Patent Publication Number: US-7591319-B2

Title: Gas activated actuator device for downhole tools

Description:
BACKGROUND 
     1. Field of Invention 
     The invention is directed to actuator devices for actuating downhole tools and, in particular, actuator devices having a material releases a gas that builds up sufficient pressure to facilitate activation of the actuator device and, thus, actuation of the downhole tool. 
     2. Description of Art 
     Some downhole tools need to be retained in an unset position until properly placed in the well. It is only when they are properly located within the well that the downhole tool is set through actuation of the tool. One prior technique for actuating the downhole tool is to open a window or passageway within the downhole tool exposing the actuating member, e.g., piston, of the downhole tool to the wellbore environment, e.g., the hydrostatic wellbore pressure. The hydrostatic pressure then acts upon the actuating member of the downhole tool and the downhole tool is actuated. In this technique, the creation of the window or passageway does not directly actuate the downhole tool. Instead, the creation of the window or passageway allows a different actuating mechanism, e.g., the hydrostatic or wellbore pressure, to actuate the tool. Additionally, in some instances, hydrostatic pressure is insufficient to actuate the tool. 
     In other prior attempts, pressures from fluids pumped down the well are used to break shear pins on the downhole tools. The use of shear pins, however, requires elevated directional pressure forces acting on the shear pins. However, in some instances sufficient pressure may not be available. Alternatively, in some wells, pressure, even if available, cannot be utilized because additional intervention steps are required which results in the well experiencing undesirable “downtime” for the additional intervention steps. Additionally, in some instances, the shear pins fail to shear when they are supposed to, causing further delays. 
     In still another prior technique, an explosive charge is included as part of the downhole tool. The explosive charge is then detonated by a detonator connected to the surface of the well through an electronic line or connected to battery pack located on the downhole tool. The force from the combustion of the explosive change then acts upon the actuating member and the downhole tool is actuated. Alternatively, smoke from the explosive charge that was activated by the heat from the battery or the electronic line may also act against the actuating member to actuate the downhole tool. 
     SUMMARY OF INVENTION 
     Broadly, the actuator devices for downhole tools have a housing or body, an actuating member, a retaining member, and a gas releasing material that is activated by a non-heat activator such as a fluid or solvent. Examples of retaining members include shear pins and chambers having equalized pressures. The retaining member prevents movement of the actuating member until the gas releasing material releases a gas and the pressure rises sufficiently to actuate the tool. In one specific embodiment, the gas is released by dissolution of the gas releasing material. Upon dissolution of the gas releasing material, gas is released and captured within a pressure chamber. As the gas pressure within the pressure chamber increases, due to the continued release of gas from the gas releasing material, the retaining member is no longer capable of preventing the movement of the actuating member. As a result, the actuating member moves and, thus, sets the downhole tool. 
     In certain specific embodiments, the gas pressure from the gas releasing material sets the downhole tool by one or more of freeing a piston to move or by any other mechanism known to persons skilled in the art. Moreover, in some embodiments, gas pressure sets the tool. Alternatively, the gas pressure from the gas releasing material sets the downhole tool may assist another setting mechanism, such as use of drilling fluid pressure or hydrostatic pressure, in setting the downhole tool. 
     The gas releasing material may be any material known to persons of ordinary skill in the art. Preferably, the gas releasing material is dissolved, disintegrated, or degraded to release the gas. In certain specific embodiments, solvents, such as water or hydrocarbon based drilling fluids or mud, can be used to dissolve the gas releasing material. Solvents include liquids, gases or other fluids, but do not include heat. 
     The actuator devices and methods disclosed herein not only permit actuation of the downhole tool, but actively assist in the actuation of the downhole tool through the release of a gas that provides a gas pressure. Thus, the gas pressure, either alone or in combination with any other actuation mechanism known to persons skilled in the art, plays an active role in actuation of the downhole tool. 
     In one aspect, one or more of the foregoing advantages may be achieved by the present actuator device for a downhole tool. The actuator device is capable of selectively actuating the downhole tool. The actuator device comprises a housing having a chamber; an actuating member operatively connected to the housing, the actuating member having a piston carried within the chamber, wherein movement of the actuating member relative to the housing causes a downhole tool to perform a specified function; a gas releasing material disposed in the chamber on one side of the piston; and a port leading to the chamber for selectively delivering an activator fluid to the chamber, wherein upon contact with the activator fluid, gas is released from the gas releasing material, which causes gas pressure to build up within the chamber sufficient to move the piston to cause the actuating member to actuate the downhole tool. 
