Patent Description:
Generally, when completing a subterranean well for the production of fluids, minerals, or gases from underground reservoirs, several types of tubulars are placed downhole as part of the drilling, exploration, and completions process. These tubulars can include casing, tubing, pipes, liners, and devices conveyed downhole by tubulars of various types. Each well is unique, so combinations of different tubulars may be lowered into a well for a multitude of purposes.

A subsurface or subterranean well transits one or more formations. The formation is a body of rock or strata that contains one or more compositions. The formation is treated as a continuous body. Within the formation hydrocarbon deposits may exist. Typically a wellbore will be drilled from a surface location, placing a hole into a formation of interest. Completion equipment will be put into place, including casing, tubing, and other downhole equipment as needed. Perforating the casing and the formation with a perforating gun is a well-known method in the art for accessing hydrocarbon deposits within a formation from a wellbore.

Explosively perforating the formation using a shaped charge is a widely known method for completing an oil well. A shaped charge is a term of art for a device that when detonated generates a focused output, high energy output, and/or high velocity jet. This is achieved in part by the geometry of the explosive in conjunction with an adjacent liner. Generally, a shaped charge includes a metal case that contains an explosive material with a concave shape, which has a thin metal liner on the inner surface. Many materials are used for the liner; some of the more common metals include brass, copper, tungsten, and lead. When the explosive detonates, the liner metal is compressed into a super-heated, super pressurized jet that can penetrate metal, concrete, and rock. Perforating charges are typically used in groups. These groups of perforating charges are typically held together in an assembly called a perforating gun. Perforating guns come in many styles, such as strip guns, capsule guns, port plug guns, and expendable hollow carrier guns.

Perforating charges are typically detonated by detonating cord in proximity to a priming hole at the apex of each charge case. Typically, the detonating cord terminates proximate to the ends of the perforating gun. In this arrangement, an initiator at one end of the perforating gun can detonate all of the perforating charges in the gun and continue a ballistic transfer to the opposite end of the gun. In this fashion, numerous perforating guns can be connected end to end with a single initiator detonating all of them.

The detonating cord is typically detonated by an initiator triggered by a firing head. The firing head can be actuated in many ways, including but not limited to electronically, hydraulically, and mechanically.

Expendable hollow carrier perforating guns are typically manufactured from standard sizes of steel pipe with a box end having internal/female threads at each end. Pin ended adapters, or subs, having male/external threads are threaded one or both ends of the gun. These subs can connect perforating guns together, connect perforating guns to other tools such as setting tools and collar locators, and connect firing heads to perforating guns. Subs often house electronic, mechanical, or ballistic components used to activate or otherwise control perforating guns and other components.

Perforating guns typically have a cylindrical gun body and a charge tube, or loading tube that holds the perforating charges. The gun body typically is composed of metal and is cylindrical in shape. Charge tubes can be formed as tubes, strips, or chains. The charge tubes will contain cutouts called charge holes to house the shaped charges.

It is generally preferable to reduce the total length of any tools to be introduced into a wellbore. Among other potential benefits, reduced tool length reduces the length of the lubricator necessary to introduce the tools into a wellbore under pressure. Additionally, reduced tool length is also desirable to accommodate turns in a highly deviated or horizontal well. It is also generally preferable to reduce the tool assembly that must be performed at the well site because the well site is often a harsh environment with numerous distractions and demands on the workers on site.

Electric initiators are commonly used in the oil and gas industry for initiating different energetic devices down hole. Most commonly, <NUM>-ohm resistor initiators are used. Other initiators and electronic switch configurations are common.

