Patent Description:
Generally, when completing a subterranean well for the production of fluids, minerals, or gases from underground reservoirs, several types of tubulars are placed downhole as part of the drilling, exploration, and completions process. These tubulars can include casing, tubing, pipes, liners, and devices conveyed downhole by tubulars of various types. Each well is unique, so combinations of different tubulars may be lowered into a well for a multitude of purposes.

A subsurface or subterranean well transits one or more formations. The formation is a body of rock or strata that contains one or more compositions. The formation is treated as a continuous body. Within the formation hydrocarbon deposits may exist. Typically, a wellbore will be drilled from a surface location, placing a hole into a formation of interest. Completion equipment will be put into place, including casing, tubing, and other downhole equipment as needed. Perforating the casing and the formation with a perforating gun is a well known method in the art for accessing hydrocarbon deposits within a formation from a wellbore.

Setting tools can be used for many applications, including setting bridge plugs. Bridge plugs are often introduced or carried into a subterranean oil or gas well on a conduit, such as wire line, electric line, continuous coiled tubing, threaded work string, or the like, for engagement at a pre-selected position within the well along another conduit having an inner smooth inner wall, such as casing. The bridge plug is typically expanded and set into position within the casing. The bridge plug effectively seals off one section of casing from another. Several different completions operations may commence after the bridge plug is set, including perforating and fracturing. Sometimes a series of plugs are set in an operation called "plug and perf" where several sections of casing are perforated sequentially.

Setting a bridge plug typically requires setting a "slip" mechanism that engages and locks the bridge plug with the casing and energizing the packing element in the case of a bridge plug. This requires large forces, often in excess of <NUM>,<NUM> lbs (<NUM> kN). The activation or manipulation of some setting tools involves the activation of an energetic material such as a pyrotechnic charge, referred to as a power charge, to provide the energy needed to set a bridge plug. The energetic material may use a relatively slow burning chemical reaction to generate high pressure gases. One such setting tool is the Model E-<NUM> Wireline Pressure Setting Tool of Baker International Corporation, sometimes referred to as the Baker Setting Tool.

A firing head may also be used in conjunction with a setting tool. A firing head is used to trigger the setting. The firing head may be activated by an electrical signal. Electricity may be provided by a wireline that ties into the cable head at the top of a tool string. The electrical signal may have to travel through several components, subs, and tools before it gets to the firing head. A reliable electrical connector is needed to ensure the electrical signal can easily pass from one component to the next as it moves down the tool string. The electrical signal is typically grounded against the tool string casing. As a result, the electrical connections must be insulated from tool components that are in electrical contact with the tool string casing.

<CIT> discloses a projectile charge for an ammunition for a gun.

<CIT> discloses a power charge for operating a downhole tool.

The present invention provides a power charge for a downhole setting tool according to claim <NUM>. The power charge has a tubular housing having a first end, a second end, and a mid-section, a main propellant within the housing proximate the mid-section comprising a main propellant, and a first ignition portion within the housing proximate the first end comprising a first mixture of the main propellant and an ignition propellant.

The ignition propellant has a propagation index of <NUM> Cal/(g °C) (<NUM> Cal/(g °C) = <NUM> J/(g °C) ) or greater and the main propellant has a propagation index of <NUM> or less It may include the ignition propellant having a propagation index of <NUM> or more. It may include the ignition propellant having a propagation index of <NUM> or more. It may include the first ignition propellant containing boron potassium nitrate. It may include the first mixture of main propellant and ignition propellant having a gradient with predominately ignition propellant towards the first end and transitioning to primarily main propellant away from the first end. It may include the gradient ranging from <NUM>% or more ignition propellant near the first end to <NUM>% or less ignition propellant away from the first end. It may include the first ignition portion extending between <NUM> inch and <NUM> inches (<NUM> inch = <NUM>,<NUM>) from the first end. It may include the ignition portion extending from the end of the housing approximately <NUM>% to <NUM>% of the length of the housing. It may include the first ignition portion being approximately <NUM>% of the power charge by weight.

