Safe arm system for a perforating apparatus having a transport mode, an electric contact mode and an armed mode

Abstract: A safe-arm or quick arm system for a perforating gun includes a body containing a detonator and an adapter head containing an electrical plug and a detonating cord shell, the body and associated detonator being rotatable relative to the adapter head and associated detonating cord shell. Upon rotation of the body relative to the adapter head, the detonator moves from a start position to a transport position. In this position, the plug is not electrically connected to the detonator and the leads connected to the detonator are short circuited. The detonator is not adapted to receive electrical power. Upon further rotation of the body relative to the adapter head, the detonator moves from the transport position to an electrical contact position. In this position, the plug is electrically connected to the detonator but the detonator is not aligned with the detonating cord shell. Upon further rotation of the body relative to the adapter head, the detonator moves from the electrical contact position to the armed position. In this position, the plug is electrically connected to the detonator and the detonator is aligned with the detonating cord shell.

Description: The present invention relates to a safe arm system for a perforating apparatus, and provides a safe arm system having three modes of operation, a transport mode, an electric contact mode, and an armed mode of operation. Various types of safe-arm, otherwise known as quick arm, systems have been devised for use in association with perforating guns. One such safe-arm system is disclosed in U.S. Patent 4,172,421 to Regalbuto. This safe-arm system involves rotatably aligning a detonator into and out of alignment with a booster. When the detonator is rotated into alignment with the booster, the system is armed, whereas when the detonator is rotated out of alignment with the booster, the system is not armed. This system contains one method for preventing an accidental detonation of the associated perforating gun. However, there is only one method used in this system for preventing accidental detonation. An improved safe-arm system would contain more than one method for preventing the accidental detonation of the perforating gun, especially during transport of the perforating gun. According to a first aspect of the present invention, there is provided a safe arm system adapted for use with a perforating apparatus, the system comprising: a housing including a body and a head, said body containing a detonator and said head containing a booster which is disposed adjacent a detonating cord adapted for connection to said perforating apparatus, and said body being rotatable with respect to said head between a transport position in which said detonator is not aligned with said booster and an armed position in which said detonator is aligned with said booster; characterised in that said body and said head include respective electrical connection means via which electrical power can be supplied to fire said detonator, said electrical connection means being adapted to be moved from an unconnected to a connected condition by rotation of said body relative to said head from said transport position to an electrical contact position intermediate said transport and armed positions. According to another aspect of the invention, there is provided a method of using a safe arm system to arm a perforating apparatus, the method comprising the step of rotating a body of said safe arm system relative to a head of said system from a transport position, in which a detonator in said body is out of alignment with a booster in said head, to an armed position, in which said detonator is in alignment with said booster, characterised in that said rotating step includes rotating said body relative to said head to an electrical contact position in which an electrical connection by which electrical power can be supplied to fire said detonator is established, said electrical contact position being intermediate said transport and armed positions. Thus, by use of preferred embodiments of the present invention, a perforating apparatus is transported from one location to another when the quick arm adapter head of the safe-arm system of the present invention is placed in a transport position relative to the quick arm body; when in the transport position, the detonator is not electrically connected to a source of power, the leads connected to the detonator are short circuited, and the detonator is out of alignment with respect to the booster connected to the detonating cord. When the quick arm adapter head is rotated with respect to the quick arm body from the transport position to the electrical contact position, a plug is connected electrically to a jack and, as a result, the detonator is connected to a source of power. However, without further rotation of the adapter head with respect to the adapter body, the detonator is out of alignment with respect to the booster or detonating cord shell. Now that electrical connection has been made, connecting the detonator to the source of power, further rotation of the quick arm adapter head with respect to the quick arm body from the electrical contact position to an armed position aligns the detonator with the booster. Therefore, when the safe-arm sysytem is not in the transport mode, two levels of