Large and small private investors
Pension Funds
Hedge Funds
Mutual Funds
Universities
Banks
Unions
Large and small corporations
Major oil companies (Exxon, British Petroleum, Arco, Shell, Conoco etc)
Oil related companies (producers, drillers, engineers, landmen, lawyers, refiners etc)
Local governments
State governments
The United States government
The United States Navy http://www.globalsecurity.org/military/facility/npr.htm