Dragline - a track-mounted machine in which the bucket is attached by cables 

 and operates by being drawn toward the machine. 



Drainage - a process in which petroleum resources in a geologic formation in 

 land controlled by one owner are depleted by the extraction of 

 petroleum from the same formation in the adjacent land of another 

 owner. 



Drill bit - The cutting or boring element used in drilling oil and gas wells. 

 Bits may be grouped into three broad categories: rotary bits, 

 percussion bits, and combination rotary-percussion bits. 



Drill string - a "string" or column of drill pipe. 



Drilling rig - The derrick, drawworks, and attendant surface equipment of a 

 drilling or workover unit. 



Dry hole - An exploratory or development well found to be incapable of producing 

 either oil or gas in sufficient quantities to justify completion as 

 an oil or gas well. 



Ecesis - The establishment of a plant or animal in a new habitat. 



Ecotone - The transitional or border area between two adjacent ecological 

 communities, usually exhibiting completition between organisms 

 common to both. 



Edaphic - Of or relating to the soil. 



Edge effect - The result of the presence of two adjoining plant communities 

 (as in an ecotone) on the numbers and kinds of animals present in 

 the immediate vicinity. 



Emulsion treater - A type of treatment apparatus used to separate oil and 

 water mixtures using chemicals, heat, or both. 



Endogenous - Growing from or on the inside. 



Evapotranspiration - Loss of water both by evaporation and by transpiration 

 from the plants growing thereon. 



Exogenous - Originating from or due to external causes. 



Exploration drilling - Well drilling in unproven territory. 



Fetch - The distance along open water or land over which the wind blows. 



Fish - Any object accidentally left in the wellbore during drilling or workover 

 operations and which must be recovered before work can proceed. 



Floating oil boom - A device that floats in water that is used to contain 

 floating petroleum. 



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