A single well that produces from two separate formation at the same time. production from each zone is segregated by running two tubing strings with packers inside the single string of production casing, or by running one tubing string with a packer through one zone while the other is produced through the annulus. in a [...]

A method of preparing a well for production in which no production casing or liner is set opposite the producing formation. reservoir fluids flow unrestricted into the open wellbore. an open-hole completion has limited use in rather special situations. also called a barefoot completion.

A very small string, usually run along the outside of the tubing and banded to the tubing. commonly used for hydraulic control of safety valves and sliding sleeves. may also transmit bottom hole gauge data.

A method of producing a well in which only production casing is set through the pay zone, with no tubing or inner production string used to bring formation fluids to the surface. this type of completion has its best application in low-pressure, dry-gas reservoirs.

Drilling in which the size of the hole is smaller than the conventional hole diameter for a given depth. this decrease in hole size enables the operator to run smaller casing, thereby lessening the cost of completion. see miniaturized completion.

A single bore-hole completion where there are distinct surface-to-zone tubing strings with isolation from each other.

A completion that uses flow to purposely increase the size of the open hole wellbore.

The action of pull out and subsequently running back into the hole a string of drill pipe or tubing. making a round trip is also called tripping.

The string of casing set in a well after the surface casing but before production casing is set. keeps hole from caving and seals off troublesome formations. also called protection casing.

An exploratory or development well found to be incapable of producing either oil or gas in sufficient quantities to justify completion as an oil or gas well.

1. refers to the installation of permanent equipment for the production of oil or gas.
2. the hardware used to optimize the production of hydrocarbons from the well. this may range from nothing but a packer on tubing above an openhole completion (“barefoot” completion), to a system of mechanical filtering elements outside of perforated pipe, to a [...]

See open-hole completion

An assembly of tools made up on drill pipe that is lowered into the hole to retrieve lost or stuck equipment. also call a fish assembly.

A downhole tool typically used with motors or assemblies that restrict the allowable fluid-circulation rates. when operated, the circulation sub allows a higher circulation rate to be established by opening a path to the annulus in the top section of the tool string. this is especially useful in applications such as drilling in slim-diameter wells, where a [...]

The column, or string, of drill pipe with attached tool joints that transmits fluid and rotational power from the kelly to the drill collars and bit. often, especially in the oil patch, the term is loosely applied to both drill pipe and drill collars. compare drill stem.