List of companies by size of oil reserves

in billions of barrels:[1]
Saudi Arabian Oil Company 295
National Iranian Oil Company 287
Qatar Petroleum 165
Abu Dhabi National Oil Company 137
Iraq National Oil Company 137
Gazprom 115
Kuwait Petroleum Corporation 107
Petróleos de Venezuela S.A. 102
Nigerian National Petroleum Corporation 62
National Oil Corporation (Libya) 45
Sonatrach 40
Rosneft 35
Northern Resources

source: http://en.wikipedia.org/wiki/List_of_petroleum_companies
, http://www.data360.org/graph_group.aspx?Graph_Group_Id=981