US Patent 9371708 Circulation sub and method for using same

Techniques for continuously circulating fluid into a drill string are disclosed. These techniques involve a circulation sub (108) including a tubular and a diverter valve (200A). The tubular has a first end connectable to the drill string, a second end connectable to a pipe segment, and a port (220) therein. The tubular has a fluid path (202) for allowing the fluid to flow from the pipe segment to the drill string and a circulation path (204) for allowing the fluid to flow from the port to the drill string. The diverter valve has a channel therethrough in selective fluid communication with the fluid path. The diverter valve is positionable between a flow through position for selectively allowing the fluid to flow through the fluid path and a diversion position for selectively allowing the fluid to flow through the circulation path whereby the fluid may continuously flow through the drill string.