Patent Description:
When a hydrocarbon well is drilled, a casing may be placed in the well to line and seal the wellbore. Cement is then pumped down the well under pressure and forced up the outside of the casing until the well column is also sealed. This casing process: (a) ensures that the well is isolated, (b) prevents uncontrolled migration of subsurface fluids between different well zones, and (c) provides a conduit for installing production tubing in the well. However, to connect the inside of the casing and wellbore with the inside of the formation to allow for hydrocarbon flow from the formation to the inside of the casing, holes are formed through the casing and into the wellbore. This practice is commonly referred to as perforating of the casing and formation. Open-hole wells are also possible, i.e., where a casing is not used and jetting, fracturing or perforation is directly applied to the formation.

To perform a perforation operation, a loading tube carrying a plurality of shaped charges is inserted into a hollow gun carrier. The assembled gun body containing the loading tube with the plurality of shaped charges mounted therein is lowered into the wellbore and positioned opposite the subsurface formation to be perforated. Initiation signals are then passed from a surface location through a wireline to one or more blasting caps located in the gun body, thereby causing detonation of the blasting caps. The exploding blasting caps in turn transfer a detonating wave to a detonator cord which further causes the shaped charges to detonate. The detonated shaped charges form an energetic stream of high-pressure gases and high velocity particles, which perforates the well casing and the adjacent formation to form perforation tunnels. The hydrocarbons and/or other fluids trapped in the formation flow into the tunnels, into the casing through the orifices cut in the casing, and up the casing to the surface for recovery.

Prior to perforating, the target wells are studied to determine the most advantageous phase angles and spacing of the perforations. The desired orientation may be selected based on the possibility of sand production, based on the heavy overburden pressure and/or shear stress existing, or based on the location of control lines and/or other downhole equipment and tools. The loading tubes are then manufactured to hold the shaped charges at the predetermined phase angles and spacing.

Conventional loading tubes are formed of steel tubes in which the shaped charges are secured. metal, A pattern of cutouts is machined into the loading tube for holding the shaped charges in the desired orientation. Commonly, the loading tube uses plastic jackets to hold the shaped charges to the cut metal loading tube, because of the relatively good shock protection. However, the plastic jackets add manufacturing cost to the perforating gun. Alternatively, the loading tube has metal tabs cut out on the loading tube to facilitate the mounting of the shaped charges.

<CIT> describes a modular perforating tool assembly with modular charge segments to provide for multiple configurations of shaped charges. The modular charge holder segments include slots and locking tabs to allow for differing offsets between charges and comprise a slit that allows the modular holder segment to be flexed or deflected to permit the loading and downloading of shaped charges. <CIT> describes a shaped charge for use with a perforating gun having an adapter that can couple the shaped charge with perforating gun systems of more than one size. An interference fit couples the adapter to the open end of a shaped charge. <CIT> describes a box by pin perforating gun system using swaged down gun bodies, a removable cartridge to hold a detonator and switch, and an insulated charge holder as an electrical feed-through. <CIT> describes a loading tube apparatus for use in a perforating gun, comprising a loading tube having first and second ends with connectors and a plurality of receptacles for receiving shaped charges, a detonating cord, wiring and an RF-safe initiator;.

Machining the steel loading tubes to mount the shaped charges in the desired orientations adds to the overall manufacturing cost of the perforating guns. This particularly true for orientations of increased complexity.

What is needed is an improved, method and apparatus for manufacturing loading tubes more efficiently and at reduced cost.

The present invention resides in a loading tube to be used in a perforating gun as defined in claim <NUM>.

In a further aspect, the invention resides in a perforating gun as defined in claim <NUM>.

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:.

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for purposes of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments are possible. This description is not to be taken in a limiting sense, but rather made merely for purposes of describing general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims.

As used herein, the terms "connect", "connection", "connected", "in connection with", and "connecting" are used to mean "in direct connection with" or "in connection with via one or more elements"; and the term "set" is used to mean "one element" or "more than one element". Further, the terms "couple", "coupling", "coupled", "coupled together", and "coupled with" are used to mean "directly coupled together" or "coupled together via one or more elements". As used herein, the terms "up" and "down"; "upper" and "lower"; "top" and "bottom"; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements.

