The petroleum complex hydrocarbon compounds occur naturally in rocks under the Earth's surface. There is a major element hydrogen and carbon from decomposition of organic bulk.
Petroleum hydrocarbon complex Occurs naturally in rocks below the earth's surface. A key element is composed of hydrogen and carbon from decomposition of organic substances in bulk.
Petroleum, hydrocarbon complex. Occurring naturally in the rocks beneath the surface of the earth is the main element is hydrogen and carbon from the decomposition of organic material).