Patent Application
20120186803
The field of the invention is fracturing systems that allow subsequent production through the fracture openings and more particularly an automatic way to control solids from entering during the transition time between fracturing and production.
A variety of systems that allow fracturing ports to be opened to fracture a zone have been developed. Some of these systems also use telescoping members that extend out of the sting and across an annular gap to contact the borehole wall. In some designs the impact with the borehole wall from an extension of these telescoping passages is intended to start the fracture process which is then continued with the delivery of fluid through the ports at high velocities that result from high applied pressures. The fluid usually contains high concentration of proppants.
The openings for fracturing are preferably not obstructed with screens for handling subsequent production. As a result the designs have provided one set of ports for fracturing and another for subsequent production where a sliding sleeve or some other valve operator is used to shift between the wide open tubular ports and the production ports that have screens. However, in this arrangement there is a transition time to shift a variety of sliding sleeves from fracturing mode to production mode. In that transition time the tubing pressure can drop below the formation pressure and some solids or proppant migration can take place into the tubular string and create operational difficulties with the uphole equipment. Putting screens in the fracturing outlets provides protection against solids or proppant return flow after fracturing operation is completed. Some examples of related previous designs are U.S. Pat. Nos. 7,401,648; 7,591,312; U.S. Publication 2010/0263871and 2010/0282469.
What is needed is a system that allows a given port to be wide open for fracturing and then have a screen material move into place over the port when the fracturing is done. In a preferred embodiment the movement of the screen would be automatic and it could further be triggered by pressure reduction in the tubing string. Optionally the movement of the screen can be tied to a differential pressure between the tubing and the surrounding annulus that moves the screen. The screen can be biased to assist in the movement and the movement can be locked against a return to the former screen position. These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.
One or more openings in a zone have an adjacent screen assembly that is axially movable to a position away from the port when pressure in the tubing exceeds the annulus pressure by a predetermined value. Upon the differential being reduced below a predetermined value or when annulus pressure exceeds the tubing pressure, the screen moves over the port to block at least some of the solids in the formation or/and proppants in fracture from entering the tubing string. The screen movement can be aided by a bias force and the movement can be locked in to prevent the screen that has moved to a position over the port from moving back away from the port.
Sleeve 32 has an external ring 36 with an o-ring 38 against the inner wall 40 of the tubular 10. The tubular 10 has an inner ring 42 with an o-ring 44 against an outer wall 46 of the sleeve 32. As a result, there is an annular variable volume 48 with access to the formation through passage 50. Arrow 52 represents formation or surrounding annulus pressure acting in volume 48.
Biasing sleeve 52 has a biasing member such as a spring 54 supported off an internal shoulder 56 from the inside wall 40 of the tubular 10. Other biasing techniques can be used such as a stack of Belleville washers or a pressurized chamber of compressible fluid. Although sleeves 32 and 52 are shown as separate sleeves they can be one integrated sleeve as to one or a row of ports 16 or to axially spaced circumferential rows of ports 16.
The telescoping members 20 can be initially extended by fluid velocity through ports 22 or by rupture discs (not shown) that can break under pressure after the telescoping assemblies 20 fully extend and pressure continues to be built up.
Depending on the strength of the spring 54 and the pressures represented by arrows 26 and 52 the sleeves 32 and 52 will be in the
Spring 54 can be nested and or stacked coil springs as an option. As another option the spring 54 can be eliminated so that movement to the
Those skilled in the art will appreciate that the movement of the screen into position by a port that had been used earlier to fracture lends many advantages. For one, the same port can be used at different times and in different conditions for fracturing and then production. Another advantage is that the system is pressure sensitive to reconfigure the fracturing ports to filtration mode on a loss or reduction of tubing pressure to a predetermined amount.
As another alternative to avoid an automatic conversion from fully open ports as in
As another configuration if the fracturing pressure is lost momentarily resulting in shifting of the screen 33 into alignment with the port 16, the pressure in the tubing passage 24 can simply be raised to reverse such movement if the fracturing process has still not been completed.
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:
