Key terms are defined as follows:

Reserves are categorised as being ‘proven’, ‘probable’ or ‘possible’ based on confidence levels, as follows:

Introduction

Reserves data were collected from each UKCS operator during January and February 2004. Oil reserves are summed in the Oil Table below at different probability levels which give a range of estimates from proven to the maximum level.

The oil reserves included are in both sanctioned fields (i.e. fields in production or approved fields under development but not yet producing) and other significant discoveries not fully appraised. The latter comprise discoveries for which there is a planned field development and start date. Proven, probable and possible reserves for a large number of individual fields have simply been summed to give the totals shown. There is, thus, a much smaller likelihood that the true figure for total reserves is outside the given range than when considering probabilities for an individual field.

Cumulative oil production to the end of 2003 has been added to proven reserves (remaining) to give the ultimate recovery figures.

Reserves in the Oil Table are presented in metric units (million tonnes) to facilitate comparison with other energy resources and the inclusion of natural gas liquids. At the bottom of the table oil reserves (remaining) are also shown in "field" units (i.e. million barrels).

Table 4.3 - Estimates of UK Oil Reserves⁽¹⁾ and Ultimate Recovery at 31 December 2003

Includes onshore as well as offshore fields. All figures include condensate, gas liquids and liquefied products.

All entries are rounded to the nearest one million tonnes or one million barrels.

Maximum is the sum of proven, probable and possible reserves.

The oil reserves include 64 proven, 65 probable and 94 possible million tonnes in approved fields under development but not yet producing.

Cumulative production to end of 2002 has been revised upwards by 5 million tonnes.

The conversion factors used are 7.5 barrels/tonne for oil, 8.5 barrels/tonne for condensate and 11.5 barrels/tonne for natural gas liquids.

Chart 4.3 Oil Reserves v Time

The chart shows how cumulative production and ultimate recovery of oil have both grown over time and also that reserves have tended to decline since 1997 following a period of steady growth. However, the flattening of the curve shows that the rate of reserves decline has lessened significantly since 2000.

Review of UK Oil Reserves

The change in UK oil reserves during 2003 arises from a combination of:

• production during the year;
• reserves revisions in established fields;
• reserves additions from new field developments and exploration;
• changes in status of a few marginal undeveloped fields between the possible reserves and Potential additional reserves categories.

From the Oil Table it can be seen that proven reserves (remaining) at the end of 2003 stand at 571 million tonnes, which is 22 million tonnes less than at the end of 2002. Annual oil production (including condensate and natural gas liquids) in 2003 was 106 million tonnes, leaving a proven reserves replacement of 84 million tonnes. This arose from a greater confidence level in reserves, following technical and economic reassessments, which resulted in reserves moving from probable to proven in a number of fields. A significant contribution to this was development approval during 2003 of three oil fields, Broom, Buzzard and Howe, and two gas condensate fields, Atlantic and Seymour.

Probable oil reserves have decreased by 41 million tonnes. The decline in probable oil reserves reflects the fact that the reallocation of possible reserves to probable reserves has not fully kept up with that from probable to proven reserves, even though there was a net reallocation of 43 million tonnes from possible to probable reserves in 2003.

Possible oil reserves have decreased by 15 million tonnes. The decline in possible reserves reflects a progression from Potential additional reserves and exploration to possible reserves that did not fully match that from possible to probable reserves, even though there was a net reallocation of 28 million tonnes from Potential additional reserves and exploration to possible reserves.

Oil reserves include both oil and the liquids and liquefied products obtained from gas fields, gas-condensate fields and the associated gas in oil fields.

Review of UK Ultimate Recovery of Oil - (i.e. Oil Reserves plus Cumulative Production)

Ultimate recovery of oil at the proven level has increased this year by 85 million tonnes and now stands at 3,481 million tonnes. This growth is equivalent to 80% replacement of 2003's production. At the proven plus probable level, the ultimate recovery of oil has increased by 44 million tonnes. Maximum ultimate recovery of oil, combining proven plus probable plus possible reserves figures, has also increased, but to a lesser extent, by 29 million tonnes to 4,177 million tonnes.

Cumulative oil production to the end of 2003 now stands at 2,910 million tonnes.

This data was last updated on : July 2004 and is due to be updated on : June 2005

If any errors are found or if you have any comments or other queries please contact:

John Webber
email: john.webber@dti.gsi.gov.uk
phone: +44 (0) 1224 254069
fax: +44 (0) 1224 254018

Back | Title | Table of Contents
Appendix 1 | Appendix 2 | Appendix 3 | Appendix 4 | Appendix 5 | Appendix 6 | Appendix 7 | Appendix 8 | Appendix 9
Appendix 10 | Appendix 11 | Appendix 12 | Appendix 13 | Appendix 14 | Appendix 15 | Appendix 16 | Appendix 17
Index Map | Plate 1 | Plate 2W | Plate 2E | Plate 3W | Plate 3E | Plate 4W | Plate 4E | Plate 5 | Plate 6
Plate 7 | Plate 8W | Plate 8E | Plate 9W | Plate 9E | Plate 10W | Plate 10E | Plate 11 | Plate 12 | Legend