safety with respect to the handling of the perforating apparatus are provided: a first level providing for the necessary electrical connection before a ballistic connection is made, and a second level providing for the necessary ballistic connection after the electrical connection has been made. In addition, the safe arm system of the present invention is easily assembled; it comprises four parts which easily interfit together, that is, a head, a body, a detonating cord module and a detonator retainer module. The detonating cord module easily fits within the head and the detonator retainer module easily fits within the body, the head and the body being threadedly connected together. BRIEF DESCRIPTION OF THE DRAWINGS A full understanding of the present invention will be obtained from the detailed description of the preferred embodiment presented hereinbelow, and the accompanying drawings, which are given by way of illustration only and are not intended to be limitative of the present invention, and wherein: figure 1 illustrates a safe-arm system for use in a perforating apparatus in accordance with the present invention; figure 2 illustrates a plurality of positions or modes associated with the safe-arm system of figure 1; figures 3A and 3B illustrate the safe-arm system of figure 1 taken long section lines 3-3 of figure 1; and figures 4A and 4B illustrate the safe-arm system of figure 1 when the system is ballistically misaligned, figure 4A, and when the system is ballistically aligned, figure 4B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to figure 1, the safe-arm system of the present invention, otherwise termed a quick arm system, is illustrated. In figure 1, the safe-arm system includes an adapter head 10 threadedly connected to a lower gun head 12 on one side and threadedly connected to a body 14 on the other side. More specifically, a modified helical threaded connection 16 exists between the adapter head 10 and the body 14; when the adapter head 10 is rotated clockwise, it approaches the body 14; when the adapter head 10 is rotated counterclockwise, it withdraws from the body 14. The modified helical threaded connection 16 is discussed in more detail below. A detonating cord module 18 is disposed within the adapter head 10, the detonating cord module 18 including a detonating cord shell 18a and an electrical plug 18b, the detonating cord shell 18a including a booster and a detonating cord disposed adjacent the booster in the shell 18a and adapted for connection to a perforating apparatus. The booster is detonated by a separate detonator 20b described below and initiates transmission of a detonating wave along the detonating cord for detonation of a plurality of explosive charges in the perforating apparatus. The plug is adapted for plugging into an electrical jack, to be described below. A portion 18c of the detonating cord module 18 contacts a ledge 10a of the adapter head 10; when the adapter head 10 is rotated clockwise relative to the body 14, due to the existence of modified helical threads 16 between head 10 and body 14, the adapter head 10 and the detonating cord module 18, including the plug 18b, approaches the body 14, since the ledge 10a of adapter head 10 contacts and forces the portion 18c of the module 18 to approach the body 14. The modified helical threads 16 will be discussed in more detail below. A detonator retainer module 20 is disposed within and physically connected to the body 14, the detonator retainer module being disposed adjacent the detonating cord module 18, the detonator retainer module 20 including a detonator 20b and an electrical jack 20a into which the electrical plug 18b "plugs" or is inserted when the adapter head 10 is rotated clockwise relative to the body 14. As a result of the physical connection between module 20 and the body 14, a rotation of the body 14 will correspondingly rotate the detonator retainer module 20. The electrical jack 20a is electrically connected to the detonator 20b. Since the body 14 is rotatable relative to the adapter head 10, the detonator retainer module 20 is also rotatable relative to the adapter head 10; therefore, when the module 20 rotates, detonator 20b rotates into and out of alignment with the detonating cord module 18 and the detonating cord shell 18a. As will be noted below, rotation of the body 14 relative to the head 10 from a "start" position or mode will cause the safe-arm system of figure 1 to pass through three positions or operate sequentially in three modes, that is, a transport position or mode, an electrical contact position or mode, and an armed position or mode. The term "modified helical threads 16" is intended to include the threads, if any, which exist between the start position and the armed position. The specific construction of each of the threads 16 which exist between (1) the start position and the transport position, (2) the transport position and the electric contact position, and (3) the electric contact position and the armed position is provided in this paragraph. Between the start position and the transport position, the threads 16 are helical; when body 14 rotates relative to head 10, head 10 advances toward body 14. Between the transport position and the electric contact position, the threads 16 are divided into a non-helical "first land" portion and a helical portion; when body 14 rotates relative to head 10, the head 10 first engages the first land