In this disclosure, unless the context requires otherwise, throughout the specification and claims which follow, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense, that is as "including, but not limited to.

In this disclosure, reference to "one embodiment" or "an embodiment" means that a particular feature or features, structures, or characteristics may be combined in any suitable manner in one or more implementations or one or more embodiments.

In this disclosure, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its broadest sense, that is, as meaning "and/or" unless the content clearly dictates otherwise.

The headings and Abstract of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

<FIG> shows a cross section of a conventional hollow carrier perforating gun carrier <NUM>. The conventional perforating gun carrier <NUM> comprises a loading tube <NUM>, a shaped charge <NUM> fitting into a jacket <NUM>, and two ballistic transfer plastics <NUM> that connect to each end of the loading tube <NUM>. The hollow carrier <NUM> is made of pressure-tight steel tubes, on which a plurality of cutouts <NUM> having the shape matching that of the jacket <NUM> are formed, in order to receive the jacket <NUM> and the shaped charge <NUM>. In a typical loading tube, the jackets <NUM> are made of plastic to hold and mount the shaped charges <NUM> inside the cutouts <NUM>, or in some cases metal tabs are cut out from the loading tube <NUM> to facilitate the mounting of the shaped charges <NUM>. The ballistic transfer plastics <NUM> are essential for precise detonation of the shaped charges <NUM>.

<FIG> is a schematic view of an embodiment of the perforating gun using a loading tube <NUM> of the present disclosure, and <FIG> is a similar view except the gun carrier <NUM> has been removed to better illustrate the loading tube <NUM>. The following discussion is made with reference to both <FIG>.

The perforating gun of the present disclosure comprises a gun carrier <NUM> having a loading tube <NUM> housed therein. The gun carrier <NUM> is flanked by an adapter <NUM> on each end. A plurality of holding structures <NUM>' are formed along the loading tube <NUM>. It is to be noted that the location of these holding structures <NUM>' are arranged according to a predetermined phase angle and spacing in order to achieve the intended perforation orientation. The loading tube <NUM> comprises a hollow core suitable for an integrated ballistic transfer for the capability of more precise detonation of the shaped charges mounted within the holding structures <NUM>'.

In the illustrated embodiment of the present disclosure, the loading tube <NUM> is divided into three sections, namely a bottom section <NUM>, an intermediate section <NUM>, and a top section <NUM>. In embodiments of the present disclosure, the length of the loading tube <NUM> can be adjusted by adding one or more intermediate sections <NUM>. For example, if the length of each intermediate section <NUM> is one foot (1ft) (<NUM> meter), then it would require twenty (<NUM>) intermediate sections <NUM> to make a twenty foot (<NUM> ft) (<NUM> meters) loading tube <NUM>.

Referring now to <FIG>, which shows the details of the top section <NUM> of the loading tube <NUM>. A portion of the intermediate section <NUM> is shown in <FIG> to illustrate the relationship and connection between the top section <NUM> and the intermediate sections <NUM>.

In order to facilitate manufacturing, the top section <NUM> is further divided into an upper component <NUM> and a lower component <NUM> that together form a complete tubular top section <NUM>. In embodiments of the present disclosure, the upper component <NUM> and lower component <NUM> are made from plastic, high density polystyrene, or any other equivalent material that can be manufactured in many ways, with high quantity and low processing time, such as injection molding or 3D printing.

The upper component <NUM> may be securely coupled to the lower component <NUM> through, for example, snap-fit structures <NUM>. It should be understood, however, that other types of secure coupling such as fasteners or clips may also be used and remain within the scope of the present disclosure.

Pins <NUM> are provided to maintain the orientation and alignment of the key spring <NUM> on the upper component <NUM>. A key spring <NUM> on the top section <NUM> of the loading tube <NUM> will sit in the key way of the gun carrier <NUM>, so as to align the loading tube <NUM> with the carrier <NUM>.

