Production tubing is a tube used in a wellbore through which

production fluid Production fluid is the fluid mixture of oil, gas and water in formation fluid that flows to the surface of an oil well from a reservoir. Its consistency and composition varies. Fluids may be described by a multitude of characteristics including ...

s are produced (travel).

Background

Production tubing is run into the drilled well after the casing is run and cemented in place. Production tubing protects wellbore casing from wear, tear, corrosion, and deposition of by-products, such as sand / silt, paraffins, and

asphaltenes Asphaltenes are molecular substances that are found in crude oil, along with resins, aromatic hydrocarbons, and saturates (i.e. saturated hydrocarbons such as alkanes). The word "asphaltene" was coined by Boussingault in 1837 when he noticed tha ...

. Along with other components that constitute the production string, it provides a continuous bore from the production zone to the

wellhead A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment. The primary purpose of a wellhead is to provide the suspension point and ...

through which

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

and

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

can be produced. It is usually between five and ten centimeters in diameter and is held inside the casing through the use of expandable packing devices. Purpose and design of production tubing is to enable quick, efficient, and safe installation, removal and re-installation. If there is more than one zone of production in the well, up to four lines of production tubing can be run.

Production casing

Production casing is the final casing string set in a well and usually reaches from the surface to TD. The type of casing used depends upon the different conditions in the well. Commonly, production casing sizes range from 4 ½" to as large as 9 ⅝". It is the last string cemented in a well unless a production liner is run. This casing isolates production in the well so that different intervals can be selectively perforated and produced. Usually, the lower zones of production are perforated first. The formations are depleted, those perforations are squeezed with cement and the casing perforated above the original perforations. The production is usually brought to the surface through tubing. Tubing is a smaller diameter pipe that is run inside of the production casing. A packer is usually set at the lower end of the casing to prevent formation fluid from entering the annulus between the tubing and the casing. A packer is an elastomer cylinder that forms a pressure seal between the tubing and the casing. Obviously, good cement placement is required in the production interval. Flow behind the casing from the production zone to a barren formation can prevent production of a large quantity of hydrocarbon.

Production liner

A production liner is a string of casing set across a production interval but does not extend all the way back the surface. Usually there is about a 500 ft (more or less) overlap between a liner and the casing string above. The production liner has the same function as a complete string of production casing. A typical casing arrangement in a well is shown in the diagram below. In this case, the surface casing is set to a depth of about 3000 ft. Two intermediate strings are set in this well — a 13 ⅜" string and a 9 ⅞" string. A 7 ⅝" production casing is set at a depth of about 15,000 ft and a 5" production liner set to TD. Probably, this well required a high mud weight at the bottom of the hole and cementing the 7 ⅝" casing at TD would have resulted in too much pressure and lost circulation. If lost circulation occurs during a primary cement job, there is little guarantee that cement will fill the designated volume behind the casing. This will require the casing be perforated and cement squeezed into the casing/well bore annulus. Production Liner

References

*
petroleum production
'. Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service. 17 Nov. 2005.

External links

Schlumberger Oilfield Glossary: production tubing
Oil wells Petroleum production Tubing (material)

Background

Production casing

Production liner

See also

References

External links