Commercial reserves and contingent resources (unaudited) working interest basis
Year ended 31 December 2009

  Africa Europe South Asia Total
  Oil
mmbbl		 Gas
bcf		 Oil
mmbbl		 Gas
bcf		 Oil
mmbbl		 Gas
bcf		 Oil
mmbbl		 Gas
bcf		 Petroleum
mmboe
  • 1.
    Proven and Probable Commercial Reserves are based on a Group reserves report produced by an independent engineer. Reserves estimates for each field are reviewed by the independent engineer based on significant new data or a material change with a review of each field undertaken at least every two years.
  • 2.
    Proven and Probable Contingent Resources are based on both Tullow’s estimates and the Group reserves report produced by an independent engineer.
Commercial reserves1                  
1 January 2009 256.5 12.3 1.8 191.4 – 130.9 258.3 334.6 314.1
Revisions 13.0 12.3 (0.4) (22.0) – – 12.6 (9.7) 11.0
Disposals – – – – – (20.3) – (20.3) (3.4)
Production (13.9) (1.2) (0.2) (30.4) – (11.6) (14.1) (43.2) (21.3)
31 December 2009 255.6 23.4 1.2 139.0 – 99.0 256.8 261.4 300.4
                   
Contingent resources2                  
1 January 2009 301.6 1,110.5 – 131.8 – 16.2 301.6 1,258.5 511.3
Revisions 83.6 7.1 – (16.9) – – 83.6 (9.8) 82.0
31 December 2009 385.2 1,117.6 – 114.9 – 16.2 385.2 1,248.7 593.3
                   
Total                  
31 December 2009 640.8 1,141.0 1.2 253.9 – 115.2 642.0 1,510.1 893.7

The Group provides for depletion and amortisation of tangible fixed assets on a net entitlements basis, which reflects the terms of the Production Sharing Contracts related to each field. Total net entitlement reserves were 265.4 mmboe at 31 December 2009 (31 December 2008: 114.5 mmboe).

Contingent Resources relate to resources in respect of which development plans are in the course of preparation or further evaluation is under way with a view to development within the foreseeable future.