The Department of Energy and Climate Change (DECC) aggregation of UK reserves and resources as at the end of 2009 is based on data collected from operators during February and March 2010. In total, 718 fields and potential developments or past discoveries, both offshore and onshore, were reviewed.

Index to UK Oil and Gas Reserves website sections

1. Introduction
2. UK Oil Reserves and Estimated Ultimate Recovery 2010
3. UK Gas Reserves and Estimated Ultimate Recovery 2010
4. Estimates of UK Potential Additional Resources 2010
5. Pie Charts Showing Potential for UK Reserves Growth
6. Estimates of UK Undiscovered Resources
7. Summary Table Giving Ranges of UK Hydrocarbon Resources
8. Appendix 1 - Field Unit Version of UK Reserves Tables
9. All the above in Printable Format

Introduction

UK reserves are presented in a similar fashion to last year; the analysis in the oil and gas tables is now focused on (remaining) reserves instead of estimated ultimate recovery. As in the past, the UK reserves tables are presented in metric units but we have now added Appendix 1 showing field unit versions of these tables.

The overall summary page presents tabular figures for discovered resources only, with an explanatory paragraph which takes account of the estimates for undiscovered resources to arrive at a best estimate of remaining recoverable UKCS hydrocarbon resources. The Summary Table is presented in billion barrels of oil equivalent (boe) to allow comparison of oil and gas data.

Key terms are defined as follows:

Term	Definition
Estimated ultimate recovery	Total recovery from a field, i.e. reserves plus past production.
Reserves	Discovered, remaining reserves which are recoverable and commercial. Can be proven, probable or possible depending on confidence level (as described below).
Potential additional resources	Discovered reserves that are not currently technically or commercially producible.
Undiscovered resources	Undiscovered potentially recoverable resources in mapped leads.

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

Reserves	Description
Proven	Reserves which on the available evidence are virtually certain to be technically and commercially producible, i.e. have a better than 90% chance of being produced.
Probable	Reserves which are not yet proven, but which are estimated to have a better than 50% chance of being technically and commercially producible.
Possible	Reserves which at present cannot be regarded as probable, but which are estimated to have a significant but less than 50% chance of being technically and commercially producible.