Patent Application
20160130902
Embodiments usable within the scope of the present invention relate to explosive-type cutters that are usable to cut tubular members and to methods for making, assembling, and using explosive-type cutters to sever tubular members from the inside. Embodiments usable within the scope of the present invention also relate to detonator assemblies usable to detonate explosive-type cutters and perforators and to methods for making, assembling, and using the detonator assemblies to detonate explosive-type cutters and perforators.
The ability to quickly and cleanly sever tubular members, such as well casings that are deep underground, is an essential step during well maintenance and salvage operations. Typically, the industry relies on mechanical or explosive devices to perform such cutting. One type of explosive device, that is often used, is a shaped charge explosive cutter, which provides a simple, fast, and inexpensive method by which to sever pipes within a wellbore. During typical operations, shaped charge explosive cutters are lowered to a selected depth within a well, using a wireline, at which time they are detonated, producing pressure and/or molten materials that cut through the casing.
A typical shaped charge tubular cutting device contains two circular layers of explosive material, each having a truncated cone shape. Outlining the sloped side faces of the explosive circular layers are thin metal rings, called half-liners. These two components are joined together, apex-to-apex, forming a shaped charge assembly having a liner with a V-shaped cross section. The shape charge assembly is sandwiched between two end plates, typically made from steel. Lastly, the six elements (two layers of explosive, two half-liners, and two end plates) are aligned coaxially and enclosed within a cylindrical housing, in the recited order.
The end plates contain an opening along the central axis to provide a pathway for an explosive detonator to be placed adjacent to the top circular layer of explosive material. The two circular layers of explosive material may also contain an opening along their central axes, providing a space for an explosive detonator to be placed between the circular layers of explosive material.
After the shaped charge tool is assembled, it is lowered into the tubular member. For optimal effectiveness, the circular shaped charges within the tool must be aligned at a substantially perpendicular angle, relative to the tubular wall. Following the placement of the shaped charge tool at the proper location within the tubular member, the shaped charge is detonated.
Once the charge is detonated, a shock wave propagates radially along the transverse plane between the circular half charges and collides with the V-shaped liner, forcing the two liner surfaces together at high speeds. The resulting impact between the two liner surfaces results in extreme pressure being generated. At these high pressures, the metal liner exhibits plastic and/or fluid-like characteristics. While the expanding shock wave folds the metal liner together into a disc shape, the shock wave continues to advance radially along the transverse plane, pushing and accelerating the liner material to flow radially along the transverse plane at extreme velocities, forming a jet of liner material able to cut through the tubular member.
Traditional fabrication procedures for circular shaped charge tools include independent fabrication of the half-liner pieces, each having a truncated cone shape, with an open base and apex surface. The circular explosive discs can be formed using half-liners as the outside wall portions of the mold. The apex surface of the explosive disc is formed against the bottom of a flat mold, the explosive material is packed into the area between the mold and the half-liner, then a top mold plate is pressed against the explosive material, solidifying and bonding the material with the half-liner. This method forms a circular disc of explosive material, with the half-liner outlining the radial walls of the disc. A unified disc of explosive material bonded with a half-liner is called a half-charge. To form the shaped charge tool, two half charges are placed apex-to-apex, in a cylindrical housing between two steel plates, as described above.
Another traditional fabrication procedure for making circular shaped charge tools includes forming the circular explosive disc without half-liners outlining the radial walls of the explosive disc. The explosive charge material is formed into a truncated cone shape by using a mold to shape every surface of the charge, including the outside wall surface. This fabrication technique results in the half-liner and the explosive material disc being separate components, which must later be arranged within a cylindrical housing.
A shaped charge assembly comprising two or more explosive charge members, such as half-charges, results in small areas of separation between such members, which allow for overrunning of the detonating shock front. As the shock wave propagates radially from the central detonation point, the areas of separation between explosive charge portions allow a shock front to travel through the empty area at faster velocities than through areas containing explosive material. This shock front collides with the center of the liner, along the transverse plane between the half-charges, before the main shock wave impacts the rest of the liner. Such non-uniform collision can cause the liner jet to scatter or to be deformed excessively at the center, as opposed to a desired compact liner jet moving in the radial direction.
