A historical- legal study on modifications over the international oil and gas concession agreements

In the1930s, the world's oil was controlled by 7 great international oil companies who were famous as the "Seven Sisters". These companies not only controlled oil transportation, refining, sale and marketing but also dominated the oil reserves. Their domination over the oil reserves was guaranteed by old concession contracts mechanism which made too much benefit to them. Management of the oil market and determination of oil price for a very long period was the natural consequence of this domination. These companies by dividing the demand market among themselves disabled the market to determine price through the mechanism of competition. These conditions caused the host countries by constituting international coalitions ( such as Organization of the Petroleum Exporting Countries "OPEC") play the main role in determination of the oil price and at the meantime by reviewing of the experiences arisen from the old concession agreements, tried to  revise them to be more nationalized.in this article, we are seeking to raise a historical-legal analysis from the trend of the changes in international petroleum concession agreements which has been started before the 1950s and amended after the world war II until the last years of the 20th century.