Patent Application
20110303418
In the drilling and completion industry and for example in hydrocarbon exploration and recovery operations, a variety of components and tools are lowered into a borehole for various operations such as production operations, for example. Some downhole tools utilize ball-seat assemblies to act as a valve or actuator. Ball-seat assemblies are used with, for example, hydraulic disconnects, circulating subs and inflatable packers.
Actuation of a ball-seat assembly generally includes releasing a ball or other plug from a releasing mechanism and allowing the ball to drop onto the ball seat and restrict a fluid conduit. The impact between the ball and the ball seat can produce pressure waves, which can cause wear and/or damage to the ball-seat assembly and other components. For example, initial impact is generally the most severe and is compounded by the suction pressure on the ball seat due to an outgoing expansion wave downstream of the seating area.
A method of restricting fluid flow includes: releasing a ball into a fluid conduit and receiving the ball in a ball receiving element disposed at the fluid conduit and at least partially restricting fluid flow; and at least partially reflecting one or more pressure waves resulting from an impact between the ball and the ball receiving element by a reflective boundary disposed in the fluid conduit.
An apparatus for restricting fluid flow includes: a ball receiving element disposed in a fluid conduit and configured to receive a ball that has been advanced through the fluid conduit and at least partially restrict fluid flow; and a reflective boundary disposed in the fluid conduit at least partially reflecting one or more pressure waves resulting from an impact between the ball and the ball receiving element.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
The apparatuses, systems and methods described herein provide for controlling downhole fluid flow and mitigating pressure waves caused by actuation of a ball-seat assembly. A downhole actuator assembly includes a conduit having a longitudinal component to guide a ball released into the conduit to a ball receiving element such as a ball seat. A reflective boundary disposed in the conduit at least partially reflects one or more pressure waves resulting from an impact between the ball and the ball receiving element. One embodiment of a method of reducing pressure waves includes pumping a first downhole fluid into the conduit, followed by pumping a second downhole fluid that has a characteristic that is different than the characteristic of the first downhole fluid, which creates a reflective boundary from the interface between the first and second fluids that acts to reflect incident pressure waves created by an impact between the ball and the ball receiving element. The reflected pressure waves destructively interfere with the incident pressure waves to reduce the amplitude of the incident pressure waves and reduce wear on downhole components such as the ball and the ball seat. Examples of such characteristics include density, viscosity, polarity, and chemical and/or physical differences causing the fluids to resist mixing or combining.
Referring to
The ball seat 24 may be an annular component connected to the conduit 22, or any other device or configuration providing a restriction in the diameter or cross-sectional area of the conduit 22 sufficient to prevent the ball 26 from passing therethrough. For example, the ball seat 24 may be attached to the inner surface of the conduit 22 or include a reduced diameter portion of the conduit 22.
In one embodiment, the tool 18 is configured to be in fluid communication with at least one pumping device 28 that is configured to introduce into and/or advance a fluid through the borehole string 12 and the fluid conduit 22. In one embodiment, a processor or other device, such as a surface processing unit 30 is in operable communication with the pumping device 28 and/or the tool 18 to communicate with and control operation of the pumping device 28 and/or the ball-seat assembly. The downhole tool 10 is not limited to that described herein. The borehole string 12 and/or the tool 18 may include any tool, carrier or component that includes a ball seat assembly. In addition, the tool 18 is not limited to components configured for downhole use.
In the first stage 41, in one embodiment, the downhole tool 18 is deployed downhole and advanced along the borehole 14 to a desired position, such as via a borehole string 12 or a wireline. In the second stage 42, a first downhole fluid having a first characteristic such as a first density is injected, pumped or otherwise introduced into the fluid conduit 22. In the third stage 43, a second downhole fluid having a second characteristic such as a second density is introduced into the fluid conduit 22 at a time proximate to or otherwise dependent on a time of release of the ball 18 or an anticipated time of actuation of the ball-seat assembly. In the fourth stage 44, the ball-seat assembly is actuated by releasing the ball 26 into the conduit 22, for example by dropping the ball 18 into the conduit 14 and/or pumping the ball 18 through the conduit 14. The ball 18 advances through the conduit 14 and impacts the ball seat 16. The different characteristics of the first and second downhole fluids create an interface or boundary that acts to reflect one or more incident pressure waves resulting from an impact between the ball 26 and the ball seat 24. The pressure waves destructively interfere with the incident pressure waves and dissipate the pressure waves to reduce the severity and duration of loads created by the pressure waves. This dissipation may also reduce the suction pressure on the ball-seat assembly due to the outgoing expansion wave downstream of the seating area. The different characteristics may be any characteristics sufficient to create a reflective boundary between the first and second fluids. For example, the fluids may have different densities or viscosities. In one embodiment, the fluids may have different chemical polarities. For example, the first fluid may be a generally polar fluid such as a water-based fluid and the second fluid may be a generally non-polar fluid such as an oil-based fluid.
An embodiment of the method 40 is described in conjunction with
The interface between fluids having the densities A and B results in a boundary 56 that provides a surface for the reflection of the incident pressure wave(s). Reflected pressure waves reflected from the boundary 56 at least partially cancel out the original pressure wave(s) created at the time of impact and reduces the net pressure resulting from impact.
The pumping of the second fluid 54 is initiated at a time so that the boundary 56 advances with the ball 26 at a selected distance from the ball 26. In this way, the distance of the boundary 56 from the ball 26 and the ball seat 24 at the time of impact can be controlled. For example, the injection or pumping of the second fluid 54 is triggered prior to or in anticipation of ball-seat actuation so that the boundary 56 is formed upstream and/or downstream of the ball 26. The pumping of the second fluid 54 may be initiated so that the boundary 56 is proximate to the ball 26, so that the boundary 56 is located proximate to the ball seat 24 at time of impact to rapidly dissipate the incident pressure wave(s).
Another embodiment of the method 40 is described in conjunction with
The apparatuses and methods described herein provide various advantages over existing processing methods and devices. Wear on the ball-seat assembly, which is a function of force over distance and time, can be reduced by reducing the force of the ball of the seat through the reduction in amplitude of the pressure wave(s). This reduction directly reduces the probability of ball-seat damage and conversely improves its reliability. The reduction of pressure waves affecting the ball-seat assembly can enable the use of a wider range of construction materials and reduce the cost and complexity of ball-seat design, for example by reducing the need for relatively complex ball seat designs to reduce impact. In addition, the apparatuses and methods can allow for the ball seat to have a larger inner diameter due to the reduced contact stress.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.
