Patent Application
20070144731
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.
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.
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.
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.
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.
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
The setting tool S is somewhat altered in
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.
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:
