Self-propelling perforating gun system

A well system includes a perforating gun having shaped charges and a detonator to controllably detonate the shaped charges. The well system further includes a propulsion head coupled to the perforating gun. The propulsion head is operable to apply thrust to the perforating gun such that the well system is self-propelling.

BACKGROUND

Field

The disclosure relates to the field of hydrocarbon well perforation. More specifically, apparatus and methods of perforating gun conveyance.

Description of the Related Art

When a hydrocarbon well is drilled, a casing may be placed in the well to line and seal the wellbore. Cement is then pumped down the well under pressure and forced up the outside of the casing until the well column is also sealed. This casing process: (a) ensures that the well is isolated, (b) prevents uncontrolled migration of subsurface fluids between different well zones, and (c) provides a conduit for installing production tubing in the well. However, to connect the inside of the casing and wellbore with the inside of the formation to allow for hydrocarbon flow from the formation to the inside of the casing, holes or tunnels must be formed through the casing and into the wellbore. This practice is commonly referred to as perforation of the casing and formation. In applications where a casing is not used (i.e. open-hole applications), jetting, fracturing or perforating is applied directly to the formation.

During the perforating process, a gun-assembled body containing a plurality of shaped charges is lowered into the wellbore and positioned opposite the subsurface formation to be perforated. Initiation signals are then passed from a surface location through a wireline to one or more blasting caps located in the gun body, thereby causing detonation of the blasting caps. The exploding blasting caps in turn transfer a detonating wave to a detonator cord which further causes the shaped charges to detonate. The detonated shaped charges form an energetic stream of high-pressure gases and high velocity particles, which perforates the well casing and the adjacent formation to form perforation tunnels. The hydrocarbons and/or other fluids trapped in the formation flow into the tunnels, into the casing through the orifices cut in the casing, and up the casing to the surface for recovery.

In markets such as the North America shale market, it is common for horizontal wells to be completed in multi-stages using known methods of pump down perforation. To facilitate the pump down perforation method, the end of the horizontal well must be perforated to initiate the ability to pump fluid into the well and deploy subsequent wireline perforating guns. The perforation of the end of the well is typically done through pressure activated sleeves or by deploying perforating guns on tubing such as coiled tubing or by use of a tractor to push the perforating guns along the horizontal section of the well.

Irrespective of a vertical, horizontal, or deviated wellbore, conveyance of the perforating guns always requires additional conveyance equipment adding to the cost, time, and complexity of the operation. What is needed is an improved method and apparatus for perforating gun conveyance.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

An embodiment of the present disclosure provides a perforating gun system for deployment in a wellbore, the wellbore having a bottom end. The perforating gun system comprises a perforating gun carrying shaped charges and a detonator actuatable to controllably detonate the shaped charges. The perforating gun system further comprises a propulsion head coupled to the perforating gun, wherein the propulsion head is operable to apply thrust to the perforating gun. The perforating gun system is self-propelling.

Another embodiment of the present disclosure provides a method of perforating. The method comprises the steps of: (a) propelling a perforating gun comprising shaped charges and a detonator through a wellbore by activation of a propulsion head coupled to the perforating gun; (b) detecting a target location in the wellbore; and (c) in response to detecting the target location in the wellbore, actuating the detonator to detonate the plurality of shaped charges.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for purposes of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments are possible. This description is not to be taken in a limiting sense, but rather made merely for purposes of describing general principles of the implementations. The scope of the described implementations should be ascertained with reference to the issued claims.

As used herein, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via one or more elements”; and the term “set” is used to mean “one element” or “more than one element”. Further, the terms “couple”, “coupling”, “coupled”, “coupled together”, and “coupled with” are used to mean “directly coupled together” or “coupled together via one or more elements”. As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements.

In this disclosure, reference to “one implementation” or “an implementation” or to “one embodiment” or “an embodiment” means that a particular feature, structures, or characteristics may be combined in any suitable manner in one or more implementations or one or more embodiments.

In this disclosure, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its broadest sense, that is, as meaning “and/or” unless the content clearly dictates otherwise.

FIG. 1is a schematic illustration of an embodiment of the perforating gun system100of the present disclosure. As shown, the perforating gun system100is traversing a wellbore102drilled through formation(s)103. The perforating gun system100is designed as a self-propelled system, which means that the system is moving or able to move without the aid of external propulsion or external conveyance, such as wireline, coiled tubing, a tractor, or the like.

