Methods and apparatus for selectively arming well bore explosive tools
First Claim
1. A well tool to be suspended in a well bore and comprising:
- a body;
an explosive device on said body;
first means on said body for detonating said explosive device including a receptor explosive, and an electrically-initiated donor explosive selectively operable for producing an explosive force of sufficient magnitude to set off said receptor explosive;
explosion-proof housing means arranged on said body enclosing said donor explosive for confining its said explosive force;
an explosion-proof barrier of a fusible material shielding said receptor explosive so long as the temperature of said barrier stays below the melting point of said fusible material; and
second means on said body operable for melting said barrier to arm said explosive device to be selectively fired in a well bore in response to the detonation of said donor explosive by an electrical signal.
2 Assignments
0 Petitions
Accused Products
Abstract
In the representative embodiments of the several methods and apparatus of the invention, a barrier formed of a low-temperature fusible metal alloy having a selected melting point greater than the anticipated well bore temperatures is arranged between a receptor explosive and a typical electrically-initiated detonator enclosed in a housing for blocking the transmission of detonation forces from the detonator to the receptor explosive until the barrier has been heated by an electrical heater adjacent to the barrier. By selecting a fusible metal alloy which has a melting point higher than the known temperatures of the well bore fluids, when the tool is exposed to those elevated temperatures, the barrier will be predictably maintained in its solid state to continue blocking the detonation path of the donor explosive if the heater fails thereby allowing the well tool carrying the explosives to be safely recovered from the well bore.
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Citations
22 Claims
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1. A well tool to be suspended in a well bore and comprising:
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a body; an explosive device on said body; first means on said body for detonating said explosive device including a receptor explosive, and an electrically-initiated donor explosive selectively operable for producing an explosive force of sufficient magnitude to set off said receptor explosive; explosion-proof housing means arranged on said body enclosing said donor explosive for confining its said explosive force; an explosion-proof barrier of a fusible material shielding said receptor explosive so long as the temperature of said barrier stays below the melting point of said fusible material; and second means on said body operable for melting said barrier to arm said explosive device to be selectively fired in a well bore in response to the detonation of said donor explosive by an electrical signal. - View Dependent Claims (2, 3, 4)
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5. Well bore apparatus comprising:
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an electrically-initiated donor explosive operable for detonating a receptor explosive in response to the explosive forces produced upon detonation of said donor explosive; a barrier formed of a fusible material positioned adjacent to said donor explosive for normally blocking the transmission of said explosive forces from said donor explosive until said barrier is melted in response to heating of said barrier above the melting point of said fusible material; and arming including electrical heating means adjacent to said barrier and operable for melting said barrier to selectively remove said barrier and enabling the transmission of said explosive forces of said donor explosive to other explosives detonating proximity of said donor explosive. - View Dependent Claims (6, 7)
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8. Well bore apparatus comprising:
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an electrically-initiated donor explosive operable for detonating a receptor explosive in response to the explosive forces produced upon detonation of said donor explosive; an explosion-proof housing enclosing said donor explosive for suppressing its said explosive forces, said housing including an opening for transmitting said explosive forces to the exterior of said housing, and a barrier formed of a fusible material for normally blocking said opening until said fusible material is melted in response to being heated to a temperature greater than the melting point of said fusible material; and arming means on said housing adjacent to said opening and including an electrically-operated heater selectively operable for heating said barrier to its said melting point for removing said barrier from its blocking position. - View Dependent Claims (9, 10, 11, 12)
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13. A perforating gun to be suspended in a well bore containing well bore fluids at elevated temperatures and comprising:
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a hollow carrier; at least one shaped charge in said hollow carrier; means in said carrier for selectively detonating said shaped charge and including an encapsulated booster explosive, and an electrically-initiated encapsulated detonator explosive spatially disposed from said booster explosive and cooperatively arranged for detonating said booster explosive in response to explosive forces produced by firing of said detonator explosive within detonating proximity of said booster explosive; an explosion-resistant enclosure having an access opening enclosing said detonator explosive and cooperatively arranged for positioning said access opening between said encapsulated explosives; a normally-solid meltable barrier blocking said access opening until said barrier is heated to its melting point; and electrical heating means adjacent to said access opening and operable for selectively heating said barrier to its said melting point for unblocking said access opening and bringing said booster explosive into detonating proximity of said detonator explosive. - View Dependent Claims (14)
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15. Well bore apparatus to be installed in a well bore perforator carrying one or more shaped explosive charges and comprising:
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an explosion-proof housing formed of a material of sufficient thickness for suppressing the explosive forces of an encapsulated electrically-initiated detonator disposed therein and having an opening in one end thereof; an encapsulated electrically-initiated detonator in said housing adjacent to and within detonating proximity of said opening; a closure member formed of a fusible material having a predetermined melting point greater than anticipated well bore temperatures cooperatively arranged in said opening for confining the explosive forces of said detonator entirely within said chamber so long as said closure member is not heated to its said predetermined melting point; and heating means including an electrical heater arranged on said housing and operable for heating said closure member to its said predetermined melting point. - View Dependent Claims (16, 17, 18)
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19. A method for performing a well service operation with a well tool having an explosive device coupled to a receptor explosive and an electrically-initiated explosive detonator for selectively dentonating said receptor explosive and comprising the steps of;
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mounting said detonator inside of an explosion-proof housing with an opening in one end thereof adjacent to said receptor explosive and blocking said opening with a barrier comprised of a normally-solid fusible material for suppressing the explosive forces of said detonator until said well tool is lowered into a well bore; lowering said well tool into a well bore for conducting a well service operation at a selected depth interval containing well fluids; applying heat to said barrier for melting said barrier to unblock said opening to expose said receptor explosive to the explosive forces of said detonator; and while said detonator and said receptor explosive are in detonating proximity of one another, selectively initiating said detonator for carrying out said well service operation. - View Dependent Claims (20)
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21. A method for perforating a well bore with a perforating gun having an enclosed fluid-tight carrier carrying at least one shaped explosive charge coupled to an encapsulated explosive booster and an electrically-initiated encapsulated explosive detonator spatially disposed therefrom for selectively detonating said booster and comprising the steps of:
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mounting said detonator inside of an explosion-proof housing with an opening in one end thereof adjacent to said booster and blocking said opening with a barrier comprised of a normally-solid fusible material for suppressing the explosive forces of said detonator while said perforating gun is lowered into a well bore containing well bore fluids at elevated temperatures less than the melting point of said fusible material and thereby rendering said detonator temporarily ineffective for setting off said shaped explosive booster; positioning said perforating gun in a well bore containing well fluids at elevated temperatures less than the melting point of said fusible material so that said barrier will continue to render said detonator ineffective to set off said explosive booster when said perforating gun has been positioned at a selected depth interval in the well bore; after said perforating gun has been positioned at a selected depth interval in the well bore, applying heat to said barrier for raising said barrier to the melting point of said fusible material for removing said barrier and rendering said detonator effective to set off said explosive booster; and selectively initiating said detonator for carrying out said perforating operation. - View Dependent Claims (22)
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Specification