Heavy weight drill pipe is a type of drill pipe whose walls are thicker and collars are longer than conventional drill pipe.
Heavy weight drill pipe was developed as an intermediate weight drill string member. It was originally developed for three reasons:
1. As a transition member to be run between heavy weight drill pipe and drill collars.
2. As a flexible weight member to be run in directional drilling.
3. As a weight member on small rigs, drilling small diameter holes.
More recently, with the advent of horizontal drilling, it has found a new application being used in the curved portion of the hole below the drill collars.