SYSTEM AND METHOD FOR DEDUPLICATING PERFORATING-GUN INITIATOR-CIRCUIT ADDRESSES

Abstract

A stack of addressable perforating guns with preassigned addresses may be configured for operation by identifying any duplicate addresses in the stack and deduplicating the addresses by assigning new addresses to at least a subset of any guns having the same address until each gun in the stack has an address unique in the stack.

Description

BACKGROUND AND SUMMARY

This invention pertains generally to technology for controlling perforating guns for deployment in, e.g., oil and gas wells. More specifically, the technology relates to control of addressable microprocessor-based gun initiator circuits to deduplicate addresses in a gun stack.

Perforating guns are used in oil and gas well to perforate casing to access oil or gas reserves. Typically, the guns are deployed into the casing in a wellbore using an electrically conductive wireline. The guns include explosive charges which, when fired, proceed from the gun through the casing, thus perforating the casing. To ensure safe operation of the guns, the firing circuit in a gun is typically disabled by default and is selectively enabled through use of an initiator circuit (also known as a switch).

To enable stacking of multiple guns and selective fire of each gun independently of other guns, the initiator circuit is typically configured with an address that is unique in the stack of guns. The initiator circuit communicates with a surface system through the wireline using its address: messages from the initiator circuit include the initiator circuit's address and messages to the initiator circuit include the initiator circuit's address. Using the address, each initiator circuit may be, e.g., queried or configured apart from the other guns in the stack.

Guns in a stack are electrically connected to each other through the initiator circuits. Typically, each initiator circuit includes a passthrough switch, which selectively connects a passthrough conductor to a conductor above it in the stack, and ultimately to a conductor in the wireline. The topmost gun in the stack will be connected to the wireline conductor and through that to the surface system. The surface system will communicate with the top-gun initiator circuit and instruct it to enable the feedthrough switch, connecting the wireline conductor to the second-from-top gun in the stack and enabling communication between the surface system and the initiator circuit of the second-from-top gun in the stack. This proceeds until all guns in the stack are connected to the surface system through the enabled passthrough switches and are registered with the surface system.

The stack “inventory” process, the process of connecting to and registering each gun in the stack, can be quite time intense as each initiator circuit in the stack goes through a handshake process with the surface system. Typically, when first powered up, the initiator circuit waits a predetermined period of time, determines the circuit's state (e.g., the presence of a detonator), and then sends an uplink to the surface system informing the surface system of the initiator circuit's address and state, and that the initiator circuit is ready for operation. The surface system will respond with a command to enable the feedthrough switch, initiating the process for the next gun in the stack. (The initiator circuit will periodically send its uplink until it receives a response from the surface system.) This handshake process, the process of establishing communication between an initiator circuit and surface system and registering the initiator circuit (thus, the gun) at the surface system, may e.g., take on the order of 350-1000 ms for each gun in the stack. Once the inventory process is complete, the field engineer can selectively fire a gun in the stack (using enable/fire commands addressed to the selected gun). After a gun is fired, the field engineer powers down the stack, repowers it, and the inventory process begins again from the start. This can pose long delays between shots. For example, in a shoot-on-the-fly situation, waiting on the inventory process (perhaps 10s for a 10-20 gun stack) before the next gun is ready to fire may result in the wireline field engineer having to slow down the winch to ensure that the guns are configured before they arrive at the next perforating interval. Thus, the inventory process may add significant time (and therefore expense) to the perforating operation.

The inventory-process delay is exacerbated by the length of the addresses used to identify the initiator circuits. Longer addresses (more bits) take more time to transmit than shorter addresses (fewer bits). But shorter addresses are more prone to risk of duplication. For example, an 8-bit address has only 256 unique configurations (2⁸) whereas a 32-bit address has 4,294,967,296 unique configurations (2³²). Thus, factory-addressed initiator circuits often use 16-bit or 32-bit addresses to ensure that there are no duplicate addresses in a gun stack. But a 32-bit address takes four times as long to transmit as an 8-bit address. Thus, ensuring initiator circuits have unique addresses can come at the cost of an extended inventory process, with the associated operating delays.

