Patent Application
20200300593
Not applicable.
Not applicable.
This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present disclosure. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The present disclosure relates to the field of hydrocarbon recovery operations. More specifically, the invention relates to a tandem sub used to mechanically and electrically connect detonation tools in a perforating gun assembly. Further still, the invention relates to an assembly residing within a tandem sub for initiating an explosive charge for a perforating gun, and further, to a detonation assembly that protects the electronics located inside of the tandem sub from wellbore fluid and debris produced by the detonation of charges from an associated perforating gun.
In the drilling of an oil and gas well, a near-vertical wellbore is formed through the earth using a drill bit urged downwardly at a lower end of a drill string. After drilling to a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the formation penetrated by the wellbore.
A cementing operation is conducted in order to fill or “squeeze” the annular volume with cement along part or all of the length of the wellbore. The combination of cement and casing strengthens the wellbore and facilitates the zonal isolation, and subsequent completion, of hydrocarbon-producing pay zones behind the casing.
In connection with the completion of the wellbore, several strings of casing having progressively smaller outer diameters will be cemented into the wellbore. These will include a string of surface casing, one or more strings of intermediate casing, and finally a production casing. The process of drilling and then cementing progressively smaller strings of casing is repeated until the well has reached total depth. In some instances, the final string of casing is a liner, that is, a string of casing that is not tied back to the surface.
Within the last two decades, advances in drilling technology have enabled oil and gas operators to “kick-off” and steer wellbore trajectories from a vertical orientation to a horizontal orientation. The horizontal “leg” of each of these wellbores now often exceeds a length of one mile, and sometimes two or even three miles. This significantly multiplies the wellbore exposure to a target hydrocarbon-bearing formation. The horizontal leg will typically include the production casing.
The wellbore 100 is completed with a first string of casing 120, sometimes referred to as surface casing. The wellbore 100 is further completed with a second string of casing 130, typically referred to as an intermediate casing. In deeper wells, that is, wells completed below 7,500 feet, at least two intermediate strings of casing will be used. In
The wellbore 100 is finally completed with a string of production casing 150. In the view of
It is observed that the annular region around the surface casing 120 is filled with cement 125. The cement (or cement matrix) 125 serves to isolate the wellbore 100 from fresh water zones and potentially porous formations around the casing string 120.
The annular regions around the intermediate casing strings 130, 140 are also filled with cement 135, 145. Similarly, the annular region around the production casing 150 is filled with cement 155. However, the cement 135, 145, 155 is optionally only placed behind the respective casing strings 130, 140, 150 up to the lowest joint of the immediately surrounding casing string. Thus, a non-cemented annular area 132 is typically preserved above the cement matrix 135, a non-cemented annular area 142 may optionally be preserved above the cement matrix 135, and a non-cemented annular area 152 is frequently preserved above the cement matrix 155.
The horizontal leg 156 of the wellbore 100 includes a heel 153 and a toe 154. In this instance, the toe 154 defines the end (or “TD”) of the wellbore 100. In order to enhance the recovery of hydrocarbons, particularly in low-permeability formations 115, the casing 150 along the horizontal section 156 undergoes a process of perforating and fracturing (or in some cases perforating and acidizing). Due to the very long lengths of new horizontal wells, the perforating and formation treatment process is typically carried out in stages.
In one method, a perforating gun assembly 200 is pumped down towards the end of the horizontal leg 156 at the end of a wireline 240. The perforating gun assembly 200 will include a series of perforating guns (shown at 210 in
After perforating, the operator will fracture (or otherwise stimulate) the formation 115 through the perforations (not shown). This is done by pumping treatment fluids into the formation 115 at a pressure above a formation parting pressure. After the fracturing operation is complete, the wireline 240 will be raised and the perforating gun assembly 200 will be positioned at a new location (or “depth”) along the horizontal wellbore 156. A plug (such as plug 112) is set below the perforating gun assembly 200 using a setting tool 116, and new shots are fired in order to create a new set of perforations. Thereafter, treatment fluid is again pumping into the wellbore 100 and into the formation 115 at a pressure above the formation parting pressure. In this way, a second set (or “cluster”) of fractures is formed away from the wellbore 156.
The process of setting a plug, perforating the casing, and fracturing the formation is repeated in multiple stages until the wellbore has been completed, that is, it is ready for production. A string of production tubing (not shown) is then placed in the wellbore to provide a conduit for production fluids to flow up to the surface 105.
