Glossary

Water drive

a recovery process in which oil or gas is driven out of a reservoir by the pressure of underlying water.

Water injection

a process whereby treated water is pumped into the reservoir rock in order to maintain the reservoir pressure. Sometimes referred to as water flood.

Wax

solid hydrocarbon that is present in some crude oils, especially in paraffinic crudes. Wax deposits in pipelines can cause mechanical problems

Weather window

the part of the year when the weather can normally be expected to be suitable for carrying out offshore operations.

Well bore

the hole in the rock made by the drill bit.

Well logging

a comprehensive record of all data collected during the drilling of a well, enabling a highly detailed picture of the strata to be built up.

Wellhead

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

Wellsite geologist

oil company's supervising geologist responsible for the drilling operation

Wet natural gas

natural gas that contains large amounts of associated liquids.

Whipstock

a wedge-shaped piece of equipment placed at the bottom of a well, thus forcing the bit and drill pipe to deviate from their original direction when drilling is resumed

Wildcat

an exploration well drilled without knowledge 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.

Working Interest

an interest in an oil and gas lease that gives the owner of the interest the right to drill for and produce oil and gas on the leased acreage and requires the owner to pay a share of the costs of drilling and production operations. The share of production to which a working interest owner is entitled will sometimes be smaller than the share of costs that the working interest owner is required to bear, with the balance of the production accruing to the owners of royalties.

Workover

the process whereby a completed production well is subsequently re-entered and any necessary cleaning, repair and maintenance work done. Often done to restore or increase production.

WOW

waiting on weather.