Abstract:
A method and apparatus for actuating a downhole tool in a wellbore. The method and apparatus including an actuator that operates the tool in response to the functioning of an energetic charge. The energetic charge may be set off as a part of a perforating operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to downhole tools and methods for operating downhole tools. More particularly, embodiments of the present invention relate to apparatus and methods for actuating downhole tools in response to perforating a downhole tubular. More particularly still, embodiments of the present invention relate to apparatus and methods for actuating a downhole valve using a chemically energetic charge. 
     2. Description of the Related Art 
     In the drilling of oil and gas wells, a wellbore is formed using a drill bit disposed at a lower end of a drill string that is urged downwardly into the earth. After drilling a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thereby formed between the string of casing and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas or zones behind the casing including those containing hydrocarbons. The drilling operation is typically performed in stages and a number of casing strings may be run into the wellbore until the wellbore is at the desired depth and location. 
     During the life of the well a number of downhole tools are used in order to maximize the production of different producing zones in the well. The casing is typically perforated adjacent a hydrocarbon bearing formation using a series of explosive or “perforating” charges. Such a series of charges are typically run into the well bore inside of an evacuated tube and that charge containing tube is known as a “perforating gun.” When detonated, the charges pierce or perforate the walls of the casing and penetrate the formation thereby allowing fluid communication between the interior of the casing and the formation. Production fluids may flow into the casing from the formation and treatment fluids may be pumped from the casing interior into the formation through the perforations made by the charges. 
     In many instances a single wellbore may traverse multiple hydrocarbon bearing formations that are otherwise isolated from one another within the Earth. It is also frequently desirable to treat such hydrocarbon bearing formations with pressurized treatment fluids prior to producing those formations. In order to ensure that a proper treatment is performed on a desired formation, that formation is typically isolated during treatment from other formations traversed by the wellbore. To achieve sequential treatment of multiple formations, the casing adjacent a lowermost formation is perforated while the casing portions adjacent other formations common to the wellbore are left un-perforated. The perforated zone is then treated by pumping treatment fluid under pressure into that zone through the perforations. Following treatment, a downhole plug is set above the perforated zone and the next sequential zone up hole is perforated, treated and isolated with an above positioned plug. That process is repeated until all of the zones of interest have been treated. Subsequently, production of hydrocarbons from these zones requires that the sequentially set plugs be removed from the well. Such removal requires that removal equipment be run into the well on a conveyance string which may typically be wire line coiled tubing or jointed pipe. 
     In the above described treatment process the perforation and plug setting steps each represent a separate excursion or “trip” into and out of the wellbore with the required equipment. Each trip takes additional time and effort and adds complexity to the overall effort. Such factors can be exacerbated when operating in wellbores that are not vertical and specialized conveyance equipment is often required in “horizontal” wellbores. 
     Therefore, there is a need for a capability of performing multiple downhole process steps in a single trip. Further, there is a need for a system that can perforate one zone and isolate another zone in the same trip. There is a need for a device that closes the bore of a casing upon receipt of an impulse from a downhole source. There is a further need for actuating downhole tools during a perforating operation. There is a need for a downhole isolation valve that can be actuated by an explosive charge. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention there is provided generally a downhole isolation valve that can be actuated by an energetic device. Further provided are methods for isolating downhole formations and performing other well bore operations in a single trip. 
     More specifically the present apparatus comprises a well bore casing string comprising: 
     at least one valve member having a first position wherein a bore of a casing is substantially unobstructed and a second position wherein the bore is substantially closed; 
     at least one fluid chamber having a first pressure configuration isolated from a fluid pressure there around and a second pressure configuration wherein the fluid pressure is communicated through a boundary of the chamber; and 
     at least one valve retainer operatively coupled between the fluid chamber and the valve member, the valve retainer configured to move in response to the communicated fluid pressure and thereby facilitate movement of the valve member from the first position to the second position. 
