Patent Application
20090078420
The invention relates generally to a perforator charge having a case including a reactive material.
To complete a well for purposes of producing fluids (such as hydrocarbons) from a reservoir, or to inject fluids into the reservoir, one or more zones in the well are perforated to allow for fluid communication between the wellbore and the reservoir. Normally, perforation is accomplished by lowering a perforating gun string that has one or more perforating guns to the desired intervals within the well. Activation of the one or more guns in the perforating gun string creates openings in any surrounding casing and extends perforations into the surrounding formation.
A perforating gun typically includes a gun carrier and a number of shaped charges mounted to the gun carrier. The gun carrier can be a sealed gun carrier that contains the shaped charges and that protects the shaped charges from the external wellbore environment. Alternatively, the gun carriers can be on a strip carrier onto which capsule shaped charges are mounted. A capsule shaped charge is a shaped charge whose internal components are sealably protected against the wellbore environment.
The explosive nature of the formation of perforation tunnels shatters sand grains of the formation. A layer of “shock damaged region” having a permeability lower than that of the virgin formation matrix may be formed around each perforation tunnel. The process of forming perforation tunnels may also produce a tunnel full of debris mixed with shaped charge debris. The extent of damage and the amount of loose debris in the tunnels, may impair the productivity of production wells or the injectivity of injector wells.
Various approaches have been proposed to address damage and the issue of debris associated with forming perforations using perforating guns. However, it is desirable for additional solutions that are not offered by conventional techniques.
In general, according to an embodiment, a perforator charge includes a case formed of a material blend that includes a reactive material that is activated during explosive detonation of the perforator charge. The reactive material of the case of the perforator charge when activated can provide for various beneficial effects, according to some embodiments. For example, a pressure pulse may be created in a wellbore interval as a result of the activation of the reactive material.
Other or alternative features will become apparent from the following description, from the drawings, and from the claims.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments are possible.
As used here, the terms “above” and “below”; “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or diagonal relationship as appropriate.
As depicted in
The perforator charges 110 in the example of
In a different implementation, the detonating cord 112 can be replaced with one or more electrical wires connecting the firing head 114 to the perforator charges. Electrical signal(s) can be sent by the firing head 114 over the one or more electrical wires to activate the perforator charges. For example, the perforator charges can be associated with electrically-activated initiators (e.g., electrical foil initiators or EFIs), which when activated by an electrical signal causes initiation of a detonator or explosive to detonate the corresponding perforator charge.
The perforating gun 106 is carried by a carrier line 116, which can be a wireline, slickline, coiled tubing, production tubing, and so forth. In accordance with some embodiments, each perforator charge 110 has an outer case that is formed of a material blend that includes a reactive material. A reactive material refers to a material that reacts with detonation gases, wellbore fluids, and/or with another reactive material during explosive detonation of the perforator charge. Reaction of the reactive material in the outer case of the perforator charge can produce a pressure pulse that can last for some amount of time longer (e.g., one or two orders of magnitude longer) than the explosive detonation of the perforator charge.
In some embodiments, the material blend of the case of the perforator charge can be a powdered material that includes the reactive material as well as a non-reactive material that provides for enhanced density and strength of the case. In a different embodiment, the material blend of the outer case can be a solid, rather than a powdered, material blend.
The pressure pulse generated as a result of activation of the reactive material during perforator charge detonation can produce a dynamic overbalance condition in a particular wellbore interval (the interval in which the perforator charge or perforating gun is located), which is a pressure condition in which the particular wellbore interval achieves a higher pressure than the pressure of a surrounding reservoir (or at least the near-wellbore region of the surrounding reservoir). Creating a dynamic overbalance condition in a wellbore interval has several potential applications, including injecting one or more target fluids into perforation tunnels, producing a transient overbalance condition, fracturing perforation tunnels, and so forth.
In some examples, the one or more target fluids that can be injected into perforation tunnels include a treating fluid such as a consolidation fluid that can be used to strengthen perforation tunnels and near-wellbore regions of the reservoir to prevent formation movement or movement of fine particles. One example type of consolidation fluid includes an epoxy fluid that is embedded with micro-capsules, where the micro-capsules have inner cavities that contain a hardener or catalyst fluid. A different type of treating fluid can be a post-wash fluid. Another type of treating fluid can be acid, such as HCl to treat a carbonate reservoir. Acidizing helps remove or reduce perforation damage. Yet another type of treating fluid can be proppant-laden fracturing fluid, where the proppant includes particles mixed with fracturing fluid, which can be used in a fracturing operation to hold fractures open.
In some embodiments, the outer case 200 can be formed of a powered material, using a compaction technique, where the powdered material includes both a non-reactive material for density and green strength (which refers to the ability of the case to undergo handling without distortion), and a reactive material that is activated by detonation gases, wellbore fluids, and/or with another reactive material during detonation of the perforator charge.
The compaction technique used to form the outer case 200 involves mixing the non-reactive and reactive material and applying compaction to the mixture to form the case 200. In other implementations, other manufacturing techniques can be used to make the outer case 200, such as an injection molding technique or other technique.
A reactive material can include just a single material or a combination of multiple reactive materials. Examples of the reactive material that can be used in the case 200 include titanium (Ti), nickel-aluminum (Ni—Al), a titanium alloy (e.g., titanium iron, titanium silicon, titanium nickel, titanium aluminum, titanium copper, etc.), a titanium powder mixed with other metal powder (e.g., magnesium, tungsten, copper, lead, tin, zinc, gold, silver, steel, tantalum, etc.), a titanium alloy powder mixed with other metal powder, and any other reactive materials. Examples of non-reactive materials include tungsten, copper, lead, bismuth, tin, and so forth.
To increase the green strength of the powdered material case 200, a high-temperature epoxy coating can be applied to the external surface of the case 200, or alternatively, the case 200 can be impregnated with a high-temperature epoxy. The epoxy can also contain a fuel and/or an oxidizer in some implementations to aid in disintegration of the case 200.
As further depicted in
During detonation of the main explosive 204, the reactive material inside the outer case 200 reacts with the detonation environment such that the reactive material is activated to generate heat or gas that increases pressure. As a result, a pressure pulse can be produced from reaction or activation of the reactive material, where the pressure pulse lasts longer than the explosive detonation of the perforator charge 110.
As noted above, the pressure pulse produces a dynamic overbalance condition in a wellbore interval, where the dynamic overbalance condition can be used for various purposes, including fluid injection, transient overbalance creation, and fracturing, as examples.
Effectively, the cap 300 and outer case 200 form a capsule that sealably defines a sealed inner chamber containing the internal components of the perforator charge. The perforator charge 110A is a capsule perforator charge, whereas the perforator charge 110 of
A further benefit of using an outer casing (particularly one formed of a powdered material) that includes a reactive material is that activation of the reactive material helps to further reduce debris associated with the perforator charge. Activation of the reactive material helps to further disintegrate the outer casing.
While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.
