Abstract:
A downhole device shifts a component from a first state to a second state. The device includes a body having the component in a bore thereof and an annular space formed within an inner and outer wall of the body. The annular space includes a first fluid chamber in fluid communication with the bore at a first location and with a pressure transducer at a second location, the transducer constructed and arranged to measure pressure of the fluid and provide a signal to circuitry controlling a valve upon reception of a predetermined fluid pressure pulse sequence. When the pulse sequence is delivered, the valve opens, placing a source of pressurized fluid in communication with an actuator that shifts the valve.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the present invention generally relate to a method and apparatus for temporarily sealing a bore of a tool. More particularly, the invention relates to a ball seat and a method and apparatus for remotely releasing the ball. 
     Description of the Related Art 
     In the completion and operation of a hydrocarbon well, it is often necessary to remotely actuate a downhole tool in order to move the tool from a first to a second state. In one example, a packer is run into the well on a string of tubulars and then actuated, thereby causing sealing members to extend radially outwards into sealing contact with walls of the wellbore. One way of remotely actuating the tool is through a temporary increase in fluid pressure adequate to shift a piston formed on the tool that in turn causes the sealing members to move. In order to increase pressure in the area of the tool, the wellbore is typically blocked at a location below the tool. In one instance, the wellbore is blocked with a ball and ball seat. In one example, a ball is dropped from the surface of the well into the ball seat. With the bore blocked, pressure is increased to a point that sets the tool. Thereafter, pressure is increased to a higher level in order to “blow out ” the ball seat, permitting the ball to fall through the seat and the bore to be re-opened. While the forgoing arrangement is operable, it necessarily requires high pressures, especially to blow out the ball seat. High pressure can damage hydrocarbon-bearing formations through shock loading due to pressure surge or water hammer effect. 
     There is a need therefore, for a ball and seat arrangement wherein the ball can be released from the seat without the use of a fluid pressure differential across the seat. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a downhole device for shifting a component from a first state to a second state. In one embodiment, the device includes a body having the component in a bore thereof and an annular space formed within an inner and outer wall of the body. The annular space includes a first fluid chamber in fluid communication with the bore at a first location and with a pressure transducer at a second location, the transducer constructed and arranged to measure pressure of the fluid and provide a signal to circuitry controlling a valve upon reception of a predetermined pressure pulse sequence. When the pulse sequence is delivered, the valve opens, placing a source of pressurized fluid in communication with an actuator that shifts the valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a cross section view of a tool according to one embodiment of the invention. 
         FIG. 2  is a cross section view of the tool of  FIG. 1  shown in a different rotational position. 
         FIG. 3  is a cross section view showing two portions of the tool in greater detail. 
         FIG. 4  is a cross section view showing a valve assembly with a valve shown in a closed position. 
         FIG. 5  is a cross section view showing the valve in an open position. 
         FIGS. 6 and 7  are section views of the valve in a different rotational position, shown in the open and closed positions, respectively. 
         FIG. 8  is a cross section view showing a lower portion of the tool including a ball seat with a ball held therein. 
         FIGS. 9  A-D are perspective views of the ball seat. 
         FIG. 10  is a cross section view shown the lower portion of the tool wherein the ball seat has been shifted to an enlarged diameter position. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a downhole tool for temporarily blocking and un-blocking a flow path through a wellbore. More particularly, the invention relates to a ball and ball seat wherein the ball can be released from the seat without the use of a pressure differential across the seat. 
       FIG. 1  is a cross section view of a tool  100  according to one embodiment of the invention. The tool is constructed and arranged to be installed in a tubular string, typically production string (not shown) and is provided with threaded connections at an upper and lower ends. As shown, the tool includes a central bore  105 , the bore including a ball seat  200 , shown in a reduced diameter position with a ball  201  therein. In the position of  FIG. 1 , the ball and ball seat are configured to block the bore  105  of the tool  100  and permit pressure to be developed in the wellbore at any location above the tool. Another tool needing pressure actuation would typically be disposed in the tubular string at a location above the tool  100 . The tool is constructed with an annular space formed between an inner  101  and outer  102  walls and in one embodiment of the invention; components are housed in the annular space. The various components are shown in greater detail in other Figures but the primary portions include a wellbore fluid chamber  110 , an annular piston  115 , a hydraulic fluid chamber  120 , electronic circuitry  125  and batteries  130 . Additionally, a number of interconnected fluid paths are formed in the annular space as well as a valve assembly  300  with a valve that is remotely openable to expose pressurized fluid in the fluid paths to an annular piston  150  that shifts the ball seat  200  to its larger diameter position in order to release the ball  201  and un-block the bore  105 . 