portion and fails to advance toward body 14; however, head 10 subsequently engages the helical portion of the threads 16 between the transport position and the electric contact position and begins to advance toward body 14. Between the electric contact position and the armed position, the threads 16 are a non-helical "second land" portion; thus, when body 14 rotates relative to head 10, between the electric contact position and the armed position, the head 10 fails to advance toward body 14. Referring to figure 2, a plurality of positions or modes associated with the safe-arm system of figure 1 is illustrated. In figure 2, since the body 14 is rotatable relative to the adapter head 10, the detonator retainer module 20 is also rotatable relative to the detonating cord module 18; therefore, detonator 20b is rotatable relative to the detonating cord shell 18a. The detonator 20b is initially placed in a "start" position 22 relative to the detonating cord shell 18a. Rotation of the detonator 20b relative to the detonating cord shell 18a from the "start" position 22 will cause the safe-arm system of figure 1 to pass through three other positions or operate sequentially in three other modes, that is, a transport position or mode 24, an electrical contact position or mode 26, and an armed position or mode 28. When the detonator 20b is rotated from the start 22 position to the transport 24 position, electrical contact has not been made between the electrical jack 20a and the electrical plug 18b, and the leads connected to the detonator 20b are short circuited by the electrical jack 20a. In addition, the detonator 20b is out of alignment relative to the detonating cord shell 18a. Therefore, when a perforating gun containing the safe-arm system of figure 1 is transported from one location to another, accidental detonation of the gun cannot occur. When the detonator 20b is rotated from the transport position 24 to the electric contact position 26, electrical contact is made between the electrical jack 20a and the electrical plug 18b and the short circuit existing between the leads connected to the detonator 20b is removed. As a result, detonator 20b is adapted to receive electrical power from a well surface via the plug 18b and jack 20a when a power switch is actuated at the well surface. However, when disposed in the electric contact position 26, the detonator 20b is still out of alignment relative to the detonating cord shell 18a. Therefore, even if power is supplied to the detonator 20b, since the detonator 20b is out of alignment relative to the shell 18a, a subsequent detonation of detonator 20b will not cause a detonation wave to transfer from the detonator 20b to a detonating cord contained in the detonating cord shell 18a. When the detonator 20b is rotated from the electric contact position 26 to the armed position 28, the electrical plug 18b still makes electrical contact with the electrical jack 20a and and the detonator 20b is aligned with the detonating cord shell 18a. Detonator 20b is adapted to receive power from the well surface (when an operator at the well surface actuates a switch initiating the transfer of electrical power from a power source to the detonator 20b via the plug 18b and the jack 20a) and, since the detonating cord shell 18a is aligned with the detonator 20b, the detonating cord contained within the detonating cord shell 18a is adapted to receive a detonation wave from the detonator 20b when the detonator 20b detonates in response to receipt of the electrical power from the well surface. Referring to figures 3A and 3B, the safe-arm system of figure 1, taken along section lines 3-3 of figure 1, is illustrated. Figure 3A illustrates the detonator retainer module in the electric contact position 26, that is, the electrical plug 18b is electrically connected to the electrical jack 20a, but the detonator 20b is out of alignment with the detonating cord shell 18a. Figure 3B illustrates the detonator retainer module in the armed position 28, that is, the electrical plug 18b is electrically connected to the electrical jack 20a, and the detonator 20b is aligned with the detonating cord shell 18a. A screw 30 locks the body 14 in the armed position 28. Referring to figures 4A and 4B, side views of the safe-arm system of figure 1 are illustrated, figure 4B being identical to the safe-arm system shown in figure 1 and illustrating the detonator 20b as being aligned with the detonating cord shell 18a, figure 4A illustrating the detonator 20b out of alignment relative to detonating cord shell 18a. Since the adapter head 10 is rotatable relative to the body 14, a rotation of body 14 will also rotate the detonator retainer module 20 which contains the detonator 20b. In figure 4A, the detonator 20b is shown disposed opposite to and therefore out of alignment with the detonating cord shell 18a. In this position, the detonator 20b is disposed half-way between the start position 22 and the transport position 24 of figure 2. An electrical connection is not made between the plug 18b and the jack 20a and the detonator 20b is out of alignment relative to detonating cord shell 18a. In figure 4B, the detonator 20b is shown aligned with the detonating cord shell 18a. In this position, the detonator 20b is disposed in the armed position 28 of figure 2. In addition, an electrical connection is made between the plug 18b and the jack 20a. In operation, referring to figures 1-4B, when