Setting Tool Power Charge Initiation

Abstract

A power charge for a packer setting tool includes an outer casing and an amount of flammable material within the casing. A heating igniter is retained within the outer casing in contact with the flammable material. The heating igniter is energized by electrical power to heat it to a temperature that is sufficient to ignite the flammable material.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to devices and methods for initiating or setting off a power charge within a wellbore.

2. Description of the Related Art

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.

SUMMARY OF THE INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a side, cross-sectional view of an exemplary wellbore containing a packer device and packer setting tool in accordance with the present invention.

FIG. 2 is a side, cross-sectional view of portions of the setting tool from FIG. 1 and related components, including a power charge in accordance with the present invention.

FIG. 3 illustrates an exemplary power charge igniter constructed in accordance with the present invention.

FIG. 4 illustrates an alternative embodiment for a power charge igniter constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary wellbore 10 which has been drilled through the earth 12 from the surface 14. The wellbore 10 is lined with metallic casing 16. A tool string 18 is shown disposed into the wellbore 10. The tool string 18 includes a wireline running string 20 from which is suspended a packer device 22. The packer device 22 may be a compression-set packer of a type known in the art. In the depicted embodiment, the packer device 22 includes an elastomeric packer element 24 which is expanded radially to set against the casing 16 by axial compression.

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.

FIG. 2 illustrates portions of the packer setting tool 26 in greater detail. The packer setting tool 26 includes an outer housing 28 which defines a recess 30 for retaining power charge 32. A piston 34 is retained within the housing 28 and is axially moveable therein. As is known, movement of the piston 34 with respect to the housing 28 will cause setting of the packer device 22.

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 (FIG. 1) at surface 14. The electrical power source 44 may be a generator, battery or other source of electrical energy which is sufficient to provide energizing power to the heating igniter 40.

FIG. 3 illustrates an exemplary heating igniter 40 in greater detail. The depicted heating igniter 40 is a metallic resistive heating element which will heat up when electrical current is applied to it. The resistive heating element is preferably made of stainless steel. However, it might also be fashioned from a bimetallic or non-metallic material or other suitable materials. In the depicted embodiment, the resistive heating element is rod shaped. However, it should be understood that the resistive heating element may have other shapes. When energized, the heating igniter 40 should achieve a temperature that is sufficient to reach the ignition temperature of the flammable material 38. This temperature may be in the range of from about 750° F. to about 900° F. Most preferably, the temperature is about 800° F.

FIG. 4 illustrates an alternative embodiment for an igniter 40′ in accordance with the present invention. The heating igniter 40′ is a coil of wire. Current power supplies in the field will provide about 200 volts of electrical power and 1 to 1.5 amps. That power can be used for up to about 10 seconds. Wire size can be varied to provide different watt densities, output temperatures and the like to adjust for different flammable material 38.

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.

Claims

1. A power charge for a packer setting tool, the power charge comprising:

an outer casing, the casing being shaped and sized to reside within a power charge recess within a packer setting tool;

an amount of flammable material within the casing; and

a non-explosive heating igniter retained within the casing and in contact with the flammable material, the heating igniter being energizable by electric power to reach a temperature sufficient to ignite the flammable material.

2. The power charge of claim 1 wherein the heating igniter comprises a metallic resistive heating element.

3. The power charge of claim 1 wherein the heating igniter comprises a coil of wire.

4. The power charge of claim 1 wherein the heating igniter is formed of stainless steel.

5. A packer setting tool for setting an associated packer device within a wellbore, the packer setting tool comprising:

a setting tool housing;

a piston which is axially moveable with respect to the setting tool housing, movement of the piston being effective to set the associated packer device;

a power charge retained within the setting tool housing, the power charge having an outer casing, the casing being shaped and sized to reside within a power charge recess within a packer setting tool; an amount of flammable material within the casing; and a non-explosive heating igniter retained within the casing and in contact with the to flammable material, the heating igniter being energizable by electric power to reach a temperature sufficient to ignite the flammable material.

6. The packer setting tool of claim 5 further comprising an electrical conduit which interconnects the heating igniter with an electric power source.

7. The packer setting tool of claim 5 wherein the heating igniter comprises a metallic resistive heating element.

8. The packer setting tool of claim 5 wherein the heating igniter comprises a coil of wire.

9. The packer setting tool of claim 5 wherein the heating igniter is formed of stainless steel.

10. A method of setting a packer device within a wellbore, the method comprising the steps of:

disposing a packer device and associated packer setting device into a wellbore, the packer setting device including a power charge with a non-explosive heating igniter;

detonating the power charge by energizing the heating igniter with electric power.

11. The method of claim 10 wherein the heating igniter is energized by a power source which is located at a surface location with respect to the wellbore.