In order to provide perforations for the multiple stages without having to pull the perforating gun 200 after every detonation, the perforating gun assembly 200 employs multiple guns in series.
Each perforating gun 210 represents various components. These typically include a “gun barrel” 212 which serves as an outer tubular housing. An uppermost gun barrel 212 is supported by an electric wire (or “e-line”) 240 that extends from the surface 105 and delivers electrical energy down to the tool string 200. Each perforating gun 210 also includes an explosive initiator, or “detonator” (shown at 594 in
The detonator is surrounded by a sensitive explosive material. When current is run through the detonator, a small explosion is set off by the electrically heated resistor. This small explosion sets off an adjacent detonating cord (shown at 595 in
The detonating cord contains an explosive compound that is detonated by the detonator. The detonator, in turn, initiates one or more shots, typically referred to as “shaped charges.” The shaped charges are held in an inner tube, referred to as a carrier tube, for security and discharge through openings 215 in the selected gun barrel 212. The detonating cord propagates an explosion down its length to each of the shaped charges along the carrier tube (shown at 500 in
The perforating gun assembly 200 may include short centralizer subs 220. In addition, tandem subs 225 are used to connect the gun barrel housings 212 end-to-end. Each tandem sub 225 comprises a metal threaded connector placed between the gun barrels 210. Typically, the gun barrels 210 will have female-by-female threaded ends while the tandem sub 225 has opposing male threaded ends.
The perforating gun assembly 200 with its long string of gun barrels (the housings 212 of the perforating guns 210) is carefully assembled at the surface 105, and then lowered into the wellbore 10 at the end of the e-line 240. The e-line 240 extends upward to a control interface (not shown) located at the surface 105. An insulated connection member 230 connects the e-line 240 to the uppermost perforating gun 210. Once the assembly 200 is in place within a wellbore, an operator of the control interface sends electrical signals to the perforating gun assembly 200 for detonating the shaped charges 215 and for creating perforations into the casing 150.
After the casing 150 has been perforated and at least one plug 112 has been set, the setting tool 120 and the perforating gun assembly 200 are taken out of the wellbore 100 and a ball (not shown) is dropped into the wellbore 100 to close the plug 112. When the plug 112 is closed, a fluid (e.g., water, water and sand, fracturing fluid, etc.) is pumped by a pumping system down the wellbore (typically through coiled tubing) for fracturing purposes.
As noted, the above operations may be repeated multiple times for perforating and/or fracturing the casing 150 at multiple locations, corresponding to different stages of the well. Multiple plugs may be used for isolating the respective stages from each other during the perforating phase and/or fracturing phase. When all stages are completed, the plugs are drilled out and the wellbore is cleaned using a circulating tool.
It can be appreciated that a reliable electrical connection must be made between the gun barrels 210 in the tool string 200 through each tandem sub 225. Currently, electrical connections are made using a side entrance port on the tandem sub 225 to manually connect wires. When the charges are fired, the electronics in each carrier tube are lost and the tandem subs are frequently sacrificed.
A need exists for a detonation system wherein the electronic switch is housed within the tandem sub such that the wiring connections may be pre-assembled before the perforating guns are delivered to the field. A need further exists for a detonation system utilizing a tandem sub having a carrier end plate and a dart, wherein the dart and end plate mechanically and fluidically seal off the tandem sub from wellbore fluids and debris following detonation of explosive charges in an associated perforating gun.
A detonation system for a perforating gun assembly is provided. The detonation system utilizes an electronic switch assembly that transmits signals to a detonator in a perforating gun. The detonator, in turn, ignites an explosive material, creating an explosion that is passed through a detonating cord. The detonating cord then ignites the shaped charges along the perforating gun.
The detonation system first includes a tandem sub. The tandem sub defines a short tubular body having a first end and a second opposing end. A circular shoulder may be provided intermediate the first and second ends. The first and second ends comprise male threads that are configured to connect to the gun barrel of adjacent perforating guns. The gun barrels are threaded onto the opposing ends of the tandem sub until they reach the intermediate shoulder.
As noted, the detonation system also includes the switch assembly. The switch assembly includes an addressable switch. Beneficially, the switch assembly with its addressable switch resides entirely within the tandem sub located adjacent to the perforating gun being fired.