Modular or "plug and play" perforating gun systems have become increasingly popular in recent years due to the ease of assembly, efficiencies gained, and reduced human error. Most of the existing plug and play systems either (<NUM>) utilize a wired in switch and/or detonator, or (<NUM>) require an initiating "cartridge" that houses the detonator, switch, electrical contacts and possibly a pressure bulkhead. The wired in switch/detonator option is less desirable, because the gun assembler must make wire connections which is prone to human error. The initiating cartridge option is less desirable because the cartridge can be a large explosive device - in comparison to a standard detonator - thus takes up additional magazine space at the user facility. There is a need for a modular perforating system in which no wire connections are required by the user AND the switch and pressure bulkhead are in pre-assembled in the gun assembly rather than in the initiating cartridge. The detonator for the proposed system has no wires and allows for simple arming by the user in the field <CIT> discloses a prior art perforating gun system.

The application discloses a perforating gun system according to claim <NUM>. Preferred embodiments are disclosed in dependent claims <NUM>-<NUM>.

The application further discloses a pre-wired shaped charge loading tube assembly according to claim <NUM>. Preferred embodiments are disclosed in dependent claims <NUM>-<NUM>.

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference numbers designate like or similar elements throughout the several figures of the drawing.

In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus, systems and method steps described herein may be used alone or in combination with other apparatus, systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.

Terms such as booster may include a small metal tube containing secondary high explosives that are crimped onto the end of detonating cord. The explosive component is designed to provide reliable detonation transfer between perforating guns or other explosive devices, and often serves as an auxiliary explosive charge to ensure detonation.

Detonating cord is a cord containing high-explosive material sheathed in a flexible outer case, which is used to connect the detonator to the main high explosive, such as a shaped charge. This provides an extremely rapid initiation sequence that can be used to fire several shaped charges simultaneously.

A detonator or initiation device may include a device containing primary high-explosive material that is used to initiate an explosive sequence, including one or more shaped charges. Two common types may include electrical detonators and percussion detonators. Detonators may be referred to as initiators. Electrical detonators have a fuse material that burns when high voltage is applied to initiate the primary high explosive. Percussion detonators contain abrasive grit and primary high explosive in a sealed container that is activated by a firing pin. The impact of the firing pin is sufficient to initiate the ballistic sequence that is then transmitted to the detonating cord.

An example embodiment may comprise a modular perforating gun system in which the selective switch is embodied in the end fitting of the loading tube assembly of the perforating gun. The top or bottom end fitting is designed to hold a selective switch, a feed through contact and orifices to insert the detonator from one end and the detonating cord from the other. The opposite end fitting is designed to connect to a pressure bulkhead containing the feed through contact. Ground is made through charge tube to the end fitting to bulkhead to baffle to gun body. The loading tube is prewired and terminated to the pressure bulkhead feed through contact at one end and the selective switch at the other end. The gun carrier is box by pin with bottom of gun carrier having a swaged and threaded end. Alternatively, may have a thin shoulder pin-pin tandem sub.

An example embodiment is shown in <FIG>. The example embodiment includes a perforating gun assembly <NUM> having a cylindrical body, in this case gun carrier <NUM>, with a lower end <NUM> and an upper end <NUM>. A baffle <NUM> with a pressure bulkhead bottom contact <NUM> disposed therein is further coupled to the lower end <NUM> of the cylindrical body <NUM>.

A charge tube <NUM> is loaded with shaped charges <NUM> and disposed within, and coupled to, the gun carrier <NUM>. In this example embodiment the charge tube <NUM> is pre-wired. The baffle <NUM> is adjacent to the bottom end fitting <NUM> which is coupled to the lower end <NUM> of the charge tube <NUM>. A charge tube is also known as a loading tube. The charge tube <NUM> has loading tube cutouts <NUM> located proximate to the lower end <NUM> and loading tube cutouts <NUM> located proximate to the upper end <NUM>. The charge tube <NUM> has a bottom end fitting <NUM> located proximate to the lower end <NUM> and a top end fitting <NUM> located proximate to the upper end <NUM>. A locking means for shaped charges <NUM> may include the tabs <NUM> located on shaped charges <NUM>. A detonator cord locking means may include the retainer fitting <NUM> located on the end of the shaped charges <NUM>. The selective switch <NUM> is grounded to the cylindrical body via ground wire <NUM> coupled to grounding screw <NUM>. Electrical conductor <NUM> is used to send signals through perforating gun <NUM> and is pre-wired into the charge tube <NUM>. Electrical conductor <NUM> is insulated from the cylindrical body <NUM>, which is conductive and acts as a ground. A detonating cord <NUM> is coupled to each of the shaped charges <NUM>. A ground wire <NUM> from the selective switch <NUM> is coupled to the case gun carrier <NUM> via fastener <NUM>.