<FIG> is a cross-sectional view of the embodiment of the top section <NUM> of the loading tube <NUM> shown in <FIG>. As can be seen in <FIG>, a booster <NUM> is connected to a detonation cord <NUM> within the hollow core formed between the upper component <NUM> and the lower component <NUM> of the loading tube <NUM>. The ballistic transfer from one perforating gun to another will be transferred through the detonation cord <NUM>, which is securely housed within the hollow core <NUM> of the top section <NUM>. As illustrated, the top section <NUM> of the loading tube <NUM> is designed in such a way that the booster <NUM> is secured in place while maintaining the booster to booster gap, which is required for successful ballistic transfer.

<FIG> is an exploded view illustrating the way in which the components of the top section <NUM> of the loading tube <NUM> are connected. Additionally shown in <FIG> is a shaped charge <NUM> for mounting within the holding structure <NUM>'.

An anti-rotation connection <NUM> (shown in detailed view in <FIG>) is provided between the top section <NUM> and the intermediate section <NUM>. The upper and lower components <NUM>, <NUM> of the top section <NUM> each have a receiving structure <NUM>, <NUM> that, when combined together, will tightly engage with a flange <NUM> of the intermediate section <NUM>. The connection is designed such that the rotation between the top intermediate sections <NUM>,<NUM> can be prevented. This anti-rotation feature is important to maintain the phase angle of each of the holding structures <NUM>' for the respective shaped charges <NUM>. This is especially important when more than one intermediate section <NUM> is employed to extend the length of the loading tube <NUM>.

An embodiment of the intermediate section <NUM> of the present disclosure is shown in <FIG> is an exploded view of the intermediate section <NUM>, and <FIG> is a partially enlarged view of the intermediate section <NUM>. As with the top section, in order to facilitate manufacturability, the intermediate section <NUM> is divided into an upper component <NUM> and a lower component <NUM>. In embodiments of the present disclosure, the upper component <NUM> and lower component <NUM> are made from plastic, high density polystyrene, or any other equivalent material that can be manufactured in many ways, with high quantity and low processing time, such as injection molding or 3D printing.

In the embodiment shown, the upper component <NUM> and the lower component <NUM> can be securely joined together by known mechanical structures, such as snap fit, to form a tubular structure with a plurality of cavities that act as holding structures <NUM>' for the shaped charges. The holding structures <NUM>' secure the charges in place with one or more snap structures <NUM>. Similar to the top section <NUM>, these holding structures <NUM>' are provided on the intermediate section <NUM> according to the predetermined phase angle and distance.

As shown in <FIG>, the intermediate section <NUM> has one or more guide features <NUM> provided to guide the detonation cord <NUM>. The guide features <NUM> ensure that the detonation cord <NUM> remains in contact with each of the shaped charges carried on the loading tube <NUM>.

An anti-rotation connection <NUM> between the intermediate section <NUM> and the bottom section <NUM>, similar to that between the top and intermediate sections <NUM>, <NUM>, can also be provided to prevent any rotation.

<FIG> illustrates a partially enlarged view of the connection between the bottom section <NUM> and the next perforating gun (not shown). As can be seen in <FIG>, a key spring <NUM> is provided in the key way of the carrier to align the loading tube <NUM> with the perforating gun carrier <NUM>. Again, pins <NUM> are provided to maintain the position of the key spring <NUM>. A similar anti-rotation mechanism can also be provided.

In the embodiments discussed above, the loading tube <NUM> and its various components are made from materials that can be molded such as plastic, high density polystyrene or equivalent material. The resulting loading tube <NUM> can be manufactured at low cost and the components are easily assembled. Additionally, the cavities or holding structures <NUM>' are formed through assembly and have a similar profile to match the shape of the shaped charges <NUM>. By combining the loading tube <NUM> and the shaped charge jackets, the manufacturing cost is further reduced. The integration of the ballistic transfer features in the top section <NUM> and the bottom section <NUM> of the loading tube <NUM> eliminates the need for separate parts to secure the booster in place for ballistic transfer.

