|  Definitions, Sources and Explanatory Notes |
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|  Category:   | Exploration & Reserves                      |
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|                             |
|  Topic:      | Crude Oil and Natural Gas Drilling Activity |
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|   Definitions |  |
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| Key Terms                     | Definition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
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| Active Well Service Rig Count | The number of rigs doing true workovers (where tubing is pulled from the well), ordoing rod string and pump repair operations, and that are, on average, crewed andworking every day of the month.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Crude Oil                     | A mixture of hydrocarbons that exists in liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface separating facilities. Depending upon the characteristics of the crude stream, it may also include: Small amounts of hydrocarbons that exist in gaseous phase in natural underground reservoirs but are liquid at atmospheric pressure after being recovered from oil well (casinghead) gas in lease separators and are subsequently commingled with the crude stream without being separately measured. Lease condensate recovered as a liquid from natural gas wells in lease or field separation facilities and later mixed into the crude stream is also included;  
Small amounts of nonhydrocarbons produced with the oil, such as sulfur and various metals;
Drip gases, and liquid hydrocarbons produced from tar sands, oil sands, gilsonite, and oil shale.
Liquids produced at natural gas processing plants are excluded. Crude oil is refined to produce a wide array of petroleum products, including heating oils; gasoline, diesel and jet fuels; lubricants; asphalt; ethane, propane, and butane; and many other products used for their energy or chemical content. |
| Natural Gas                   | A gaseous mixture of hydrocarbon compounds, primarily methane, used as a fuelfor electricity generation and in a variety of ways in buildings, and as rawmaterial input and fuel for industrial processes.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Offshore                      | That geographic area that lies seaward of the coastline. In general, the coastline is the line of ordinary low water along with that portion of the coast that is in direct contact with the open sea or the line marking the seaward limit of inland water.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Rotary Rig                    | A machine used for drilling wells that employs a rotating tube attached to a bit for boring holes through rock.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
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| For definitions of related energy terms, refer to the   EIA Energy Glossary. |
|  	Sources |
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|  |
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|  | Rotary Rigs in Operation: By Site - Baker Hughes, In., Houston, Texas, "Rotary Rigs Running - By State".
Rotary Rigs in Operation: By Type - Baker Hughes, Inc., Houston, Texas,weekly phone recording. 
Active Well Service Rig Count: Weatherford International, Ltd., Houston, Texas. |
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|  	Explanatory Notes |
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|  | Rotary rigs in operation are reported weekly. Monthly data are averages of 4- or 5-week  reporting periods, not calendar months. Annual data are averages over 52 or 53 weeks, not  calendar year. Published data are rounded to the nearest whole number.  
   Total rotary rigs in operation is the sum of rigs drilling for crude oil, rigs   drilling for natural gas, and other rigs (not shown) drilling for    miscellaneous purposes, such as other service wells, injection wells, and   stratigraphic tests.  
   Geographic coverage is the 50 States and the District of Columbia. |
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