Oceanic Oil Exploration

Exploring for oil at sea is both different and very similar to land exploration. The initial exploration is done using a seismic survey, but the technology employs sonar. Drilling is still the only way to reach the oil, but the drilling rig is on the surface of the water.

On land, a seismic survey is conducted with explosives or powerful vibrating plates. These produce loud sound waves in the earth. Sensitive microphones called geophones listen for the outgoing and return waves. Every layer of rock, and every crack or discontinuity in the underlying material bounces the sound waves back to the surface. These signals can be turned into pictures that show all the layers, cracks and folds in the rock below.

At sea, the sound source is a powerful sonar generator. It makes loud, sharp sounds using small explosives or an explosive release of air. The generator is towed underwater, near the surface. Behind it is a long string of hydrophones to listen for the return waves. The sound waves penetrate the water easily and enter the sea floor below. Just like a scan on land, the sound waves return from cracks, layers and folds in the rock. So again, the result is a picture of the geology.

When the geologists select a spot to drill, the company moves a drilling rig into place. If the water is less than 150 feet deep, drilling is relatively easy and safe. A fixed rig is floated to the site and filled with water. It sinks, feet first, and comes to rest on the sea floor, with its top well above the surface of the water. On top of this platform, all the drilling equipment is installed and drilling commences. In deep water, the drilling platform is actually floating. It must be continuously adjusted with thrusters to stay in position above the drill site.

All these activities have consequences. The sonar emits sounds so loud they can destroy tissue. There is some suspicion that whales and dolphins have lost their hearing due to high-power sonar. It isn’t proven, just possible. Because sound travels for long distances underwater with little loss of power, it is possible to harm animals many miles from the sound source.

As we have all seen with BP, the risks of drilling in deep water are far greater than those in shallow water. The Gulf coast is full of shallow water drilling platforms that have been quietly producing oil for years with no issues at all. Unfortunately, it seems to require a major disaster to open our eyes to the dangers of risky behavior in the absence of intelligent and meaningful regulation.