The perforating gun system100may be deployed into the wellbore102from a surface location104by initiation of the propulsion system. Depending on the application and the orientation of the well, the perforating gun system100may be deployed by releasing the self-propelled perforating gun system100directly into the wellbore102from the surface. In some embodiments, the perforating gun system100may be initially deployed via a conveyance tool (not shown) to a target location such as a horizontal section of the wellbore or to a target branch in a multilateral wellbore. Once in the target location, the perforating gun system100is released from the conveyance tool and further travel of the perforating gun system100is enabled through initiation of its propulsion system.

In one embodiment of the present disclosure, the perforating gun system100includes a perforating gun105carrying shaped charges114and a propulsion head106coupled to the perforating gun105. The term “propulsion head,” as used herein, means a device or system that can push an attached load forward. The propulsion head106may be, for example, a propulsion motor, such as a rocket motor, a hydraulic propulsion system, an electric propulsion system, a magnetic propulsion system, or a motor driven propeller that is powered electrically, magnetically or energetically.

By coupling the propulsion head106to the perforating gun105, the perforating gun system100is able to move as a unit through sections of the wellbore102, whether horizontal, deviated, or vertical, without any other external force. The term “external,” as used herein with “force”, means outside of or separate from the perforating gun system100. In some embodiments, as will be described herein, the perforation gun system100may include a capability to detect a target location in the wellbore102. The propulsion head106may propel the perforating gun system100to the target location, at which point the detonator (as illustrated inFIG. 3)126located within the firing head128is actuated and the shaped charges114of the perforating gun105are fired to perforate the casing (or other tubing)108lining the wellbore102, or a wall of the wellbore102in open hole applications.

In other embodiments of the present disclosure, the propulsion head106may propel the perforating gun system100until the nose132of the perforating gun system100strikes the end or bottom134of the wellbore102. In such embodiments, the impact of the nose132with the end134of the wellbore102generates an impact energy that is transferred to the detonator126within the firing head128for actuation. For instance, the detonator126may include a percussion detonator that activates upon impact and transfers the impact energy to the detonation cord124. It should be understood, that any known methods of transferring the impact energy may be used and remain within the purview of the present disclosure.

FIG. 2shows an example embodiment of a propulsion head106of the present disclosure wherein the propulsion head106is a type of rocket motor. As shown, the propulsion head106includes a shell150that is closed at one end152and open at the opposing end through a propulsion nozzle154. The propulsion head106is attached or affixed to the perforating gun system100approximate its closed end152. As should be understood, the propulsion head106may be attached or affixed by means known in the art such as threaded connections, or may be attached or affixed through the use of adapters, or may be integrated into the body of the perforating gun system100. All such alternate embodiments fall within the purview of the present disclosure.

The shell150of the propulsion head106may be charged with a gas generating material, e.g., propellant156. In an embodiment of the present disclosure, an electrode158in electrical communication with the propellant156applies electrical current to the propellant156when the propulsion head106is activated. The propulsion head106may include a control circuit (not shown) to determine when the electrical current is applied to the propellant156through the electrode158.

In general, any suitable arrangement of propellant(s) and any suitable method of applying current to the propellant(s) in order to burn the propellant(s) may be used. The propellant156burns in response to the applied current, generating gases in the process. The gases expand through the nozzle154, resulting in a thrust157that illustrated inFIG. 2as an arrow. The thrust157propels the propulsion head106and a load (i.e. the perforating gun105) that is attached to the propulsion head106. The direction of the thrust157is opposite to the direction of the expanding gases.

In one example embodiment of the present disclosure, the amount of propellant156may be selected such that the propellant is exhausted approximate the time that the perforating gun system100is at the target location within the wellbore102. In other embodiments, the amount of propellant is selected to ensure that the perforating gun system100reaches the bottom (or end)134of the wellbore102. In such embodiments, the impact of the perforating gun system100with the bottom134of the wellbore102acts as the stop for the perforating gun system.

Returning toFIG. 1, the travel of the perforating gun system100through the wellbore102may be guided by the trajectory of the wellbore102. In some embodiments of the present disclosure, low friction devices, such as rollers or low friction pad materials, may be provided on the external surface of the perforating gun system100, such as on the collars109to improve the efficiency of travel for the perforating gun system100.

The perforating gun105used in embodiments of the perforating gun system100of the present disclosure may employ any perforating gun design known in the art. For illustrative purposes,FIG. 3shows an example structure of the perforating gun105. InFIG. 3, the perforating gun104includes a gun carrier110. A loading tube112inside the carrier110has a plurality of shaped charges114mounted within. Each shaped charged114may be an encapsulated shaped charge114including a charge casing116, a sealing cap118that cooperates with the charge casing116to provide a sealed chamber119, and an explosive material120disposed within the sealed chamber119. The shape, material, and position of the liner122inside the charge casing116are designed to direct the energy of the explosive material120upon detonation in a desired direction to form perforations into a target formation.

