This invention is related to a safety arming device for use as part of an apparatus for perforating oil wells, etc. and to methods of providing an armed device. More particularly, the invention is related to a detonator assembly for initiating perforating charges in an underground perforating gun.
Underground perforating guns are used in the production of oil and gas for provision of perforations through an oil well casing and into a hydrocarbon producing formation to provide access from the formation into the wellbore such that oil and gas may be produced.
After the oil well has been drilled, a steel casing is lowered into the wellbore and cemented into place to protect the wellbore and to prevent migration of formation fluid from one formation to another.
A perforating gun is then lowered into the steel casing and perforations are made at a desired spacing through the steel liner and into the formation such that hydrocarbons in the desired formation may flow into the oil wellbore and from there be produced to the surface.
An electrically-actuated or so-called xe2x80x9celectricxe2x80x9d detonator (initiator) is typically employed for operating the explosive charges on a perforating gun. In a typical arrangement, a gun is dependently supported in a wellbore by a so-called wireline (suspension) cable which has electrical conductors connected to a surface power source. The electric detonators that are most commonly used on oilfield well tools have a fluid-tight hollow shell in which is encapsulated an ignitor charge (such as a black powder or an ignition bead) that is disposed around an electrical bridge wire and positioned next to a primer explosive charge (such as lead azide or some other sensitive primary explosive). In some detonators, a booster charge of a secondary explosive (such as RDX, PETN, HMX, HNS or PYX, etc.) is arranged in a serial relationship with the primer charge to be detonated.
The electric detonator detonates an explosive detonating cord (detcord) which, in turn, sets off the charge(s) carried by the gun, once the tool is positioned at a desired depth location in a wellbore.
One practice in the industry is for an end user to purchase perforating guns in an unassembled or partially assembled condition and transport these to the oil well site. One reason for this is that the configuration of a perforating gun (spacing and number of charges, gun length and diameter, number of gun housings to be strung together, etc.) varies from wellbore to wellbore. Oil well sites are often in locations remote from assembly shops. For safety reasons, the shaped charges are transported separate from the detonating devices so that if the detonating devices were accidentally discharged, the shaped charge perforating units would not be detonated in turn.
A practice in the industry is thus to complete assembly and arm a gun on-site. A detonator is connected to an electrical conductor and then grounded to the gun housing. The detonating cord (previously strung between charges mounted on a charge holder and installed in the gun housing), an end of which sticks out of an end of the gun housing is clamped to the detonator or the detonator is slid axially onto the detonating cord. The detonator is inserted into the end of the gun housing, which can be either the top or bottom end of the gun. An end cap is then sealingly fastened to the end of the gun with the electrical conductor connecting the detonator and surface power source being strung through the cap, and/or through the gun, provision being made to seal the passage by which the conductor emerges from the gun to preclude entry of well fluids into the gun housing. As mentioned above, an alternative arrangement includes a booster.
In the context of this industry practice, the possibility exists of premature detonation of gun components during arming of the gun. In arrangements in which the detonator is directly connected to the detonating cord, it is possible to kink the detonating cord as the detonator is pushed into the gun housing and the sealing cap screwed onto the gun housing. In arrangements in which there is a booster attached to the detonating cord, it is possible to crush the booster. It is thus possible to short the wires when replacing the sealing cap in this manner.
This situation, which can lead to premature actuation, or unintended detonation, is clearly a hazard to the persons charged with gun assembly. While safe arm devices exist, many are designed to operate outside the practice of arming a gun on-site to meet the needs of a particular wellbore. It is in the context of this practice that the present invention presents a solution.
The invention includes a safety arming device for an underground well tool having an explosive charge mounted in a longitudinal housing. In one embodiment, the device includes:
a hollow member for connection at an end of the housing, the member having an outer wall which defines a window to permit lateral insertion therethrough of a detonator into an operable position in the member when the member is connected to the housing; and
a sealing member for mounting on the hollow member in sealing engagement therewith, so as to preclude ingress of liquids into the member through the window.
