Heavy weight drill pipe is used most commonly in directional drilling because it bends more easily and helps to control torque and fatigue in high-angle operations. Heavy weight is also knows as hevi-wate or HWDP in the industry.
Heavy weight drill pipe has a 'center upset', also known as wear pad, that increases tube life by protecting the tube from wearing on the outer diameter by keeping the tube away from the hole wall. It also reduces hole drag and differential sticking problems.
The walls of heavy weight drill pipe are thicker and have longer upsets compared to conventional drill pipe, as well as being stronger with high tensile strength. There are variety of specifications of heavy weight drill pipe.
Heavy weight drill pipe used between standard Drill Pipe and Drill Collars to provide a smooth transition between the different sections of the drill string components. This provents the DP from buckling.