The detonation system also comprises an inner bore within the tandem sub. The inner bore extends from the first end of the tandem sub to the second opposing end. The electronic switch assembly resides within the inner bore of the tandem sub proximate the first end.
The detonation system additionally comprises a contact pin. The contact pin also resides within the inner bore of the tandem sub. The contact pin has a head that extends from a bulkhead and into the electronic switch assembly. The contact pin is fabricated substantially from a conductive material, and is configured to receive instruction signals from the surface.
The detonation system also has an end plate. The end plate resides between the carrier tube of a connected perforating gun, and the tandem sub. The end plate includes an inner conduit having an angled surface. Of interest, the inner bore of the tandem sub receives one or more wires from the electronic switch assembly, passing them through the inner conduit en route to the carrier tube.
The detonation system further comprises a detonator. The detonator resides within the carrier tube and is in electrical communication with the electronic switch assembly by means of the one or more wires. The detonator receives a detonation signal from the electronic switch assembly by means of the wires. Heat is generated within the detonator as described above, igniting an explosive material within an adjacent detonating cord. The detonator and detonating cord reside in the perforating gun. The detonating cord connects to explosives associated with shaped charges along the carrier tube.
The detonation system additionally includes a dart. The dart comprises a base portion and a tip. The base portion defines an outer diameter that is greater than the inner conduit of the end plate, but with the tip extending at least partially into the inner conduit. Of interest, the dart is configured to seal against the inner conduit of the end plate in response to a pressure wave generated by detonation of the one or more charges in the perforating gun. In this way, the electronic switch assembly and tandem sub are protected from the pressure wave and may be used again as part of a subsequent perforating operation, with minimal cleaning.
The perforating gun comprises a gun barrel threadedly connected to the tandem sub at the first end of the tandem sub, and a carrier tube residing within the gun barrel. The carrier tube carries the shaped charges used in the formation of perforations.
In one embodiment, the detonation system also includes a dart retainer. The dart retainer resides within the carrier tube adjacent the end plate. The dart retainer defines a tubular body having an inner diameter. The inner diameter is dimensioned to slideably hold at least a portion of the base of the dart before the charges are detonated.
In another embodiment, the detonation system comprises a tubular stem. The tubular stem has an inner diameter and an outer diameter. A first end of the stem is threadedly connected to the end plate, aligning the inner diameter of the stem with the conduit of the end plate. A head of the contact pin extends into the inner diameter of the stem, while the addressable switch resides along the outer diameter of the stem. Note that the stem itself resides within the bore of the tandem sub proximate the first end.
In the detonation system, the gun barrel may be downstream of the tandem sub. Alternatively and more preferably, the gun barrel is upstream of the tandem sub. In either instance, the tandem sub preferably and uniquely has no intermediate port.
In operation, the detonation system is part of the perforating gun assembly. The perforating gun assembly is run into a wellbore at the end of an electric line. More specifically, the perforating gun assembly is pumped into the horizontal portion of the wellbore. The contact pin is in electrical communication with the e-line, with the e-line extending from the perforating gun assembly up to the surface. When a signal is sent through the e-line, it is carried through the perforating gun assembly by means of the signal line residing within the string of perforating guns and tandem subs.
The addressable switch filters instruction signals from the operator at the surface. When the addressable switch receives a signal associated with its perforating gun, the addressable switch will send a detonation signal through one or more wires and back up to the detonator. The detonator, in turn, ignites the explosive material that passes through the detonating cord and on to the charges along the carrier tube.
In addition to the detonation system, a tandem sub for a perforating gun assembly is also provided herein. The tandem sub comprises a first end and an opposing second end. The first end represents a male connector and is threadedly connected to a first perforating gun. Similarly, the second end represents a male connector and is threadedly connected to a second perforating gun.
The first end abuts a first end plate while the second end abuts a second end plate. An inner bore extends between the first end of the tandem sub and the second end.
An electronic switch assembly resides within the inner bore at the first end of the tandem sub. The switch assembly comprises an addressable switch configured to receive instruction signals from an operator at the surface. In addition, a receptacle is positioned within the inner bore of the tandem sub proximate the second end. The receptacle is dimensioned to closely receive a bulkhead, wherein the bulkhead comprises:
The contact pin is fabricated substantially from a conductive material. The contact head transmits instruction signals from the electric line to a downstream perforating gun, and more particularly to the addressable switches located within downstream perforating guns. When an instruction signal is recognized by an addressable switch, the addressable switch will send a detonation signal to an associated detonator.
