Patent Application
20190032447
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.
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.
Relevant art includes U.S. Pat. No. 8,573,295; U.S. Pat. No. 9,079,246 and US 20130146302.
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.
Referring to
Arrows 38 in
Some of the bead screen inserts in production ports 26 in
The size of the chamber 36 can be designed to create a desired acid concentration in the fluid volume between the ball seats 18 and 22. 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.
In
Another alternative is to use the shifting of the sleeve 24 to 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.
The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers, etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
