Note: The slot length and slot pattern can be adjusted according to the special requirements of the user. 

●  STRAIGHT MILL SLOTTING

This was the first type of slot manufactured. It has straight sides, equal width throughout the wall of the casing, and is more easily clogged by sand grains from the formation, than the Keystone slot. 

As more and more slots became plugged with sand, a decreasing quantity of oil is obtained until finally a fraction of the oil available is produced. The most successful down hole slot cleaning method to date is hydro-washing.

    

● KEYSTONE OR UNDERCUT SLOTTING

梯形缝设计使管体外表面缝隙宽度要比内表面缝隙宽度小，这样的缝型设计使缝隙堵塞的几率大大降低。

通常，梯形缝的夹角设计为6°。