In another traditional manufacturing process, the circular explosive discs are fabricated in several pieces, such as in quarters. These quarters are then arranged to form circular explosive discs when assembling the components in a cylindrical housing. A half charge may comprise four or more segments (e.g., wedge-shaped segments that together form a circle). Such an arrangement creates multiple areas of separation between the segments of explosive material, subject to the same difficulties present when using half-charges: as the shock wave propagates, the areas of separation provide empty pathways through which the shock front travels at faster velocities than through areas containing explosive material. This overrunning shock front collides with the liner in certain areas before the main shock wave impacts the rest of the liner, resulting in a non-uniform collision, causing the liner to be deformed and/or scattered excessively at points along the areas between adjacent segments of explosive material.
In addition to configurations that include multiple segments of explosive material, the space between two half liners, or between other configurations involving multiple liner pieces, also contributes to improper liner jet formation. As the shock wave impacts and collapses the V-shaped liner, the small space between the two half liners, or between other portions, allows the passage of expanding gasses into the standoff space, disrupting the formation of a uniform jet or slug. A deformed or non-symmetrical jet or slug reduces the penetrating efficiency of the shaped charge cutting tool.
Conventional tubular cutter tools typically incorporate explosive material sections that are relatively thick throughout (i.e. from the detonator to the liner). Other designs incorporate top and bottom housing plate surfaces that are sloped or that contain sharp edges or angles. Uneven plate surfaces can cause shock wave deflections in various directions within a thick layer of explosive material. Shock wave deflections may cause shock front overrunning along the path of deflection through the explosive material. This results in certain parts of the shock wave striking an area of the liner along the vertical plane before the main shock wave strikes the rest of the liner. A non-symmetrical collision causes the liner to be deformed unevenly, resulting in a non-symmetrical liner jet formation, thus reducing the effective penetration capabilities of the cutter and causing uneven severing of a tubular member. Shock wave deflections may also cause shock wave cross propagation, which occurs when shock waves having opposite directional component vectors collide and interfere with one another. Such shock wave collisions result in explosive energy loss, which also reduces the effective penetration capabilities of the cutter.
An energy loss due to separation between the upper and lower end plates prior to jet formation is also a common problem with many conventional shaped charge cutting tools. As the explosive material is detonated, explosive energy is released in all directions. If the area between the end plates expands prior to jet formation, energy is lost when deforming and accelerating these end plates, resulting in less energy available to be utilized toward liner jet formation.
Over years of experimentation, shaped charge cutter technology has developed extensively. Certain physical characteristics of shaped charge elements and certain relationships between those elements have been revealed as significant, even though prior understanding of the technology labeled them as unimportant. Departures from conventional methods, that may have previously been thought of as minute or insignificant, have led to unpredictable results, significant performance improvements, and reductions in material and fabrication costs.
A need exists for a shaped charge tubular cutter tool that overcomes the deficiencies of conventional cutters by preventing detonation front overrunning along the transverse plane between adjoining partial charges and between adjoining explosive material segments.
A further need exists for a shaped charge cutter tool that eliminates internal shock wave deflections, which can result in shock front overrunning and shock wave cross propagation.
A need also exists for a casing cutter tool that is highly efficient, utilizing more explosive energy into the cutting action than standard explosive tubular cutters.
Embodiments usable within the scope of the present disclosure relate to an explosive cutter assembly comprising a housing assembly having an upper plate and a lower plate, wherein the upper and lower plates each comprise a flat surface positioned parallel relative to each other, a vertical surface extending in a transverse relationship to the flat surface, and a diagonal surface adjacent to the vertical surface. Embodiments of the cutter assembly can further comprise a circular liner having an upper diagonal liner section, a lower diagonal liner section, and a vertical liner section positioned between the upper and lower diagonal liner sections, wherein the circular liner comprises a single-piece construction. The cutter assembly can also comprise an explosive charge having a main charge and a detonation disc, wherein the main charge is positioned between the circular liner and the vertical and diagonal surfaces of the upper and lower plates, wherein the detonation disc is positioned between the flat surfaces of the upper and lower plates, and wherein the explosive charge comprises a single-piece construction.
In an embodiment of the explosive cutter assembly, the upper and lower diagonal liner sections can comprise truncated conical shapes, oriented apex to apex, and the vertical liner section can comprise a cylindrical shape. In an embodiment, the lengths of the upper and lower diagonal sections and the length of the vertical section can be equal or substantially equal.