An example embodiment may include a second ignition portion within the housing proximate the second end comprising a second mixture of the main propellant and the ignition propellant.

A variation of the example embodiment may include the ignition propellant containing boron potassium nitrate. It may include the first mixture of main propellant and ignition propellant having a gradient with predominately ignition propellant towards the first end and transitioning to primarily main propellant away from the first end and the second mixture of main propellant and ignition propellant having a gradient with predominately ignition propellant towards the second end and transitioning to primarily main propellant away from the second end. It may include the first gradient ranging from <NUM>% or more ignition propellant near the first end to <NUM>% or less ignition propellant away from the first end and the second gradient ranging from <NUM>% or more ignition propellant near the second end to <NUM>% or less ignition propellant away from the second end. It may include the first ignition portion extending between <NUM> inch and <NUM> inches from the first end and the second ignition portion extending between <NUM> inch and <NUM> inches from the second end. It may include the ignition portion extending from the end of the housing approximately <NUM>% to <NUM>% of the length of the housing. It may include the first and second ignition portion combined being approximately <NUM>% of the power charge by weight.

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 in which reference numbers designate like or similar elements throughout the several figures of the drawing.

In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus, systems and method steps described herein may be used alone or in combination with other apparatus, systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.

<FIG> show an example setting tool with an electrical connection <NUM> an igniter <NUM>, a power charge <NUM>, and a piston <NUM>. In operation, signals through electrical connection <NUM> cause igniter <NUM> to emit heat and, typically, flames. The output of igniter <NUM> ignites a propellant in power charge <NUM>, via pathway <NUM>, which produces pressure that ultimately drives piston <NUM>, to actuate a tool, such as a wellbore plug. Sometimes, a secondary material such as pyrodex is placed in an ignition path between the igniter and power charge to improve reliability of the ignition transfer.

A propellant can be classified by its propagation index (PI), defined by the ratio of the energy output (ΔHReaction) in Calories per gram over auto ignition temperature (TIgnition) in degrees Celsius.

Power charges typically include a main propellant, typically with a metallic fuel and an oxidizer with a binder like epoxy. In some examples, these components are mixed in ratios of <NUM>-<NUM>% epoxy, <NUM>-<NUM>% fuel, and <NUM>-<NUM>% oxidizer. In one example, the fuel is aluminum and the oxidizer is potassium nitrate in an epoxy binder. Other possible fuels for the main propellant include: Iron, Magnesium, Magnalium (Magnesium/Aluminum <NUM>/<NUM> alloy), Titanium, Tungsten, Zinc, Zirconium, Boron, Sulfur, Charcoal, and Graphite. Other possible oxidizers for the main propellant include: Ammonium Nitrate, Ammonium Perchlorate, Barium Chlorate, Barium Chromate, Barium Nitrate, Barium Peroxide, Iron (III) Oxide (red), Iron (II, III) Oxide (black), Lead Chromate, Lead Dioxide, Lead Oxide, Lead Tetroxide, Potassium Chlorate, Potassium Perchlorate, Sodium Nitrate, and Strontium Nitrate. A main propellant typically has a propagation index of less than <NUM> Cal/(g deg C). Example main propellants may have a propagation index of less than <NUM> Cal/(g deg C). Example main propellants may have an auto ignition temperature of over <NUM> degrees Celsius. Example main propellants may have an energy output of <NUM> Calories per gram or less.

In an example embodiment of <FIG>, a power charge <NUM> is shown in a tubular housing <NUM>. The tubular housing has a first end <NUM>, a second end, <NUM> and a mid-section between the first and second ends. There is a main propellant <NUM> in the mid-section of housing <NUM>.

