Petroleum (L. petroleum, from Greek πετρέλαιον, lit. "rock oil") or crude oil is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds.
The term "petroleum" was first used in the treatise De Natura Fossilium, published in 1546 by the German mineralogist Georg Bauer, also known as Georgius Agricola.
Figure 1 Pumpjack pumping an oil well model C-Pumpunit
Petroleum is used mostly, by volume, for producing fuel oil and gasoline (petrol), both important "primary energy" sources. 84% by volume of the hydrocarbons present in petroleum is converted into energy-rich fuels (petroleum-based fuels), including gasoline, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas. The lighter grades of crude oil produce the best yields of these products, but as the world's reserves of light and medium oil are depleted, oil refineries are increasingly having to process heavy oil and bitumen, and use more complex and expensive methods to produce the products required. Because heavier crude oils have too much carbon and not enough hydrogen, these processes generally involve removing carbon from or adding hydrogen to the molecules, and using fluid catalytic cracking to convert the longer, more complex molecules in the oil to the shorter, simpler ones in the fuels.
Petroleum or crude oil is an oily, flammable liquid that occurs naturally in deposits, most often found beneath the surface of the earth. Over millions of years, plant and animal remains fall to the floor of shallow seas. As the seas recede, the plant material is covered by sediment layers, such as silt, sand, clay, and other plant materials.
Upstream is everything to do with exploration, drilling, development, production, processing and transport terminal or gas processing facility.
Downstream is a term to use describe all post production process, further transport, refining and marketing, supply of petroleum and petroleum products. Essentially, once hydrocarbons are transferred to customers, they are downstream.
Midstream is a word not as widely used, more company specific, sometimes referring specially to gas, after it leaves the production facility, storage, transport further processing, such as separation of Natural Gas Liquids, production of Natural Gas Liquids, production of NGL’s, natural gas liquids, production of LNG, liquid natural gas and gas gathering stations.
Some companies used the word midstream to describe the processing, storage and transportation of all hydrocarbons.
- OFFSHORE FIELD ENGINEERING LEARNING MODULES (Preface to Offshore Geotechnical Soil Investigation) SapuraCrest Petroleum.