the body 14 is rotated relative to the adapter head 10, since the detonator retainer module 20 is physically connected to the body 14, the detonator retainer module 20 rotates with the body 14. Since the detonator 20b is disposed within the module 20, rotation of module 20 rotates detonator 20b. The detonator 20b is initially disposed in the start position 22. Upon rotation of body 14 and module 20 relative to head 10, detonator 20b moves from the start position 22 to the transport position 24. When left in this position, the detonator 20b is not adapted to electrically receive a source of electrical power, since the plug 18b is not electrically connected in jack 20a and the detonator 20b is out of alignment relative to the detonating cord shell 18a. A perforating gun, containing the safe-arm system in this configuration (the detonator 20b is in the transport position), may be safely moved from one location to another without fear of accidental detonation. Upon further rotation of body 14 and module 20 relative to head 10, detonator 20b moves from the transport position 24 to the electric contact position 26. In this position, the detonator 20b is adapted to electrically receive the source of power since the plug 18b is now electrically connected in jack 20a; however, the detonator 20b is still out of alignment relative to the detonating cord shell 18a. Therefore, even if the detonator 20b does detonate, a detonation wave cannot transfer to the detonating cord within the detonating cord shell 18a. Upon further rotation of body 14 and module 20 relative to head 10, detonator 20b moves from the electric contact position 26 to the armed position 28. In this position, the detonator 20b is still adapted to electrically receive the source of power since the plug 18b is still electrically connected in jack 20a; however, in addition, the detonator 20b is now aligned relative to the detonating cord shell 18a. Therefore if the detonator 20b detonates, a detonation wave transfers to the detonating cord within the detonating cord shell 18a.

Claims: A safe arm system adapted for use with a perforating apparatus, the system comprising: a housing (12) including a body (14) and a head (10), said body containing a detonator (20b) and said head containing a booster which is disposed adjacent a detonating cord adapted for connection to said perforating apparatus, and said body being rotatable with respect to said head between a transport position in which said detonator is not aligned with said booster and an armed position in which said detonator is aligned with said booster; characterised in that said body (14) and said head (10) include respective electrical connection means (18b, 20a) via which electrical power can be supplied to fire said detonator, said electrical connection means being adapted to be moved from an unconnected to a connected condition by rotation of said body relative to said head from said transport position to an electrical contact position intermediate said transport and armed positions. The safe arm system of claim 1, including means for short-circuiting the input to the detonator (20b) when said body (14) and said head (10) are in the transport position. The safe arm system of claim 1 or claim 2, wherein said body (14) and said head (10) are threadedly connected together, and wherein said connection means (18b, 20a) comprises an electrical plug (18b) adapted to be inserted into an electrical jack (20a) upon relative rotation of said body (14) and said head (10) from said transport position to said electrical contact position. The safe arm system of claim 3, wherein the threaded connection (16) between said head (10) and said body (14) comprises a helical portion which causes the insertion of said plug (18b) into said jack (20a) during relative rotation of said head and said body from said transport position to said electrical contact position. The safe arm system of claim 4, wherein the threaded connection (16) between said head (10) and said body (14) comprises a land portion adjacent said helical portion, such that no significant further advancement of the plug (18b) takes place during relative rotation of said head and said body from said electrical contact position to said armed position. A method of using a safe arm system to arm a perforating apparatus, the method comprising the step of rotating a body (14) of said safe arm system relative to a head (10) of said system from a transport position, in which a detonator (20b) in said body is out of alignment with a booster (18a) in said head, to an armed position, in which said detonator is in alignment with said booster, characterised in that said rotating step includes rotating said body (14) relative to said head (10) to an electrical contact position in which an electrical connection by which electrical power can be supplied to fire said detonator is established, said electrical contact position being intermediate said transport and armed positions.

Inventors: ASELTINE CLIFFORD, DAILEY TERRELL, GONZALEZ MANUEL, ASELTINE, CLIFFORD, DAILEY, TERRELL
Applicants: SCHLUMBERGER HOLDINGS, SCHLUMBERGER LTD, SCHLUMBERGER SERVICES PETROL, SCHLUMBERGER TECHNOLOGY BV, SCHLUMBERGER HOLDINGS LIMITED, SCHLUMBERGER LIMITED, SCHLUMBERGER TECHNOLOGY B.V., SERVICES PETROLIERS SCHLUMBERGER, (FORMERLY SOCIETE DE PROSPECTION ELECTRIQUE SCHLUMBERGER)
Application year: 1991
Main classification: E21B43
IPC codes: E21B43, F42D1