if the borehole has an irregular or oval shape the end rings 53 a b and 54 a b may be provided with inwardly projecting pins 57 that slide within longitudinal grooves 58 in the outer wall of the tubing 56 to maintain the stabilizer blades 51 a b and 52 a b in fixed substantially equally distributed positions around the outer circumference of the tubing 56 fig6 a 6d show an expandable flow restrictor made of a woven assembly of helical fibers 61 the fibers 61 are woven at opposite pitch angles and the material shown is known as green tweed or pec in fig6 a the fibers 61 are stretched and tightly surround the slurry injection tubing not shown fig6 b d show successive shapes of the fiber assembly when the upper and lower ends 62 and 63 of the assembly are moved towards each other as indicated by the arrows 64 a d fig6 d shows the final fully expanded shape obtained in the annulus where the granular packer is to be set if a slurry comprising balls or patches of packed metallic fibers or felt is injected upwardly against the expanded fiber assembly a permeable barrier layer is formed against which a granular plug of sand or gravel particles can be set so that only the carrier fluid seeps through the barrier layer and a compacted granular plug is sucked against the annular barrier layer in all cases where a bow spring centralizer assembly is used as an expandable carrier frame the expandable screen assembly may be run in an unfolded mode or in a folded mode in.