A contoured map of a subsurface geological formation based on the time taken to reflect seismic impulses rather than the subsequently computed/interpreted depths on a depth map.TIE-IN
The action of connecting one pipeline to another or to equipment. Hence "pipeline tie in" commonly describes the connection itself.TIGHT HOLE
Drilling a well in which the information obtained is restricted and passed only to those authorized to receive it. TOTAL DEPTH (T.D)
The target depth for a well. The achieved (drilled) depth in a well at any one time. TRAP
Any geological structure which precludes the migration of oil and gas through subsurface rocks, causing the hydrocarbons to accumulate into pools. TRIP GAS
High pressure gas in a well which must be carefully controlled when withdrawing the drill string (making a trip).TURNKEY CONTRACT
Contract under which contractor carries out and completes his assignment for a fixed fee, as opposed to working on per diem basis. TWIST OFF
Breaking the drill pipe due to fatigue or excessive torque.
An area of a structure where the top of the formation is higher than the point under consideration.UPSTREAM
The exploration and production portions of the oil and gas industry.US$ or USD
The resistance of a fluid to flow, due to the mutual adherence of its molecules.
WAITING ON CEMENT (W.O.C.)
Time period that drilling is suspended while the cement used to hold casing in the well bore hardens. WATER SATURATION
The proportion of water in the pore spaces of a reservoir. See Porosity.WEIGHT ON BIT (WOB)
The amount of downward force placed on a bit by the weight of the drill stem.WELLHEAD
"Wellhead" is descriptive of a location or function rather than a specific item of equipment. See Production Wellhead.WELL LOGGING
Recording information about subsurface geologic formations; methods include records kept by the driller, mud and cutting analysis, core analysis, drill stem tests, electric and radioactivity procedures. WELL TESTING
Testing in an exploration or appraisal well is directed at estimation of reserves in communication with that well, in addition to well productivity.WILDCAT WELL
An exploration well in an unproved area.WIRELINE
A slender rod-like or threadlike small-diameter piece of metal used to lower tools, such as logging tools, perforating guns, valves, and fishing tools into a well. May include electrical conductors to power and control instruments and to convey data to the surface.WORKOVER
A maintenance job on a well usually to replace equipment or to stimulate production.