Historical Gross Proved Reserves 1

  2010 2009 2008 2007 2006
Oil and liquids (mmbbls)          
Opening balance 531.9 544.5 749.3 766.5 736.1
Discoveries, additions and extensions 33.5 29.0 36.9 29.3 80.0
Purchase of reserves 4.7 1.2 0.3 1.1 26.2
Sale of reserves (19.4) (53.7) (19.5) (18.0) (15.6)
Net revisions and transfers 27.8 87.8 (140.8) 58.2 34.0
Production (68.8) (76.9) (81.7) (87.8) (94.2)
Closing balance 509.7 531.9 544.5 749.3 766.5
Natural gas (bcf)          
Opening balance 5,272.7 5,338.4 5,464.2 5,402.9 5,416.6
Discoveries, additions and extensions 1,151.7 861.7 395.3 475.7 564.1
Purchase of reserves 83.7 24.6 18.1 251.8 3.7
Sale of reserves (876.4) (426.6) (65.3) (211.3) (64.7)
Net revisions and transfers 104.3 (56.9) (17.6) 0.2 (33.8)
Production (499.1) (468.5) (456.3) (455.1) (483.0)
Closing balance 5,236.9 5,272.7 5,338.4 5,464.2 5,402.9
boe (mmboe)2          
Opening balance 1,410.7 1,434.3 1,659.8 1,667.0 1,638.8
Discoveries, additions and extensions 225.5 172.6 102.8 108.5 174.1
Purchase of reserves 18.6 5.3 3.3 43.1 26.8
Sale of reserves (165.5) (124.8) (30.3) (53.2) (26.4)
Net revisions and transfers 45.2 78.3 (143.5) 58.1 28.4
Production (152.0) (155.0) (157.8) (163.7) (174.7)
Closing balance 1,382.5 1,410.7 1,434.3 1,659.8 1,667.0
  1. See the notes found in this Annual Report.
  2. Six mcf of natural gas equals one boe.