US 20070209802 A1
A trigger device keeps a downhole tool from setting until it is properly positioned. Regardless of the type of tool or the type of associated trigger, the retainer of the present invention is combusted. The material is preferably one that combusts readily such as a material used in fuses for explosives. The battery requirements are to simply create the brief spark that starts the combustion, making the battery size significantly smaller than what would be needed to power a heater to melt materials that were used in the past.
1. A trigger device for a downhole tool for selectively actuating the tool, comprising:
an actuating member mounted to said body whose movement sets the tool;
a restraining member to selectively directly or indirectly restrain movement of said actuating member with respect to said body, said restraining member when subjected to an initial energy input initiates a process within said restraining member that continues without further energy input to the point of allowing said actuating member to move.
2. The device of
said process releases heat.
3. The device of
said process comprises a chemical reaction.
4. The device of
the response of the restraining member to energy input is pyrotechnic.
5. The device of
said restraining member comprises an explosive material.
6. The device of
said energy input comprises a spark.
7. The device of
said spark is supplied by a battery supported by said housing.
8. The device of
said spark is generated mechanically.
9. The device of
said actuating member comprises a piston that is subjected to an initial force.
10. The device of
said restraining member comprises a wire that initially retains said piston.
11. The device of
said wire passes through said piston.
12. The device of
said restraining member comprises a wire fuse.
13. A method of selectively actuating a downhole tool, comprising:
retaining directly or indirectly a triggering member with a restraining member;
applying energy to the restraining member to initiate a response in said restraining member;
removing said applied energy while said response continues; and
defeating said restraining member to let the triggering member move.
14. The method of
releasing heat from said response.
15. The method of
creating a chemical reaction as said response.
16. The method of
using a wire fuse for said restraining member.
17. The method of
making said response a pyrotechnic one.
18. The method of
obtaining said response without the presence of oxygen.
19. The method of
creating a spark for said applying energy.
20. The method of
using a piston as said triggering member;
using a wire to retain said piston;
passing said wire around or through said piston; and
allowing said response to break said wire.
21. The device of
said restraining member opens a port as a result of being subjected to said energy input.
22. The device of
said actuating member comprises a piston flanked by chambers; said restraining material is disposed initially in a port in one of said chambers such that application of said energy input opens said port to create a net force on said piston to set the tool.
23. The device of
said port, when opened admits hydrostatic well pressure to one of said chambers.
24. The device of
said body further comprises a pressurized chamber, said port, when opened allows pressure from said pressurized chamber to reach said piston via one of said chambers to set the tool.
25. The device of
the other of said chambers is exposed to well hydrostatic pressure.
26. The device of
said restraining member comprises a final element that is in contact with the actuating member and said heat compromises said final element to allow the actuating member to move.
27. The device of
said final element comprises a cord connected to the actuating member that fails from said heat.
28. The device of
said wire holds a plurality of sleeve segments together until said initial energy input starts a process that undermines said wire.
29. The device of
said wire holds a split ring together around said piston until said initial energy input starts a process that undermines said wire.
The field of this invention is trigger devices that are actuated downhole to operate a tool and more particularly triggers that are held immobilized until properly positioned and then released preferably with a spark, however initiated.
Space is always a concern in downhole tool design. Some tools need to be retained in an unset position until properly placed in the well. It is only when they are properly located that it is desired to set the tool. Such tools in the past have had trigger mechanisms that are retained in an immovable position for run in until proper placement of the associated downhole tool is achieved. One technique for holding things immobile until the tool is properly placed has involved disabling the trigger with a mechanical device that is held against movement by a Kevlar® high strength fiber and an associated electrically powered heat source generally powered by stored batteries in the downhole tool. The generation of sufficient heat burns the fibers and releases the trigger so that the tool can set. Such a system is described in U.S. Pat. No. 5,558,153. The problem is that to generate enough heat downhole to burn the fibers and not damage adjacent components proves to be challenging for several reasons. One issue is the physical size of the battery pack to get a heater hot enough for long enough to compromise the fibers. Another issue is the very high temperatures needed to undermine the fibers and the effect on the overall design of the tool from having to keep heat sensitive components away from the heated area.
Another design featured a battery operated heater coil in a downhole tool to release the trigger by applying heat and melting a plug to start the setting sequence. This design is reflected in U.S. Pat. No. 6,382,234. Here again the same problems described above are encountered. The battery size to have the required electrical capacity to create enough heat to melt the fusible plug presents a very real space concern in a downhole tool where space for a large power supply is at a premium. The cost and the reliability of a large battery pack is an issue. On many occasions, safety is another issue since some batteries need special shipping and handling requirements.
