The upstream sector
The
upstream sector involves the exploration for and extraction of
petroleum crude oil and
natural gas. The upstream oil sector is also known as the
exploration and production (E&P) sector.
The upstream sector includes the searching for potential
underground or underwater oil and gas fields, drilling of exploratory
wells, and subsequently operating the wells that recover and bring the
petroleum crude oil and/or raw
natural gas to the surface.
The midstream sector
The
midstream involves storing, marketing and transporting petroleum crude oil, natural gas,
natural gas liquids (mainly
ethane,
propane and
butane) and byproduct
sulfur. Midstream operations are sometimes included in the downstream category.
The downstream sector
The
downstream sector involves the
refining of petroleum crude oil and the
processing of raw natural gas. It includes the selling and distribution of processed natural gas and the products derived from petroleum crude oil such as
liquified petroleum gas (LPG),
gasoline (or petrol),
jet fuel,
diesel oil, other
fuel oils,
petroleum asphalt and
petroleum coke.
The downstream sector includes
petroleum refineries,
[1] petroleum product distribution, retail outlets and natural gas distribution companies.
Byproduct sulfur
Petroleum crude oil is a mixture of hundreds of
hydrocarbons,
many of which contain sulfur that is removed during the refining of the
crude oil. Raw natural gas also has sulfur-containing compounds, which
are removed in processing of the raw natural gas before it is
distributed to consumers. The sulfur-containing compounds removed in the
refining and processing of petroleum crude oil and raw natural gas are
subsequently converted into byproduct elemental sulfur. The production
and marketing of the byproduct sulfur is considered to be part of the
downstream sector.
The vast majority of the 64,000,000 metric tons of sulfur
produced worldwide in 2005 was byproduct sulphur from refineries and
natural gas processing plants.
[2]
Petrochemical industry
The
petrochemical industry
is not generally considered to be a part of the petroleum industry.
However, it is sometimes listed as a part of the downstream sector and
sometimes as a fourth sector of the petroleum industry.
- Source (http://en.citizendium.org/wiki/upstream,_midstream_and_downstream_%28petroleum_industry%29)