A detonation cord124may be routed through the loading tube112and is in communication with the plurality of shaped charges114. A firing head128may be attached to one end of the gun carrier110. The firing head128includes a detonator126that when activated at a determined time and location initiates detonation of the detonation cord124. The detonation cord124in turn initiates detonation of the shaped charges114. The firing head128may be coupled to the propulsion head106as shown inFIG. 1.

As shown inFIG. 3, a connector cap130may be attached to the end of the gun carrier110opposite the firing head128. The connector cap130may include features to couple the perforating gun105to the nose132, may act as an adapter, or may be coupled to an adapter for purposes of connecting additional perforating guns.

The detonator126in the firing head128may be any known detonator that may be activated chemically, mechanically, electrically, or by any other known method to ignite the detonation cord124. The method used to activate the detonator126will generally depend on the design of the detonator126. In one example, the detonator126may be activated electrically by sending an initiation signal from a control unit located at the surface104to the detonator126. For example, as shown inFIG. 4, a control line, tether cable, or other communication link known in the art (“collectively “communication line”)131extending from the surface104and in communication with the detonator126(inFIG. 3) may be used to send the initiation signal. In other example embodiments, the detonator126may be actuated wirelessly via a wireless signal generated from the surface104or from a downhole tool capable of generating a wireless signal.

It should be understood that in embodiments that use a communication line131to send the trigger signal to the detonator126, the communication line131does not propel the perforating gun system100through the wellbore. Rather, the perforating gun system100is self-propelled by the propulsion head106.

In general, the perforating gun system100of the present disclosure remains in the wellbore after activation. However, in some embodiments, a tether cable (such as the communication line131shown inFIG. 4) may be used to retrieve the perforating gun system100after its activation. In alternate embodiments, an opposing propulsion head106a(shown by the dashed lines inFIG. 4) may be affixed to the nose132of the perforating gun system100and pointed in an up-hole direction to enable the gun to be propelled back to surface in a controlled manner. In such embodiments, the tether131may be combined with the opposing propulsion head106aand the opposing propulsion head106aassists or initiates recovery through use of the tether131.

In alternate embodiments having an opposing propulsion head106a, activation of the opposing propulsion head106amay assist with the placement of the perforating gun system100. For example, to slow the rate of travel of the perforating gun system100to assist with the proper location of the perforations, the opposing propulsion head106amay be activated to oppose the force of the propulsion head106. The propulsion force of the opposing propulsion head106amay be less than or in shorter duration than the propulsion force of the propulsion head106to ensure that the perforating gun system100does not reverse, but rather slows to a controlled rate of travel. The opposing propulsion head106amay be necessary to ensure that the shaped charges114have time to fire in the instance of a perforating gun system100travelling at a high rate of speed.

In another example of the present disclosure, illustrated inFIG. 5, the detonator126may be activated when the perforating gun system100hits a predetermined internal feature or restriction (136inFIG. 5), such as a shoulder, in the wellbore102. In embodiments of the present disclosure, the internal feature136may additionally act as a stop for the perforating gun system100or may act to initiate a breaking feature such as activation of an anchor or an opposing propulsion head.

In other embodiments of the present disclosure, activation of the detonator126may depend on environmental conditions within the wellbore102. For example, when a pressure sensor carried by the well perforating system100senses a predetermined pressure within the wellbore102(that can be correlated to a specific depth in the wellbore), the pressure sensor may send a signal to the firing head128to activate the detonator126.

In another example, illustrated inFIG. 6, the casing108in the wellbore102may include RFID tag(s) (“RFID Tag)”)138, and the firing head128may include an RFID tag reader (“RFID Reader”)139, wherein the detonator126is activated when the RFID Reader139detects a particular RFID Tag138in the wellbore102. Alternatively, the RFID Reader139may be located at a target location in the wellbore102, and the firing head128may include an RFID Tag138such that when the RFID Reader139detects the RFID Tag138in the firing head128, a signal is sent to the firing head128that activates the detonator126. In embodiments having multiple perforating guns105, there may be multiple RFID Tags138and RFID Readers139. The RFID Tags138and the RFID Readers may be encoded such that they are specific to each individual perforating gun105such that activation only occurs when the specific gun passes through the matched RFID Reader139.