The top end fitting <NUM> includes a selective switch <NUM>, a wireless detonator <NUM>, a detonating cord orifice <NUM>, and a top contact <NUM>. A closer view of top end fitting <NUM> is shown in <FIG>. The ground lug <NUM> allows the selective switch <NUM> to be grounded to the charge tube <NUM>. The selective switch <NUM> is connected to the wireless detonator <NUM> via the detonator connector receptacle <NUM>. The detonator connector receptacle <NUM> has an auto-shunting feature whereby the wireless detonator <NUM> is shunted until the correct connector is inserted. A detonating cord <NUM> wraps around the outside of the charge tube <NUM>, connecting to all of the shaped charges <NUM> via connectors <NUM>, and terminates within the charge tube <NUM>, through the loading tube cutout <NUM>, and into the detonating cord orifice <NUM>, which is located proximate to the wireless detonator <NUM>. The detonating cord <NUM> may be located in an end-to-end or side-by-side configuration with the wireless detonator <NUM>.

The lower end <NUM> of the perforating gun assembly <NUM> is shown in <FIG> including a baffle <NUM> coupled to the lower end <NUM> and located proximate to the lower end fitting <NUM>. The pressure bulkhead bottom contact <NUM> is coupled to an insulated wire <NUM>. The loading tube <NUM> includes shaped charges <NUM> having locking tabs <NUM> for locking into the loading tube <NUM>. The shaped charges <NUM> have detonating cord locking clips <NUM> that couple to a detonating cord <NUM> wrapped along the outside of the loading tube <NUM>.

Two perforating guns, a lower gun <NUM> and an upper gun <NUM> are shown in <FIG> and <FIG> depicting a close up of the gun-to-gun connection. The two perforating guns <NUM> and <NUM> are configured similarly and this example embodiment shows how the guns are coupled together. The perforating gun <NUM> has a charge tube <NUM> located within a cylindrical body <NUM>. The charge tube <NUM> contains shaped charges <NUM> coupled to detonating cord <NUM> and an upper end fitting <NUM>. Upper end fitting <NUM> contains a selective switch <NUM> coupled to a wireless detonator <NUM>, which is further located adjacent to a detonating cord orifice <NUM>. The upper contact <NUM> couples to the pressure bulkhead bottom contact <NUM> of perforating gun <NUM>. Pressure Bulkhead bottom contact <NUM> is disposed within and coupled to bottom end fitting <NUM>. Perforating gun <NUM> also contains a charge tube <NUM> located within a cylindrical body <NUM> and containing perforating charges <NUM> coupled to detonating cord <NUM>. Perforating gun <NUM> also has an upper fitting <NUM> that contains a selective switch <NUM> coupled to a wireless detonator <NUM>, which is further located adjacent to a detonating cord orifice <NUM>. Upper connector <NUM> couples to the pressure bulkhead bottom contact of a possible third perforating gun. Electrical conductor <NUM> is used to send signals through perforating gun <NUM> and is pre-wired into charge tube. Electrical conductor <NUM> is insulated from the cylindrical body <NUM>, which is conductive and acts as a ground. The selective switch <NUM> is grounded to the cylindrical body via ground wire <NUM> coupled to grounding screw <NUM>. Electrical conductor <NUM> is used to send signals through perforating gun <NUM> and is pre-wired into charge tube. Electrical conductor <NUM> is insulated from the cylindrical body <NUM>, which is conductive and acts as a ground. The selective switch <NUM> is grounded to the cylindrical body via ground wire <NUM> coupled to grounding screw <NUM>.