     Further, the present methods comprise isolating a portion of a well bore comprising: 
     providing a valve member for obstructing a bore of a casing in the well bore; 
     providing a first fluid flow path having a first predetermined location, from the well bore to a formation surrounding the well bore, the valve member being located along the well bore between the first predetermined location and an earth surface opening of the well bore; and 
     opening a second fluid flow path, having a second predetermined location, through a wall of the casing and obstructing the bore of the casing with the valve member, by activating a first energetic device, the second predetermined location being along the well bore between the valve member and the Earth surface opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the above recited features may be understood in more detail, a more particular description of the features, 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 the present 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 schematic view of a wellbore according to one embodiment. 
         FIG. 2  is a schematic view of a downhole tool according to one embodiment. 
         FIG. 3  is a schematic view of a downhole tool according to one embodiment. 
         FIG. 4  is a schematic view of a downhole tool according to another embodiment. 
         FIG. 5  is a schematic view of a downhole tool according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic view of a cased wellbore  1 . The casing  10  is positioned inside the wellbore  1 . An annulus  30  between the casing  10  and the wellbore  1  is typically filled with cement (not shown) in order to anchor the casing and isolate one or more production zones  40 A-N, or formations. “A-N” is used herein to indicate a variable number of items so designated, where the number of such items may be one or more up to and including any number “N”. Optionally, any item designated with the suffix “A-N” may include one or more whether or not the suffix is used in a given context. In one embodiment, one or more tools  50 A-N is located in the casing string. Each of the tools  50 A-N includes a fluid reservoir or chamber  60 A-N for operating the respective tool  50 A-N, as will be described in more detail below. An energetic device  90  or devices  90 A-N are shown located within the casing  10 . The one or more energetic devices  90 A-N may comprise any suitable deformation and/or perforating mechanism. Exemplary energetic devices  90 A-N include explosive shaped charge perforating guns, bulk explosive charges, wellbore perforating rotary drills and erosive fluid operated drills, compressed gas charges, and corrosive chemical based cutters and reduced pressure chambers (“atmospheric chambers”). Each of the energetic devices  90 A-N is capable of deforming, perforating or impinging energy upon a boundary structure of one or more of the respective chambers or reservoirs  60 A-N. In one embodiment, the energetic device  90  is a perforating gun which includes one or more shaped charges  80 . Typically each charge  80  generates a metallic plasma jet when the charge is detonated and typically that jet hydrodynamically penetrates the surrounding casing and formations including the reservoir  60 . One or more sets of charges  80  may be used in order to perforate multiple production zones  40 A-N. 
     In use the energetic device (or devices)  90 A-N is run into the wellbore  1  on a conveyance  70 . The conveyance  70  may be a wire line, a slick line, coiled tubing, jointed tubing, or any other suitable conveyance mechanism. A plurality of energetic devices  90 A-N may be lowered into the wellbore  1  on a common conveyance  70 . Such a plurality may be configured to be selectively initiated such as one at a time, in predetermined groups or all at once. One or more energetic devices  90 A-N each comprising one or more of the sets of charges  80  is located near the production zone  40 A-N that is to be perforated. The charges  80  are initiated, thereby creating perforations through the casing  10  and into the surrounding formation  40 A-N. At least one of the charges  80  also impinges upon a boundary of the reservoir or chamber  60 A-N thereby causing the respective tool  50 A-N to function, as will be described in more detail below. In one embodiment the tool  50 A-N includes a valve member which closes a bore  100  of the casing  10 . After the tool  50 A-N is actuated, the energetic device  90  may be moved to another production zone  40  and the process repeated. In another embodiment, each of the one or more sets of charges  90 A-N is spaced on the conveyance  70  to correspond with the locations of the production zones  40 A-N. In that instance the energetic devices  90 A-N may be initiated in sequence or at substantially the same time in order to perforate all of the formations  40 A-N, without having to move the conveyance  70 . 
       FIG. 2  is a schematic of one embodiment of the tool  50  and the reservoir  60 . The tool  50  and reservoir  60  are shown as separate and spaced components coupled together on a tubular  200 ; however, it should be appreciated that the tool  50  and the reservoir  60  may be integral components and may be coupled to a tubular sub or directly to the casing  10 . The tubular  200  may be a part of or connected to any tubular string used downhole such as a casing, production tubing, liner, coiled tubing, drill string, etc. As shown the tubular  200  includes threads  210  for forming a threaded connection with the casing  10 . The reservoir  60  has a chamber  220  for containing a fluid  230 . The fluid  230  may be a gas or a liquid or any other suitable pressure transfer medium. 