Other alternatives still involved the large battery pack to accomplish a release of the trigger. For example, U.S. Pat. No. 5,558,153 also suggests using solder wire that melts at relatively low temperatures to be the trigger material or using the stored power in the battery to advance a knife to physically cut the fiber as opposed to undermining it with a battery operated heat source.
The present invention seeks to address the issues described above with the prior designs. One way it approached the problem is to choose a material that will readily go away by being combustible. The power then required to release the trigger is greatly reduced since it takes significantly less energy to create a spark that will create a burning of the trigger retainer to result in a release of the tool. What is proposed in one embodiment is the use of fuse material that is designed to be readily ignited. While no explosives need be set off, the fuse material that serves to hold the trigger against the setting of the tool simply readily ignites with a brief spark and burns to the point where it releases its hold on the setting mechanism and the tool simply sets. In another embodiment the wire burns and removes a barrier to flow that in turn set the tool. These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the preferred embodiment that is described below along with the associated drawings while recognizing that the claims further below indicate the scope of the invention.
A trigger device keeps a downhole tool from setting until it is properly positioned. Regardless of the type of tool or the type of associated trigger, the retainer is combusted which results in setting the tool. This can happen by freeing a piston to move, or allowing flow through a port or by other mechanisms. The material is preferably one that combusts readily such as a material used in fuses for explosives. The battery requirements are to simply create the brief spark that starts the combustion, making the battery size significantly smaller than what would be needed to power a heater to melt materials that were used in the past.
The wire 20 is such that initial energy input to it, preferably in the form of a brief spark that can be actuated electrically, mechanically or by other equivalent methods, sets in motion an event that continues without need for further energy input. Because of this feature, the battery or other energy source 22 and the ultimate recipient of the energy or power that creates a spark 24 collectively can be significantly smaller than prior designs that required continuous power input to disable the wire 20. Mechanical spark devices that employ relative movement to create a spark can also be used as well as other devices that will transmit the initial burst of energy necessary to disable the wire 20. For example the wire 20 can be made from PYRO FUZE® which consists of two metallic elements in intimate contact with each other. When these two elements are brought to the initiating temperature, they alloy rapidly resulting in instant deflagration without support of oxygen. Initiation is by heat and heat alone. All that is required is the exposure of the composite to the proper minimum temperature. The trigger reaction will reach temperatures in excess of the boiling point of the constituents. Once started, the reaction will not stop until alloying is completed or the unalloyed composite is subjected to some form of massive cooling that overwhelms the composite so that it cannot reach minimum operating temperature. The reaction end products consist normally of tiny discreet particles of the alloy of the participating materials. The present PYROFUZE composition was chosen for a number of desirable characteristics; it is a composite of alloys of Palladium and Aluminum. It is available in the following physical forms: Wire; and, Ribbon rolled from wire.
The PYROFUZE® reaction is not of an explosive or pyrotechnic nature. The only energy released is thermal (approximate minimum reaction temperature 2800° C./5000° F., 325 calories per gram, 2890 calories per cubic centimeter). The minimum initiation temperature is 650° C./1200° F.
Other materials are contemplated that also have explosive materials incorporated into the wire or result in a pyrotechnic response with the distinguishing characteristic being that the initial energy input that leads to the weakening of the wire 20 that ultimately lets the tool set continues after it is started without continuous energy input of the prior designs. Regardless of composition of the wire or the mechanism of the response to the energy input the defining difference is that the process continues without further energy input. Accordingly, fuses that are used to set explosives could function as wire 20.
In a different alternative a pressurized chamber can be isolated from one side of the piston by a plug as illustrated in
In yet other embodiments the heat given off from the spark igniting the material that continues to combust can also be harnessed to trigger the tool to set. In such embodiments the heat given off can cut a cord or compromise the actual retaining device to allow the tool to set.
While the retaining member has been illustrated in the preferred embodiment to be a wire, other shapes are contemplated as it is the mechanism of what happens after initial energy input that sets the present invention apart and a variety of shapes for the retaining member are contemplated to be within the scope of the invention apart from a wire shape.
While the preferred embodiment has been set forth above, those skilled in art will appreciate that the scope of the invention is significantly broader and as outlined in the claims which appear below.