Well definitions

Appraisal well: exploration well drilled to establish the extent and size of a petroleum deposit that has already been discovered by a wildcat well.

Development well: a generic term for wells used for production of petroleum, production wells, injection wells and observation wells, and possible combinations thereof. 

Exploration well: a well drilled in order to establish the existence of a possible petroleum deposit or to acquire information in order to delimit an established deposit. Exploration well is a generic term for wildcat and appraisal wells.

Injection well: a development well or test development well used for injection of gas, water or other medium.

Junked well: a well, which during the drilling phase, has been permanently plugged for technical reasons.

Multilateral well: well drilled to produce and/or inject from several well paths simultaneously.

Observation well: a development well or test development well used to measure specific well parameters.

Other boreholes: holes drilled in order to acquire information on the rock characteristics and/or carry out geotechnical examinations for the location of installations and which are not drilled to discover or delimit a petroleum deposit or to produce or inject petroleum, water or other medium.

Production well: a development well used for production of petroleum or of water for injection purposes.

Subsea completed well: development well completed with the wellhead either on the seabed or on a template, and connected to a production or injection facility.

Technical sidetracking: necessary drilling sideways (new well track) in order to bypass unforeseen obstacles in the well and where the geological and drilling operational well target remains unaltered.

Test development well: a well used for test development.

Well: a well is a borehole which is drilled in order to discover or delimit a petroleum deposit and/or to produce petroleum or water for injection purposes, to inject gas, water or other medium, or monitor well parameters. There are several categories of wells. A well may consist of one or several well paths and may have one or several termination points.

Well path (well bore): designates the location of the well from one termination point to the wellhead. A well path may consist of one or more well tracks.

Well target: geological well target: that or those geological unit(s) into which the well is to be drilled, drilling operational well target: the termination point of the well path (includes geographical coordinates and depths in meters).

Well track: that part of a well path which extends from a point of drilling out on the existing well path to a new termination point for the well.

Wildcat well: exploration well drilled to establish (prove) whether petroleum exists in a potential petroleum deposit.