Two perforating guns, a lower gun <NUM> and an upper gun <NUM> are shown in <FIG> depicting a close up of the gun-to-gun connection. The two perforating guns <NUM> and <NUM> are configured similarly and this example embodiment shows how the guns are coupled together. The perforating gun <NUM> has a charge tube <NUM> located within a cylindrical body <NUM>. The charge tube <NUM> contains shaped charges <NUM> coupled to detonating cord <NUM> and an upper end fitting <NUM>. Upper end fitting <NUM> contains a selective switch <NUM> coupled to a wireless detonator <NUM>, which is further located adjacent to a detonating cord orifice <NUM>. Electrical contact <NUM> electrically couples the electrical conductor <NUM> with the upper contact <NUM>. Ground spring <NUM> electrically grounds the selective switch <NUM> to the cylindrical body <NUM> in the ground recess <NUM>. The upper contact <NUM> couples to the pressure bulkhead bottom contact <NUM> of perforating gun <NUM>. Pressure Bulkhead bottom contact <NUM> is disposed within and coupled to bottom end fitting <NUM>. Perforating gun <NUM> also contains a charge tube <NUM> located within a cylindrical body <NUM> and containing perforating charges <NUM> coupled to detonating cord <NUM>. Perforating gun <NUM> also has an upper fitting <NUM> that contains a selective switch <NUM> coupled to a wireless detonator <NUM>, which is further located adjacent to a detonating cord orifice <NUM>. Electrical conductor <NUM> is used to send signals through perforating gun <NUM> and is pre-wired into charge tube. Electrical conductor <NUM> is insulated from the cylindrical body <NUM>. Electrical conductor <NUM> is used to send signals through perforating gun <NUM> and is pre-wired into charge tube. Electrical conductor <NUM> is insulated from the cylindrical body <NUM>, which is conductive and acts as a ground. Electrical contact <NUM> electrically couples the electrical conductor <NUM> with the upper contact <NUM>. Ground spring <NUM> electrically grounds the selective switch <NUM> to the cylindrical body <NUM> in the ground recess <NUM>. In this example embodiment the detonating cord <NUM> is coupled to detonating cord orifice <NUM>, which is in a side-by-side configuration relative to the 1ireless detonator <NUM>. In this example embodiment the detonating cord <NUM> is coupled to detonating cord orifice <NUM>, which is in a side-by-side configuration relative to the wireless detonator <NUM>.

Wireless detonator, as used in this specification, is defined as a detonator that is pre-wired prior to installation and does not require any wiring in the field to function. This wireless capability allows the detonator to become effectively a plug-and-play device that establishes the necessary electrical connections for its function by plugging it into the perforating gun.

The example embodiments disclose a modular gun system that is a box by pin design consisting of a steel loading tube with an end fitting pre-installed at each end. One end fitting centers and orients the loading tube and embodies a selective switch, feed through contact and orifices to insert a wireless detonator from the outer end and detonating cord into the inner end.

The loading tube is pre-wired with insulated wire which is terminated at the selective switch in one end fitting and the pressure bulkhead at the opposite end. The opposite end fitting centers the loading tube and provides electrical contact from the pre-installed insulated wire on the loading tube to the pressure bulkhead contact adjacent to the end fitting. The pressure bulkhead is pre-installed into a baffle in the pin end of the gun carrier. The selective switch is grounded to the loading tube which is electrically connected to the baffle which is threaded into the gun carrier.