In one aspect, the first end plate comprises a bore that represents a first internal chamber formed at a first end of the end plate, and a second internal chamber formed at a second end of the end plate. A conduit connects the first internal chamber to the second internal chamber. One or more wires pass from the addressable switch, back up through the bore, and to a detonator residing within the first perforating gun. The detonator is configured to receive a detonation signal from the addressable switch.
As noted above, the detonator defines a small aluminum housing having a resistor inside. The resister is surrounded by a sensitive explosive material. When current is run through the detonator, a small explosion is set off by the electrically heated resistor. This small explosion ignites an explosive material placed within the detonating cord. As the explosive material is ignited, the detonating cord delivers the explosion to shaped charges along the first perforating gun.
In a preferred embodiment, a dart resides in the first internal chamber of the first end plate and opposite the switch assembly. The dart further comprises a base located in the first internal chamber, with the base having a diameter that is larger than the conduit. This prevents the dart from traversing through the conduit following detonation of the shaped charges in the first perforating gun. The dart also has a tip that extends at least partially into the conduit between the first and second internal chambers.
So that the manner in which the present inventions can be better understood, certain illustrations, charts and/or flow charts are appended hereto. It is to be noted, however, that the drawings illustrate only selected embodiments of the inventions and are therefore not to be considered limiting of scope, for the inventions may admit to other equally effective embodiments and applications.
For purposes of the present application, it will be understood that the term “hydrocarbon” refers to an organic compound that includes primarily, if not exclusively, the elements hydrogen and carbon. Hydrocarbons may also include other elements, such as, but not limited to, halogens, metallic elements, nitrogen, carbon dioxide, and/or sulfuric components such as hydrogen sulfide.
As used herein, the terms “produced fluids,” “reservoir fluids” and “production fluids” refer to liquids and/or gases removed from a subsurface formation, including, for example, an organic-rich rock formation. Produced fluids may include both hydrocarbon fluids and non-hydrocarbon fluids. Production fluids may include, but are not limited to, oil, natural gas, pyrolyzed shale oil, synthesis gas, a pyrolysis product of coal, nitrogen, carbon dioxide, hydrogen sulfide and water.
As used herein, the term “fluid” refers to gases, liquids, and combinations of gases and liquids, as well as to combinations of gases and solids, combinations of liquids and solids, and combinations of gases, liquids, and solids.
As used herein, the term “subsurface” refers to geologic strata occurring below the earth's surface.
As used herein, the term “formation” refers to any definable subsurface region regardless of size. The formation may contain one or more hydrocarbon-containing layers, one or more non-hydrocarbon containing layers, an overburden, and/or an underburden of any geologic formation. A formation can refer to a single set of related geologic strata of a specific rock type, or to a set of geologic strata of different rock types that contribute to or are encountered in, for example, without limitation, (i) the creation, generation and/or entrapment of hydrocarbons or minerals, and (ii) the execution of processes used to extract hydrocarbons or minerals from the subsurface region.
As used herein, the term “wellbore” refers to a hole in the subsurface made by drilling or insertion of a conduit into the subsurface. A wellbore may have a substantially circular cross section, or other cross-sectional shapes. The term “well,” when referring to an opening in the formation, may be used interchangeably with the term “wellbore.”
Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment.
The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention; instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to attaching two perforating guns to each other through a tandem sub. In the following, the terms “upstream” and “downstream” are being used to indicate that one gun barrel may be situated above and one below, respectively. However, one skilled in the art would understand that the invention is not limited only to the upstream gun or only to the downstream gun, but in fact can be applied to either gun. In other words, the terms “upstream” and “downstream” are not necessarily used in a restrictive manner, but only to indicate, in a specific embodiment, the relative positions of perforating guns or other components.
