S.D. Butt

Experimental Study of Sand Production from a Supported Wellbore in Weakly Consolidated Sandstone

Deployment of expandable technology for sand control is experiencing rapid growth. While several expandable systems have been developed, assessment of their long-term performance and effectiveness has not. To alleviate some concerns and uncertainties, criteria are provided in this paper for assessing the possibility of sanding in wellbores that employ reticulated expandable completions and to illustrate an in-depth understanding of the mechanism under which such screens may prevent sand grain mobilization. To investigate these issues, a series of experiments were conducted using hollow cylinder synthetic sandstone samples involving both fine- and coarse-grained sands. A stiffener of two different opening sizes supported the central hole to check if sanding takes place and if so, how great the influence of the opening size relative to the grain size is in dictating the operational limits. The experiments on weakly-consolidated sandstones showed that expandable completions were successful in preventing any shear failure around the wellbore. Under excessive drawdown/depletion, volumetric failure (pore collapse) proved to be a plausible failure mechanism in the material. Nevertheless, much less sanding occurred, and this improvement was attributed to grain-to-grain friction, enhancements of effective stresses at the wellface, and some degree of conservation of the original structure of the material, although at the state of pore collapse.