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Well Completion Design
COMPLETION OF WELL
- During boring of the well hole by any method it should be ensured that bored hole remains straight and vertical.
- If well hole is located in consolidate formation, water enters the well hole directly and no casing is required as all the surroundings are quite stable.
- But if formations are unconsolidated a casing is necessary to support the outside material and also to help in freely admitting the water into the well.
- The casing should either contain perforations or its lower part may be replaced by a screen or strainer so that water may enter the well.
- Sometimes in order to increase the effective diameter of the well, the screen or strainer is surrounded by a layer of gravel.
- Gravel layer keeps fine material out of the well.
- Such a gravel packed well will have a greater specific capacity than one of the same diameter not surrounded by gravel.
- The thickness of the gravel may vary with type of formation and method of drilling.
- However a minimum thickness of 15 cm is generally used.
- While drilling a new tube well it should be ensured that it would not affect the discharge of other nearby existing tube wells.
- The distance of the proposed well from existing wells should not normally be less than 1.5 km.
- The diameter of the well pipe may be reduced theoretically, as we go deep down the well; but it is not recommended.
- A single sized or at the most two sized tube may be used in actual practice.
- The velocity of flow through the tube is generally limited between the range of 1.5 m/sec to 4.5 m/sec.
- Once the design discharge of the tube well and the velocity of flow are known, the diameters of the pie can be easily found out.