     A further feature of the actuator device is that the actuator device may further comprise a restraining member mounted to the actuating member for preventing movement of the actuating member until the gas pressure reaches a selected level. Another feature of the actuator device is that the gas releasing material may comprise a metal that dissolves and releases hydrogen when contacted by water. An additional feature of the actuator device is that the gas releasing material in the chamber may be disposed above the piston for moving the piston downward relative to the housing when contacted by the activator fluid. Still another feature of the actuator device is that, prior to releasing the gas, the piston may have substantially equal pressures on its opposite sides. A further feature of the actuator device is that the port may extend to an exterior portion of the housing and the activator fluid is located in the wellbore. Another feature of the actuator device is that the actuator device may further comprise a rupture disk mounted in the port, which ruptures at a sufficient wellbore pressure to allow the activator fluid in the wellbore to enter the chamber. An additional feature of the actuator device is that the actuator device may further comprise a check valve in the port between the rupture disk and the chamber for allowing the activator fluid in the wellbore to enter the chamber after the rupture disk has ruptured but resisting flow of gas from the gas releasing material out the port to the wellbore. Still another feature of the actuator device is that the actuator device may further comprise a dissolvable membrane disposed in the port for blocking flow of the activator fluid in the wellbore to the chamber, the membrane dissolving after sufficient contact with the activator fluid in the wellbore. 
     In another aspect, one or more of the foregoing advantages may be achieved by the present actuator device comprising a housing; an actuating member operatively connected to the housing, wherein the movement of the actuating member causes a downhole tool to perform a specified function; a piston operatively associated with the actuating member, the piston being carried in a chamber in the housing, separating the chamber into a first chamber portion and a second chamber portion; a dissolvable gas releasing material disposed in the first chamber portion; a port extending through the housing from the first chamber to an exterior portion of the housing for admitting wellbore fluid to the first chamber; and a blocking member in the port for selectively delaying entry of wellbore fluid to the first chamber, wherein when the blocking member opens the port, wellbore fluid contacts and begins dissolving the gas releasing material, causing a gas to be released within the first chamber portion, creating a net differential force on the piston, which moves into the second chamber portion and causes the actuating member to actuate the downhole tool. 
     A further feature of the actuator device is that the gas releasing material may comprise a metal that dissolves and releases hydrogen when contacted by water. Another feature of the actuator device is that the blocking member may comprise a membrane that dissolves at a selected rate when immersed in wellbore fluid. An additional feature of the actuator device is that the first chamber portion may have a first chamber pressure and the second chamber portion may have a second chamber pressure, and the first pressure chamber pressure may be substantially equal to the second pressure chamber prior to the release of the gas from the gas releasing material. Still another feature of the actuator device is that the blocking member in the port may comprise a rupture disk that ruptures upon reaching a selected wellbore pressure. A further feature of the actuator device is that the blocking member may comprise a valve. Another feature of the actuator device is that actuator device may further comprise a one-way check valve in the port between the blocking member and the first chamber portion that allows wellbore fluid to flow into the first chamber portion but resists flow of gas from the first chamber portion to the wellbore. 
     In another aspect, one or more of the foregoing advantages may be achieved by the present improved actuator device for actuating a downhole tool having an actuating member. The improved actuator device comprises at least one gas releasing material operatively associated with a restraining member wherein activation of the gas releasing material by an activator fluid causes a gas to be released from the gas releasing material such that the restraining member no longer restrains movement of the actuating member such that the actuating member is capable of moving, causing actuation of the downhole tool. 
     In still another aspect, one or more of the foregoing advantages may be achieved through the present method of selectively actuating a downhole tool. The method comprises the steps of: (a) providing a downhole tool with a piston within a chamber having a gas releasing material located therein on one side of the piston; (b) lowering the tool into a wellbore and contacting the gas releasing material with an activator fluid capable of causing release of a gas from the gas releasing material; and (c) capturing the gas within the chamber and creating a pressure differential across the piston, causing the piston to move and actuate the downhole tool. 
     A further feature of the method is that step (b) may be performed by contacting the gas releasing material with a wellbore fluid. Another feature of the method is that step (b) may further comprise selectively delaying contact of the wellbore fluid with the gas releasing material. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of one specific embodiment of the actuator device of the present invention shown in its initial or run-in position 
         FIG. 2  is a cross-sectional view of the actuator device shown in  FIG. 1  in its actuated position. 
