Connection cartridge for downhole string

A cartridge assembly for use with a perforating system having a contact terminal that connects to a perforating signal line when inserted into a receptacle end of a perforating gun. A detonator may be included in an end of the cartridge assembly for initiating a detonating cord in the perforating gun. The cartridge assembly is a modular unit that replaces the manual connections made when assembling a string of perforating guns. The cartridge assembly may optionally include a controller switch for controlling current flow through the cartridge assembly.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates generally to the field of oil and gas production. More specifically, the present invention relates to a modular apparatus for providing communication between members of a downhole string. Yet more specifically, the present invention relates to a cartridge inserted into an end of a perforating gun equipped with a receptacle or contact at both ends for connection to a signal line through a perforating gun string.

2. Description of Prior Art

Perforating systems are used for the purpose, among others, of making hydraulic communication passages, called perforations, in wellbores drilled through earth formations so that predetermined zones of the earth formations can be hydraulically connected to the wellbore. Perforations are needed because wellbores are typically completed by coaxially inserting a pipe or casing into the wellbore. The casing is retained in the wellbore by pumping cement into the annular space between the wellbore and the casing. The cemented casing is provided in the wellbore for the specific purpose of hydraulically isolating from each other the various earth formations penetrated by the wellbore.

Perforating systems typically comprise one or more perforating guns strung together, these strings of guns can sometimes surpass a thousand feet of perforating length, but typically shorter in a wireline application. InFIG. 1an example of a prior art perforating system10is shown disposed in a wellbore12and made up of a string of perforating guns14connected in series. Typically, subs15may connect adjacent guns to one another. The perforating system10is deployed from a wireline16that spools from a service truck18shown on the surface20. Generally, the wireline16provides a raising and lowering means as well as communication and control connectivity between the truck18and the perforating system10. The wireline16is threaded through pulleys22supported above the wellbore12. In some instances, derricks, slips and other similar systems are used in lieu of a surface truck for inserting and retrieving the perforating system into and from a wellbore. Moreover, perforating systems may also be disposed into a wellbore via tubing, drill pipe, slick line, coiled tubing, to mention a few.

Included with each perforating gun14are shaped charges24that typically include a housing, a liner, and a quantity of high explosive inserted between the liner and the housing. When the high explosive in a shaped charge24is detonated, the force of the detonation collapses the liner and ejects it from one end of the shaped charge24at very high velocity in a pattern called a “jet”26. The jet26perforates casing28that lines the wellbore12and cement30and creates a perforation32that extends into the surrounding formation34.

Shown inFIGS. 2A-Dare sectional views of the prior art perforating gun14ofFIG. 1. As shown, the shaped charges24are typically connected to a detonating cord36, which when detonated creates a compressive pressure wave along its length that initiates detonation of the shaped charges24. A detonator38is typically used to set off detonation within the detonation cord36. InFIG. 1, the detonator38is shown in a firing head40provided in the string of perforating guns14. Initiating detonation of the detonation cord36generally takes place by first sending an electrical signal from surface20to the detonator38via the wireline16. Referring back toFIGS. 2A-D, an upper connection sub42contains a terminal44for receiving signals transmitted along the wireline16. A signal line46attaches to the terminal44and conveys signal(s) from the wireline16to the remaining portions of the perforating system10, including the detonator38. Multiple connectors48are used to make up the signal line46through the successive connecting subs15and perforating guns14. The signal through the signal line46initiates high explosive in the detonator38that transfers to the attached detonation cord36. Detonators38may sometimes be provided within connecting subs15for transferring the detonating charge along the entire string of perforating guns14. Without proper continuity between the wireline16and detonator(s)38, the shaped charges24cannot be detonated. However, failure points in the signal line46are introduced with each connector48.

Generally the detonators are connected to the detonating cords in the field just prior to use. Thus they are shipped to the field with the electrical portions and high explosive coupled together in a single unit. Because of the risks posed by the high explosives and the threat of a transient electrical signal, shipment and storage of the detonators is highly regulated, this is especially so when being shipped to foreign locations. Additional problems may be encountered in the field when connecting detonators to the detonating cord. Perforating guns when delivered to the field generally have the shaped charges and detonating cord installed; to facilitate detonator connection some extra length of detonating cord is provided within the gun. Connecting the detonator to the detonating cord involves retrieving the free end of the detonating cord and cutting it to a desired length then connecting, usually by crimping, the detonator to the detonating cord. These final steps can be problematic during inclement weather. Additionally, these final steps fully load a perforating gun and thus pose a threat to personnel in the vicinity. Accordingly benefits may be realized by reducing shipping and storage concerns, increasing technician safety, and minimizing the time required to finalize gun assembly in the field.

