TECHNICAL FIELD
The present application relates generally to perforating and more specifically to shaped charges having liners with varying thicknesses.
BACKGROUND
A shaped charge, in general, can have a metal charge case. High explosive material is disposed inside the case. A liner retains the explosive material in the case. A primer column can provide a detonating link between a detonating cord and the main explosive.
When the shaped charge is detonated a portion of the liner forms a jet portion which can be moving at a velocity of ˜1 km/sec. (tail) to ˜7 km/sec. (tip). The jet is propelled away from the case in a direction toward a target. Another portion of the liner is propelled away from the casing and forms what is known as a slug or carrot portion which is moving at a velocity of only a few hundred meters per second. When the shaped charge is used in a perforating gun, the target is normally the downhole formation rock. Upon detonation, the jet portion of the liner is propelled through the case and penetrates the downhole formation to enhance recovery of downhole hydrocarbons. The slug portion, in general, is designed to breakup to avoid plugging the hole on the casing formed by the jet.
Often times, about ˜30 percent of the shaped charge liner mass is converted into the jet. The jet density, velocity profile, jet material, jet straightness, and target properties determine the ability of the jet to penetrate a given target.
A factor determinative of the jet velocity profile is the thickness profile of the liner. More particularly, as described herein in connection with embodiments, a varying cross-sectional thickness of the liner can produce a jet formed of essentially separate parts (i.e., a segmented jet) that improves penetration over a single part jet (i.e., a linear jet). This idea is illustrated in FIGS. 7-9.
Liners for shaped charges can been fabricated using pure metals, alloys, ceramics or a combination of them. The metals used to form the liners can be powder metals, which may, for example, comprise of tungsten, lead or copper. Liners for shaped charges can be fabricated using different solid materials for the jet and the slug. One such example of a liner utilizes solid copper for the jet and solid zinc for the slug. Liners can be pressed, forged, or made by any other known production method.
Depth of penetration is important in the perforating art and constant improvement is desired. Embodiments herein address that issue and others related thereto.
SUMMARY
The following is a brief summary according to features of the present application.
Embodiments in the present application relate to a shaped charge having a case defining a volume therein. A liner is located in the volume. An explosive is located between the case and the liner. The liner defines an interior volume and an opening thereto. The liner also has an apex portion that is distal from the opening. The liner comprises a first thick portion and a second thick portion. A thin portion is located between the first thick portion and the second thick portion in the direction extending from the apex along the liner toward the opening. The thin portion is thinner than the first thick portion and thinner than the second thick portion.
Other or alternative embodiments having fewer or additional features will be apparent from the following description, from the drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Certain embodiments are described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
FIG. 1 shows a typical shaped charge including a case and a liner;
FIG. 2 shows a cross section of an embodiment of a liner according to an embodiment;
FIG. 3 shows a cross section of a portion of a liner according to an embodiment;
FIG. 4 shows a cross section of a portion of a liner according to an embodiment;
FIG. 5 shows a cross section of a portion of a liner according to an embodiment;
FIG. 6 shows a cross section of a portion of a liner according to an embodiment;
FIG. 7 shows a numerical simulation penetration result graphically where the jet is segmented due to variations in liner thickness;
FIG. 8 shows a numerical simulation penetration result graphically where the jet is not segmented, e.g., a continuous jet; and
FIG. 9 shows a side-by-side comparison of the numerical simulation results between the segmented jet and the single part jet.
The figures mentioned herein are meant to help illustrate various features and are not meant in any way to unduly limit the scope of any present or future claims related to this application.
DETAILED DESCRIPTION
In the following description, numerous details are set forth to provide an understanding of various embodiments and related features. However, it will be understood by those skilled in the art that those embodiments presented may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
In the specification and appended claims, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly described some embodiments.
The present application relates to shaped charges. FIG. 1 shows a shaped charge 1 having a liner 100, explosive 200 and a case 300. The case 300 defines an interior volume in which the liner 100 is positioned. The liner 100 defines an interior volume 400 and has an opening thereto. The opening is surrounded by a rim portion 120 of the liner 100. The explosive 200 is located between the liner 100 and the casing 300.
