Stage cementing is one application where valves are sequentially operated to open ports for the passage of cement into a surrounding annulus. After the cement is delivered the valves need to be closed. This not only increases the integrity of the well, but helps isolate certain zones of the completion allowing to operate other tools or to pressure test the string itself. Sliding sleeve valves have been used for this purpose in the past.
The shifting of the sliding sleeve from the open position to the closed position has been performed with a plug that latches into a profile in the sliding sleeve. A pressure application from above shifts the plug and sleeve in tandem to close the cementing ports at a given location. The problem with this design is that after the cementing application there may still be residual cement on the sleeve profile to the extent that the plug that had to enter the sleeve and latch with a collet type mechanism would not land properly. This prevents effective use of pressure above the landed plug to shift the sleeve shut isolating the ports.
What is needed and provided by the present invention is a better way to close the passage above the open port so that when pressure is applied the sliding sleeve shifts reliably to close the lateral port. The designs of the present invention can be a two sleeve design or a single sleeve design. In the two sleeve design an external sleeve is responsive to internal pressure to shift to open the ports for an operation such as cementing. After the cement passes through the open port a ball is landed on a seat integrated into the sliding sleeve and preferably located at the upper end of the sliding sleeve. Pressure is then applied to move the ball and sleeve in tandem to close the ports. Alternatively, a single internal sleeve constructed with differing end areas is subjected to internal pressure that results in a net force on the sleeve to slide it to a ports open position. After the cementing or other operation, a ball is landed on a seat preferably at the top of the sliding sleeve and pressure from above is applied so that the sleeve and the ball move in tandem to close the ports previously opened with internal pressure. If multiple sliding sleeves in multiple ported subs are used their movement can be staggered with breakable devices designed to release at different pressures. The sliding sleeves can be rotationally locked to expedite milling out the seats. The dropped balls can disintegrate after a time to avoid milling the balls out. The above described design is thought to more reliably obtain either a seal or to minimize leakage when pressure is applied sufficiently to generate the necessary closing force to the ball with no risk of the ball coming through the seat. Thus even with residual cement on the seat there is still a reliable way to close the port in a given ported sub. These and other aspects of the present invention will be more readily understood by those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.
The following patents discuss sliding sleeve valves in general terms: U.S. Pat. Nos. 8,157,012; 6,543,538 and 7,066,264.
USPTO Backgrounds
USPTO Backgrounds