Survey ships use both compressed air guns and explosives to emit shock waves. With the aid of computers, seismologists can then analyze the information to pinpoint possible traps in the Earth. If the shock wave reaches a change in rock layers, it bounces back up toward hydrophones dragged behind the survey ship. Sound travels at different speeds through different types of rock. This method, known as sparking, involves sending shock waves down through the water and into the ocean floor. Surveyors can also detect possible traps through the use of seismic surveying. These readings allow geologists to hunt for the telltale signs of underground traps. By using sensitive magnetic survey equipment, a ship can pass over an area and map any magnetic anomalies that occur. When close to the surface, certain rocks affect the Earth's normal magnetic field. But as this method can only help find seeping deposits, oil companies largely depend on two other means of locating traps. When searching for fossil fuels at sea, oil geologists are able to use special sniffer equipment to detect traces of natural gas in seawater. Not all of these options are particularly viable, however, if the terrain you're canvassing is thousands of feet below pitching ocean waves. Geologists study surface features and satellite maps, check soil and rock samples, and even use a device called a gravity meter to find subtle gravitational fluctuations that might indicate a subterranean flow of oil. Needless to say, these fossil fuel deposits don't just start bubbling crude every time a hillbilly fires a rifle. Solid petroleum deposits often take the form of oil shale or tar sands. We call liquid petroleum oil and gaseous petroleum natural gas. Millions of years of heat and pressure eventually transformed this organic material into vast deposits of liquid, gas and solid petroleum, all capped in traps under thick layers of rock. ![]() In this oxygen-free environment, a kind of slow cooking process took place. This decaying matter drifted to the bottom of the ocean and, over time, was covered with sand and mud. All of this oil began as tiny plants and animals called plankton, which died in the ancient seas between 10 and 600 million years ago. However, most of the world's petroleum is trapped between 500 and 25,000 feet (152 and 7,620 meters) under dirt and rock. To find even older evidence, you don't have to look any farther than the prehistoric animals unlucky enough to have been consumed by the world's tar pits. Spanish conquistadors observed oil rising to the surface in the Gulf of Mexico in the 16th century, and the Chinese drilled for it in the ground as early as 347 A.D. While fossil fuels have only become the driving force behind human civilization in the last couple of centuries, oil and natural gas have been making their way back to the Earth's surface for millions of years. Marli Miller/Visuals Unlimited/ Getty Images ![]() In this article, we'll examine how petroleum companies go about sniffing out this buried, black gold and the methods they use to extract it.ĭr. In an effort to sustain their fossil fuel dependency, humans have built some of the largest floating structures on Earth. Other massive production facilities sit atop undersea towers that descend as far as 4,000 feet (1,219 meters) into the depths - taller than the world's most ambitious skyscrapers. Some are basically floating cities, employing and housing hundreds of people. Today's oil rigs are truly gigantic structures. Even the North Sea, which endures nearly constant inclement weather, is currently home to many offshore drilling sites. In 1947, a consortium of oil companies built the first platform that you couldn't see from land in the Gulf of Mexico. In the years that followed, petroleum companies moved even farther into the ocean. The structure was little more than a barge with a drilling outfit mounted on top, but it set the example for decades of advancements to come. In 1928, a Texan oilman unveiled the first mobile oil platform for drilling in wetlands. In the years to follow, oil prospectors pushed out into the ocean, first on piers and then on artificial islands. ![]() The first of these platforms was constructed in 1897 at the end of a wharf in California. To surmount these obstacles, petroleum companies have invested billions into the development of offshore drilling and offshore oil platforms. How do you drill in lightless ocean depths and transport all that liquid, gas and solid petroleum back to the surface? How do you keep from polluting the ocean? And how do you do all of this, with tons of special equipment, in the middle of rough seas? After all, drilling on land is an undertaking on its own. Reaching these undersea drilling sites poses quite a challenge.
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