         FIG. 3  is a cross-sectional view of an additional specific embodiment of the actuator device of the present invention. 
         FIG. 4  is a cross-sectional view of still another specific embodiment of the actuator device of the present invention. 
         FIG. 5  is a cross-sectional view of yet another specific embodiment of the actuator device of the present invention. 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF INVENTION 
     Referring now to  FIGS. 1-4 , in one embodiment, actuator device  10  is included as part of downhole tool  100 . Downhole tool  100  is lowered on a string of conduit into the well and may be used for setting a packer, a bridge plug, or various other functions. Actuator device  10  has an actuating member, which as shown in  FIGS. 1-2 , is piston  12 . Generally, movement of piston  12  sets downhole tool after it is properly located in a well (not shown). As shown in  FIG. 1 , piston  12  is in its initial or “run-in” position. The initial position is the position prior to actuation of downhole tool  100 .  FIG. 2  shows piston  12  in the actuated position. 
     In this example, piston  12  includes a depending sleeve  11  carried in an annular chamber around a central mandrel assembly  13  of tool  100  and within a housing  15  of tool  100 . Sleeve  11  has inner and outer seals  18  that slidably engage mandrel assembly  13  and the inner side wall of housing  16  when actuated. Sleeve  11  of piston  12  is connected to an actuating member  22  by key  23  extending through an elongated slot  13   a  in mandrel assembly  13  to move actuating member  22  downward when piston  12  moves downward. Actuating member  22  performs a desired function, such as setting a packer. When actuated, a force is applied to piston  12  in the direction of the arrow. As disclosed herein, the force is created, at least in part, by the build-up of gas pressure within upper chamber  14  from the gas being released from gas releasing material  60  contained within upper chamber  14 . Additionally, the force can come from a variety of other sources operating in combination with the gas pressure. These other sources include hydrostatic pressure, fluid pressure pumped from the surface, or various springs or other energy storage devices or equivalents. When applied, the force moves piston  12  and sleeve  11  in the direction of the arrow. 
     Actuator device  10  also includes chamber  21 . Chamber  21  has a lower chamber  20  and an upper chamber  14 . The lower chamber  20  is located on the opposite side of piston  12  from upper chamber  14 . In one embodiment, the pressure within upper chamber  14  and lower chamber  20  maintain, or retain, piston  12  in the run-in position until the gas is released from the gas releasing material contained within upper chamber  14 . In a preferred embodiment, the pressure within upper chamber  14  is equalized with the pressure in lower chamber  20  during run-in. Actuator device  10  would normally be connected to a device (not shown) being set, such as a packer, which would provide resistance to movement of piston  12  during run-in. Optionally, a shear pin  28  maintains, or retains, piston  12  in the run-in position until the gas is released from the gas releasing material contained within upper chamber  14 . Shear pin  28  is secured between sleeve  11  and housing  15 . If shear pin  28  is employed, the pressures in upper chamber  14  and lower chamber  20  could initially differ during run-in. 
     At least a portion of upper chamber  14  is filled with the gas releasing material  60 . In the specific embodiment shown in  FIG. 1 , the entire volume of upper chamber  14  is filled with the gas releasing material. The term “gas releasing material” as used herein means that the material is capable of releasing a gas, such as hydrogen, carbon dioxide, carbon monoxide, or steam, when contacted with an activator fluid such as water or hydrocarbons. In a preferred embodiment, the gas releasing material is dissolvable. 
     The term “dissolvable” as used herein means that the material is capable of dissolution in a solvent disposed within the well, such as in tubing, casing, the string, or the downhole tool. The term “dissolvable” is understood to encompass the terms degradable and disintegrable. Likewise, the terms “dissolved” and “dissolution” also are interpreted to include “degraded” and “disintegrated,” and “degradation” and “disintegration,” respectively. 
     The gas releasing material may be any material known to persons of ordinary skill in the art that is capable of releasing a gas. In the embodiments in which the gas releasing material releases a gas upon dissolution, the gas releasing material may be any material known to persons of ordinary skill in the art that can be dissolved, degraded, or disintegrated to release the gas over an amount of time by a fluid such as water-based drilling fluids, hydrocarbon-based drilling fluids, or natural gas. In a preferred embodiment, the gas releasing material is TAFA Series 300-301 Dissolvable Metal from TAFA Incorporated of Concord, N.H. This material releases hydrogen gas when contact with water. For example, 100 grams of TAFA Series 300-301 Dissolvable Metal placed in contact with 8.3 liters of water within a chamber of having the same volume, releases enough hydrogen gas to create more than 1,500 psi. 