Each perforating gun 310 comprises a tubular housing having first and second opposing ends. Each end comprises female threads 315. In the view of
An electronic switch 332 is located inside the tandem sub 325. The switch 332 is electrically connected through signal line 334 to the e-wireline (shown at 240 in
Where a series of gun barrels is used in a perforating gun assembly 200, the signal from the wireline 240 will be transmitted through the series of gun barrels 210, 210′, etc. and a corresponding contact pins (shown at 570 in
The switches “listen” for a detonation signal sent through the signal line 334/336. When a detonation signal is received, the switch 332 sends a corresponding detonation signal through the line 334 to the detonator (not shown) for activating a shaped charge 330 (also shown at 520 in
In
Thus, it is desirable to have a detonation system wherein the inside electronics are protected from the debris and wellbore fluids generated by the pressure wave caused by the detonation of the downstream charges so that, after a perforating process is completed, both the tandem sub 325 and its electronics 332 can be reused. It is also desirable to provide a novel tandem sub having an inner bore that houses the electronic switch assembly, coupled with a novel end plate that receives a sealing dart. This may be referred to herein as a sealed explosive initiation assembly.
The tandem sub 400 includes externally machined threads 404. The threads 404 are male threads dimensioned to mate with female threaded ends 315 of a gun barrel housing, such as perforating guns 310, 310′ of
Interestingly, if the operator begins having multiple misruns due to a problem with the detonator, then the portless tandem sub 400 (and internal electronic assembly 550 and dart 700, described below) allow the operator to switch to a new batch number, or even to switch vendors completely. The detonation system of the present invention also allows the operator to select the gun lengths, shot densities and phasing that are available on the market. Thus, a plug-n-play system that may be used with perf guns from different vendors is provided.
Intermediate the length of the tandem sub 400 and between the threads 404 is a shoulder 406. The shoulder 406 serves as a stop member as the tandem sub 400 is screwed into the end 317 of a gun barrel 310. Optionally, grooves 407 are formed equi-radially around the shoulder 406. The grooves 407 cooperate with a tool (not shown) used for applying a rotational force to the tandem sub 400 without harming the rugosity of the shoulder 406.
The tandem sub 400 includes a central bore 405. As will be described in greater detail below, the bore 405 is dimensioned to hold novel electronics associated with a perforating gun assembly 210. Such electronics represent an electronic switch assembly as shown at 550 in
An electronic detonator and a detonating cord (shown at 594 and 595 in
The stem 540 is preferably fabricated from steel or other durable metal. The stem 540 extends from the bottom end plate 524 of the perforating gun assembly 600. As seen in
A wiring board 554 is provided along the stem 540 opposite the addressable switch 552. The wiring board 554 may be a circuit board, or more preferably is a simple 3-pin push connector. Communication wires 556 extend from the circuit board 554 to the addressable switch 552. These wires 556 are received from an upstream detonator 594 as shown more fully in
A separate communications wire 597 extends from the addressable switch 552. The communications wire 597 provides signals for the “next” selection gun as a signal line.
A separate communications wire 597 extends from the addressable switch 552. The communications wire 597 provides signals for the “next” selection gun.
Also visible in
The switch assembly 550 of
Of interest, a base 704 is seen extending out of the dart retainer 710. The base 704 is actually a lower end of a dart sleeve. The dart sleeve is shown at 706 in
A detonator block 592 is shown above the dart retainer 710. The detonator block 592 holds a detonator (shown at 594 in
Returning to
As shown in
As observed in connection with
In operation, the dart 700 is loosely placed in the first internal chamber 523 so that the tip 705 is located partially inside the conduit 521, i.e., between the first 523 and second 527 chambers. The one or more wires 556 extend from the addressable switch 552, through the conduit 521, out of the first internal chamber 523, into the carrier tube 500, and to the detonator 594. The one or more wires 556 pass along an exterior of the dart 700, held closely to the dart 700 by the dart retainer 710. Note that when charges 520 are detonated and the dart 700 seals against the conduit 521, the wires 556 will be pinched and severed.
A detonator assembly 590 is seen in the upstream gun barrel 212. The detonator assembly 590 includes the detonator block 592, the detonating cord 595 and the detonator 594 itself. At the same time, the electronic switch assembly 550 resides within the tandem sub 400, and more particularly within a bore of the tandem sub 400.