FIG. 2 shows an embodiment of a liner 100 having a “wavy” profile, e.g., having variations in the cross-sectional thickness of the liner. The liner 100 defines an interior volume 400 having an opening that is defined by a rim portion 120. An apex portion 110 is distal to the opening and the rim portion 120. The body of the liner 100 extends from the apex portion 110 to the rim portion 120 and has a varying cross-sectional thickness along that length as illustrated. For example, the liner 100 has a first thick portion having a thickness 102 and a second thick portion having a thickness 104. The liner has a thin portion with a thickness 101. The thickness 101 is smaller than the thickness 101 and the thickness 104. The thin portion is located between the first portion and the second portion along the liner 100 in the direction extending from the apex 110 to the rim portion 120, thereby defining a recess between the first thick portion and the second thick portion. Other portions having thickness 103 that is different or the same as the thickness 102, thickness 101 or thickness 104 is possible. The variations of the liner 100 producing the various thicknesses of the portions is shown as being present on one side of the liner 100, e.g., the inner surface of the liner 100. The variations of the liner 100 could be present on the outer surface of the liner. The thick/thin portion can extend circumferentially about the liner, e.g., perpendicular to a direction extending from the apex portion 110 to the opening/rim portion 120.
A distance x and a distance z are shown between thick portions. The distance x and z can be manipulated depending on desired performance.
Preferably the differences in thicknesses between the thick portion of the liner and the thin portion of the liner can be from a few percent of the liner thickness to ˜50% to the thickness of the liner. For example, the difference could be anywhere between 5%-10%, 10%-20%, 20%-30%, 30%-40%, or 40%-50%.
FIG. 3 shows a close-up of a portion of the liner 100 according to an embodiment. A thin portion of the liner 100 has a thickness 101 adjacent to a thick portion of the liner 100 having a greater thickness 102. The transition between the thin portion and the thicker portion is a curved surface of the liner 100. This curve can generally be a sinusoidal type curve. The variations of the liner 100 producing the various thicknesses of the portions is shown as being present on one side of the liner 100, e.g., the inner surface of the liner 100. The variations of the liner 100 could be present on the outer surface of the liner.
FIG. 4 shows a close-up of a portion of the liner 100 according to an embodiment. A portion of the liner 100 has a thin portion having a thickness 101 adjacent to a thicker portion having a greater thickness 102. There is a transition between the thin portion and the thick portion that is a flat surface angled with regard to the extension of the liner 100, e.g., a ramp shaped configuration. FIG. 3 shows a distance x between a portion of the thicker portions of the liner 100. The distance x extends along the direction extending from the apex portion 110 toward the rim portion 120. That distance can vary depending on desired performance. The variations of the liner 100 producing the various thicknesses of the portions is shown as being present on one side of the liner 100, e.g., the inner surface of the liner 100. The variations of the liner 100 could be present on the outer surface of the liner.
FIG. 5 shows a close-up of a portion of a liner 100 according to an embodiment. A thin portion of the liner 100 has a thickness 101 and a thick portion of the liner 100 has a thickness 102 adjacent to the thin portion. The variations of the liner 100 producing the various thicknesses of the portions can be on both sides of the liner 100, e.g., the inner surface of the liner 100 and the outer surface of the liner 100.
FIG. 6 shows a close-up of a portion of the liner 100 according to an embodiment. A thin portion of the liner 100 has a thickness 101 adjacent to a thick portion having a thickness 102. There is a transition between the thin portion and the thick portion that is stepped, e.g., in the shape of a step having a substantially vertical portion intersecting the two portions. The variations of the liner 100 producing the various thicknesses of the portions is shown as being present on one side of the liner 100, e.g., the inner surface of the liner 100. The variations of the liner 100 could be present on the outer surface of the liner.
FIG. 7 shows numerical simulation of penetration where the jet is segmented.
FIG. 8 shows numerical simulation of penetration where the jet is not segmented, e.g., a continuous jet.
FIG. 9 shows a side-by-side comparison of the experimental results between the segmented jet and the continuous jet, thereby illustrating the improved penetration with the segmented jet which can be produced by the “wavy” liner with a varying thickness.
Although only a few embodiments have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this application. Such modifications are intended to be included within the scope as defined in the present and any future claims.
Patent Application
20100319562
