Ordnance – Well perforators
Reexamination Certificate
1999-08-03
2001-06-12
Eldred, J. Woodrow (Department: 3644)
Ordnance
Well perforators
C166S055200, C102S312000
Reexamination Certificate
active
06244157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a perforating gun used for retaining a plurality of explosive charges in an angular phased array.
2. Related Art
Perforating guns are well known in the art and are used to form openings in subterranean wells, such as oil wells. Generally, a perforating gun is an assembly of explosive charges which, upon detonation, cause penetrations through the casing of a well bore into a geological formation allowing for the flow of, e.g., oil and gas, into the well bore, thence to the well head.
U.S. Pat. No. 4,875,413, which issued on Oct. 24, 1989 and is entitled “Apparatus For Perforating Wells”, discloses a perforating gun apparatus comprising one or more shaped charges retained either by being screwed into threaded holes in a strip carrier as illustrated in FIGS. 11 and 12 or by being retained in a four-wire carrier. The latter is illustrated in FIGS. 9 and 10 and is described at col. 3, lines 51-68. The four-wire carrier is comprised of two pairs 42 and 44 of straight, parallel wires (46, 48 and 50, 52) which contain bent portions 54 and 56 to accommodate the extensions 20 (FIG. 10) and 30 (FIG. 9) of the shaped charges 10. See column 3, lines 59-66, and column 4, lines 9-19. The pairs 42 and 44 of wires include connectors 58 and 60, respectively, which hold the wires together. See column 3, lines 67-68.
U.S. Pat. No. 5,638,901, which issued on Jun. 17, 1997 and is entitled “Spiral Strip Perforating System”, discloses a perforating gun apparatus comprising an elongated spiral strip carrier on which a plurality of shaped charges is threadably mounted. Related (confinuation-in-part) U.S. Pat. No. 5,662,178, which issued on Sep. 2, 1997 and is entitled “Wave Strip Perforating System”, discloses a spiral strip carrier which is not helical or spiral, but is described as a wave or non-linear zigzag form as seen in plan view. See the Abstract, FIGS. 10 and 11 and col. 4, line 48 to col. 5, line 25 of this Patent.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a perforating gun for retaining a plurality of explosive charges in an angularly phased, linear array. The perforating gun comprises a plurality of support wires extending in an undulating path about a common longitudinal axis to define a longitudinally extending retainer cage. A plurality of explosive charges has respective discharge ends and initiation ends, the initiation ends being dimensioned and configured to receive a detonation signal transmission member, e.g., a detonating cord. The plurality of explosive charges is retained in a linear array within the retainer cage with the discharge ends thereof disposed along the undulating path and facing outwardly of the retainer cage. In this way, the discharge end of each succeeding explosive charge is at a selected angular orientation relative to the other explosive charges, which angular orientation is determined by the configuration of the undulating path.
In one aspect of the present invention, the support wires are helically twisted whereby to define the undulating path as a helical path.
In another aspect of the present invention, the support wires are arranged in a wire pair in which the support wires thereof are connected to each other by a series of connector ties disposed at intervals along the length of the wire pair.
Another aspect of the present invention provides for the support wires to be arranged in one or more wire pairs in which the support wires of a wire pair are in side-by-side alignment with each other (either in abutting contact with, or spaced from, each other) in a series of longitudinal segments of the wire pair, with the longitudinal segments being longitudinally spaced from each other by a series of loops, e.g., a series of closed loops. The loops are formed by the respective support wires of the wire pair diverging from each other and then re-converging towards each other to define the loops.
Yet another aspect of the present invention provides for the perforating gun to have a first connector at one end of the retainer cage and a second connector at the longitudinally opposite end of the retainer cage. The first and second connectors may be dimensioned and configured to connect the retainer cage to one or both of (a) additional retainer cages and (b) other fixtures such as, for example, hoisting equipment or a conveyor sub.
Other aspects of the present invention are provided by the following features, alone or in combination: the perforating gun may comprise at least one wire pair defined by two of the support wires cooperating with each other to define the wire pair; the explosive charges of the perforating gun may have respective engagement members on at least one of their discharge and initiation ends, which engagement members are retained between the support wires of the wire pair; and the support wires of the wire pair may be connected to each other by connector ties at intervals along the length thereof, to provide at least one wire pair.
In one aspect of the invention, wherein the explosive charges have respective engagement members comprising protuberant noses on their discharge ends and the protuberant noses are retained between the support wires of the wire pair.
Still another aspect of the present invention provides for the retainer cage to comprise at least a first support wire engaged with respective discharge ends of the explosive charges and at least a second support wire engaged with the respective initiation ends of the explosive charges, and a plurality of crosspieces connecting the first and second support wires to reinforce the retainer cage. For example, the retainer cage may comprise (1) a first pair of the support wires cooperating to provide a first wire pair engaging the discharge ends of the explosive charges and (2) a second pair of the support wires cooperating to provide a second wire pair engaging the initiation ends of the explosive charges.
Yet another aspect of the invention provides for a plurality of crosspieces connecting at least one support wire of the first wire pair to at least one support wire of the second wire pair in order to reinforce the retainer cage.
In accordance with another aspect of the present invention, one or more of the explosive charges of the perforating gun may be replaced by non-explosive spacer bodies, for example, a plurality of the explosive charges may be replaced by non-explosive spacer bodies.
In a related aspect of the present invention, the explosive charges have thereon respective engagement members which are dimensioned and configured to be engaged by the support wires of the retainer cage, and one or more of the explosive charges are replaced by non-explosive spacer bodies having thereon spacer engagement members which simulate the dimensions of the engagement members of the explosive charges.
The spacer members may comprise, for example, discs and the spacer engagement members may comprise peripheral grooves in the discs.
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Eldred J. Woodrow
Libert Victor E.
Libert & Associates
Spaeth Frederick A.
The Ensign-Bickford Company
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