Increasing the inventory speed, then, can improve the perforating operation. One approach to speeding the inventory process is to limit the use of the addresses in the inventory process (see, e.g., U.S. patent application Ser. No. 17/879,856, assigned to Applicant and incorporated herein by reference). Another approach is to use shorter addresses and assign unique addresses to every initiator circuit at the job site once the gun stack is assembled for use (see, e.g., U.S. Pat. No. 10,900,335). The approach of the present disclosure is to deduplicate preassigned addresses at the job site once the gun stack is assembled for use.

In an aspect of the invention, a perforating system includes a multi-gun stack, each gun with an addressable initiator circuit, and a control system (e.g., a test or firing system). The control system is configured to read the addresses of each initiator circuit in the stack, establish the top gun's initiator circuit in the stack as a reference address, and determine if any subsequent gun in the stack has an address that is a duplicate of any other gun in the stack. The control system is further configured to change gun addresses other than the top-gun address so that each gun in the stack has an address that is unique in the stack. In another aspect of the invention, the duplicate addresses are changed to a random address to establish a gun-stack sequence of addresses that may be used to identify the stack/job in postprocessing of the firing (and other) data.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawings where:

FIG. 1 is a functional block diagram illustrating perforating guns deployed in a cased wellbore via a wireline.

FIG. 2 is a functional block diagram illustrating an exemplary perforating-gun initiator circuit.

FIG. 3 is a functional block diagram illustrating the initiator circuits of an exemplary gun stack as it would be deployed in a wellbore.

FIG. 4 is a flowchart illustrating an exemplary address-deduplication algorithm according to an aspect of the invention.

FIG. 5 is a flowchart illustrating an exemplary address-deduplication algorithm according to an aspect of the invention.

FIG. 6 is a flowchart illustrating an exemplary address-deduplication algorithm according to an aspect of the invention.

DETAILED DESCRIPTION

In the summary above, and in the description below, reference is made to particular features of the invention in the context of exemplary embodiments of the invention. The features are described in the context of the exemplary embodiments to facilitate understanding. But the invention is not limited to the exemplary embodiments. And the features are not limited to the embodiments by which they are described. The invention provides a number of inventive features which can be combined in many ways, and the invention can be embodied in a wide variety of contexts. Unless expressly set forth as an essential feature of the invention, a feature of a particular embodiment should not be read into the claims unless expressly recited in a claim.

Except as explicitly defined otherwise, the words and phrases used herein, including terms used in the claims, carry the same meaning they carry to one of ordinary skill in the art as ordinarily used in the art.

Because one of ordinary skill in the art may best understand the structure of the invention by the function of various structural features of the invention, certain structural features may be explained or claimed with reference to the function of a feature. Unless used in the context of describing or claiming a particular inventive function (e.g., a process), reference to the function of a structural feature refers to the capability of the structural feature, not to an instance of use of the invention.

Except for claims that include language introducing a function with “means for” or “step for,” the claims are not recited in so-called means-plus-function or step-plus-function format governed by 35 U.S.C. § 112(f). Claims that include the “means for [function]” language but also recite the structure for performing the function are not means-plus-function claims governed by § 112(f). Claims that include the “step for [function]” language but also recite an act for performing the function are not step-plus-function claims governed by § 112(f).

Except as otherwise stated herein or as is otherwise clear from context, the inventive methods comprising or consisting of more than one step may be carried out without concern for the order of the steps.

The terms “comprising,” “comprises,” “including,” “includes,” “having,” “haves,” and their grammatical equivalents are used herein to mean that other components or steps are optionally present. For example, an article comprising A, B, and C includes an article having only A, B, and C as well as articles having A, B, C, and other components. And a method comprising the steps A, B, and C includes methods having only the steps A, B, and C as well as methods having the steps A, B, C, and other steps.

