Circulation sub with indexing mechanism

摘要

A downhole circulation sub or valve (105) includes a tubular housing with an outer port (140) and a valve piston (170) slidably disposed in the housing. A primary fluid flow path (130) extends through an inner flow bore of the housing and valve piston. In a first position, the valve piston isolates the outer port to prevent fluid communication between the inner flow bore and a well bore annulus. In a second position, the valve piston is moved to obstruct the inner flow bore and expose the outer port to the inner flow bore and allow fluid communication between the inner flow bore and the well bore annulus. An indexing mechanism (165) is coupled between the housing and the valve piston to guide the valve piston between the first and second positions. In some embodiments, the indexing mechanism includes a rotatable component (175).