     The chamber  220  is in fluid communication with a piston  260  via a control line  240 . The chamber  220 , as shown, is in fluid communication with a lower side of the piston  260  although it should be appreciated that the terms lower and upper and other directional terms used herein are only used for reference to the figures. A fluid within the piston chamber portion  261  above the piston  260  is preferably a gas and preferably at atmospheric pressure, although it should be appreciated that the fluid may be at other reduced pressures relative to the wellbore. Although the control line  240  is shown as an external line, it should be appreciated that the control line  240  may be integral with the tubular  200 . As shown, the tool  50  includes a valve  270  having spring  280  for biasing the valve closed, and a hinge  290 . As shown, the valve  270  is a flapper valve; however, it should be appreciated that the valve could be a ball valve, gate valve, butterfly valve or any other suitable valve. Further, the valve  270  includes a valve seat  295 . The seat  295  allows the valve  270  to sealing obstruct the bore  100 . In one embodiment, fluid pressure above the valve  270  holds the valve shut once the valve has been closed. If there is sufficient fluid pressure below the valve  270  to overcome bias of the spring  280  and any fluid pressure above the valve  270  the valve  270  will open allowing fluids to flow upward through the bore  100 . A latch (not shown) may be used in order to hold the valve  270  in the closed position. 
     The piston  260  includes a valve retainer  262  coupled thereto or integral therewith. The valve retainer  262  retains the valve  270  in a casing bore open position. Alternatively, the valve retainer  262  may be operatively coupled to the valve member  270  or hinge  290  such that the valve retainer  262  may affirmatively move, or exert a motive force upon, the valve member  270  from a first position to a second position such as for example from an open position to a closed position or visa versa. The valve retainer  262  may comprise a rod, a bar, a key, a cylinder, a portion of a cylinder, a linkage, a cam, an abutment or any other suitable structure for retaining and/or moving the valve  270 . In certain embodiments the valve retainer  262  is operatively connected to the hinge  290 , for example at a location radially outward of the hinge pivot point of the hinge  290  such that upward movement of the valve retainer  262  acts to move the valve member  270  to a closed position and downward movement of the valve retainer  262  acts to move the valve member  270  to an open position. 
     Referring to  FIGS. 1 ,  2  and  3 , the tool  50  and reservoir  60 , in operation, are lowered into the wellbore  1  preferably as part of a string of casing or liner. The fluid  230  in the chamber  220  may be pneumatic or hydraulic. The energetic device  90  is lowered into the bore  100  and initiated. The charge  80  of the energetic device  90  creates openings  295  in the casing wall and in the boundary of chamber  220 . In the embodiment shown there is spacing between the reservoir  60  and the tool  50 . Such spacing may help to reduce any possibility that the tool  50  would be damaged by a pressure impulse from the energetic device  90 . Such spacing may be minimal or may be such that the reservoir  60  and the tool  50  are distanced by many joints of casing and depends on the embodiment used and other functional circumstances. One or more holes  295 , as shown in  FIG. 3 , puncture the chamber  220 . The wellbore fluids, not shown, enter the chamber  220  and apply wellbore pressure to the fluid  230 . The wellbore pressure traverses through line  240  and exerts a force below piston  260 . The piston  260  and valve retainer  262  move upward in response to the exerted pressure, toward a valve releasing position. As the piston  260  moves, the valve retainer  262  moves with it until the valve  270  is movable to close the bore  100 . Once in the closed position fluid pressure from above the valve  270  and/or a latch (not shown) may hold the valve in the closed position. 
     In another embodiment, the fluid  230  is a hydraulic fluid. The energetic device  90  may be designed to create a dent  296  in the chamber  220 . The energetic device  90  is initiated and thereby creates the dent  296 . The dent  296  decreases the volume of the chamber  220  forcing the fluid  230  to traverse through line  240  and push the piston  260  upwardly. Optionally, the line  240  may extend to the surface of the wellbore, either directly or as an additional extension in fluid communication with an interior of chamber  220 , and fluid pressure therein may be adjusted from the surface. As described above the piston  260  and the valve retainer  262  then move toward the valve releasing position and release the valve  270 . Further, the energetic device  90  may create the hole  295  in the chamber  220 . In that event, the valve will operate as described in the foregoing paragraphs. 