The bottom end plate 524 is shown between the upstream gun barrel 212 and the tandem sub 400. The dart retainer 710 is also visible along with the dart 700. It can be seen that the base portion 702 of the dart 700 resides along the dart retainer 710 but the tip 705 extends into the bottom end plate 524. An inner diameter (or conduit 521) of the bottom end plate 524 is dimensioned to prevent the base portion 702 of the dart 700 from passing through to the tandem sub 400. This protects the switch assembly 550 upon detonation of the charges 520 in the upstream gun barrel 212. Note that in this view the dart 570 is shown in a somewhat deformed state for illustrative purposes.
It is understood that the relative arrangement of the gun barrel 212, the bottom end plate 524, the dart 700, the electronic switch assembly 550 and all other components of the perforating gun assembly 600 may be “flipped.” In this way, the switch assembly 550 is protected from a pressure wave upon detonation of charges in a downstream gun barrel 212′ by use of the dart 700.
In
In operation, a detonation signal is sent from the surface 105 through the electric line 240. The signal reaches the electrical contact pin 570 by means of a signal wire. The contact pin 570 is fabricated from an electrically conductive material and transmits the detonation signal to an addressable switch 552. The electrical contact pin 570 resides within the tandem sub 400, with the contact head 572 extending into the stem 540. The contact head 572 is caused to contact the proximal contact pin 560 (shown in
The pressure wave from the charges acts against the dart 700, causing it to deform against an angled inner surface (shown at 529 in
As can be seen, a novel detonation system is provided. The detonation system provides protection for the electronics within the tandem sub during detonation of an upstream (or adjacent) perforating gun. In one embodiment, the detonation system first includes the novel tandem sub. The tandem sub defines a generally tubular body having a first end and a second end. The first end and the second end each comprise male connectors. This allows the tandem sub to be threadedly connected, in series, to respective perforating guns. Thus, the first end is threadedly connected to a first perforating gun (or, more precisely, a female threaded end of a gun barrel), while the second end is threadedly connected to a second perforating gun (or, again, a female threaded end of a gun barrel).
Beneficially, the tandem sub 400 need not have a wiring port. Removing the port from the sub eliminates problems associated with known ports such as gun-flooding due to a missing o-ring and pinched wires under the plug port. The detonator is installed later in the field to comply with DOT and ATF regulations and API-RP67 recommendations.
The first end of the tandem sub abuts a first (or bottom) end plate. Similarly, the second opposing end of the tandem sub abuts a second (or top) end plate. These may be in accordance with the bottom 524 and top 522 end plates described above. An inner bore is formed between the first end and the second end of the tandem sub. Detonation and signal wires from the tandem sub extend up through the bottom end plate.
An electronic switch assembly resides within the inner bore at the first end of the tandem sub. The switch assembly comprises an addressable switch configured to receive instruction signals from an operator at the surface.
In addition, a receptacle is formed within the inner bore of the tandem sub. The receptacle is dimensioned to closely receive a bulkhead. The bulkhead comprises:
The electrical contact pin and its contact head are fabricated substantially from a conductive material such as brass. The contact pin permits instruction signals to be transmitted from the tandem sub down to a next (downstream) perforating gun.
The first end plate comprises a bore that defines a first internal chamber formed at a first end of the end plate, a second internal chamber formed at a second end of the end plate, and a conduit connecting the first internal chamber to the second internal chamber.
One or more wires pass from the addressable switch, through the conduit of the first end plate, and to a detonator residing within the first perforating gun. The detonator is configured to receive detonation signals from the addressable switch, and ignite an explosive material within a detonating cord. The explosive material travels to shaped charges associated with the first perforating gun to ignite the charges. Thus, the tandem sub is an electrical feed-thru, pressure barrier that has been configured to allow room for a switch assembly.
All electrical connections for the detonation system may be made at the gun building facility, that is, except for the wires being connected to the detonator. The end plate on the gun barrel (or gun carrier) is removed, and the pre-wired electronic switch assembly is installed. Beneficially, the pre-wired switch assembly can be tested at the gun building facility to reduce the chance of a mis-wired connection.
A dart resides in the first internal chamber of the first end plate, opposite the switch assembly. The dart has a tip that extends at least partially into the conduit between the first and second internal chambers. The dart further comprises a base located in the first internal chamber. The base has a diameter that is larger than the conduit. The dimension of the base prevents the dart from traversing through the conduit following detonation of the shaped charges.
In addition to the detonation system discussed above, a method of detonating explosive charges associated with a perforating gun is presented herein.
The method 2100 first comprises placing an electronic switch assembly into a chamber of a tandem sub. This is provided in Box 2110.
