Well liner with inwardly convergent passages

Claim 1

A WELL LINER PROVIDED THEREIN WITH A PLURALITY OF RADIAL PASSAGES EACH OF WHICH, VIEWED IN CENTRAL CROSS SECTION, INCLUDES: (A) AN OUTER ZONE EXTENDING RADIALLY INWARDLY FROM THE OUTER SURFACE OF THE LINER AND DEFINED BY RADIALLY INWARDLY CONVERGING OUTER WALLS INCLUDING THEREBETWEEN AN ANGLE AT LEAST EQUAL TO ABOUT 55*, BUT NOT GREATER THAN ABOUT 105*; (B) AN INNER ZONE EXTENDING RADIALLY INWARDLY FROM THE APEX OF SAID OUTER ZONE INTO COMMUNICATION WITH THE INTERIOR OF THE LINER AND DEFINED BY SUBSTANTIALLY PARALLEL INNER WALLS; (C) THE RADIAL DIMENSION OF SAID OUTER ZONE BEING SUFFICIENT TO ENABLE SAID OUTER WALLS TO FORM AND SUSTAIN A SAND BRIDGE SUBSTANTIALLY PREVENTING PASSAGE OF SAND INTO SAID INNER ZONE; AND (D) THE DISTANCE BETWEEN SAID INNER WALLS BEING SO RELATED TO THE RADIAL DIMENSION THEREOF AS TO RESIST PLUGGING OF SAID INNER ZONE BY SAND.