Abstract: A triple layer non-plugging screen for use with a vibrating screening machine to filter particles from a liquid has an upper filtering layer made of warp and shute wires that intersect to form an array of small openings, a lower strengthening layer having an array of large openings, and an anti-plugging layer. The anti-plugging layer is sandwiched between the upper filtering and lower strengthening layers and is made of warp and shute wires that intersect to form an array of openings. The upper filtering and anti-plugging layers are oriented within the screen so that at least one of the warp and shute wires of the anti-plugging layer obstructs at least some of the openings in the upper filtering layer. This reduces the likelihood of entrapment of undesirable particles in the obstructed openings of the upper filtering layer.

Abstract: A screen for use with a vibrating screening machine to filter undesired particles from a liquid uses a filter cloth having a substantially rectangular mesh suitable for separating the undesired particles from the liquid bonded in laminar relationship to a back-up having a substantially coarser mesh. The substantially rectangular mesh is formed by a lengthwise array of parallel individual wires woven with a transverse widthwise array of parallel groups of at least three wires. The individual wires are distorted from rectangular proximate the ends of the rectangles by bows in the individual wires at their area of intersection with each of the parallel groups of wires. This configuration provides improved throughput and life characteristics over known screens. A plastic grid of mesh substantially greater than the back-up mesh may be fused to the bonded lamination of the filter cloth and the back-up.

Abstract: A screen for removing undesirable particles from a liquid has a flat parallel array of shute filaments spaced apart less than a preselected minimal linear dimension of the undesirable particles transverse to a parallel array of groups of 3 to 10 warp filaments, the warp filaments of each group being oppositely woven about and between the shute filaments taken individually or in pairs to secure the shute filaments and maintain the spaces therebetween, the spaces between groups of warp filaments being greater than the preselected minimal linear dimension of the undesirable particles so that the screen is characterized by rectangular flow apertures therethrough, the diameter of the shute filaments being in the order of at least 1.1 times the diameter of the warp filaments so that the apertures have an aspect ratio ranging as great as 4 to 10 or more, even for filaments having diameter ranging as small as 0.0070 to 0.0010 inches or less.

Abstract: A screen for filtering undesirable particles from a liquid has a flat parallel array of warp filaments spaced apart less than a preselected minimal linear dimension of the undesirable particles transverse to a parallel array of pairs of shute filaments, the shute filaments of each pair being oppositely woven about and twisted 180.degree. at the warp filaments to secure the warp filaments and maintain the spaces therebetween, the spaces between pairs of shute filaments being greater than the preselected minimal linear dimension of the undesirable particles so that the screen is characterized by rectangular flow apertures therethrough, the apertures being an access ratio ranging as great as 4 to 10, even for filaments having diameter ranging as small as 0.007 to 0.001 inches.

Abstract: A screen for filtering undesirable particles from a liquid has a flat parallel array of warp filaments spaced apart less than a preselected minimal linear dimension of the undesirable particles transverse to a parallel array of pairs of shute filaments, the shute filaments of each pair being oppositely woven about the warp filaments to secure the warp filaments and maintain the spaces therebetween, the spaces between pairs of shute filaments being greater than the preselected minimal linear dimension of the undesirable particles so that the screen is characterized by rectangular flow apertures therethrough, the apertures being an access ratio ranging as great as 4 to 10, even for filaments having diameter ranging as small as 0.007 to 0.001 inches.

Abstract: Zones of lost circulation and other undesired fluid communication channels into a wellbore are sealed by isolating a volume in the well including such a zone and applying greater than formation pressure to a novel slurry spotted in the zone until it hardens into a solid, drillable seal. Redrilling the bore can be accomplished even in soft, geologically young formations, without damaging the seal. The slurry contains per barrel from 5-50 pounds diatomaceous mix (see below), from about 35 to about 350 pounds of oil well cement, and at a minimum about 5 to 6 pounds of a flake type lost-circulation agent. Preferably, the weight per barrel of lost circulation agents is in the range of about 15 to 30 pounds of a mixture containing flakes, fibers, and hard granules.Diatomaceous mix is powdered diatomaceous earth containing about 2% of ground lime and 8% of ground asbestos fibers.