Single ball activated hydraulic circulating tool

1. A circulating sub comprising:

an elongate outer member having a longitudinal internal bore extending therethrough and at least one exit port;

an elongate inner member disposed within the internal bore and having an internal channel extending therethrough, in which a nozzle is formed within the channel;

a plurality of locking elements adapted to releasably maintain the inner and outer members in a longitudinally fixed relationship, each locking element comprising:

an elongate arm having a projecting ear positionable within a groove formed within the internal bore; and

a catch member attached to the arm and partially extending within the channel;

wherein the inner member is configured to move relative the outer body such that the inner member is movable between:

a locked position, in which fluid does not pass through the exit port; and

an open position, in which fluid passes through the exit port.

2. The circulating sub of claim 1 in which when the inner member is in the locked position, the ears are positioned within the grooves and the exit port is not in fluid communication with the internal bore.

3. The circulating sub of claim 1 in which the inner member is also movable to an intermediate position, in which a ball is engaged with the catch members and the ears are not positioned in the grooves.

4. The circulating sub of claim 1 in which when the inner member is in the open position, a ball is seated on the nozzle, the ears are not positioned within the grooves and the exit port is in fluid communication with the internal bore.

5. The circulating sub of claim 1 further comprising a spring disposed within the internal bore below the inner member, in which the spring is compressed when the inner member is in the open position.

6. The circulation sub of claim 5 in which the spring is relaxed when the inner member is in the locked position.

7. The circulating sub of claim 1 further comprising a hollow sleeve having at least one opening positioned above the inner member that is movable with the inner member.

8. The circulating sub of claim 1 in which each locking element may be disengaged from its locked position by a ball in response to downward, but not upward, pressure applied thereto.

9. A method of using the circulation sub of claim 1 while it is carried by an underground tubular string, comprising:

lowering a ball within the tubular string until the ball engages with the catch members; and

increasing fluid pressure above the ball so that the inner member is moved from the locked position to the open position.

10. The method of claim 9 further comprising:

releasing fluid from the circulation sub through the exit port and into a wellbore surrounding the sub;

decreasing fluid pressure within the circulation sub such that the inner member is moved into the locked position; and

increasing fluid pressure within the sub until the ball is extruded through a nozzle.

11. The method of claim 10 further comprising:

lowering the extruded ball into a downhole tool positioned below the circulation sub.

12. A circulation sub system comprising:

an elongate tubular string that extends underground; and

the circulation sub of claim 1 , in which the sub is positioned within the tubular string.

13. The circulation sub system of claim 12 in which a ball is engaged with the catches.

14. The circulation sub system of claim 12 in which a ball is seated on the nozzle.

15. The circulation sub system of claim 12 in which the elongate tubular string is coiled tubing.

16. The circulation sub system of claim 12 in which the elongate tubular string is formed from rigid pipe sections.