Wire-wrapped screens offer another alternative for retaining the gravel in an annular ring between the screen and the formation. and cut in standard carbon steel-pipe grades can rust and will either close or reconfigure the slot opening so that they do not function properly unless they are coated, protected, or stored indoors before use. minimum available slot size (approximately 0.012 in.).limited flow area (2 to 3%, creating a low tolerance to plugging).The disadvantages of the slotted liner are: The primary advantage of a slotted liner over wire-wrapped screens is usually cost however, small gauge, high-density slot patterns may cost as much as wire-wrapped screens. Slot width tolerance is generally ± 0.003 in. long slots for slot widths between 0.030 to 0.060 in., and 2½-in. The length of the individual slots is measured on the inside diameter (ID) of the pipe. 3-Straight and keystone-shaped slots (courtesy of Baker Oil Tools). Slotted liners also plug more readily than screens they are used where well productivity is small and economics cannot support the use of screens.įig. While the slotted liners are usually less costly than wire-wrapped screens, they have smaller inflow areas and experience higher pressure drops during production. Slots formed in this way have an inverted “V” cross-sectional area and are less prone to plugging because any particle passing through the slot at the outside diameter (OD) of the pipe will continue to flow through, rather than lodging within the slot. The keystone slot is narrower on the outside surface of the pipe than on the inside. The slots can be straight or keystone shaped, as illustrated in Fig. The single-slot staggered pattern is slotted with an even number of rows around the pipe with a typical 6-in. The staggered pattern also gives a more uniform distribution of slots over the surface area of the pipe. The single-slot staggered, longitudinal pattern is generally preferred because the strength of the unslotted pipe is preserved. in width involve high costs because of excessive machine downtime to replace broken saw blades that overheat, warp, and break. The minimum slot width that can be achieved is about 0.012 in. The machining consists of cutting rectangular openings with small rotary saws. 2-Slotted-liner geometries (courtesy of Baker Oil Tools).
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