     In certain embodiments, water or some other chemical could be used alone or in combination with time and/or well temperature to dissolve the dissolvable material. Other fluids that may be used to dissolve the dissolvable material include alcohols, mutual solvents, and fuel oils such as diesel. 
     It is to be understood that the apparatuses and methods disclosed herein are considered successful if the gas releasing material releases sufficient gas such that the actuating member, e.g., piston, is moved from its initial or “run-in” position to its actuated or “setting” position so that the downhole tool is set. In other words, the apparatuses and methods are effective even if all of the gas from the gas releasing material does not dissolve. In one specific embodiment, at least 50% of the gas contained in the gas releasing material is released. In other specific embodiment, at least 90% of the gas contained in the gas releasing material is released. 
     It is also to be understood that the gas pressure from the gas releasing material may assist another setting mechanism, such as use of drilling fluid pressure or hydrostatic pressure, in setting the downhole tool. Accordingly, as long as the downhole tool is set through the assistance, either alone or in conjunction with another setting mechanism, the apparatuses and methods disclosed herein are considered successful. 
     Still with reference to  FIG. 1 , actuator device  10  also includes rupture disk  17  that is designed to break-away at predetermined depths due to hydrostatic pressure of the well fluid or fluid pressures applied by pumps at the surface of the well. Rupture disks  17  are known in the art. Passageway  19  contains rupture disc  17  and is in fluid communication with upper chamber  14 . 
     Although passageway  19  is shown horizontally disposed within housing  15 , passageway  19  may be disposed at an angle such that the intersection of passageway  19  with the wellbore environment is lower than the intersection of passageway  19  with upper chamber  14 . Therefore, gas being released by the gas releasing material within upper chamber  14  would have to flow downward to escape through passageway  19  into the environment. Thus, it is more difficult for the gas to escape upper chamber  14 . 
     As illustrated in detail in  FIG. 3 , passageway  19  may include one-way check valve  30  to permit wellbore fluid to enter passageway and, thus chamber  14  and to prevent the gas being released by the gas releasing material  60  within upper chamber  14  from escaping into the wellbore environment. Check valve  30  includes head  31  and stem  32  that extends through a check-valve passage  36 . Head  31  moves between upper and lower positions and seals against seat  35  while in the upper position (shown in  FIG. 3 ). Check valve  30  also includes coil spring  33  and spring retainer  34  so that coil spring  33  urges head  31  outward against seat  35 . In its initial position (shown in  FIG. 3 ) prior to the rupture of rupture disc  17 , head  31  engages seat  35  and blocks or prevents fluid from flowing from upper chamber  14  through passageway  19 . 
     After rupture disc  17  is ruptured, wellbore fluid presses against head  31  urging head  31  inward against coiled spring  33 , causing coiled spring  33  to be compressed between head  31  and spring retainer  34 . As a result, wellbore fluid is permitted to flow around head  31 , through check-valve passage  36 , and into contact with the gas releasing material  60  contained within upper chamber  14 . Gas is then released from gas releasing material  60  and is captured within upper chamber  14  because the gas pressure initially is not high enough to overcome the wellbore fluid pressure. When the gas pressure becomes high enough to overcome the wellbore fluid pressure, the gas pressure acts on head  31  of check valve  30  and urges, with the assistance of coiled spring  33 , head  31  outward until against seat  35 . Therefore, gas is not permitted to escape from upper chamber  14 . Moreover, in a preferred embodiment, any gas remaining within gas releasing material  60  continues to be released from the gas releasing material after check valve  30  closes to prevent additional wellbore fluid from entering upper chamber  14 . Therefore, even after wellbore fluid is blocked from entering upper chamber  14 , the gas pressure of the gas being released from the gas releasing material continues to increase to actuate piston  12 . 
