Patent Application
20180202248
The invention relates generally to devices and methods for initiating or setting off a power charge within a wellbore.
Power charges are used to generate gases needed to apply compressive force for an affixed setting tool. A typical use for a power charge is as the motive force for a wireline setting tool. Such a setting tool is used to set bridge plugs, cement retainers and production packers or other downhole devices which must be anchored within a wellbore. Power charges are typically initiated by an igniter which uses electrical current to detonate a small amount of explosive material. A jet of hot burning gases created by the igniter will detonate a secondary pellet which, in turn, initiates the setting tool.
Some conventional igniters have reliability problems. A nichrome wire which is in contact with black powder within the igniter tends to suffer corrosion. As a result, there can be an unacceptable failure rate for such igniters after one year of shelf life. These conventional igniters are usually rated as explosive material, requiring special packaging and handling and thus increasing costs and delivery times.
The invention provides improved systems and methods for initiating a power charge when the setting tool is within a wellbore. Power charges are described which include at least one heating igniter which is non-explosive and which detonates the power charge by generating a high temperature which is sufficient to cause the flammable material within the power charge to ignite. Electrical voltage is supplied to the igniter to energize it. In preferred embodiments, electrical current is provided from the surface via wireline. In one embodiment, the igniter is a resistive heating element. In an alternative embodiment, the igniter is an uninsulated coil of wire.
In accordance with preferred methods of use, a power charge containing a heating igniter is incorporated into a packer setting tool. The packer setting tool and an affixed packer device are then run into a wellbore using a wireline running string. When the packer device is at a location wherein it is desired to set the packer device, the power charge is detonated by energizing the heating igniter thereby setting the packer device within the wellbore.
For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:
The packer device 22 is affixed to a packer setting tool 26. The packer setting tool 26 is operable to set packer device 22 by applying compressive force to portions of the packer setting tool 26. Except where otherwise described herein, the packer setting tool 26 can be constructed and operated in the same manner as the E-4 packer setting device which is available commercially from Baker Hughes Incorporated of Houston, Tex.
The power charge 32 includes an outer casing 36 which contains an amount of flammable material 38. The flammable material 38 may be made up using different recipes or mixtures, as is known in the art, to allow burning at various rates to allow optimum setting times for different types of packer devices. The flammable material 38 is a material in the solid phase of matter that can readily undergo combustion in the source of ignition under standard circumstances, i.e., without artificially changing variables such as pressure or density or by adding accelerants. Flammable material is readily combustible. It may cause or contribute to fire through friction. Readily combustible materials can be powdered, granular or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source. Flammable material 38 is very energetic and produces high temperature gaseous products on combustion which leads to high energy density needed for producing the required propulsive force. Flammable material 38 can consist of several chemical ingredients such as oxidizer, fuel, binder, plasticizer, curing agent, stabilizer and cross-linking agent. The specific chemical composition depends on the desired combustion characteristics for a particular application. Different chemical ingredients and their proportions result in different physical and chemical properties, combustion characteristics and performance. The outer casing 36 is shaped and sized to reside within the recess 30 in a complementary manner. A heating igniter 40 is also contained within the casing 36 in contact with the explosive 38. Electrical conduit 42 is interconnected with the heating igniter 40. The electrical conduit 42 will extend upwardly along the wireline 20 to an electrical power source 44 (
In an exemplary method of operation, the packer setting tool 26 and packer device 22 are run into the wellbore 10 on wireline running string 20. When the packer device 22 is at a location wherein it is desired to set the packer device 22 within the wellbore 10, the packer setting tool 26 is actuated by initiating the power charge 32 within. Initiation of the power charge 32 is done by energizing the heating igniter 40 or 40′.
Because heating igniter 40 or 40′ is non-explosive, it is believed that use of them will provide improved safety and reduced costs. Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.