     In another embodiment, shown in  FIGS. 4 and 5  the tool  50  and the reservoir  60  are particularly suited for use in wellbores having reduced hydrostatic pressure. The chamber  220  may be filled with a relatively incompressible fluid such as a water or oil based liquid. The chamber  220  is pressurized. That pressure may result from either exclusively or with additional overpressure, the force of the biasing member  282  exerted on the fluid in the closed chamber  220  through the piston  260  and is sufficient to maintain the biasing member  282  in a compressed position. The pressure in chamber  220  communicates to piston chamber  250  and in maintaining compression of the biasing member correspondingly maintains the piston  260  in a valve retaining position. 
     The chamber  220  is in fluid communication with a piston and cylinder assembly  240 . The piston and cylinder assembly  240  includes a piston chamber  250  and the piston  260 . The piston  260  moves upwardly in order to release the valve  270  to a casing bore closure position. The piston  260  may include a biasing member  282 . The biasing member  282 , as shown, is a coiled spring; however, it could be a stack of Belleville washers, a gas accumulator, a silicone oil “spring” or any other suitable biasing member. The biasing member  282  biases the piston  260  toward a valve releasing position. Optionally, a port  300  communicates wellbore pressure to a lower surface of piston  260 . 
     A port  300 , as shown, connects the bore  100  to a section  310  of the piston chamber  250  located on the biased or lower side of the piston  260 . The port  300  may additionally or alternatively be arranged to connect the section  310  with an area exterior of the tubular  200 . The port allows the section  310  to fill with wellbore fluids (not shown) as the tool  50  is lowered into the wellbore  1 . As the fluid pressure in the bore  100  increases, the pressure in the section  310  increases. As the pressure in the section  310  increases, the piston  260  transfers that pressure to the fluid  230  on the opposite or upper side of the piston  260 . However, the piston  260  will not move to the actuated position due to the pressure of the fluid  230  in the closed chamber  220 . 
     In one embodiment, a surface control line (not shown) is connected to chamber  220  and in fluid communication with fluid  230 . Such surface control line extends to the surface of the wellbore such that pressure within the surface control line and correspondingly the chamber  220  may be adjusted from the surface. Pressure may be bled from the surface control line whereby the biasing member  282  moves the valve retainer  262  upwardly and the valve  270  moves to a closed position. Optionally, the valve retainer  262  is operatively connected to the valve  270 , for example by connection to the hinge  290 . An increase in pressure within the surface control line and correspondingly above the piston  260  moves the valve retainer  262  downward and moves the valve  270  to an open position. Alternatively, such a pressure increase in the surface control line moves the valve retainer  262  downward and through the valve member  270  thereby bending, rupturing or shattering the valve member  270  and/or the hinge  290  such that the bore  100  is free from obstruction by the valve member  270 . 
     Referring to  FIGS. 1 ,  4  and  5 , the tool  50  and reservoir  60  are lowered into the wellbore  1 . The energetic device  90  is positioned such that at least a portion of energetic device  90  is proximate the reservoir  60 . The energetic device  90  is actuated thereby creating one or more holes  295 , as shown in  FIG. 5 , through a boundary of the chamber  220  and/or the piston chamber  250 . The one or more holes  295  release the pressure in the chamber  220  and correspondingly piston chamber  250  thereby allowing pressure to escape into the wellbore and to equalize across the piston  260 . The biasing member  280  then pushes the piston toward the valve releasing position. The piston  260  moves and the valve retainer  262  moves with it until the valve  270  are allowed to close the bore  100 . The valve  270 , as shown, is coupled with the tubular  200  by a hinge and may include a spring biasing the valve  270  to rotate about the hinge  290  toward the casing bore closed position. Therefore, the valve  270  automatically closes upon the piston  260  reaching the actuated position. 
