A technique involves collecting formation fluids through a single packer having at least one drain located within the single packer. The single packer is designed with an outer structural layer that expands across an expansion zone to facilitate creation of a seal with a surrounding wellbore wall. An inflatable bladder can be used within the outer structural layer to cause expansion, and a seal can be disposed for cooperation with the outer structural layer to facilitate sealing engagement with the surrounding wellbore wall. One or more drain features are used to improve the sampling process and/or to facilitate flow through the drain over the life of the single packer.