text: Most upstream work in the oil field or on an oil well is contracted out to drilling contractors and oil field service companies.
  Aside from the NOCs which dominate the Upstream sector, there are many international companies that have a market share.  For example:
  BG Group
  BHP
  ConocoPhillips
  Chevron
  Eni
  ExxonMobil
  First Texas Energy Corporation
  Hess
  Marathon Oil
  OMV
  TotalEnergies
  Tullow Oil
  Rosneft
  Midstream
  Midstream operations are sometimes classified within the downstream sector, but these operations compose a separate and discrete sector of the petroleum industry. Midstream operations and processes include the following:
  Gathering: The gathering process employs narrow, low-pressure pipelines to connect oil- and gas-producing wells to larger, long-haul pipelines or processing facilities.
  Processing/refining: Processing and refining operations turn crude oil and gas into marketable products. In the case of crude oil, these products include heating oil, gasoline for use in vehicles, jet fuel, and diesel oil. Oil refining processes include distillation, vacuum distillation, catalytic reforming, catalytic cracking, alkylation, isomerization and hydrotreating. Natural gas processing includes compression; glycol dehydration; amine treating; separating the product into pipeline-quality natural gas and a stream of mixed natural gas liquids; and fractionation, which separates the stream of mixed natural gas liquids into its components. The fractionation process yields ethane, propane, butane, isobutane, and natural gasoline.