|  Definitions, Sources and Explanatory Notes |
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|  Category:   | Crude Reserves & Production |
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|  Topic:      | Crude Oil Proved Reserves   |
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|   Definitions |  |
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| Key Terms                               | Definition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
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| Acquisitions                            | The volume of proved reserves gained by the purchase of an existing fields or properties,from the date of purchase or transfer.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Adjustments                             | The quantity which preserves an exact annual reserves balance within each State or Statesubdivision of the following form: Adjustments + Revision Increases - Revision Decreases - Sales + Acquisitions + Extensions +New Field Discoveries + New Reservoir Discoveries in Old Fields - Report Year Production =Published Proved Reserves at End of Report YearThese adjustments are the yearly changes in the published reserve estimates that cannot beattributed to the estimates for other reserve change categories because of the survey andstatistical estimation methods employed. For example, variations as a result of changes inthe operator frame, different random samples or imputations for missing or unreported reservechanges, could contribute to adjustments.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| Crude Oil                               | A mixture of hydrocarbons that exists in the liquid phase in natural undergroundreservoirs and remains liquid at atmospheric pressure after passing through surfaceseparating facilities. Crude oil may also include:Small amounts of hydrocarbons that exist in the gaseous phase in natural undergroundreservoirs but are liquid at atmospheric pressure after being recovered from oil well(casinghead) gas in lease separators, and that subsequently are comingled with the crude stream without being separately measured. 
Small amounts of nonhydrocarbons produced with the oil.
When a State regulatory agency specifies a definition of crude oil which differs from thatset forth above, the State definition is to be followed.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| Extensions and Discoveries              | Additions to a county's proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reserves through additional drilling in periods subsequent to discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Extensions                              | The reserves credited to a reservoir because of enlargement of its proved area. Normally the ultimate size of newly discovered fields, or newly discovered reservoirsin old fields, is determined by wells drilled in years subsequent to discovery. Whensuch wells add to the proved area of a previously discovered reservoir, the increasein proved reserves is classified as an extension.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| New Field Discoveries                   | The volumes of proved reserves of crude oil, natural gas and/or natural gas liquidsdiscovered in new fields during the report year.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| New Reservoir Discoveries in Old Fields | The volumes of proved reserves of crude oil, natural gas, and/or natural gas liquidsdiscovered during the report year in new reservoir(s) located in old fields.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Production, Crude Oil                   | The volumes of crude oil which are extracted from oil reservoirs during the report year. These volumes are determined through measurement of the volumes delivered from leasestorage tanks, (i.e., at the point of custody transfer) with adjustment for (1) netdifferences between opening and closing lease inventories, and for (2) basic sedimentand water. Oil used on the lease is considered production.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Proved Reserves of Crude Oil            | Proved reserves of crude oil as of December 31 of the report year are the estimatedquantities of all liquids defined as crude oil, which geological and engineering datademonstrate with reasonablecertainty to be recoverable in future years from known reservoirs under existingeconomic and operating conditions.Reservoirs are considered proved if economic producibility is supported by actual productionor conclusive formation test (drill stem or wire line), or if economic producibility issupported by core analyses and/or electric or other log interpretations.The area of an oil reservoir considered proved includes: (1) that portion delineated bydrilling and defined by gas -- oil and/or gas -- water contacts, if any; and (2) theimmediately adjoining portions not yet drilled, but which can be reasonably judged aseconomically productive on the basis of available geological and engineering data. In theabsence of information on fluid contacts, the lowest known structural occurrence of hydrocarbons is considered to be the lower proved limit of the reservoir.Volumes of crude oil placed in underground storage are not to be considered proved reserves.Reserves of crude oil which can be produced economically through application of improvedrecovery techniques (such as fluid injection) are included in the "proved" classificationwhen successful testing by a pilot project, or the operation of an installed program inthe reservoir, provides support for the engineering analysis on which the project or programwas based.Estimates of proved crude oil reserves do not include the following: (1) oil that maybecome available from known reservoirs but is reported separately as "indicated additionalreserves"; (2) natural gas liquids (including lease condensate); (3) oil, the recoveryof which is subject to reasonable doubt because of uncertainty as to geology, reservoircharacteristics, or economic factors; (4) oil that may occur in undrilled prospects; and(5) oil that may be recovered from oil shales, coal, gilsonite, and other such sources.It is necessary that production, gathering or transportation facilities be installed oroperative for a reservoir to be considered proved. |
| Revisions                               | Changes to prior year-end proved reserves estimates, either positive or negative,resulting from new information other than an increase in proved acreage (extension).Revisions include increases of proved reserves associated with the installation ofimproved recovery techniques or equipment. They also include correction of priorreport year arithmetical or clerical errors and adjustments to prior year-endproduction volumes to the extent that these alter reported prior year reservesestimates.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Sales                                   | The volume of proved reserves deducted from an operator's total reserves whenselling an existing field or property, during the calendar year.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
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| For definitions of related energy terms, refer to the   EIA Energy Glossary. |
|  	Sources |
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|  | "Form EIA-23L, "Annual Report of Domestic Oil and Gas Reserves (County Level Version)": Survey Form | Statistical Details. |
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|  	Explanatory Notes |
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|  | Miscellaneous includes Arizona, Missouri, Nevada, New York, South Dakota, Tennessee,  and Virginia.  
   The production estimates in this table are based on data reported on Form EIA-23L,    "Annual Survey of Domestic Oil and Gas Reserves." They many differ from the official   Energy Information Administration production data for crude oil contained   in the    Petroleum Supply Annual.  
  Related data and background information are published in the      U.S. Crude Oil and Natural Gas Proved Reserves Annual Report.  
Maps of Selected State Subdivisions. |
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