In an embodiment, the main charge can adhere to the circular liner, and/or be compressed against the circular liner, for resulting in a physical bond therebetween. The main charge can include a vertical main charge section that can extend in a transverse relationship to the detonation disc; and in an embodiment, the main charge can include a diagonal main charge section that can extend from the vertical main charge section. In an embodiment, the main charge can be at least twice as thick as the detonation disc.
In an embodiment of the explosive cutter assembly, the upper and lower plates can comprise a thicker construction adjacent to the main charge and a thinner construction adjacent to the detonation disc. In an embodiment, the edges between the vertical surfaces and the flat surfaces of the upper and lower plates can be truncated. In an embodiment, the lower plate can extend about the outer surface of the circular liner to define a standoff space for formation of the liner jet.
Further embodiments usable within the scope of the present disclosure relate, generally, to an explosive cutter that can comprise an upper plate having an upper flat surface, a lower plate having a lower flat surface, wherein the upper and lower flat surfaces are facing each other and are parallel to each other. The explosive cutter can also comprise a liner having three liner sections connected to each other and oriented at selected angles relative to each other, wherein the liner comprises a unitary construction. The explosive cutter can also comprise an explosive charge having a main charge and a detonating charge. The main charge can include three main charge sections having a generally uniform thickness, which can be oriented at the selected angles relative to each other, and wherein the selected angles between the three liner sections and between the three main charge sections can be essentially the same. Also, the explosive charge can comprise a unitary construction, the main charge can adhere to the liner, and the detonating charge can comprise a generally flat configuration.
Another embodiment usable within the scope of the present disclosure relates to a detonator adapter configured for connection with an explosive cutting or perforating device. The detonator adapter can comprise a generally cylindrical body having at least one external threaded portion and an internal bore extending along the longitudinal axis thereof, wherein the internal bore can be configured to retain a detonator charge, a booster charge, a blasting cap, or combinations thereof. The generally cylindrical body can be configured to connect to a wireline, a cable, a tubular string, or other means for transporting the explosive cutter or perforating device within a tubular or other object to be severed. The detonator adapter can also comprise at least one threaded member connectable about the generally cylindrical body, wherein the lower threaded member can retain the generally cylindrical body in position within the explosive cutting or perforating device.
Other embodiments usable within the scope of the present disclosure relate to methods for forming a cut in a tubular object. More specifically, the methods can comprise the steps of positioning a cutting assembly relative to the tubular object, wherein the cutting assembly can comprise a liner comprising three sections integrally formed and oriented at different angles relative to each other. The cutting assembly can further comprise an explosive charge having a unitary construction comprising a first area of explosive material disposed adjacent to an inner surface of the liner and a second area of explosive material extending from the liner to the axial center of the cutting assembly. The steps of the method can include the step of providing a detonator in association with the second area of explosive material. Lastly, embodiments of the methods can comprise the step of actuating the detonator, thereby detonating the second area of explosive material which detonates the first area of explosive material, wherein detonation of the first area of explosive material can compress the liner and propel the liner toward a target to be cut.
In the detailed description of various embodiments usable within the scope of the present disclosure, presented below, reference is made to the accompanying drawings, in which:
Before describing selected embodiments of the present disclosure in detail, it is to be understood that the present invention is not limited to the particular embodiments described herein. The disclosure and description herein is illustrative and explanatory of one or more presently preferred embodiments and variations thereof, and it will be appreciated by those skilled in the art that various changes in the design, organization, order of operation, means of operation, equipment structures and location, methodology, and use of mechanical equivalents may be made without departing from the spirit of the invention.
As well, it should be understood that the drawings are intended to illustrate and plainly disclose presently preferred embodiments to one of skill in the art, but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views as desired for easier and quicker understanding or explanation. As well, the relative size and arrangement of the components may differ from that shown and still operate within the spirit of the invention.
Moreover, it will be understood that various directions such as “upper,” “lower,” “bottom,” “top,” “left,” “right,” and so forth are made only with respect to explanation in conjunction with the drawings, and that the components may be oriented differently, for instance, during transportation and manufacturing as well as operation. Because many varying and different embodiments may be made within the scope of the concepts herein taught, and because many modifications may be made in the embodiments described herein, it is to be understood that the details herein are to be interpreted as illustrative and non-limiting.