SUMMARY OF INVENTION

Disclosed herein is an example of a perforating string insertable into a wellbore. In this example the perforating string is made up of a perforating gun having an upstream end with a receptacle fitting, a signal line with an end electrically connected to the receptacle fitting. Included with the example perforating string is a cartridge sub having a connector inserted into electrical connection with the receptacle fitting, a detonator in the cartridge sub and having a detonating end adjacent to and directed towards the upstream end, and a lead line in the cartridge sub having an end in selective communication with an electrical source and another end in communication with an inlet to the detonator. Optionally, the connector is an annular member that circumscribes a downstream end of the cartridge sub, and wherein the connector coaxially inserts into the receptacle fitting. In an embodiment, the perforating string further includes a switch in the lead line for selectively regulating electricity to the detonator. In this example, a ground lead is optionally included that is connected between the detonator and the switch, wherein the switch selectively communicates the ground lead to ground. In one example, the switch, the lead line, and the detonator are provided within an elongated body that coaxially inserts within an annular housing to define the cartridge sub. In one optional embodiment, further included with the perforating string is a transfer lead line having an end in selective communication with the electrical source and another end in communication with the connector for selectively providing communication between the electrical source and the signal line. A downstream cartridge sub may also optionally be included that has an inlet line in electrical communication with the signal line, an outlet lead line in communication with a bridge plug assembly, so that when an electrical signal is applied to the signal line, the electrical signal is transferred through the downstream cartridge sub to the bridge plug assembly for deploying a bridge plug in the bridge plug assembly.

Also provided herein is an example of a connector assembly for connecting an upstream perforating gun to a downstream perforating gun. In one example the connector assembly includes an annular housing, an elongated cartridge body inserted within the housing, an annular connector provided on a downstream end of the body and inserted into electrical contact with a receptacle in the downstream perforating gun, a detonator in the cartridge body for initiating a detonating cord in the perforating gun, and a lead line in the cartridge body having an end in selective communication with an electrical source and another end electrically connected to the connector. Optionally, a switch may be included in the body that is connected to the lead line and to an inlet line on the detonator. Also further Optionally included is an outline line that connects between the switch and the detonator, and a ground line that connects between the switch and ground, so that when a detonation signal and detonation current is sent to the switch, the inlet line, outlet line, and ground line form a circuit for flowing current through the detonator for initiating detonation of the detonator and the detonating cord.

An example method of perforating is provided herein that in one example includes providing a perforating gun with shaped charges, a detonation cord, a receptacle connection, and a signal line in communication with the receptacle connection. A cartridge sub is also provided that has an upstream end, a downstream end, a connector in the downstream end, and a lead line electrically connected to the connector. In the example method, the connector is connected with the signal line by inserting the downstream end of the cartridge sub into the receptacle connection, the shaped charges are detonated by providing a detonation signal to the detonator. In one example, the step of providing a detonation signal to the detonator includes directing electricity from an electrical source to an inlet line connected to the detonator. Optionally in the method, a switch is provided in the cartridge sub for providing electrical communication between the electrical source and the detonator, and for providing electrical communication between an outlet line on the detonator and ground for completing an electrical circuit through the detonator. In one example of the method, the perforating gun is a downstream perforating gun. In this example, further includes is a step of diverting some of the electricity from the electrical source through the lead line, to the connector and the receptacle for initiating detonation of shaped charges in a perforating gun downstream of the downstream perforating gun.

DETAILED DESCRIPTION OF INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

InFIG. 3an example embodiment of a perforating system60is shown in a side sectional view. In this example, the perforating system60includes perforating guns621,622each having a series of shaped charges64disposed within. Each perforating gun621,622further includes a detonating cord66disposed lengthwise therein so it is positioned proximate each of the shaped charges64; thus when the detonating cord66is initiated, it may in turn initiate detonation of the shaped charges64. Initiating the detonation cords66forms a pressure wave that travels the length of the detonation cords66. In the example embodiment ofFIG. 3, the pressure wave travels in the direction of arrows A, and as will be described in more detail below, an initiation signal reaches perforating gun621before reaching perforating gun622. Thus for the purposes of reference only, perforating gun621is referred to as an “upstream” gun whereas perforating gun622is referred to as a “downstream gun”.

