|  Definitions, Sources and Explanatory Notes |
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|  Category:   | Natural Gas Exploration & Reserves |
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|  Topic:      | Dry Natural Gas 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 and Discoveries - 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.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Dry Natural Gas                         | Natural gas which remains after: 1) theliquefiable hydrocarbon portion has been removed from thegas stream (i.e., gas after lease, field, and/or plant separation);and 2) any volumes of nonhydrocarbon gases have beenremoved where they occur in sufficient quantity to render thegas unmarketable. (Note: Dry natural gas is also known asconsumer-grade natural gas. The parameters for measurementare cubic feet at 60 degrees Fahrenheit and 14.73 poundsper square inch absolute.)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 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 of Natural Gas, Dry          | The volume of natural gas withdrawn from reservoirs during the report year less (1) the volume returned to such reservoirs in cycling, repressuring of oil reservoirs, and conservation operations; less (2) shrinkage resulting from the removal of lease condensate and plant liquids; and less (3) nonhydrocarbon gases where they occur in sufficient quantity to render the gas unmarketable. Volumes of gas withdrawn from gas storage reservoirs and native gas, which has been transferred to the storage category, are not considered production. This is not the same as marketed production, because the latter also excludes vented and flared gas, but contains plant liquids. For estimation methodology, see Estimation of Reserves and Resouces.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Proved Reserves                         | Proved reserves of natural gas as of December 31 of the report year are the estimatedquantities which analysis of 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 a gas 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 natural gas placed in underground storage are not to be considered proved reserves.For natural gas, wet after lease seperation, an appropriate reduction in the reservoir gasvolume has been made to cover the removal of the liquefiable portions of the gas in lease and/orfield separation facilities and the exclusion of nonhydrocarbon gases where they occur insufficient quantity to reder the gas unmarketable.For dry natural gas, an appropriate reduction in the gas volume has been made to cover theremoval of the liquefiable portions of the gas in lease and/or field separation facilities,and in natural gas processing plants, and the exclusion of nonhydrocarbon gases where theyoccur in sufficient quantity to render the gas unmarketable.It is not necessary that production, gathering, or transportation facilities be installed oroperative for a reservoir to be considered proved. It is to be assumed that compressionwill be initiated if and when economically justified. |
| 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)".  Natural Gas Survey Forms and Instructions
 	Explanatory Notes
  Related data and background information are published in the      U.S. Crude Oil and Natural Gas Proved Reserves Annual Report. |