Setting mechanisms for downhole tools are described that take advantage of hydrostatic pressure in the wellbore which is harnessed to set a tool after exposure to well fluids for a given time or temperature defeats a lock and allows hydrostatic forces to trigger the setting of the tool. Alternatively, some other biasing source is released to set the downhole tool after exposure to well fluids for a time or a temperature and time defeats a lock and allows the biasing source to set the tool. While applications to packers are preferred, other downhole tools can be set in his manner removing the need for an inner string, dropping a ball on a seat or pressurizing the wellbore to achieve the setting of the downhole tool.

FIELD OF THE INVENTION  
       [0001]     The field of this invention relates to setting devices for downhole tools that automatically actuate them after certain conditions are met and more particularly focuses on time or temperature or combinations of those conditions.  
       BACKGROUND OF THE INVENTION  
       [0002]     Devices to actuate downhole tools such as external casing packers, for example normally require an inner string to shift a sliding sleeve or a straddle tool to bridge over an inflate port to set the downhole tool. Other techniques involve dropping a ball on a seat or pressurizing the wellbore. Each of these techniques for setting a downhole tool has limitations in certain well conditions and associated costs to implement.  
         [0003]     What is needed and made possible by the present invention is a technique to set a downhole tool in an alternative way based on conditions that exist in the wellbore. In a specific embodiment exposure to well fluids at a predetermined temperature for a predetermined time allows the tool to be set. These and other advantages of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings and the claims that all appear below.  
       SUMMARY OF THE INVENTION  
       [0004]     Setting mechanisms for downhole tools are described that take advantage of hydrostatic pressure in the wellbore which is harnessed to set a tool after exposure to well fluids for a given time or temperature defeats a lock and allows hydrostatic forces to trigger the setting of the tool. Alternatively, some other biasing source is released to set the downhole tool after exposure to well fluids for a time or a temperature and time defeats a lock and allows the biasing source to set the tool. While applications to packers are preferred, other downhole tools can be set in his manner removing the need for an inner string, dropping a ball on a seat or pressurizing the wellbore to achieve the setting of the downhole tool. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a section view in the run in position of a first embodiment that allows hydrostatic or applied well pressure to set a tool after a restraining member is defeated;  
         [0006]      FIG. 2  is the view of Figure  1  where the restraining member is sufficiently removed to allow the tool to be set;  
         [0007]      FIG. 3  is alternative embodiment to  FIG. 1  shown in the run in position;  
         [0008]      FIG. 4  is the view of  FIG. 3  in the tool set position;  
         [0009]      FIG. 5  is a section view in the run in position of an alternative embodiment that employs a stored force within the mechanism to be released and set the downhole tool;  
         [0010]      FIG. 6  is the view of  FIG. 5  in the tool set position; and  
         [0011]      FIG. 7  is an alternative to the  FIG. 5  design showing a different restraining material whose removal under well conditions, in the depicted position, sets the tool. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]     The mandrel  1  of the depicted setting tool S extends to a schematically illustrated downhole tool T that is preferably a packer but can be another type of tool known in the art. Mandrel  1  has a port  9  that is initially covered by a sleeve  6  that has seals  3  and  8  straddling the port  9  to keep it closed. Sleeve  6  is disposed in an internal recess  14  with a restrainer  5  on one side and an energy source  7  on the other side. Energy source  7  can't move the sleeve  6  as long as restrainer  5  is serviceable. A protective sleeve  4  overlays sleeve  6 , energy source  7  and restrainer  5  to protect hem from tools or other objects moved through mandrel  1 . Sleeve  4  allows well fluids in the mandrel  1  to get to restrainer  5  and energy source  7  as will be described below.  
         [0013]     Piston  2  covers port  9  and is mounted to mandrel  1  with seals  12  located at or near opposed ends. Seal  13  seals between the mandrel  1  and the piston  2  in a way to define atmospheric chamber  10  near the end opposite from tool T. The energy source  7  can take a variety of forms. It can be a spring, a pressurized chamber, a material that is resilient and installed in a compressed condition or it can be made of a material that grows on contact with well fluids or can in other ways be triggered to assume another shape such as a shape memory material that reverts to a larger size in response to a triggering signal. In whatever form it takes, it needs to be strong enough to shove sleeve  6  over so that seals  3  and  8  no longer straddle port  9  and pressure in mandrel  1  can reach atmospheric chamber  11  to pressurize it and move piston  2  against the tool T. However, non of that can or should happen until the restrainer  5  stops holding sleeve  6  against a force coming from energy source  7 . Restrainer  5  can take various forms. It can be a material that reacts or otherwise interacts with well fluids to get smaller, as shown in  FIG. 2  so that well fluid in mandrel  1  could get past port  9  into chamber  11  and slide piston  2  to set the tool T. It can be a material sensitive to the hydrostatic pressure to fail at a given depth. It can be a material sensitive to exposure to a predetermined temperature over a predetermined time so as to allow enough of a delay period for properly positioning the tool T before piston  2  can set it. The selection of the material can be from known materials that exhibit the desired properties. The main desired effect is to allow a sufficient time delay once the tool gets close to where it will be set so that it can be properly positioned before it is automatically set. The specific design of  FIGS. 1 and 2  is but one way to accomplish the automatic setting with a delay feature. Having the ability to do this takes away the need for running an inner string or dropping a ball or applying pressure from the surface to set a tool that is delivered dowhhole.  