The sealing member of the device can be a hollow sleeve longitudinally movable with respect to the hollow member between an open position and a closed position, wherein:
in the open position, the sleeve is located to permit access to the window for said insertion of the detonator therethrough, and in the closed position, the sleeve is in said sealing engagement with the hollow member.
The hollow member can be provided with threads at a first longitudinal end thereof and the sleeve is provided with threads for engagement of the threads of the hollow member to secure the sleeve in the closed position.
The sealing engagement can be provided by first and second circumferential seals located between the sleeve and hollow member, the seals being positioned longitudinally on either side of the window.
The hollow member can be adapted to be connected directly to the gun housing.
The hollow member can include threads for threaded connection at said end of the housing.
In another aspect, the invention provides a safety arming device for an underground well tool having an explosive charge mounted in a tubular longitudinal housing, the charge being actuatable by a detonator connected thereto by a detonation cord. The device can include:
a first sleeve having a wall defining a sleeve interior, the sleeve being adapted to be sealingly affixed to the tubular housing, wherein the wall has an aperture therein sized to permit lateral insertion therethrough of the detonator into the sleeve interior and, when the sleeve and housing are connected, the sleeve interior is in communication with an interior of the housing containing the charge; and
a second sleeve, axially moveable with respect to the first sleeve, between an open position and a closed position; wherein,
in the open position, the second sleeve is located to provide clearance for the detonator to be inserted through the aperture into the interior of the first sleeve, and in the closed position, the second sleeve is in sealing engagement with the first sleeve to preclude ingress of liquids into the sleeve interior through said aperture.
In another embodiment, the invention is a safety arming device for an underground well tool having an explosive charge mounted in a tubular longitudinal housing, the charge being actuatable by a detonator in operable connection with a booster connected to the charge by a detonation cord. In this embodiment, the device includes:
a first sleeve having a wall defining a sleeve interior, the sleeve being adapted to be sealingly affixed to the tubular housing, wherein:
the wall has an aperture therein sized to permit lateral insertion therethrough of the detonator into the sleeve interior;
the wall defines an interior sleeve portion for receipt of the booster therein to locate the booster in operable proximity to the detonator when the booster and cord are connected to each other; and
a second sleeve, axially moveable with respect to the first sleeve, between an open position and a closed position; wherein:
in the open position, the second sleeve is located to provide clearance for the detonator to be inserted through the aperture into the interior of the first sleeve, and in the closed position, the second sleeve is in sealing engagement with the first sleeve to preclude ingress of liquids into the sleeve interior through said aperture.
The second sleeve can be external of the first sleeve and be of substantially circular cross section; and the first sleeve can include external first threads and the second sleeve includes internal second threads, the first and second threads being mutually threadingly engageable for securing the second sleeve in the closed position.
The first sleeve can include first and second seals disposed around an exterior surface thereof located longitudinally on first and second sides, respectively, of the aperture and to be in abutting contact with an interior surface of the second sleeve when in the second position so as to provide said sealing engagement. There can be a plurality of said first seals and a plurality of said second seals.
In another aspect, the present invention is a safety arming device for an underground perforation gun having an explosive charge mounted in a tubular housing having a major longitudinal axis, the charge being actuatable by a detonator connected thereto by a detonation cord. The device includes:
a hollow inner sleeve having threads at a first end for threaded connection to a threaded end of the housing such that respective interiors of the housing and sleeve are in communication with each other;
a hollow outer sleeve disposed around the inner sleeve, axially moveable between a first position distal to the first end of the inner sleeve and a second position proximal to the first end of the inner sleeve; wherein:
the inner sleeve includes a tubular wall having an aperture therein, accessible when the outer sleeve is in the distal position, the aperture being sized to permit lateral insertion therethrough of the detonator into the interior of the inner sleeve; and
the tubular wall of the inner sleeve has external threads located axially between the aperture and the proximal end thereof and an interior surface of the outer sleeve is threaded at a proximal end thereof for threaded engagement of the external threads of the inner sleeve, to secure the outer sleeve in the second position;
at least a first seal disposed around the exterior of the inner sleeve, located axially between the aperture and the external threads of the inner sleeve;
at least a second seal disposed around the exterior of the inner sleeve, located axially between the aperture and the distal end of the inner sleeve; and wherein:
when the outer sleeve is secured in the second position, the seals are in abutting contact with the exterior surface of inner surface and interior surface of the outer sleeve so as to preclude ingress of liquid into the interior of the inner sleeve.
