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. The gas reserves quoted comprise all the gas reserves expected to be available for sale from dry gas fields, gas condensate fields, oil fields with associated gas and a small amount from coal bed methane projects. Gas reserves are summed in the Gas Table below at different probability levels which give a range of estimates from proven to the maximum level.

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

Reserves in the Gas Table are presented in units of billion standard cubic metres (bcm). At the bottom of the table gas reserves (remaining) are also shown in "field" units (i.e. trillion standard cubic feet, tcf). Note that billion means thousand million and trillion means million million.

Estimates of UK Gas Reserves ⁽¹⁾ and Ultimate Recovery at 31st December 2003

Table 4.4 Estimates of UK Gas Reserves ⁽¹⁾ and Ultimate Recovery at 31st December 2003

Notes on Gas Table

Includes onshore as well as offshore discoveries but excludes flared gas and gas consumed in production operations.

All entries are rounded to the nearest one billion cubic metres or to 0.1 trillion cubic feet (tcf).

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

The gas reserves include 37 proven, 38 probable and 22 possible billion cubic metres in approved fields under development but not yet producing.

The conversion factor used is 35.31 bcf/bcm.

To download this table click the appropriate format: Excel or CSV file.

The chart shows how cumulative production and ultimate recovery of gas have both grown over time and that reserves have been steadily declining since 1997. There is also a trend of higher annual production since 1997.

Review of UK Gas Reserves

The change in UK gas 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 the status of a few marginal undeveloped fields between the possible reserves and Potential additional reserves categories.

From the Gas Table it can be seen that proven reserves (remaining) at the end of 2003 stand at 590 bcm which is a decrease of 38 bcm from the figure for last year. Annual gas production in 2003 was 102 bcm, leaving a proven reserves replacement of 64 bcm. 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 the development approval during 2003 of five offshore dry gas fields, Carrack, Cromarty, Nuggets N4, Rose and Rhum, and two gas condensate fields, Atlantic and Seymour. The approval of two oil fields, Buzzard and Howe, also added to proven associated gas.

Probable gas reserves have decreased by 54 bcm. The decline in probable gas reserves reflects the fact that the firming up of possible reserves to probable reserves has not fully kept up with that of probable to proven reserves, even though there was a net reallocation of 10 bcm from possible to probable reserves.

Possible gas reserves have increased slightly by 5 bcm. This increase in possible reserves reflects a progression from Potential additional reserves and exploration to possible reserves that was greater than that of possible to probable reserves. There was a net reallocation of 15 bcm from Potential additional reserves and exploration to possible reserves.

Several UKCS fields have both oil and gas condensate reservoirs and the gas reserves from these are split appropriately.

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

Ultimate recovery of gas at the proven level has increased this year by 64 bcm and now stands at 2,418 bcm. This growth is equivalent to 63% replacement of 2003's production. At the proven plus probable level, the ultimate recovery of gas has increased by 9 bcm. Maximum ultimate recovery of gas, combining proven plus probable plus possible reserves, has also increased, by 15 bcm to 3,070 bcm.

Cumulative gas production to the end of 2003 now stands at 1,828 bcm.

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

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