In some embodiments of the present disclosure, the RFID Tags138and RFID Readers139(collectively the “RFID System”) may be additionally used to control the rate of travel. For instance, when the perforating gun system100passes a particular location, the RFID System may activate a breaking system such as deploying spring actuated arms or other mechanical anchoring devices (not shown) from the perforating gun system100that engage the wellbore102to slow the rate of travel of the gun system100or to stop the travel of the gun system100altogether. Alternatively, in embodiments of the present disclosure having an opposing propulsion head106asuch as shown inFIG. 4, the RFID System may actuate the opposing propulsion head106ato slow the rate of travel of the perforating gun system100.

The self-propelled perforating gun system100of the present disclosure may be used in any well to perform a perforation, stimulation, or other operation in the well. For instance, the perforating gun system100of the present disclosure may be used in a horizontal well that is to be completed in multiple stages and fractured using the pump down perforating method. In this multistage application, the gun perforating system100is used to perforate the wellbore102at the lower or bottom end134of the well to initiate the pumping of fluid into the well and thus deploy subsequent wireline gun systems.

In some embodiments, of the present disclosure, the self-propelled perforating gun system100may be extended to perform other operations besides perforating a wellbore. For example,FIG. 7shows an embodiment of the perforating gun system100that may enable a stimulation operation in addition to a perforating operation. InFIG. 7, an expander tool162has been added to the perforating gun system100. The expander tool162may be as described in U.S. Pat. No. 9,033,041 (Baihly), the disclosure of which is incorporated herein by reference, or may be other type of expander tool to install a seat assembly in a well. In one example, the expander tool162includes an anchor164, such as a hydraulically set anchor, to temporarily anchor the tool100in place in the wellbore. The expander tool162further includes a seat assembly166and a tapered expander168.

When the system100is deployed into the well, the seat assembly166is disposed between the anchor164and the tapered expander168. An operator mandrel170extends through the seat assembly166such that when the expander tool162operates to set the seat assembly166, the tool100retracts the mandrel170to pull the expander168through the interior of the seat assembly166, which forces the seat assembly166to radially expand. The perforating gun system100may be used to perforate the casing (or other tubular string in the well) prior to or after installing the seat assembly166.

As described above, in embodiments of the perforating gun system100of the present disclosure, the perforating gun system100may be dropped or abandoned in the well102after actuation, or in other embodiments the perforating gun system100may be retrieved by a tether or other fishing tool. In yet other embodiments of the present disclosure, the perforating gun system100may be made of structures and/or materials that disintegrate such that the perforating gun system100essentially disappears after perforating the casing/well. A disappearing perforating gun system is described in, for example, U.S. Pat. No. 9,695,677, and the principles disclosed in this patent may be used in constructing the perforating gun system100of the present disclosure.

FIG. 8illustrates a multiple gun system101of the present disclosure. In this embodiment, multiple perforating guns105a,105b, are connected and propelled by the propulsion head106. As shown, the perforating guns105a,105bare connected through use of an adapter180. It should be understood that any of the propulsion and actuation systems and methods described herein are applicable to the multiple gun system101. Additionally, although illustrated with a single firing head128, the multiple gun system101may have multiple firing heads128and/or multiple detonators126that enable independent actuation of the perforating guns105a,105b. This would enable, for example, the target zones to be perforated or stimulated from toe to heel or heel to toe.

FIG. 9AandFIG. 9Billustrate another stimulation application of the perforating gun system100of the present disclosure. As shown inFIG. 9A, the gun system100has been propelled into the wellbore by any of the propulsion methods described herein and the shaped charges114have been fired to generate the perforations182in the wellbore102. A chemical fluid pill184, such as an acid pill, is shown approximate the perforating gun system100. As is known in the art, treatment fluids such as acids are used to enhance the production of reservoir fluids. After perforating the wellbore102, and as shown inFIG. 9B, the pumping pressure (indicated by arrow186) from the surface is increased such that the acid pill184flows into the perforations182, as indicated by arrows188, to acidize the formation. The acid acts to remove near-wellbore formation damage and other damaging substances in order to enhance production by increasing the effective well radius.

Other well systems may be designed as self-propelled systems. That is, a propulsion head106may be coupled to other well tools besides a perforating gun to enable the well tools to be self-propelled. Examples of applications where a self-propelled well system may find use include, but are not limited to, a propellant stimulating system, a dumping tool for acid or similar treatment, a cutter or triggered device.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words “means for” together with an associated function.