Use of expandable technology for sand control has rapidly grown in recent years. While several expandable systems have I been developed, assessment of their long-term performance and effectiveness has hitherto not been objectively completed. To address some of the concerns and uncertainties on this front, this paper provides criteria for the assessment of sanding from well-: bores completed by expandable completion techniques. It also: provides an in-depth understanding of the mechanism under. Which expandable screens control mobilization of sand grains. A series of experiments were conducted using hollow cylinder, unconsolidated sand samples. The primary objective was to assess the influence of the opening size relative to the grain size in dictating the operational limits. A stiffener, representative of a general expandable completion technique, supported the central hole. The stiffener contained a network of small perforations. Experiments were conducted on both single- and two-phase flow media. This was to explore the possible effect of a second phase in sand production in the presence of the stiffener. Experiments showed that the mobilized friction between the, grains plays a major role in preventing sand production. The experiments also confirm that even with a large aperture size of an order of magnitude greater than the maximum grain size, sanding did not take place under routine operational conditions in a two-phase medium. On the contrary, instant sanding from the sandpack in single-phase experiments took place, which emphasized the important role of capillarity.