Towards the Expandable Reservoir Completion: The Case for Open-hole Completions
Authors: Gee Nicholas , Jones Colin , Ferguson Stuart 
Published: October 2008

The widespread use of expandable sand screens has demonstrated the potential value to the industry of expandable technology. Solid expandable technology has also shown that a means exists to achieve economically efficient open-hole completions that possess cased-hole functionality by using compliantly expanded solid devices to seal against the formation.

Significant productivity benefits accrue from completing open-hole. Being able to achieve cased-hole functionality (water zone isolation, selective completion and production, shale isolation) in an open-hole completion can provide enormous benefit to the industry.

Over 250 expandable sand screen installations have been made around the world, the majority in open-hole applications but a significant number in cased-hole applications. The data available from a portion of these installations, combined with other petroleum engineering theory and productivity data from wells with a variety of sand control techniques, demonstrate the productivity benefit of open-hole completions.

Wells are completed with cased-hole largely due to the requirement to achieve isolation, either at the time of completion or later in producing life. The compromise to productivity is offset by the ability to control water production isolate shale sections, or produce zones selectively. Expandable reservoir completions offer the ability to achieve the required isolation with open-hole productivity.

Introduction

When the use of expandable slotted tubulars (EST) was first envisaged in wells requiring sand control, it was as an openhole device. The concept of effectively eliminating the screento- well-bore annulus without loss of diameter was believed to have productivity, sand control and well cost benefits. Twelve or more years on and the application of the technology has demonstrated support for those beliefs. In addition expandable sand screens (ESS) have been used in a wide variety of wells and fields across the globe, and in both cased-hole and openhole environments.

The techniques applied to control sand down hole have changed little over the last 80 years or so. Most solutions involve a pipe-based filter, which is installed in the well either alone (a stand alone screen) or with surrounding gravel pack. These techniques are applied in both open-hole and cased-hole environments. It is assumed that in most cases the rationale for cased-hole application is one of either need for zonal isolation between producing zones, or to satisfy other geological and rock mechanical issues. In either case, the consequent generally poor productivity of cased-hole gravel packs led the industry to develop the cased-hole frac-pack. This has proven to be a successful technique to control sand in cased-hole wells whilst overcoming the productivity impairment. Running stand-alone screens is operationally relatively simple whereas gravel-packing operations can be complex involving fluid and gravel pumping.

Expandable sand screens were seen to offer the opportunity to realise the benefits of gravel packing (borehole support with a filtering media) together with the operational simplicity of stand-alone screens. In addition the larger diameter and increased flow area could improve productivity, recovery and sand control capability.

Since the first commercial application of ESS in January 1999, over 250 wells have been completed, with over 160,000 ft of screen being deployed.