In the first end <NUM> of the housing, there is a first ignition portion <NUM> of pyrotechnic material made of a mixture of a main propellant <NUM> and an ignition propellant. The ignition propellant is a material that is generally more sensitive to ignition than the main propellant and generally has a greater energy output than the main propellant. In some examples, the ignition propellant has an auto ignition temperature no higher than <NUM> degrees Celsius. In some examples, the ignition propellant has an energy output of at least <NUM> Calories per gram. In some examples, the ignition propellant has an energy output of over <NUM> Calories per gram. An ignition propellant typically has a propagation index of at least <NUM> Cal/(g deg C). An ignition propellant typically has an auto ignition temperature of <NUM> degrees Celsius or less. Examples ignition propellant have a propagation index of <NUM> or more Cal/(g deg C).

Examples of ignition propellant are boron potassium nitrate (BKNO<NUM>), zirconium potassium perchlorate (ZPP), titanium hydride potassium perchlorate (THPP), Pyrodex, Triple <NUM>, Black Powder, aluminum potassium perchlorate. BKNO<NUM> has a heat of reaction of approximately <NUM>,<NUM> Calories/gram and an auto ignition temperature of <NUM> degrees Celsius, giving a propagation index of <NUM> Cal/(g deg C). Pyrodex and Triple <NUM> have a heat of reaction of approximately <NUM>,<NUM> Calories/gram and an auto ignition temperature of <NUM> degrees Celsius, giving a propagation index of <NUM> Cal/(g deg C). Black Powder has a heat of reaction of approximately <NUM> Calories/gram and an auto ignition temperature of <NUM> degrees Celsius, giving a propagation index of <NUM> Cal/(g deg C). In some examples, there is a second ignition portion <NUM> near the second end <NUM> of the housing as shown in <FIG>. In some examples, the first ignition portion <NUM> and the second ignition portion <NUM> combined may be approximately <NUM>% of the power charge by weight.

Preferably, the mixture in the first ignition portion <NUM> or second ignition portion <NUM> is mixed in a gradient with predominately ignition propellant towards the first end and transitioning to primarily main propellant away from the first end. In some examples, the mixture will range from <NUM>% or more ignition propellant near the end of the housing to <NUM>% or less ignition propellant away from end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend approximately <NUM> inch from the end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend approximately <NUM> inch from the end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend approximately <NUM> inch from the end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend approximately <NUM> to <NUM> inch from the end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend approximately <NUM> to <NUM> inches from the end of the housing. In some examples, the ignition portions <NUM> or <NUM> extend from the end of the housing approximately <NUM>% of the length of the housing. In some examples, the ignition portions <NUM> or <NUM> extend from the end of the housing approximately <NUM>% of the length of the housing. In some examples, the ignition propellant is approximately <NUM>% of the power charge by weight. In some examples, the ignition propellant is approximately <NUM>% of the power charge by weight. In some examples, the ignition propellant is approximately <NUM>% of the power charge by weight. In some examples, the first ignition portion is approximately <NUM> % of the power charge by weight.

The main propellant <NUM> is in the interior of the housing adjacent to the ignition portion. In some examples, the housing <NUM> is a cardboard tube.

Further examples include a method of manufacturing a power charge. In one method, the housing is placed vertically with the first end down with a cap over it. The ignition propellant <NUM> is then placed inside the housing so that it settles in the first end. The main propellant is then poured into the housing where it partially mixes with the ignition material to form the first ignition portion. The main propellant then sets, such as an epoxy binder portion of the main propellant curing. Optionally, ignition material can also be added to the housing after the main propellant has been put into the housing to create the second ignition portion.

Each of the examples for the ignition portion can apply to an ignition portion at the first end or the second end.

Claim 1:
A power charge (<NUM>) for a downhole setting tool, the power charge comprising:
a tubular housing (<NUM>) having a first end (<NUM>), a second end (<NUM>), and a mid-section;
a main propellant portion (1within the tubular housing (<NUM>) proximate the mid-section comprising a main propellant (<NUM>) having a propagation index of less than <NUM> J/(g deg C) (<NUM> Cal/(g deg C)); and
a first ignition portion (<NUM>) within the tubular housing (<NUM>) proximate the first end (<NUM>) comprising a first mixture of the main propellant and an ignition propellant; wherein the ignition propellant has a propagation index of at least <NUM> J/(g deg C) (<NUM> Cal/(g deg C)).