Multilateral and advanced wells (DIACS)

Advanced wells refers to wells completed with valves or chokes downhole in the reservoir and with equipment which can be operated from the surface.

Since its first installation of this kind, on Snorre A in the North Sea during 1997, and up to May 2006, Statoil had installed this type of equipment – including 136 valves – in 45 wells.

Such hardware has been applied in several configurations in both platform- and subsea-completed wells, and with both injectors and producers.
Implementing this technology offers several advantages. These are listed below.

Shut off unwanted production

The production engineer can now control individual well sections through the reservoir. Unwanted water production can be turned off from a particular zone in the well, for instance. That boosts oil production while reducing water handling at the surface.

Control water injection

Injecting water in the reservoir for improved sweep is an efficient method of increasing the oil recovery factor. This is further enhanced by controlling the injection rate in each reservoir layer.

Eliminate the need for well intervention

Remotely operated valves placed in the reservoir permit instant changes to well characteristics, which can be reversed or repeated as many times as desirable. That contrasts with conventional well intervention, which can be an expensive and hard-to-reverse operation with an element of risk.

This feature is beneficial in several well configurations, but particularly for subsea completions where the cost of intervention is high.

Improved reservoir description

When the well is divided into several sections, data can be collected for each interval. This enhances the reservoir description, permitting improved location of new wells and optimised reservoir drainage.

Increase ultimate recovery factor

Injecting water or gas into the reservoir for improved sweep efficiency offers another effective way to increase the oil recovery factor, and is further enhanced by controlling the injection rate in the individual reservoir layer.
An advanced well completion does increase cost, since it requires more equipment and takes longer to implement.

These costs must be weighed against the benefits expected for each particular field, and Statoil has procedures for such evaluations.