Referring initially to
The exterior shape of the housing assembly (16) can be essentially cylindrical for enabling insertion into and passage through tubular members while permitting a minimal amount of water and/or debris in the annular space between the side surface (22) of the cutter assembly (10) and the inner surface of the tubular member. During insertion of the cutter assembly (10) into a tubular member and/or prior to detonation, the side surface (22) is positioned along or adjacent to the inner surface of the tubular member.
During typical use, the presence of water, or other matter between the cutter assembly (10) and the inner surface of the tubular to be cut, is undesirable, as such material can act as impediments through which the liner must pass before contacting the tubular. Such impediments can result in a loss of energy, which can cause an incomplete or uneven severing of the tubular member. The top housing plate (12) and the bottom housing plate (14) are shown secured together by a plurality of screws (18) inserted through the top housing plate (12) and threaded into the bottom housing plate (14), however, other methods of connection are also usable, including welding, force and/or interference fits, other types of connectors and/or fasteners, or integral formation of the housing assembly (16) as a single component. An 0-ring (19) or similar sealing element can be used between the top and bottom housing plates (12, 14), to prevent fluids and/or other contaminants from entering the interior of the housing assembly (16).
Reference now to
It should be understood that while the description herein refers to the main charge (35) and the radial detonation disc (32) separately, they can be integrally formed and/or connected; therefore, references to discrete areas of explosive material are primarily conceptual and used to illustrate the structure and the functionality of different portions of the shaped charge disc (30). Embodiments of the shaped charged disc (30) usable within the scope of the present disclosure can include a continuous unitary body of explosive material, with no physical separation between the described first and second areas of explosive material. As such,
Referring now to
In
As further depicted in
Conventional designs of explosive cutting tools (not shown) do not incorporate a thin radial detonation disc (32), as depicted in
Furthermore, conventional designs (not shown) also typically include top and bottom housing plate surfaces that are sloped or that contain sharp edges or angles, which disturb the shock front and the uniform and symmetrical detonation propagation. As depicted in
During cutter operation (e.g. detonation), the penetration of the target and pressure fracture is improved when uniform, homogenous jet formation is possible. The embodiment of the radial detonation disc (32), depicted in
Furthermore, a single-piece liner also prevents shock wave overrunning into the standoff space (39) before the liner (37) is collapsed. As the shock wave impacts a conventional V-shaped liner, a small space between the two half liners can allow the passage of expanding gasses into the standoff space, disrupting the formation of a uniform jet or slug. As shown in
As described above, conventional shaped charge assemblies (not shown) can be constructed using two half charges, assembled apex-to-apex. Other conventional designs can include explosive material that is further segmented into multiple parts. An assembly of two or more explosive charge members can create thin areas of separation between such members, which provide a path for expanding gasses to overrun the main detonating shock front. Conversely, the shaped charge disc (30), depicted in the embodiment of the cutting tool (10) shown in
As depicted in
As shown in
In another embodiment (not shown) of the adaptor sub (40), the threaded portion may cover all or most of the external surface of the adaptor insert section (44), allowing the upper and lower threaded nuts (53, 54) to engage the threaded portion along most or the entire length of the insert section (44). In still another embodiment (not shown), the adaptor sub (40) can comprise a single threaded nut (54) engaging the lower male thread (52). In the embodiment, the housing assembly (16) can be retained between the adaptor head section (42) and the lower threaded nut (54), which can be tightened against the bottom housing plate (14). Although
The adaptor sub (40), depicted in
Although the adaptor sub (40), depicted in
In addition to the screws (18), shown in
Embodiments of the present cutter assembly (10) thereby incorporate features that provide enhanced energy efficiency, thus enhanced cutting efficacy. For example, the embodiment depicted and described above achieves a superior cut when compared to conventional devices, while effectively using up to 70% or more of the explosive energy generated, thus enabling less explosive material to be used in some embodiments. Embodiments described herein further prevent detonation front overrunning, shock wave deflections, and shock wave cross propagation common to conventional alternatives.
While various embodiments usable within the scope of the present disclosure have been described with emphasis, it should be understood that within the scope of the appended claims, the present invention can be practiced other than as specifically described herein.
