun impulses, even at ranges as close as 3.9 m and with the air-gun operating at 150 cubic inches and 2000 pounds per square inch. These sound levels did not produce clear, reliable Temporary Threshold Shift [temporary hearing injury] in any dolphins tested.

Fish

The Australian energy company Woodside Ltd funded a research study in Australia on the potential impact of seismic on reef fish. The study was carried out by several Australian and U.S. Universities, and a video of the study is available online. No significant effects on fish were found, nor any significant effects on corals.