         [0014]     The setting tool S is somewhat altered in  FIGS. 3 and 4 . The main difference is that sleeve  6  has a larger diameter o-ring  3  at one end than o-ring  8  at the other end. As a result of these unequal diameters, the hydrostatic pressure in the mandrel  1  normally exerts a force toward tool T at all times. However, for run in the restrainer  5  is in position and prevents the unbalanced force from moving the sleeve  6 . Since there is always a net unbalanced force on sleeve  6  during run in, there is no longer any need for energy source  7 , as, in effect, the energy source is now the hydrostatic pressure that creates the unbalanced force on sleeve  6  due to the differing end diameters. As before with  FIGS. 1 and 2  in the embodiment of  FIGS. 3 and 4  nothing happens until the restrainer  5  stops being there by a variety of mechanisms. The time it takes to go away is the delay period that allows proper positioning of the tool T. In the preferred embodiment exposure to a predetermined temperature level for a predetermined time makes the restrainer fail or stop restraining and allows the unbalanced pressure on sleeve  6  to shift it to pressurize chamber  11  which allows the piston  2  to move, since chamber  10  is at atmospheric.  FIG. 4  shows the shifted position of piston  2  to set the tool T. The restraint  5  can be a polymer with a glass transition temperature near the expected well temperature at the setting depth. As the temperature is reached the material softens to allow shifting of sleeve  6 , opening of port  9  and the ultimate shifting of the piston  2 . Alternatively the sleeve  6 , restrainer  5  and energy source  7  can be replaced with a sleeve of a shape memory material that initially blocks port  9  but then resumes a former shape that allows flow through port  9 , preferably through a thermal input from being run to the desired location.  
         [0015]      FIG. 5  shows another variation using the mandrel  1  and the piston  2  to actuate a tool T. Mandrel  1  has a tab  30  and another tab  32  and between them the restrainer  5  is disposed. Chamber  34  is at atmospheric and is sealed by seals  3  and  6  but piston  2  can't move in response to the hydrostatic pressure acting on it because of restrainer  5 . Ports  36  allow well fluids to reach the restrainer  5  to ultimately make it get smaller or just go away so that there is no longer resistance to the hydrostatic pressure acting on piston  2  thereby allowing it to shift to the right to set the tool T. The set position is shown in  FIG. 6 . If a dissolving polymer is used for the restrainer  5  the remains of it will pass through the ports  36  as chunks or in solution.  FIG. 7  shows an alternate embodiment to the restrainer  5  that can be a polymer with a low T g  so that it simply collapses as seen by comparing  FIGS. 5 and 7 . Alternatively the restrainer  5  in  FIGS. 5-7  can be a foam or mechanical device that collapses, preferably after a delay upon getting the tool T to a proper depth so as to allow time for proper placement before the automatic setting.  
         [0016]     What has been presented in the present invention is a way to automatically actuate tools downhole without the need for a running string, dropping balls or pressuring the wellbore. The common features of the various embodiments are a way to deliver the tool to close to where it will be actuated without it immediately being set. Then, the delay time between the start of the sequence and the actual actuation can be used to secure a final position of tool before it is set. Preferably the delay involves exposure to well fluids coupled with time. Alternatively, there can be an overlay involving the temperature of the well fluids and the time of exposure. The layout of the components and the nature of the material that is used as the restrictor determine the parameters involved in creating the delay insofar as initiating the period and its duration. The selection of materials that are used as a restrictor can vary with the anticipated well conditions. The invention is not necessarily the use of a given material that changes properties over time, in and of itself. Rather, it is the application of such known materials in the context of an automatic setting mechanism that can actuate a wide variety of downhole tools. While a preferred use is actuation of packers, other downhole tools can as easily be actuated such as sliding sleeves, anchors, bridge plugs to name just a few examples. The ultimately unleashed stored force can be available hydrostatic pressure, a resilient material that is installed to hold a stored force, a shape memory material, a pressurized chamber, one or more springs of various types, just to name a few examples.  
         [0017]     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: