What is Petroleum

February 16, 2016

NOTE: The website this information came - energy4me - from contains some older information from 2010 that may no longer be accurate, but it also provides a good basic background about oil and natural gas.

How is Petroleum Formed?

Oil and natural gas were formed from the remains of prehistoric plants and animals—that’s why they’re called “fossil fuels!” Hundreds of millions of years ago, prehistoric plant and animal remains settled into the seas along with sand, silt and rocks. As the rocks and silt settled, layer upon layer piled up in rivers, along coastlines and on the sea bottom trapping the organic material. Without air, the organic layers could not rot away. Over time, increasing pressure and temperature changed the mud, sand and silt into rock (known as source rock) and slowly “cooked” the organic matter into petroleum. Petroleum is held inside the rock formation, similar to how a sponge holds water.

Over millions of years, the oil and gas that formed in the source rock deep within the Earth moved upward through tiny, connected pore spaces in the rocks. Some seeped out at the Earth’s surface, but most of the petroleum hydrocarbons were trapped by nonporous rocks or other barriers. These underground traps of oil and gas are called reservoirs. Reservoirs are not underground “lakes” of oil; they are made up of porous and permeable rocks that can hold significant amounts of oil and gas within their pore spaces. Some reservoirs are hundreds of feet below the surface, while others are thousands of feet underground.

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.

Read more at Energy4me.com.


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