Low profile dual screen prepack

A sand screen for placement within a well bore comprising, in combination:

• an elongated tubular mandrel having a plurality of longitudinally spaced apertures formed radially therethrough;
• an inner wire screen mounted onto said mandrel, said inner wire screen having circumferentially spaced, longitudinally extending inner rib wires and a screen wire wrapped externally about said inner rib wires in a longitudinally spaced pattern, said inner screen wire being welded to said inner rib wires at substantially all points of contact therewith, thereby defining longitudinally spaced inner screen apertures for conducting fluids through said inner screen;
• an outer wire screen mounted onto said mandrel in substantially concentric alignment with said inner screen, said outer wire screen having circumferentially spaced, longitudinally extending outer rib wires and an outer screen wire wrapped externally about said outer rib wires and welded thereto at substantially all points of contact therewith, thereby defining longitudinally spaced outer screen apertures for conducting formation fluids through said outer screen;
• an annular weld formed on said mandrel and connecting the end portions of said inner and outer screen wires and said inner and outer rib wires together for centering said inner screen in radially spaced relation within said outer screen, thereby defining a prepack annulus;
• and,
• a permeable gravel deposit disposed within said prepack annulus.

A sand screen assembly for separating particulated material from formation fluid comprising, in combination:

• a perforated mandrel;
• an inner wire screen mounted onto said perforated mandrel, said inner wire screen having inner screen wire turns wrapped directly onto said perforated mandrel in a longitudinally spaced pattern, thereby defining longitudinally spaced inner screen apertures which are coincident with the flow apertures of said perforated mandrel;
• a fluid-porous, particulate-restricting member mounted onto said mandrel in radially spaced relation with respect to said inner wire screen, thereby defining a prepack annulus therebetween, said fluid-porous, particulate-restricting member including circumferentially spaced, longitudinally extending outer rib wires mounted onto said inner wire screen and having an outer screen wire wrapped externally about said outer rib wires in a longitudinally spaced pattern thereby defining longitudinally spaced screen apertures for conducting formation fluid through said outer screen, said longitudinally extending outer rib wires being disposed in said prepack annulus;
• and,
• a fluid, permeable gravel deposit disposed within said prepack annulus.