Charges are inserted into the loading tube and held in place by locking features fixed to the shaped charge. Detonating cord is inserted into the back of each charge via locking features fixed to the shaped charge. The detonating cord terminates into the detonating cord orifice in the end fitting. A wireless detonator is inserted into the end fitting from outside of the gun assembly such that the explosive load end of the detonator is adjacent to the detonating cord in an end to end position. The wireless detonator has an auto-shunting feature that does not un-shunt until a mating receptacle is inserted.

The selective switch has a ribbon pigtail with the un-shunting receptacle attached. After inserting the wireless detonator, the connector receptacle connected to the switch is attached to the end of the detonator, disengaging the shunt of the detonator. The loaded and armed modular gun assemblies are screwed together such that the top contact makes electrical contact to the bottom contact of the adjacent gun assembly. The box by pin gun configuration is accomplished by swaging and threading the outer diameter of one end of the gun. Alternatively, the pin end is accomplished by installing a pin by pin tandem sub into one box end of a box by box gun body.

The end fitting is purposefully designed via a mold or machining method to house a selective switch designed to selectively initiate the detonator of a perforating gun. The end fitting is pre-assembled with a spring-loaded top contact wired to the input of the selective switch. The end fitting is pre-assembled such that the through wire of the selective switch is connected to the insulated wire pre-installed onto the loading tube. The end fitting is pre-assembled such that the output wires of the selective switch are insulated ribbon or wires which has the detonator connector receptacle affixed to its end. The end fitting is purposefully designed via a mold or machining method to insert detonating cord through the inner end and a detonator from the outer end such that the detonator is adjacent to the detonating cord on the horizontal axis of the gun body. Alternatively, the end fitting is designed such that the detonating cord and detonator overlap each other such that the end of the detonating cord and detonator are side by side.

The pressure bulkhead is pre-installed into the baffle of the pin end of the gun carrier. Alternatively, the pressure bulkhead is pre-installed into the pin by pin tandem sub which is inserted into one end of the gun carrier. Alternatively, the pressure bulkhead is pre-installed to the end of the charge tube end fitting. The gun assembly is armed by inserting a wireless electric detonator, connector end facing up, into the end fitting detonator orifice, followed by attaching the connector receptacle attached to the end fitting into the outer end of the detonator.

The selective switch is attached to, or contained within, the pre-wired loading tube and the wires with the detonator connector receptacle pass through the upper end fitting. The selective switch is contained within the lower end fitting, wherein the insulated wire is connected to the switch within the same lower end fitting and the detonator connector receptacle wire runs the length of the loading tube and the receptacle end passes through the upper end fitting.

Claim 1:
A perforating gun system (<NUM>) comprising:
a cylindrical housing (<NUM>) with a bottom end (<NUM>) and a top end (<NUM>);
a prewired loading tube assembly (<NUM>) disposed within the cylindrical housing (<NUM>) and having a corresponding bottom end (<NUM>) and top end (<NUM>);
an upper end fitting (<NUM>) coupled to the top end (<NUM>) of the prewired loading tube (<NUM>) and the top end (<NUM>) of the cylindrical housing (<NUM>);
a lower end fitting (<NUM>) coupled to the bottom end (<NUM>) of the prewired loading tube (<NUM>) and the bottom end (<NUM>) of the cylindrical housing (<NUM>);
upper electrical connections coupled to the upper end fitting (<NUM>);
lower electrical connections coupled to the lower end fitting (<NUM>);
a selective switch (<NUM>) coupled to a detonator connector receptacle (<NUM>) disposed within the upper end fitting (<NUM>); and characterized by
an auto-shunting modular detonator (<NUM>) electrically coupled to the selective switch (<NUM>) and further disposed within the upped end fitting (<NUM>); wherein the auto-shunting modular detonator does not un-shunt until a mating receptacle is inserted, which disengages the shunt of the detonator (<NUM>); and wherein the upper end fitting (<NUM>) contains a portion to receive the detonator (<NUM>) by electrically connecting it to a mating receptacle of the selective switch (<NUM>) and affixing the detonator (<NUM>) proximate to a detonating cord (<NUM>).