In another aspect, the invention is a safety arming device for an underground well tool having an explosive charge mounted in a tubular housing having a major longitudinal axis, the charge being actuatable by a detonator in operable connection with a booster connected to the charge by a detonation cord. The device includes:
a hollow inner sleeve having threads at a first end for threaded connection to a threaded end of the housing, such that respective interiors of the housing and sleeve are in axial alignment with each other, the sleeve having an internal wall defining a first zone for receipt of the booster therein;
a hollow outer sleeve disposed around the inner sleeve, axially moveable between a first position distal to the first end of the inner sleeve and a second position proximal to the first end of the inner sleeve; wherein:
the inner sleeve includes a tubular wall having an aperture therein, accessible when the outer sleeve is in the distal position, the aperture being sized to permit lateral insertion therethrough of the detonator into a second zone of the interior of the inner sleeve, to permit spaced apart positioning of the detonator and booster in axial alignment with each; and
the tubular wall of the inner sleeve has external threads located axially between the aperture and the proximal end thereof and an interior surface of the outer sleeve is threaded at a proximal end thereof for threaded engagement of the external threads of the inner sleeve, to secure the outer sleeve in the second position;
at least a first seal disposed around the exterior of the inner sleeve, located axially between the aperture and the external threads of the inner sleeve;
at least a second seal disposed around the exterior of the inner sleeve, located axially between the aperture and the distal end of the inner sleeve; and wherein:
when the outer sleeve is secured in the second position, the seals are in abutting contact with the exterior surface of inner surface and interior surface of the outer sleeve so as to preclude ingress of liquid into the interior of the inner sleeve.
A safety arming device of the invention can includes a joining member for connecting the hollow member to the gun housing, the joining member having an aperture therethrough so as to permit communication between an interior of the housing and an interior of the hollow member for passage of the detonator cord therethrough.
The hollow member can define an aperture dimensioned to receive a detonator therein, so as to be positioned in axial alignment with a booster received with the aperture of the joining member.
The invention also includes a method of installing a safety arming device on a longitudinal underground perforating gun. The method includes steps of:
providing a hollow member for connection at an end of a housing of the gun, wherein the hollow member comprises an outer wall which defines a window dimensioned to permit insertion therethrough of a first detonator into an interior of the member;
providing a sealing member for mounting to the hollow member in sealing engagement therewith, so as to preclude ingress of liquids into the member through the window; and
installing the hollow member to the housing such that the window is positioned to permit lateral insertion of the detonator therethrough into the interior of the hollow member and with the interior of the housing positioned (i) to receive therein a first end of a detonating cord having a second end connected to a charge within the housing therein, or (ii) to permit positioning of the detonator therein with respect to a booster connected to a said first end of the detonating cord for actuating the booster by the installed detonator.
The method can be conducted with a sealing member that includes a hollow sleeve longitudinally movable with respect to the installed hollow member between an open position and a closed position, wherein:
in the open position, the sleeve is located to permit access to the window for said insertion of the detonator therethrough, and in the closed position, the sleeve is in said sealing engagement with the hollow member.
The method can be carried out where the hollow member is provided with threads at a first longitudinal end thereof and the sleeve is provided with threads for engagement of the threads of the hollow member to secure the sleeve in the closed position.
The said sealing engagement can be provided by first and second circumferential seals located between the sleeve and hollow member, the seals being positioned longitudinally on either side of the window.
