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Essential Energy Educationissues, careers, classroom resources

Petroleum – Oil and Natural Gas

How is Petroleum Found?

From ancient times through the early 1900s, finding oil and gas was largely a matter of luck. Early explorers looked for oil seeps at the surface, certain types of rock outcrops and other surface signs that oil might exist below ground. This was a hit-or-miss process. But science and technology quickly developed to improve the industry’s ability to determine what lies below the ground.

Geologists study rocks on the Earth’s surface and underground. They make a map of the rocks where they think oil and gas might be found. Engineers use the geology map to drill a well under the Earth’s surface using a rig. If successful, the well will bring a steady flow of oil and gas to the surface. After the rig is removed, a pump is placed on the well head. An electric motor drives a gear box that moves a lever. The lever pushes and pulls, forcing the pump up and down, and creates a suction that draws up the oil.

Three factors affect the amount of oil or gas that can be recovered from a known reservoir: rock properties, technology and economics. While the industry cannot change the properties of the rock, it can develop new techniques to remove more oil from the rock. The industry has also made significant advances to enhance recovery from known reservoirs in the US and abroad, adding to the reserves base.

Where is Petroleum Found?

The oil and natural gas that power our homes, transportation and businesses are found in small spaces (called “pores”) between layers of rock deep within the Earth. Many offshore wells, for example, are drilled in thousands of feet of water and penetrate tens of thousands of feet into the sediments below the sea floor.

Natural gas is usually found near petroleum. Oil is then transported to refineries and distilled into fuel or base chemical products. Natural gas is pumped from below ground and travels in pipelines. Natural gas is difficult to transport across long distances. In most countries, natural gas is consumed within the country or exported to a neighboring country by pipeline. Technology for liquefying natural gas so that it can be transported in tankers (like oil) is improving, but the volume of natural gas exported in this manner is still limited. As technology expands the options for gas transportation, demand for natural gas is expected to grow.

More than 100 countries produce petroleum. Most of those countries produce both oil and natural gas; a few produce only natural gas.

Many factors can affect oil production, such as civil unrest, national or international politics, adherence to quotas, oil prices, oil demand, new discoveries, and technology development or application.

The larger subsurface traps are the easiest deposits of oil and gas to locate. In mature production areas of the world, most of these large deposits of oil and gas have already been found, and many have been producing since the 1960s and 1970s. The oil and gas industry has developed new technology to better identify and access oil and gas:

  • Improved seismic techniques (such as 3D seismic) have increased the odds of correctly identifying the location of smaller and more difficult to find reservoirs.
  • New drilling techniques can intersect a long, thin reservoir horizontally first that then turns vertically making an “L” shape. This enables the oil or gas from the reservoir to be recovered with fewer wells.

World oil production comes from more than 800,000 oil wells. More than 500,000 of these wells are in the United States, which has some of the most mature producing basins in the world. On average, an oil well in the US produces only 10 B/D, compared with 248 B/D in Russia, 3,077 B/D in Norway, and 5,762 B/D for a well in Saudi Arabia. Comparable data for natural gas wells are not readily available.

There are still many oil and gas reserves left to be discovered and produced. Future discoveries will be in deeper basins and in more remote areas of the earth. Advanced technologies also can be used to locate small reservoirs found in existing oil and gas areas.

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