<FIG> shows another embodiment of the loading tube of the present disclosure. In this embodiment, the loading tube mounted within the hollow gun carrier <NUM> is a skeletal loading tube <NUM> having a plurality of shaped charges <NUM>. In the embodiment shown, the wall 100a of the gun carrier <NUM> may have one or more scallops aligned with the shaped charges <NUM>. But it is understood that gun carriers <NUM> without scallops may also be used with embodiments of the skeletal loading tube <NUM> of the present invention.

<FIG> shows a more detailed view of an embodiment of a skeletal loading tube <NUM> of the present disclosure having a plurality of holding structures <NUM> integrally formed with a hollow tube <NUM> that allows the detonating cord (not shown) to contact each of the shaped charges <NUM> to pass and transfer ballistic shock to them. The holding structures <NUM>, or cavities, have profiles to match the shaped charges <NUM> to be mounted therein. The orientation of each holding structure <NUM> is predetermined according to the preferred phase angles of the shaped charges <NUM>. Each of the holding structures <NUM> may have one or more locking tabs <NUM> such that once the shaped charge <NUM> is inserted, the locking tab <NUM> secures the shaped charge <NUM> to the skeletal loading tube <NUM> in the correct orientation.

<FIG> shows another embodiment of the skeletal loading tube <NUM> of the present disclosure. As can be seen in <FIG>, the skeletal loading tube <NUM> in this embodiment comprises the holding structures <NUM> integrally formed with the hollow tube <NUM> that allows the detonating cord to pass therethrough. This embodiment further comprises plastic clips <NUM>.

In this embodiment, each holding structure <NUM> is sized and shaped to receive a shaped charge <NUM>. Once in place, the protrusions <NUM> of the holding structures <NUM> engage, or are engaged by, the plastic clips <NUM> to lock the shaped charge <NUM> in place within the holding structure. In this embodiment, three clips <NUM> are shown. However, in other embodiments, depending on the size and shape of the shaped charge, any number of clips <NUM> may be used and remain within the purview of the present disclosure.

<FIG> shows another embodiment of the skeletal loading tube <NUM> of this disclosure. As seen in <FIG>, the skeletal loading tube <NUM> consists of two parts: a plurality of jackets <NUM> that are mounted on a hollow tube <NUM>. A snap mechanism is provided on the bottom of the jacket <NUM>, such that when the jacket <NUM> is inserted into the cutouts <NUM> formed on the hollow tube <NUM>, the jacket <NUM> can stay in place. Similar to previous embodiments, the cutouts <NUM> in the hollow tube <NUM> enable proper phasing of the shaped charges <NUM>.

Each jacket <NUM> further comprising a securing mechanism (such as the tab <NUM>) to secure the shaped charge <NUM> once the shaped charge <NUM> is inserted into the jacket <NUM>. The detonating cord will pass through the hollow tube <NUM> to contact each of the shaped charges <NUM> in order to transfer the ballistic shock to each of the shaped charges <NUM>.

In embodiments of the skeletal loading tube <NUM> of the present disclosure, the loading tube <NUM> may be formed by molding a material such as plastic, high density polystyrene or any other equivalent material. The skeletal loading tube <NUM> may be formed by methods such as injection molding or by 3D printing, for example. In other embodiments, casting can also be an option to manufacture the parts, depending on the materials used.

Claim 1:
A loading tube to be used in a perforating gun, comprising:
a hollow tube (<NUM>; <NUM>) to hold a detonating cord (<NUM>), the hollow tube (<NUM>) comprising a bottom section (<NUM>), at least one intermediate section (<NUM>) and a top section (<NUM>), the top section (<NUM>) comprising an upper component (<NUM>) and a lower component (<NUM>), each of the upper and lower component (<NUM>, <NUM>) having a receiving structure (<NUM>, <NUM>) configured to engage with a flange (<NUM>) of the at least one intermediate section (<NUM>) so that rotation between the top section (<NUM>) and the intermediate section (<NUM>) is prevented; and
a plurality of holding structures (<NUM>') affixed to the hollow tube (<NUM>;<NUM>);
wherein each of the plurality of holding structures (<NUM>') is spaced at a predetermined distance and phase angle from the next of the plurality of holding structures (<NUM>'); and
wherein each of the plurality of holding structures (<NUM>') is adapted to securely engage a shaped charge (<NUM>).