Completion (oil and gas wells)

However, advances in interventions such as coiled tubing and tractors means that barefoot wells can be successfully produced.

However, excessive gas and water production is difficult to control, and may require frequent clean outs.

This designation refers to a range of completions where no casing or liner is cemented in place across the production zone.

In competent formations, the zone might be left entirely bare, but some sort of sand-control and/or flow-control means are usually incorporated.

Openhole completions have seen significant uptake in recent years, and there are many configurations, often developed to address specific reservoir challenges.

There have been many recent developments that have boosted the success of openhole completions, and they also tend to be popular in horizontal wells, where cemented installations are more expensive and technically more difficult.

The liner is prepared with multiple small drilled holes, then set across the production zone to provide wellbore stability and an intervention conduit.

Multiple sliding sleeves can also be used in conjunction with openhole packers to provide considerable flexibility in zonal flow control for the life of the wellbore.

Openhole completions (in comparison with cemented pipe) require better understanding of formation damage, wellbore clean-up and fluid loss control.

There are an increasing number of ideas coming into the market place to extend the options for openhole completions; for example, electronics can be used to actuate a self-opening or self-closing liner valve.

This might be used in an openhole completion to improve clean-up, by bringing the well onto production from the toe-end for 100 days, then self-opening the heel-end.

Most service companies uses an alpha and beta wave design to cover the total length of the horizontal well with gravel.

It's known that very long wells (around 6000 ft) were successfully gravel packed in many occasions, including deepwater reservoirs in Brazil.

However gas and water build up is difficult to control and selective stimulation not possible the well can't be easily deepened and additional rig time may be needed.

This time additional expense in perforating the casing is incurred, also log interpretation is critical and it may be difficult to obtain good quality cement jobs.

This is the pressure containing equipment at the surface of the well where casing strings are suspended and the blowout preventer or Christmas tree is connected.

Production tubing may be manufactured using various grades of alloys to achieve specific hardness, corrosion resistance or tensile strength requirements.

When closed the DHSV forms a barrier in the direction of hydrocarbon flow, but fluids can still be pumped down for well kill operations.

On wells with gas lift capability, many operators consider it prudent to install a valve, which will isolate the A annulus for the same reasons a DHSV may be needed to isolate the production tubing in order to prevent the inventory of natural gas downhole from becoming a hazard as it became on Piper Alpha.

This device is used for artificial lift to help provide energy to drive hydrocarbons to surface if reservoir pressure is insufficient.

During installation, the power cable is spliced into the ESP then attached to the outside of the tubing by corrosion resistant metal bands as it is run in the hole.

A completion component fabricated as a short section of heavy wall tubular with a machined internal surface that provides a seal area and a locking profile.

Landing nipples are included in most completions at predetermined intervals to enable the installation of flow-control devices, such as plugs and chokes.

The information obtained from these monitoring devices can be used to model reservoirs or predict the life or problems in a specific wellbore.

If used, it will normally be positioned below the packer and will offer an alternative entry path for reservoir fluids into the tubing in case the shoe becomes blocked, for example, by a stuck perforation gun.

It is intended to make pulling out wireline tools easier by offering a guiding surface for the toolstring to re-enter the tubing without getting caught on the side of the shoe.

This involves the injection of chemicals to eat away at any skin damage, "cleaning up" the formation, thereby improving the flow of reservoir fluids.

In these cases, coiled tubing may be used to pump nitrogen at high pressure into the bottom of the borehole to circulate out the brine.