The method 2100 next includes attaching the tandem sub to a downstream perforating gun. This is indicated at Box 2120.
The method 2100 also includes providing an end plate at a top end of the tandem sub. The end plate will reside between the tandem sub and an upstream perforating gun. This is shown at Box 2130. The end plate is preferably a bottom end plate as it resides at the bottom of the upstream perforating gun.
The method 2100 further comprises providing a dart to an internal chamber of the end plate. This is shown at Box 2140. In the step of Box 2140, the dart is configured to seal an inner conduit that would otherwise be in fluid communication with the chamber of the tandem sub. In this way, a pressure wave generated by detonation of charges associated with the upstream perforating gun does not propagate into the tandem sub or damage the switch assembly. Note that the step of Box 2140 is broad enough to include using a dart retainer adjacent the end plate, with the dart sealing a conduit through the dart retainer.
The method 2100 also includes attaching the tandem sub to the upstream perforating gun. This is indicated at Box 2150. Stated another way, the upstream perforating gun is attached to the tandem sub at an end opposite the downstream perforating gun. A perforating gun assembly is thus formed.
In practice, the electronic switch assembly may be installed onto a bottom end plate, which is connected to a charge carrier tube, which in turn is housed in a gun barrel with the dart. The tandem sub is then installed onto the gun barrel with the internal bore of the tandem sub enclosing over the electronic switch assembly.
The method 2100 further comprises pumping the perforating guns and tandem sub into a wellbore. This is seen at Box 2160. Preferably, the perforating gun assembly is pumped into the horizontal portion of the wellbore for perforating casing.
The method 2100 then includes activating the upstream perforating gun without damaging the electronic switch assembly in the tandem sub. This is provided in Box 2170. Activating the upstream perforating gun means that charges associated with the upstream perforating gun are detonated in response to a charge signal sent to a detonator within the perforating gun.
In operation, the operator will send a control signal from the surface, down the e-line (such as e-line 240 of
The charges in the upstream perforating gun are detonated. Due to the soft characteristic of the material from which the dart is made, the dart will deform to fully occupy a portion of the inner conduit. Although the power and control wires passing through the conduit are severed during this process, the integrity of the switch assembly in the tandem sub is preserved and, thus, the switch assembly may be reused for another perforation operation. Similarly, the contact pin, the bulkhead, and the tandem sub itself are protected for later re-use.
Before the detonation of the upstream perforating gun, the electronic switch can feed current down to a next perforating gun (or to a bulkhead associated with a next perforating gun), depending on the instruction.
The disclosed embodiments provide methods and systems for preventing electronics located inside a switch sub from being damaged by detonation of an adjacent perforating gun. It should be understood that this description is not intended to limit the invention; on the contrary, the exemplary embodiments are intended to cover alternatives, modifications, and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
Further, variations of the detonation system and of methods for using the detonation system within a wellbore may fall within the spirit of the claims, below. It will be appreciated that the inventions are susceptible to other modifications, variations, and changes without departing from the spirit thereof.
The present application is filed as a Continuation-In-Part of U.S. Ser. No. 15/808,290 filed Nov. 9, 2017. That application is entitled “Switch Sub With Two Way Sealing Features and Method.” The '290 application claimed the benefit of U.S. Ser. No. 62/423,648 filed Nov. 17, 2016. That application is entitled “Switch Sub.” The present application further claims the benefit of U.S. Ser. No. 62/890,242 filed Aug. 22, 2019. That application is entitled “Explosive Initiation Assembly For a Tandem Sub.” This application further claims the benefit of U.S. Ser. No. 62/987,743 filed Mar. 10, 2020. That application is entitled “Detonation System Having Sealed Explosive Initiation Assembly.” The present application is also filed as a Continuation-In-Part of U.S. Ser. No. 16/838,193 filed Mar. 31, 2020. That application is entitled “A Bulkhead Assembly for a Tandem Sub, and an Improved Tandem Sub.” Each of these applications is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62423648 | Nov 2016 | US | |
| 62890242 | Aug 2019 | US | |
| 62987743 | Mar 2020 | US | |
| 62845692 | May 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15808290 | Nov 2017 | US |
| Child | 16894512 | US | |
| Parent | 16836193 | Mar 2020 | US |
| Child | 15808290 | US |