Coupled in series with the downstream perforating gun622is a cartridge sub68having a cartridge assembly70set within the housing of the cartridge sub68. In the embodiment ofFIG. 3, the cartridge assembly70is shown made up of an elongated body71, and within the body71are a switch assembly72and an optional circuit board74for selectively performing switching operations within the switch assembly72. In one example of operation, the switch assembly72regulates transmission therethrough of electrical signals through the switch assembly72that are received by an inlet lead76in the cartridge sub68from the upstream perforating gun621. The switch assembly72also includes a ground lead78on the side with the inlet lead76; the ground lead78is selectively in electrical communication with the switch assembly72such as by the switching action provided by the circuit board74. Exiting the switch assembly72, on a side opposite the inlet lead76, is a supply lead80that is in electrical communication with a communication line82shown extending within the downstream perforating gun622. In an example embodiment, inlet lead76selectively couples with an electrical source for receiving electricity. Also exiting the switch assembly72are a signal lead84and a ground lead86. In an example, the leads84,86make up a detonator connection that provides selective electrical communication between the signal assembly72and a detonator88shown set in an end of the cartridge assembly70adjacent the downstream perforating gun622. As illustrated inFIG. 3, the modular cartridge assembly70can be inserted within the annular cartridge sub68for easy assembly and removed from within the cartridge sub68for replacement and/or repair.

When an initiating signal is received by the switch assembly72, the circuit board74operates to provide an initiating current through the signal line84and further allow continuity between the ground lead86and ground lead78, thereby closing a circuit through the detonator88for initiating the detonator88. As shown, an end of the detonator88is directed towards the detonating cord66within the downstream perforating gun622, so that as the pressure wave of detonation passes along the length of the detonating cord66, the attached shaped charges64will in turn initiate to create perforations in an adjacent formation (not shown). Further illustrated in the embodiment ofFIG. 3, a collar-like connector90is provided on the downstream end91of the cartridge sub68. In an example, the connector90is formed from a conductive material and is an annular member that circumscribes the downstream end91. Further in the example ofFIG. 3, the diameter of the cartridge sub68reduces at the downstream end91. When the cartridge sub68is connected to the downstream perforating gun622, connector90coaxially inserts within an annular electrical receptacle92shown provided in the downstream perforating gun622. The electrical receptacle92is electrically conductive, so that the combination of the electrical receptacle92and connector90provides an electrical coupling between the exit lead80and communication line82. The coupling thus provides a means for transferring a signal or signals between the cartridge sub68and the downstream perforating gun622, and along the length of the perforating system60. It should be pointed out that the orientation of the cartridge sub68and perforating guns621,622is reversible; so that when a string of multiple guns is formed, the signal that passes along the signal lines and through the switch assembly72may start at the lower end of a perforating gun string and travel upwards, or initiate at the upper end of the string and travel downwards within the wellbore.

FIG. 4illustrates an example embodiment of a lower end of the perforating system60and with an alternate embodiment of a cartridge sub68A. In this example, an inlet lead76and ground lead78extend through the cartridge assembly70A to a switch assembly72. However, the exit or downstream side of the switch assembly72includes a single continuous signal line84A that terminates at a connector90A. The example of the connector90A illustrated inFIG. 4is a hemispherical-shaped member with a collar-like base circumscribing a cylindrical tip of the cartridge assembly70A. Similar to the connector90ofFIG. 3, connector90A ofFIG. 4is formed from an electrically conducting material. Further, in the embodiment ofFIG. 4, the perforating system60is set within a wellbore93lined with casing94that is cemented within the formation96. In this embodiment, a bridge plug98is shown set within a bridge plug sub100to form a bridge plug setting tool mounted on the end of the cartridge sub68A having the connector90A. Optionally, some other pressure actuated device may be provided on the end of the cartridge sub68A. In the example ofFIG. 4, the connector90A contacts an igniter (not shown) in the bridge plug sub100thereby providing electrical continuity between the signal line84A and the igniter. Delivering an electrical signal or electricity can activate the igniter for setting the bridge plug98. Setting the bridge plug98can cause it to expand from within the bridge plug sub100and into contact with the inner circumference of the casing94, thereby pressure isolating that section of the wellbore from another.

