- A -
Acidize - to treat an underground formation with acid to enlarge its void spaces and allow more oil and/or gas production.

Anticline - an arched underground rock formation; usually favorable for finding oil.

- B -
Basement - the nearly impervious base rock which lies beneath sedimentary rock formations.

Basin - a general region of land area with a history of subsidence and a thick sedimentary section.

Blowout - the uncontrollable flow of oil and/or gas from a well due to failure of preventive measures. In many cases, the flow will catch fire.

- Back to Top -

- C -

Casing - larger diameter steel pipe which is put in the well and cemented in place for protection of the well bore (hole) and to allow production.

Circulation - the continuous cycling of drilling mud down through the drill pipe and up the walls of the well to the surface. Lost circulation is when the drilling mud escapes into a porous formation and does not circulate back to the surface.

Completion Costs - all costs following open hole logging, which are directed toward establishing the well as an oil and/or gas producer.

- D -

Development Well - a well intended to be drilled next to a previously discovered oil and/or gas reservoir. (Also known as developmental drilling, step-out well or offsets.)

Dry Hole (Duster) - a well that does not produce oil or gas in commercial quantities.

- Back to Top -

- E -

Exploratory Well - a well drilled outside a proven oil and/or gas producing area, or to a previously untested depth of a proven oil and/or gas producing area. (Also known as a Wildcat well.)

- F -

Farm out - an agreement by a lease owner to sublease his acreage to another party who earns his well interest in return for exploratory and/or developmental drilling.

Fish - to attempt recovery of equipment or material accidentally lost in a well hole.

- G -

Gusher - a well from which oil flows spontaneously under a strong gas and/or water drive.

- H -

Hydraulic Fracturing (Frac) - high pressure injection of oil and sand into a formation to increase permeability.

- J -

Joint - a single section of tubular steel such as drill pipe, casings or tubing.

- Back to Top -

- K -

Kelly - a hollow, 40-foot square piece of steel hitch is connected to the drill pipe and turned by the rotary table during drilling.

- L -

Lease Price (Bonus) - the amount of money paid to the mineral owner (usually the land owner), in addition to his royalty interest, for the right to drill for oil and gas for a limited period of time.

Log (Logging) - the determination and recording of certain electrical characteristics (geological and geophysical data) of formations through which a well is drilled. A log can indicate which formations have the potential to produce gas and/or oil

Lost Circulation - the failure of drilling fluid (usually drilling mud) to return to the surface due to its loss into and underground formation with high permeability.

- Back to Top -

- M -

Mud Log - a log used to provide a continuous analysis of the well by analyzing the cuttings as they are brought to the surface by mud circulation.

- O -

Offset - a drilling location next to a producing well.

Oil & Gas Lease - a conditional contract for a fixed period of time conveying to the oil and gas operator a share of the mineral interest for drilling and production purposes.

Operator - person or organization responsible for all decisions relating to drilling, testing, and completion of a well.

- P -
Packer - a long rubber cylinder which expands against the walls of a well to temporarily seal off a particular zone of interest.

Pay-Out - the period of time it takes to recoup the total investment in a well.

Pay Zone - underground geological formation which are thought to contain oil and/or gas.

Perforate - to blow holes in the casing with explosive charges.

Permeability - the capacity of void spaces to allow the flow of fluids (oil or gas) to the well.

Pits - excavations on a drilling site which hold and store drilling mud, cuttings from the well, water, and waste material.

Plug - to seal a well by cementing a block inside the casing so it can be abandoned.

Porosity - void space in a rock formation which can hold oil or gas.

Proven Reserves - the amount of oil and/or gas which can be produced (recovered) from a well or field.

- Back to Top -

- R -

Re-entry - a previously abandoned well that has had the plugs removed in an attempt to re-establish production.

Rotary Drilling - a method of digging a well by rotating drill pipe and drill bit, producing cuttings which are forded from the hole by a mud circulating system.

Roughneck - a person who works on a drilling crew.

Royalty - the fractional free interest in oil and gas production retained by the mineral owner (usually the land owner). No production expenses are charged against the royalty interest.

- Back to Top -

- S -

Secondary Recovery (Enhanced Recovery) - a method of producing oil left in a reservoir by pumping water or injecting gas into a formation to force out the lighter oil, or heating heavy oil underground so it can flow more easily.

Spud - the initiation of drilling at a well.

Squeeze - pumping cement under high pressure behind casing to seal off non-productive zones or to remedy a poor cement job.
"TD" - total depth of an oil and/or gas well.

- T -

Tight - a formation lacking in porosity or permeability.

Tight Hole - a well on which no information is available to the public.

Top Lease - leasing an oil and gas property that is currently under lease to someone else, with the hope that the current lease will expire before the lease holder discovers oil or gas. The drilling rights will then belong to the holder of the Top Lease.

Trip - to completely remove the drill pipe from a well to change a bit, perform a test or run a log.

Tubing - smaller diameter pipe which is placed inside the casing and allows oil and/or gas to reach the surface.

- W -

Wet Formation - an underground zone that contains too much water to allow commercial production of oil or gas.

Wildcat Well (Wildcat) - drilling activity seeking new oil and/or gas production predicted on distance or depth from current or past production.

Wildcatter - someone who drills wells in hope of finding oil and/or gas in areas not known to be an oil and/or gas field

- Back to Top -