Next-Generation Expandable-Completion Systems
Authors: Denney Dennis 
Published: February 2015

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 97281, "Next-Generation Expandable-Completion Systems," by Gareth Innes, SPE, Quentin Morgan, SPE, Ally Macarthur, SPE, and Annabel Green, SPE, Weatherford, prepared for the 2005 SPE/IADC Middle East Drilling Technology Conference and Exhibition, Dubai, UAE, 12–14 September.
In many cases, openhole completions could provide maximum well productivity. However, use of the method has been impeded by the inability to achieve effective zonal isolation. An expandable completion that combines slotted- and solid-expandable technology and uses conventional unexpanded premium connections can deliver freely configurable completion architecture.

Introduction
Expandable sand screens provide direct contact of the screen with the formation as a means of reducing completion skin and improving sand-retention characteristics. The base technology is being integrated with new and conventional downhole technologies to enable multizone completions.
A common conventional approach used to complete and commingle multizone unconsolidated reservoirs has been to, first, set and cement casing in the wellbore to isolate zones. The zones of interest then would be perforated before installation of a screen and placing gravel to control solids migration. This cased-hole sand-control technique has worked reasonably well but has a history of high completion skins. Also, the resulting smaller inside diameter makes the subsequent design and installation of selective-production upper-completion strings difficult, limiting the overall achievable functionality. In many cases, emulating an openhole high-deviation or horizontal completion strategy can increase well productivity. To enable these productivity gains and facilitate selective production handling, zonal-isolation technologies were combined with compliantly expanded screens to create a sandface completion with cased-hole functionality. Zonal-isolation technologies that satisfy functionality and expandable performance criteria include swelling elastomers and solid expandables.

Expandable-Completion Development
An expandable screen comprises three sandwiched layers: the base pipe, filter media, and outer protective shroud. The base pipe is slotted, as is the outer shroud. These slots open during expansion to accommodate the change in diameter, while overlapped layers of filter media slide across each other to maintain sand-retention integrity. The use of slots allows expansion ratios up to 80% greater than the original diameter.
The entire length of the original design was expanded, including the connectors. The original expandable screen was designed for use in single-zone openhole applications. Large exposed filter area and variable borehole contact (known as compliant expansion) provide gravel-pack functionality. The design premise was that a compliantly expanded filter that could eliminate as much of the annular gap as practicable would promote rapid formation stabilization and minimize the movement of sand particles around the screen during the transient sand-production period. The large, directly exposed filter surface was designed to minimize pressure drops in the screen and sandpack composite caused by mud particles and formation fines.