W

Water Injection
Method of enhanced recovery in which water is injected into an oil reservoir to increase pressure and maintain or improve oil production.

Waterflooding
One method of secondary recovery in which water is injected into an oil reservoir to force additional oil out of the reservoir rock and into the well bore of producing wells.

Well
A hole bored or drilled into the earth for the purpose of obtaining water, oil or gas, or other natural resources.

Well Bore
The hole in the rock made by the drill bit.

Well Completion
The techniques of preparing a newly drilled well for production.

Well Jacket
A protective structure built around an offshore well to keep boats or floating debris from damaging the wellhead.

Wellhead
The control equipment fitted to the top of a well casing, incorporating outlets, valves, blowout preventers, etc.

Wet Gas
Natural gas that contains large amounts of associated liquids.

Wildcat
An exploration well drilled in "unproven territory," without direct evidence of the contents of the underlying rock structure.

Wildcat Appraisal Well
An appraisal well drilled with minimum preliminary information about the underlying structure and conditions; it usually follows a wildcat well that reported shows of oil or gas.

WTI
An abbreviation for West Texas Intermediate. WTI is a specific grade of crude oil that is a benchmark commodity of the U.S. oil industry. 

Working Interest
The operating interest in an oil and gas lease.

Workover
The process whereby a completed production well is subsequently re-entered and any necessary cleaning, repair and maintenance work done.