Modern offshore oil exporation requires the use of seismic surveys. Seismic surveys use compressed air to create sound waves that reflect back to the surface. Airguns towed by survey ships are fired, typically every few seconds around the clock for a week or two at a time, to penetrate sedimentary layers on the ocean floor. This enables mapping and estimation of location and quantity of reserves. Both petroleum and natural gas, and sometimes methane hydrates, are the targets of the surveys.
The auditory assault from seismic surveys has been found to damage or kill fish eggs and larvae and to impair the hearing and health of fish and marine mammals, making them vulnerable to predators and leaving them unable to locate prey or mates or communicate with each other. These disturbances can disrupt and displace important migratory patterns, pushing marine life away from suitable habitats like nurseries and foraging, mating, spawning, and migratory corridors. In addition, seismic surveys have been implicated in whale beaching and stranding incidents. Loggerhead turtles and Right Whales are of particular concern off South Carolina.
Noise from a single seismic airgun survey, used to discover oil and gas deposits hundreds of kilometers under the sea floor, can blanket an area of over 300,000 km2 , raising background noise levels 100-fold, continuously for weeks or months. Seismic airgun surveys are loud enough to penetrate hundreds of kilometers into the ocean floor, even after going through thousands of meters of ocean. Since this exposes large portions of a cetacean population to chronic noise, the International Whaling Commission’s Scientific Committee noted “…repeated and persistent acoustic insults [over] a large area…should be considered enough to cause population level impacts
Seismic survey companies, largely supported by the Department of the Interior's Bureau of Ocean Energy Management, maintain that while damage to marine life and fish could be extensive,
it will not affect the sustainability of a given species. Scientists disagree on how sustainability should be defined and measured. The killing of marine life is euphemistically called 'taking.' Industry supporters lay claim to effective mitigation procedures. Some scientists and nearly all environmentalists deride the benefits of these techniques.
Fundamentals of Drilling Offshore.
Bloomberg reports that if offshore drilling costs could be reduced by 20%, then oil extraction from the ocean floor would start to be profitable at $70 per barrel. Today's (April 2015) price of $50 is an impediment to investment and will remain so until Saudi Arabia is content it has shown the American frackers that they will not go unchallenged. The Saidi lesson is also meant to remind American drillers of who holds the key levers to pricing decisions.
The difficulty and danger of drilling offshore are proportional to the depth of the ocean and the nature of the ocean substrate being penetrated. In some locations the substrate is more rigid than in others, lessening the risk of sub-sea equipment shifting.