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Casing is primarily used to seal off overburden, weathered surface formations, and large fissures in the formation. Casing permits drilling fluids to circulate and return cuttings to the surface. Sizes are specified by the DCDMA to allow nesting or telescoping and interchangeability between manufacturers.
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The "W" DCDMA Standard Flush Joint Heavy Duty Casing is made from steel tubing and is flush inside and outside, with no internal coupling. "W" Casing is a heavy wall type with a shoulder chamfer and coarse square threads. (Coupled sections butt on connection)
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| "W" Design Casing Specifications | |||||||
| Size | O.D. | I.D. | Threads per inch | Weight | |||
| inches | mm. | inches | mm. | lbs./ft. | kg./m. | ||
| EW | 1-13/16 | 46.0 | 1-1/2 | 38.1 | 4 | 2.8 | 4.2 |
| AW | 2-1/4 | 57.1 | 1-29/32 | 48.4 | 4 | 3.9 | 5.8 |
| BW | 2-7/8 | 73.0 | 2-3/8 | 60.3 | 4 | 7.0 | 10.4 |
| NW | 3-1/2 | 88.9 | 3 | 76.2 | 4 | 8.4 | 12.5 |
| HW | 4-1/2 | 114.3 | 4 | 101.6 | 4 | 11.7 | 17.4 |
| PW | 5-1/2 | 139.7 | 5 | 127.0 | 3 | 16.0 | 23.8 |
| SW | 6-5/8 | 168.2 | 6 | 152.4 | 3 | 20.0 | 29.8 |
| UW | 7-5/8 | 193.6 | 7 | 177.8 | 2 | 23.4 | 34.8 |
| ZW | 8-5/8 | 219.0 | 8 | 203.2 | 2 | 23.8 | 35.4 |