In one example embodiment, the connection between the cartridge sub68and upstream perforating gun may be a terminal assembly made up of a rod and pin connector, where the pin connector is mounted on a free end of the rod. In this example, a bushing circumscribes a mid-portion of the rod. The pin connector is in electrical communication with connector in the sub68by connections that extend through the end wall of the sub68. Circumscribing the portion of the terminal assembly adjacent the end wall is a spring connector that is in electrical communication with another connector in the sub68by connections extending through the end wall. Provided at a downstream end of the cartridge sub68opposite the terminal assembly is a downstream connector in which the exit lead80is connected at an end opposite its connection to the switch assembly72. Coaxially projecting from the end of the cartridge sub68and adjacent the detonator88is a spring connector; the spring connector communicates with the downstream connector by connection through the end wall at the downstream end of the sub68.

The spring connectors can provide connectivity on the upstream and downstream sides of the cartridge sub68. More specifically when the cartridge sub68is inserted within an example embodiment of a perforating string60, a connector sub couples to the upstream end of the cartridge sub68and receives the terminal assembly, within an axial bore formed through the connector sub. A receptacle is formed within the connector sub at a location set back from the entrance to the bore. The receptacle provides terminals for communication between a signal wire within the connector sub and the pin connector. As such, a signal traveling through the signal wire is transmitted through the terminals to the pin connector for delivery to the switch assembly. Also the insertion of the downstream side of the cartridge sub68into an end of the downstream perforating gun622. A connection assembly may be set within a bore formed in the end of the downstream perforating gun622. The connection assembly can be made up of a disc-like flange member set into close contact with the spring connector. A cylindrically-shaped base may depend coaxially from a side of the flange opposite the spring connector and set within a reduced diameter portion of the bore. Setting the base and bore diameters at about the same value anchors the connector assembly within the perforating gun622. A communication line, similar to the line82ofFIG. 3, may attach to the flange thereby providing communication from the exit lead80, through the assembly of connectors and spring connector, flange, and into and through the perforating gun622.

One example of a substantially complete perforating system60in accordance with the present disclosure is shown in a partial sectional view inFIG. 5. In this example, a string115of perforating guns621-nis disposed within wellbore93for perforating through the casing94and into the surrounding formation96. Further in this example, the cartridge sub68and the string are oriented so that signals received in the switch assembly72are from a location farther downhole; thus signals traveling in the string in a direction towards the surface. Depending on the instructions programmed into the switch assemblies72, the direction of perforating may also travel upwards within the bore hole92rather than from the top to the bottom.

In one example, the string115is assembled by providing cartridge subs68with a cartridge70within. Each of the cartridge subs68can then be coupled with a perforating gun62so connectors90in their respective downstream ends91mate into electrical receptacles92as illustrated inFIG. 3. Connector subs116may optionally be provided for coupling upstream ends of the cartridge subs68with an upstream perforating gun. As described above, engaging the cartridge sub68with the downstream perforating gun provides a generally seamless way of forming an electrical connection between adjacent bodies in a perforating string. Moreover, the electrical connection occurs substantially simultaneously with coupling of the cartridge sub68and perforating gun62, so that manually forming electrical connections is unnecessary. Thus by connecting a repeating series of perforating guns62and cartridge subs68, the string115can be formed so that electrical communication extends substantially the length of the string115via contact between successive connectors90and receptacles92.

Further illustrated in the example embodiment ofFIG. 5is a wire line132shown suspending the string of perforating guns62that is controlled from a surface truck134. An optional pulley system136aligns the wire line132above the wellbore93. An attachment sub138is provided on an upper end of the string for attachment and electrical connection between the perforating gun62and wire line132. A power source140and controller142are schematically depicted in communication with the surface truck134. The power source140and controller142also may selectively connect with the wireline132. While shown adjacent the surface truck134, the power source140and controller142may instead be housed in the surface truck134. In one optional embodiment, the controller142can generate and/or send control signals to the perforating gun string115via the wireline132. Thus examples exist wherein each cartridge sub68in the string115, and all components in each cartridge sub68, are in signal communication with the controller142by virtue of the connectivity between the connectors90and receptacles92. Similarly, electricity from the power source140can be delivered throughout the perforating string115and components therein for initiating detonation of the detonators88and bridge plug98.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, the signals may include instructions for selective operation of the switch assemblies, may include electricity, or may be in the form of a pressure wave within a detonation cord. Optionally, instructions may be provided in the switch assemblies, either by storing the instructions in hardware, such as the circuit boards, or by signals traveling in the perforating string. Moreover, the connection embodiments described above may be used for connecting to any ballistic device in a downhole string. Examples include release tools, multiple backoff shots, firing heads, redundant firing heads, severing tools, setting tools, combinations thereof, and the like. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.