Exploration

Aero-magnetic surveys

Magnetometers, towed by aircraft, help to detect magnetic anomalies or to distinguish geologic features that might appear similar from seismic data alone.

Air gun

Air gun array is most common technique used for seismic surveying offshore. Compressed air is released from a chamber to produce shock waves in earth.

Appraisal drilling

Drilling to determine physical extent, reserves and likely production rate of a reservoir, together with properties of oil or gas.

Appraisal well

A well drilled as part of an appraisal drilling programme.

Bottom-hole assembly

Components, together as a group, that make up lower end of drill-string (drill bit, drill collars, drill pipe and ancillary equipment).

Capping

Tightly closing a well so that hydrocarbons cannot escape.

Casing

Steel lining used to exclude unwanted fluids; control well pressures; support sides of well bore. Casing Seat - lowest point at which casing is set. Casing head - top of casing set in well; part of casing that protrudes above surface and to which control valves and flow pipes are attached.

Cement

Pumped into space between casing and well bore wall in order to hold casing in place.

Choke

Device to restrict rate of flow during testing of an exploratory discovery.

Circulation

Techniques for bringing cuttings from bottom of well bore to surface by continuously pumping drilling mud down through drill-string and up annulus during rotary drilling.

Coiled tubing

Used to carry production tubing to bottom of well.

Compensator

Keeps drill-sting stationary while semi-submersible and derrick move.

Conductor

Wide-diameter pipe from drilling platform to sea-bed to guide drilling and contain drilling fluid.

Deep-Water Discovery

An offshore discovery located in at least 200 metres of water.

Derrick

Elongated pyramid of latticed steel mounted over bore hole for suspending and rotating drill pipes.

Discovery well

An exploratory well that finds hydrocarbons.

Down hole

A term to describe tools, equipment and instruments used in well bore.

Drill bit

Located at end of drill-string cutting head is generally designed with three cone-shaped wheels tipped with hardened teeth. Drill bits used for extra-hard rock are studded with thousands of tiny industrial diamonds.

Drill collars

Heavy pipe-sections that put weight on drill bit.

Drill cuttings

Lifted continually to surface during drilling by a circulating-fluid system driven by a pump. To facilitate removal of cuttings, mud is constantly circulated down through drill pipe, out through nozzles in drill bit, and then up to surface through space between drill pipe and well bore through earth (diameter of bit is somewhat greater than that of pipe).

Drill-string

Series of connected 9 metre length drill pipes (joints).

Dry Hole

Unsuccessful well, drilled without finding commercial quantities of hydrocarbons.

Exploration

Search for hydrocarbons by Geological and Geophysical (G&G) surveys that may be followed by exploration drilling.

Exploration well

Drilling to determine whether hydrocarbons are present.

Farm-in

Transfer of part of an oil or gas interest in consideration for an agreement by transferee(s) to meet certain expenditure that would otherwise have to be undertaken by licensee(s).

Geophysics

Branch of science that applies physical principles to study of planet earth.

Gravity surveys

Measure density variations in local rock masses. Surveys are based on use of a gravimeter down bore holes.

Horizontal Drilling

Technique for cutting a bore hole in geological strata in a horizontal, rather than normal vertical, direction.

Kick

Back pressure in well from invading oil/gas/water.

Killing a well

Filling bore with drilling mud of suitable density to stop flow of oil / gas.

Liner

Small diameter casing extending into producing layer from just inside bottom of final string of casing cemented in a well.

Modular formation dynamics tester

Measures fluid pressures and collects small samples in a well.

Plugging

Process whereby a well that is no longer needed is filled with concrete and abandoned.

Rotary Drilling

Being coupled to rotating table on derrick floor rotates drill-string.

Rotary Table/Drilling Table

Turning device on derrick floor in which drill-string is held and rotated.

Round trip

Complete process of pulling out and running in drill-string.

Seismic surveys

Measurements of seismic-wave travel. Seismic exploration is divided into refraction and reflection surveys, depending on whether the predominant portion of the seismic waves’ travel is horizontal or vertical. Refraction seismic surveys are used in exploration. Seismic reflection surveys detect boundaries between different kinds of rocks; this detection assists in mapping of geologic structures.

Shale shaker

Drilling mud passed over to sieve out cuttings.

Sidetrack Drilling

A remedial operation that results in creation of a new section of well bore for purpose of detouring around «junk», redrilling a lost hole or straightening crooked holes.

Spud

Commencement of drilling operations.

Suspended discovery

An oil or gas field identified by a discovery well but not being produced or developed.

Three-dimensional Seismic/3-D Seismic Three-dimensional images created by bouncing sound waves off underground rock formations; used to determine best places to drill for hydrocarbons.

Top drive

Powerful electric motor that rotates whole drill-string from top down.

Well Nomenclature (E&A)

Appraisal (APP)

Deviated (DEVW)

Discovery (DISC)

Exploration (EXP)

Junked & Abandoned (JA)

Plugged & Abandoned (PA)

Re-entry (RE)

Suspended (SP)

Testing (TE)

Tight Hole (TIGHT)

Wildcat

Exploration well drilled in an unproven area. (Term wild- catter comes from West Texas, where in early 1920s drilling crews encountered many wildcats as they cleared locations for exploratory wells. Shot wildcats were hung on oil derricks, and wells became known as wildcat wells.)