The hollow member can further include means for connecting the member to a gun delivery system, at a distal end of the member with respect to the gun housing.
The connecting means can be provided by threads or another connecting means suitable for the purpose, as would be readily understood by the skilled person.
The hollow member can include an opening in a wall thereof, the opening being sealable against ingress of well fluids thereinto, for installing a conductive wire therethrough to electrically connect the detonator to an aboveground power source.
Installing the hollow member on the housing can include threadingly engaging threads of the member with threads of the housing.
The gun can include a second detonator connected to a said first end of the detonating cord, and the method can further comprise the steps of:
providing an apertured member having an aperture therethrough; and
prior to installing the hollow member on the housing, installing a first longitudinal end of the apertured member to the end of the housing with the aperture extending between longitudinal ends of the apertured member and passing a free end of the first end of the detonating cord connected to the second detonator through the aperture to permit connection thereof to the first detonator.
The invention also includes a method of arming an underground perforating gun having a longitudinal housing. The method can include the steps of:
mounting a hollow member at an end of a housing of the gun, wherein the hollow member comprises an outer wall which defines a window dimensioned to permit insertion therethrough of a first detonator into an interior of the member, and wherein the interior of the hollow member is positioned (i) to receive therein a first end of a detonating cord having a second end connected to a charge within the housing therein, or (ii) to permit positioning of the detonator therein with respect to a booster connected to a said first end of the detonating cord for actuating the booster by the installed detonator;
inserting the detonator through the window to install the detonator in the interior of the hollow member and:
connecting the first end of the detonating cord thereto, or positioning the detonator with respect to a booster connected to the first end of the detonating cord for actuating the booster by the installed detonator; and
securing a sealing member to the hollow member in sealing engagement therewith, so as to preclude ingress of liquids into the member through the window.
The method can also include connecting the detonator to an electrically conductive wire connected to a power source.
The sealing member can include a hollow sleeve longitudinally movable with respect to the installed hollow member between an open position and a closed position, wherein:
in the open position, the sleeve is located to permit access to the window for said insertion of the detonator therethrough, and in the closed position, the sleeve is in said sealing engagement with the hollow member.
The hollow member can be provided with threads at a first longitudinal end thereof and the sleeve is provided with threads for engagement of the threads of the hollow member to secure the sleeve in the closed position and securing the sealing member to the hollow member includes mutually engaging the respective threads of the hollow and sealing members.
The sealing engagement can be provided by first and second circumferential seals located between the sleeve and hollow member, the seals being positioned longitudinally on either side of the window.
The method can include connecting the hollow member to a gun delivery system.
Connecting the hollow member to the gun delivery system can include threadingly engaging threads of the hollow member to counterpart threads of an element of the gun delivery system.
The hollow member can include an opening in a wall thereof, the opening being sealable against ingress of well fluids thereinto, and comprising the further steps of installing a conductive wire through the opening and electrically connecting the detonator to an above-ground power source.
Installing the hollow member on the housing can include threadingly engaging threads of the member with threads of the housing.
The gun can include a second detonator connected to a said first end of the detonating cord, and the method further comprises the steps of:
providing an apertured member having an aperture therethrough; and
prior to installing the hollow member on the housing, installing a first longitudinal end of the apertured member to the end of the housing with the aperture extending between longitudinal ends of the apertured member and passing a free end of the first end of the detonating cord connected to the second detonator through the aperture to permit said connecting thereof to the first detonator.
The invention is also a method of manufacturing a safety arming device for an underground well tool having an explosive charge mounted in a longitudinal housing. The method includes the steps of:
manufacturing a hollow member for connection at an end of the housing with an outer wall;
contouring the wall to define a window to permit lateral insertion therethrough of a detonator into an operable position in the member when the member is connected to the housing; and
manufacturing a sealing member for mounting on the hollow member in sealing engagement therewith, so as to preclude ingress of liquids into the member through the window.