       FIG. 2  is a cross section view of the tool of  FIG. 1  shown in a different rotational position and illustrates a first fluid path  250  (shown on the left side of the annular space) in greater detail.  FIG. 3  is a cross section view showing two portions of the tool  100  in greater detail. In particular, the upper portion of the Figure illustrates an aperture  122  leading from the bore  105  of the tool to the annular wellbore fluid chamber  110 . The aperture  122  permits fluid pressure communication between the bore and the first fluid path  250  disposed in the annular area of the tool. As will be shown, the pressure of the fluid in the bore, and with it the pressure in the annular chambers  110 ,  120  can be increased or decreased and delivered in pulses. A predetermined delivery of such pulses can be used to open the valve and ultimately shift the ball seat  200  from the smaller diameter position of  FIG. 1  to a larger diameter position. Wellbore fluid chamber  110  is separated from hydraulic fluid chamber  120  by an annular piston  115  in order to prevent contamination of the hydraulic fluid while allowing it to be effected by pressure and pulses from the bore of the tool. The first fluid path  250  extends from the hydraulic fluid chamber  120  to a tubing pressure transducer  155  that is placed in the fluid path  250  where it receives and measures pressures and pulses in the bore of the tool as well as timing associated with those pressures and pulses and then generates an electrical signal based upon those values to circuitry  125  disposed in an adjacent area of the annular space ( FIG. 1 ). The first fluid path  250  is connected to a second fluid path  252  extending from one side of the annular space to the other. Located just above the tubing pressure transducer  155  on the left side of the Figure is a port  254  that leads into the second fluid path  252  around the annular body terminating at another port  255  visible on the right side of the Figure. Port  255 , in turn is connected to a third fluid path  256  that leads to the valve assembly  300  not visible in  FIG. 3  but visible in  FIG. 4 . 
       FIG. 4  is a cross section view showing the valve assembly  300  with a valve  302  shown in a closed position. As shown, the third fluid path  256  leads to the valve. In the embodiment shown, the valve assembly  300  includes a Kevlar fuse  350  which is designed to operate based upon an electronic signal from the on-board circuitry  125  in the tool  100 . The valve  302  includes a plunger  305  which in the closed position, blocks a fluid path through the valve  302  that otherwise connects the third fluid path entering the valve with a fourth fluid path  258  leading from valve. The plunger  305  is biased towards an open position due to a spring  306  but is initially held in a closed position, against the force of the compressed spring by retaining members  310  that are equipped with electrodes (partially shown)  312  causing them to fail in the event of a predetermined electrical signal from the circuitry  125 . One example of a Kevlar fuse-type device is shown and described in U.S. Pat. No. 5,558,153 and that patent is incorporated by reference in its entirety herein. 
       FIG. 5  is a cross section view showing the valve  302  in an open position. As shown, the retaining members  310  have been caused to fail and the plunger  305  has been moved from a first closed position ( FIG. 4 ), in which port  257  is blocked by the plunger  305 , to an second, open position ( FIG. 5 ) wherein fluid traveling in port  257  is free to enter and pass through the valve due to the extended spring  306  which was initially held in a compressed position.  FIGS. 6 and 7  are section views of the valve assembly  300  from a different rotational position, shown in the open and closed positions, respectively. Visible in each is the valve  302  with its plunger  305  biased by the spring  306 . In  FIG. 6  the port  257  (not shown) leading into the valve is blocked by a plunger member  307 . In  FIG. 7  however, port  257  is visible and the fluid therein is in communication with the fourth fluid path  258  leading out of the valve. 
