text: In 1949 the first offshore oil-drilling at Oil Rocks (Neft Dashlari) in the Caspian Sea off Azerbaijan eventually resulted in a city built on pylons.In the 1960s and 1970s, multi-governmental organizations of oil–producing nations – OPEC and OAPEC –  played a major role in setting petroleum prices and policy. Oil spills and their cleanup have become an issue of increasing political, environmental, and economic importance. New fields of hydrocarbon production developed in places such as Siberia, Sakhalin, Venezuela and North and West Africa. With the advent of hydraulic fracturing and other horizontal drilling techniques, shale play has seen an enormous uptick in production. Areas of shale such as the Permian Basin and Eagle-Ford have become huge hotbeds of production for the largest oil corporations in the United States. Structure
  The American Petroleum Institute divides the petroleum industry into five sectors:
  upstream (exploration, development and production of crude oil or natural gas)
  downstream (oil tankers, refiners, retailers and consumers)
  pipeline
  marine
  service and supply
  Upstream
  Oil companies used to be classified by sales as "supermajors" (BP, Chevron, ExxonMobil, ConocoPhillips, Shell, Eni and TotalEnergies), "majors", and "independents" or "jobbers". 