The seven sisters were the modern day OPEC

via @chigrl:

They were;:
1. Anglo-Iranian (started as Anglo-Persian) Oil Company..later became $BP
2. Gulf Oil (later part of Chevron)
3. Royal Dutch Shell
4. Standard Oil Company of California (SoCal, now Chevron)

5. Standard Oil Company of New York (Socony, later Mobil, also now part of ExxonMobil
6. Standard Oil company of New Jersey (ESSO then later part of XOM)
7. Texaco (later merged into Chevron)