       FIG. 8  is a cross section view showing a lower portion of the tool  100  including ball seat  200  with ball  201  held therein. The ball seat is constructed of a plurality of castellations  202 , equally spaced around a perimeter of a sealing ring  205  and more completely illustrated in  FIGS. 9  A-D, which include various perspective views of the ball seat  200 . Each castellation  202  has an angled inner surface  203  and is mounted at a lower end to a sealing ring  205 . The ring  205  includes at least one O-ring (visible in  FIGS. 8, 10 ) for sealing against an upwardly facing shoulder  207  formed in the body of the tool and constructed and arranged to retain and seal the ball seat  200  in the bore  105  of the tool  100 . The purpose of the angled inner surface  203  of each castellation  202  is to mate with and move upwards relative to a conical surface  210  formed on an outer diameter of a sleeve  211  installed in the bore  105  of the tool above the ball seat  200 . Visible in  FIG. 8  is an annular shifting piston  150  with a piston surface  152  formed on a lower end thereof and in communication with the lower end of fourth fluid path  258  extending from the valve  302  (when the valve is open). A space  153  above the piston  150  is filled with air at atmospheric pressure permitting the gap to be reduced in volume as the piston moves. 
       FIG. 10  is a cross section view showing the lower portion of the tool  100  wherein the ball seat  200  has been shifted to an enlarged diameter position. As shown, the annular shifting piston  150  has moved from a first lower to a second higher position relative to the ball seat due to fluid pressure acting on the piston surface  152  of the piston  150 . Consequently, the space  153  has been reduced in volume. In operation, an upwardly facing shoulder  154  of the annular piston  150  that is in contact with a lower surface  212  of the castellations  202  has forced the ball seat  200  with its castellations  202  upwards along the conical surface  210 , thereby enlarging the inner diameter of the sealing ring  205  to a size exceeding the outer diameter of the ball  201 . In this manner, the ball is released and fluid communication is reestablished between the portions of the bore above and below the ball seat  200 . 
     In one embodiment, the invention is practiced in the following manner: A tool  100  including the ball seat  200  is run into a wellbore in a string of tubulars to a predetermined depth. The ball seat is in its smaller diameter position as shown in  FIG. 1 , however, the bore through the tool is open because there is no ball in the seat during run in. At some later time, an operator decides to set a pressure-actuated tool, like a packer disposed in the string above the tool  100 . A ball is dropped from the surface and lands in the seat as shown in  FIG. 1 . With the bore of the tool blocked, pressure in the tubular string is increased to a predetermined threshold, typically by pumping from the surface, until the pressure-actuated tool is set. Thereafter, there is a need to remove the ball from the seat and reopen the bore through the tool. 
     In one embodiment, the ball seat  200  is shifted from its smaller to larger diameter state based upon predetermined parameters consisting of signals to circuitry  125  housed in the tool. Those signals begin as pressure pulses delivered to the tubing pressure transducer  155  from the bore of the tool via aperture  122  ( FIG. 3 ). A complete “pulse” in one instance is a specified pressure applied via the tubing to the tubing pressure transducer followed by a “bleeding off” of that pressure to zero. In one example, the circuitry is programmed to operate the Kevlar fuse of the valve assembly  302  in the event that it receives data from the transducer  155  indicating three separate and distinct pulses have been received. In another example, the data includes not only pulses but pulses separated by a predetermined time delay in seconds or minutes. Additionally, the circuitry can include programming that delays the operation of the fuse for a predetermined period of time after the data has been received. Numerous variations are available limited only by the ability to provide pulses from the bore of the tool to the transducer  155 . In one embodiment, an annulus pressure transducer  156  ( FIG. 1 ) is provided. The annulus pressure transducer is in fluid communication with the annulus between the tool  100  and the wellbore walls. By calculating the difference between tubing and annulus pressure, an effective pressure can be determined and that effective pressure data provided to the circuitry for operation of the valve assembly  302  with its Kevlar fuse. 
     Once conditions for operation of the Kevlar fuse have been met, the electrodes operate to break the retaining members retaining the valve  302  in a closed position and the valve moves from the closed position of  FIG. 4  to the open position of  FIG. 5 . As described in conjunction with  FIG. 5 , the open valve permits fluid to flow into the fourth fluid path  258  to the annular shifting piston  150 , thereby moving the ball seat from the position of  FIG. 8  to the position of  FIG. 10 . With the seat  200  in its larger diameter position, the ball  201  is released, the bore  105  unblocked and wellbore operations can be resumed without having subjected the wellbore and surrounding formations to a pressure surge. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.