     The valve  270  or valve member may be made of a dissolvable, breakable or frangible material, such as aluminum, plastic, glass or ceramic or any other suitable material. Such dissolvable or breakable material allows an operator to open the valve by shattering or dissolving it when desired. The valve member may be a ball valve and the piston may be coupled to a ball valve actuator whereby movement of the piston changes the position of the valve from, for example, open to closed, by rotating the ball through, for example, 90 degrees. 
     In one embodiment the reservoir  60  may include a “knock-off” or “break” plug (not shown) through a wall thereof and extending partially into the bore  100  of the casing. In that instance the energetic device  90  may comprise a weight bar or perforating gun body. A fluid communication path is formed through the boundary wall of the reservoir  60  by running the weight bar or gun body into the “break” plug thereby breaking the plug and opening the fluid path there through. Alternatively or additionally, a wall of the reservoir  60  may include a rupture disk in fluid communication with the bore  100 . A fluid pressure impulse created in the bore  100  by the energetic device  90  ruptures the disk thereby opening a fluid flow path through a boundary wall of the reservoir  60 . 
     In one operational embodiment it is desirable to treat hydrocarbon bearing formations with pressurized treatment fluids without making multiple trips into the wellbore. To ensure that a proper treatment is performed on a given formation, it is desired that the formation be isolated from other formations traversed by the wellbore during treatment. For performing a treatment operation in accordance with methods disclosed herein, the tools  50 A-N, shown in  FIG. 1 , may be one or more of the valves  270  described above. The tools  50 A-N are located below each of the respective production zones  40 A-N. The energetic device  90 A is lowered to the lower most production zone  40 A. The energetic device  90 A is initiated thereby perforating the production zone  40 A and actuating the tool  50 A. The tool  50 A seals the bore  100  below the production zone  40 A. Pressurized treatment fluids (not shown) are then introduced into the production zone  40 A through the fluid flow paths or perforations created by the energetic device  90 A. The tool  50 A allows the bore  100  below the production zone  40 A to remain isolated from the pressurized fluids while the treatment operation is performed. The energetic device  90 B is located adjacent to the next production zone  40 B. Alternatively, the expended energetic device  90 A is removed from the wellbore and second and an unexpended energetic device  90 B is lowered into the wellbore adjacent production zone  40 B. The next production zone  40 B is then perforated and the tool  50 B seals the bore  100  thereby isolating the previously perforated and treated production zone  40 A below the production zone  40 B. Treatment fluids may then be introduced into the next production zone  40 B through the perforations created by the energetic device  90 B. The tool  50 B isolates the next production zone  40 B from the production zone  40 A, thus allowing treatment of only the production zone  40 B. This process may be repeated at any number of production zones  40 A-N in the wellbore  1 . 
     When the one or more treatment operations are complete, the wellbore may be prepared to produce production fluid. Production tubing (not shown) is run into the wellbore  1  above the uppermost tool  50 N. The overbalanced hydrostatic pressure above the uppermost tool  50 N is relieved until the pressure below the tool  50 N is greater than the pressure above the tool  50 N. The tool  50 N may be one of the valves  270  described above. The tool  50 N automatically opens when the pressure is greater below the tool  50 N thereby allowing production fluids from the one or more production zones  40 A-N to flow upwardly and into the production tubing (not shown). The production fluid continues to flow upward through the tools  50 A-N as long as the pressure below the tools  50 A-N is greater than the pressure above those respective tools. If the pressure above the tools  50 A-N increases or the pressure below the tool decreases, the thus affected tool will automatically close the bore  100 . In order to perform operations below the tools  50 A-N once they are closed, it may be necessary to open the tools  50 A-N. The tools  50 A-N may be opened for example by breaking, dissolving, drilling through, or manipulation of the valve member. With the tool  50 N open, for example, an operation may be performed below the tool  50 N while a lower zone  40 N−1 is still isolated by a subsequent tool  50 N−1 (where N−1 may be A or B as shown on  FIG. 1 ). The next tool  50 N−1 may then be opened in order to perform additional operations below that next tool  50 N−1. 
     While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope of the present invention, and the scope thereof is determined by the claims that follow.