Sliding sleeve valve with degradable component responsive to material released with operation of the sliding sleeve

Salt or acid solution is stored inside a frac sleeve instead of being pumped from a surface location. A mechanically-actuated valve releases the stored salt or acid solution into the borehole to electrochemically degrade the frac ball and allow it to pass through the seat. The stored fluid can be immediately released upon mechanical actuation or released after a specified delay using an integrated timer. In multiple sleeve applications a first ball shifts a first sleeve to open treatment ports and a second ball shifts a second sleeve to close the treatment port and open screened production ports while releasing the stored material either between the seated objects or above one of the seated objects to initiate the disintegration that will allow objects on both seats to disintegrate and pass through.

FIELD OF THE INVENTION

The field of the invention is sliding sleeves shifted with a landed object on a seat and more particularly where the material that initiates degradation or disintegration of the object or seat is released directly or indirectly with sleeve movement.

BACKGROUND OF THE INVENTION

Traditionally, salt or acid solutions are pumped downhole to electrochemically degrade material in the frac ball (i.e., IN-Tallic®) to shrink the ball and pass it through the ball seat. However, this method is relatively slow and is not always possible due to adverse downhole conditions such as packing off of proppant above the seat.

IN-Tallic® is an electrochemically degradable material commonly used in frac balls and ball seats. When an electrolyte such as KC1 is pumped downhole, a galvanic corrosion reaction is initiated that degrades the frac ball or ball seat, eventually allowing the ball to be cleared from the seat. However, adverse downhole conditions can sometimes make it impossible to pump a salt or acid solution downhole to reach the degradable material. For example, proppant can build up above the ball seat, preventing the solution from reaching the frac ball. Additionally, depending on formation properties, operators may not want to add a large amount of salt or acid to the frac fluid. A high concentration of salt or acid solution (i.e., 10% KC1) is required at surface to achieve an adequate concentration (i.e., 2% KC1) at the frac sleeve, which may be 8,000 meters downhole in an offshore well.

The production ports of the upper sleeve of multi-sleeve tools have inserts filled with beads to provide screening of the production fluid. These inserts are known as bead-pack screens or bead screens. Such tools have several rows of production ports, each with several bead screens arranged along the circumference. In these tools a first sleeve is shifted to open treatment ports and then a second sleeve is shifted to open the screened production ports while closing the treatment ports.

In one aspect, the present invention presents a mechanically-actuated valve that allows the storage and release of fluid from a chamber inside a frac sleeve to degrade the frac ball or ball seat, allowing the ball to pass through the seat. The salt or acid solution is contained in a chamber inside the frac sleeve to ensure the solution will reach the degradable material. Pressuring up behind a seated ball causes the sleeve to shift and open a valve which releases the solution from an inner chamber into the fluid surrounding the frac ball. After the mechanical actuation of the valve, the released solution will initiate a galvanic corrosion reaction in the frac ball to degrade it and pass it through the seat.

A frac sleeve can be built with an inner chamber that is filled with a high-concentration salt or acid solution selected to electrochemically degrade the frac ball or seat. The chamber has a valve that is normally closed, containing the fluid inside the sleeve until activation. Once the ball is seated and pressure is built up, an inner sleeve is shifted. The shifting of the sleeve can either instantly open the valve to the inner chamber or initiate a timer to open the valve after a set time. Once the valve is opened, the salt or acid solution is released from the chamber into borehole, where it surrounds the frac ball and seat and begins the electrochemical degradation of the material. After enough material has been removed from the outside of the ball or inner wall of the seat, the ball will pass through the seat and subsequent operations such as production can be carried out.

The invention ensures the frac ball/seat will degrade even with adverse downhole conditions such as packing off of proppant above the seat; faster degradation of frac ball; elimination of delay from pumping down the salt or acid solution and/or reduced volume of salt or acid solution needed to degrade a ball. Placement in the sleeve reduces loss of concentration from pumping down fluid. Applications in a variety of tools that use degradable materials is envisioned.

SUMMARY OF THE INVENTION

Salt or acid solution is stored inside a frac sleeve instead of being pumped from a surface location. A mechanically-actuated valve releases the stored salt or acid solution into the borehole to electrochemically degrade the frac ball and allow it to pass through the seat. The stored fluid can be immediately released upon mechanical actuation or released after a specified delay using an integrated timer. In multiple sleeve applications a first ball shifts a first sleeve to open treatment ports and a second ball shifts a second sleeve to close the treatment port and open screened production ports while releasing the stored material either between the seated objects or above one of the seated objects to initiate the disintegration that will allow objects on both seats to disintegrate and pass through.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 2a ported sleeve assembly10being one of many that are used in a treatment and which are axially spaced to treat isolated portions of an interval using annulus packers (not shown) is illustrated. It has a lower sleeve12that initially closes treatment ports14until an object such as a ball16is landed on seat18and pressure is applied to move sleeve12into theFIG. 2position. After the treatment is completed another object such as ball20is delivered to seat22such that pressure applied on seated ball20shifts the upper sleeve24to open screened production ports26. Referring toFIG. 1, sleeve24is initially pinned with shear pin or pins28which break when sleeve24is moved with pressure on ball20when seated on seat22. Annular chamber30is formed between seals32and34sealing against sleeve24until sleeve24is shifted with pressure to move past at least seal32to allow the material or disintegrating agent36that will initiate disintegration of balls16and20to be released.

