Patent Application
20130043039
Actuation of downhole tools in the drilling and completion industry is ubiquitous. Many operations in the downhole environment require the use of tools that are run in the hole in a first position to be actuated later to a second position. There are many ways to actuate such tools using hydraulic pressure, mechanical actuation, electric actuation, etc. Many of the current tools in order to actuate, must be configured to overcome tubing pressure. This is because tubing pressure acts against a feature such as a piston against which an actuator does work to actuate the tool. In such situation, an activator in such actuator system must not only generate energy to move the tool but must overcome the tubing pressure acting against the activator at the same time. Attempts have been made to isolate tubing pressure but suffer from dynamic friction at the seals that hampers the operation as well as causing systems to have increased cost to net acceptable longevity. The art would therefore well receive alternative arrangements that reduce activation energy required so that reliability and cost factors can be improved.
A tubing pressure insensitive, pressure compensated actuator system includes a housing having a bore therein; a force transmitter sealingly moveable within the bore the force transmitter defining with the bore two fluid chambers, the two fluid chambers being in fluid communication with each other, one at each longitudinal end of the force transmitter; an activator in one or both of the two fluid chambers and operatively connected to the force transmitter; at least two seals sealingly positioned between the housing and the force transmitter, one of the seals disposed near one end of the force transmitter and another of the seals disposed near another end of the force transmitter; and a separate compensation piston disposed in the housing so as to expose one end of the compensation piston to tubing pressure and to expose the other end of the compensation piston to a fluid volume including the fluid chambers.
A tubing pressure insensitive pressure compensated actuator system for an electric surface controlled subsurface safety valve includes a subsurface safety valve housing supporting a flow tube, a flapper and a power spring, the housing having a force transmitter bore therein; a force transmitter sealingly moveable within the bore the force transmitter defining with the bore two fluid chambers, the two fluid chambers being in fluid communication with each other, one at each longitudinal end of the force transmitter; an activator in one or both of the two fluid chambers and operatively connected to the force transmitter; at least two seals sealingly positioned between the housing and the force transmitter, one of the seals disposed near one end of the force transmitter and another of the seals disposed near another end of the force transmitter; and a separate compensation piston disposed in the housing so as to expose one end of the compensation piston to tubing pressure and to expose the other end of the compensation piston to a fluid volume including the fluid chambers.
A method for reducing force requirements of an actuator in a downhole environment including sealing a force transmitter within a housing to isolate ends of the force transmitter from tubing pressure during use, respective ends being in communication with fluid chambers fluidly connected with each other; applying tubing pressure to a fluid in the fluid chambers; and initiating an activator to urge the force transmitter in a direction commensurate with activating a downhole tool, the activator generating enough force to activate the downhole tool other than to overcome tubing pressure.
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
Referring to
Returning to the actuation system 10, and focusing upon
Moving to
With the configuration as described and in the embodiment shown, an electric or mechanical activator 52 disposed in one or both of chambers 19 and 21 (19 as illustrated) is connected to the force transmitter 20 by connection 54. This connection may be a lead screw or other mechanical connection (e.g. motor or solenoid). The Activator(s) need generate only enough force to actuate the tool being actuated without having to overcome tubing pressure to do so. More specifically, in the case of the subsurface safety valve as illustrated, the force generated only need be sufficient to compress the power spring 38 and rotate the flapper 36 (likely against the biasing force of a torsion spring not numbered). This is significantly less force than would be needed if tubing pressure also had to be overcome. In addition, since dielectric fluid (e.g. oil or even air in some cases if compressibility is acceptable in a specific application) in bore 18 and bore 40 would be pressure compensated by the action of compensation piston 48, there would be little to no dynamic pressure across seals 22 and 24, thereby reducing friction that would otherwise have to be overcome. Another benefit is that the seals will wear longer since there is no significant differential pressure across them.
While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