     In another embodiment, shown in  FIG. 4 , an actuatable valve  40  placed within passageway  19  may be opened to let water or other solvent from the wellbore into passageway  19 . Actuatable valve  40  may then be closed. Valve  40  is shown schematically, and it could be operated remotely in a variety of manners. For example, valve  40  may be a sleeve valve or a ball valve that is opened and closed hydraulically or through any other method known to persons skilled in the art. When valve  40  is open, solvent or water within passageway  19  then dissolves dissolvable membrane  44  that separates passageway  19  from upper chamber  14 . After the dissolvable membrane is dissolved, the solvent or water then contacts the gas releasing material to dissolve the gas releasing material and release the gas. 
     Suitable dissolvable membranes may be formed from polymers and biodegradable polymers, for example, polyvinyl-alcohol based polymers such as the polymer HYDROCENE™ available from Idroplax, S.r.l. located in Altopascia, Italy, polylactide (“PLA”) polymer 4060D from Nature-Works™, a division of Cargill Dow LLC; TLF-6267 polyglycolic acid (“PGA”) from DuPont Specialty Chemicals; polycaprolactams and mixtures of PLA and PGA; solid acids, such as sulfamic acid, trichloroacetic acid, and citric acid, held together with a wax or other suitable binder material; polyethylene homopolymers and paraffin waxes; polyalkylene oxides, such as polyethylene oxides, and polyalkylene glycols, such as polyethylene glycols. These polymers may be preferred in water-based drilling fluids because they are slowly soluble in water. 
     Referring now to  FIG. 5 , in another embodiment, dissolvable membrane  44  is within upper chamber  14 , thereby dividing upper chamber  14  into upper portion  51  and lower portion  53 . Gas releasing material  60  is disposed within upper portion  51 , but not in lower portion  53 . In this embodiment, actuatable valve  40  is opened to permit hydrostatic pressure and wellbore fluid to enter passageway  19 . Hydrostatic pressure then acts on piston  12 ; however, in this embodiment, the hydrostatic pressure is not sufficient to fully actuate the downhole tool without additional assistance from another actuator device. In these circumstances, actuatable valve  40  can be closed and the wellbore fluid can dissolve the dissolvable membrane  44 . After dissolution of the dissolvable membrane  44 , the wellbore fluid can activate gas releasing material  60  to release the gas. The pressure increase caused by the release of gas from gas releasing material  60  then assists the hydrostatic pressure to fully actuate the downhole tool. 
     Moreover, in certain embodiments, dissolvable membrane  44  is not required. For example, actuatable valve  40  may be opened for a period of time to permit the wellbore fluid to begin releasing the gas from the gas releasing material  60 . However, before the gas pressure reaches a level where it overcomes the wellbore fluid pressure, the valve is closed. In this embodiment, a certain amount of gas can be released before the gas releasing material is isolated from the wellbore environment. 
     In operation, downhole tool  100  is lowered into a well (not shown) containing a well fluid by a string (not shown) of conduit that would be attached to mandrel assembly  13 . In one technique, during the running-in, the portion of piston  12  above seals  18  and retaining member  14  are isolated from wellbore fluid, and actuating member  22  and the portion of piston  12  below seals  18  are also isolated from wellbore fluid. The pressure on the upper and lower sides of piston seals  18  would be at atmospheric. Likewise, the pressure in upper chamber  14  and lower chamber  20  is also atmospheric. 
     The pressure difference on the exterior and interior sides of rupture disk  17  would be the difference between the hydrostatic pressure of the well fluid and atmospheric. Upon reaching a certain depth or a certain hydrostatic pressure of well fluid, rupture disk  17  breaks away placing passageway  19  and upper chamber  14  in contact with the wellbore environment. Fluid from the wellbore such as water, drilling fluid, or some other solvent capable of dissolving the gas releasing material within chamber  14  then contacts the gas releasing material  60 . As the gas releasing material dissolves, gas is released into upper chamber  14 , causing the pressure within upper chamber  14  to increase and exert a downward force on piston  12  because the pressure in lower chamber  20 , as well as below seals  18 , i.e., is atmospheric. As a result, piston  12  moves downward and actuates downhole tool  100  by moving actuating member  22  downward to the position shown in  FIG. 2 . If shear pin  28  is employed, the pressure build-up in upper chamber  14  would be sufficient to cause it to shear. 
     It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the pressure in the lower chamber and, thus, below the seals, may be initially higher than the pressure in the upper chamber so that the piston is urged upward to maintain the downhole tool in its “run-in” position. As is apparent, in such an embodiment, the gas pressure in the upper chamber as a result of the gas being released from the gas releasing material must be higher to overcome the pressure in the lower chamber and the area below the seals before the tool can be actuated. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.