Advanced well completion
Advanced well completion has been in use for many years. Troll and Snorre are examples of fields on the Norwegian continental shelf (NCS) which have utilised zone control to improve recovery. The technology could have a substantial potential on a number of fields.
Equipment utilised in this solution allows inflow to be managed along the well path without using tools which have to be run into it.
Injection wells can also feature advanced completion, where injection is managed downhole with the aid of preinstalled equipment. Managing injection or production along a well path is also referred to as zone control. In an advanced well, the latter is accomplished from a facility using remotely operated valves or with autonomous systems detecting a value which triggers an operation.
Zone control using valves
The simplest form of zone control without the use of intervention can take the form of valves installed as part of a sand screen in the reservoir. These will even out the pressure drop along the well path, while postponing and reducing coning effects of water and/or gas into the well. A standard solution for many horizontal wells on the NCS, this is no longer seen as advanced.
Further development of such equipment has led to the autonomous inflow control valve (AICV). That permits automatic choking and closing of valves based on the fluid type in the flow.
A more advanced completion solution will involve valves installed in various reservoir zones which can be hydraulically or electrically opened or closed from the surface. This will normally also feature pressure and temperature monitoring in each zone, which provides valuable information for operating the valves and thereby for optimum reservoir management.
Valves controlled from the surface will also be useful in stimulation, for example, and/or clean-up of dedicated zones.
An important precondition for ensuring that all types of zone control in advanced well completions function is that zones to be managed are isolated from each other, either by packing or cement
Standard on Troll
Troll is one of the fields on the NCS where advanced wells have become standard. As well as drilling multilateral wells where each lateral can be controlled, most laterals feature a form of advanced completion through the reservoir.
The animation below shows how remotely operated valves can control the flow from both laterals and zones in a single lateral (modified from Statoil).
Snorre is another field where extensive use has been made of zone control through surface-managed downhole valves to shut off water and gas in highly permeable zones. Studies show that reserves on Snorre could increase substantially if these systems function as intended.