Arrows38inFIG. 3show the material37escaping and traveling toward balls16and20.FIG. 4shows sufficient disintegration of ball20to allow it to pass seat22and land on ball16.FIG. 5shows sufficient disintegration of ball16to allow balls16and20to pass seat18. The same thing happens at other assemblies10located at other isolated intervals in the borehole as part of the treatment followed by production from the various intervals. Preferably, the intervals are treated and production ports opened in a bottom up direction. While just the balls or objects such as16and20can be disintegrated and production occur with seats18and22intact, the material for the seats18and22can also disintegrate.

FIG. 6shows a three sided cap38that holds a solid form of a material or agent that will initiate disintegration of the objects such as for example land on seat22. The cap38has an open face against outer surface42of upper sleeve24such that in theFIG. 6position the material or disintegrating agent40that is preferably in solid form in this embodiment can be held between seals32and34until shifting of sleeve24exposes the material40to tubing fluid and the material or agent is put into solution and travels to seats22and then18to initiate disintegration of at least balls16and20as previously described. Arrows44inFIG. 7schematically illustrate this effect. The material40can travel due to gravity in a vertical well or/and due to a higher specific gravity than the well fluids to reach the seats18and22.

Some of the bead screen inserts in production ports26inFIG. 6could be replaced with a plug with the same housing dimensions but without the beads. This plug would be filled with acid and will be sealed to prevent the acid from leaking to the annulus outside the tool. The metal plug could have a pocket molded with an acid such as polylactic acid (PLA) or polyglycolic acid (PGA). Before the sleeve24is shifted, the acid40is sealed in the plugs. After the sleeve24is shifted, the acid dissolves into the borehole fluid and can be weighted so that is will sink downwards to the ball seats22and18.

FIG. 6shows a possible embodiment of an acid-filled plug in a tool. The left row of production ports have standard bead screen inserts while the right row of ports has acid-filled plugs. The plugs have a metal housing that is threaded into the sleeve from the OD like standard bead screens, but have a metal cap to seal the acid40in the plug. O-rings32and34are placed on the uphole and downhole end of the row of ports to prevent fluid from reaching the acid40in the plugs.

FIG. 8integrates into seat22an annular chamber36for the material that initiates disintegration using seals32and34as previously described. An array of ports46is disposed on an opposite side of annular chamber36from seal34. As ball seat22shifts from pressure on ball20on seat22as shown inFIGS. 10 and 11, seal34enters a groove48in housing50allowing material to bypass seal34and enter between seated balls20and16. The disintegration of both balls can begin. It should be noted that the volume of chamber36can be decreased as seal34enters groove48by configuring the location of radial surface52to decrease the volume of chamber36to push out the material that is stored therein. The fluid can be forcibly displaced from chamber36by lifting ball20off of seat22.FIG. 9shows the opening of the treatment ports14with the initial movement of lower sleeve12as previously discussed.

The size of the chamber36can be designed to create a desired acid concentration in the fluid volume between the ball seats18and22. For example, if the seats are 18″ apart on a tool with 3.7″ ID, a 2″ long chamber filled with near-100% concentration acid would produce a solution concentration of about 3%, which should be adequate for dissolution of IN-Tallic® material. The spacing of the seats, size of the acid chamber, and type of acid can be optimized to increase acid concentration of the solution and the corrosion rate of the degradable material.

InFIGS. 1-5the assumption is that the frac sleeve will be roughly oriented vertically, as is commonly the case in offshore wells, so that gravity will carry the salt or acid solution downhole to both the ball seats. However, the location and number of the chambers can be customized to fit the well orientation. For example, a second chamber and valve could be added between the ball seats as inFIG. 11to release salt or acid solution between the ball seats.

Another alternative is to use the shifting of the sleeve24to initiate a timer for a delayed release of the salt or acid solution. The addition of a timer could potentially enable application in a traditional frac sleeve with a single port and ball seat. Shifting the sleeve would allow normal hydraulic fracturing through the port. After the specified time (after fracturing is completed), the valve releases the solution and initiates the galvanic corrosion reaction on the frac ball. This allows the ball and seat to seal off the stage from lower stages until fracturing is complete to avoid re-fracking lower stages in the string.