Terms of degree, such as “substantially,” “about,” and “roughly” are used herein to denote features that satisfy their technological purpose equivalently to a feature that is “exact.” For example, a component A is “substantially” perpendicular to a second component B if A and B are at an angle such as to equivalently satisfy the technological purpose of A being perpendicular to B.

Except as otherwise stated herein, or as is otherwise clear from context, the term “or” is used herein in its inclusive sense. For example, “A or B” means “A or B, or both A and B.”

FIG. 1 illustrates a stack of perforating guns 100a, 100b, 100c deployed in casing 120 in a wellbore as is known in the art. The stack of guns is connected to a surface system 110 via a wireline 116 that runs from a winch 112, through sheaves 114, through pressure control equipment 118, and into the wellbore.

The guns 100a, 100b, 100c in the stack each include one or more explosive charges 104a, 104b, 104c connected to an initiator circuit 102a, 102b, 102c through a detonation cord 106a, 106b, 106c (or other explosive train). As explained in more detail below, each initiator circuit 102a, 102b, 102c includes a microprocessor circuit that is associated with an address (unique in the stack) and that is connected to a detonator. The detonator is in turn connected to the detonator cord 106a, 106b, 106c. The guns 100a, 100b, 100c are connected one-to-the-other through feedthrough lines 108a, 108b, 108c.

In use, the surface system 110 communicates with the initiator circuits 102a, 102b, 102c through use of the addresses of the initiator circuits 102a, 102b, 102c. For example, each gun 100a, 100b, 100c in the stack would be assigned a unique address: e.g., 0xAA, 0xAB, 0xAC; uphole to downhole respectively in the figure. Firing the top gun, 0xAA, would entail sending a signal from the surface system 110 over the wireline 116 wherein the signal includes a firing command associated with the address 0xAA. Similarly, firing the middle gun 102b would use the address 0xAB and the bottom gun would use the address 0xAC. Each initiator circuit 102a, 102b, 102c that receives a signal will determine if the command is directed to it through comparison of the address in the command to the initiator circuit's assigned address. If it is the same address, the initiator circuit 102a, 102b, 102c will enable a route for a firing signal to the detonator to trigger the explosive charges 104a, 104b, 104c. In this way, each gun 100a, 100b, 100c in the stack may be selectively fired. Messages other than a firing command may be exchanged between the surface system 110 to the guns 100a, 100b, 100c. For example, the surface system 110 typically performs an inventory of guns 100a, 100b, 100c in the stack. In such a process, the surface determines what guns are in the stack, what the status of each gun is, and registers each gun's address.

FIG. 2 is a functional block diagram illustrating an exemplary initiator circuit 202 comprising a microprocessor circuit 220, a feedthrough switch 222, a high firing switch 224, a low firing switch 226, and a detonator 228 connected to a detonation cord 206. The microprocessor circuit 220 controls the feedthrough 222 and firing 224, 226 switches through a microprocessor 221. For example, the switches may be implemented as field effect transistor switches controlled with signals provided by the microprocessor circuit. The microprocessor circuit 220 also includes communication and support circuitry (not shown) as is known in the art.

On startup, when adequate power is provided to the microprocessor circuit 220 via a supply voltage on a conductor 209 connected to a wireline conductor (perhaps through feedthrough lines and switches of any uphole guns), the microprocessor 221 formulates and sends a ready/status message via the wireline-connected conductor 209 to inform a control system of its status, including its address. The microprocessor 221 continues to periodically send this message until it receives a response from the control system. At some point, the control system will instruct the microprocessor 221 to enable the feedthrough switch 222. The microprocessor 221 then enables the feedthrough switch 222 thereby providing power to the microprocessor circuit of the next gun in the stack. This process continues until all gun initiators in the gun stack have registered with the control system.

The startup routine for a gun stack may be understood with reference to FIG. 3, which depicts the initiator circuits of a n-gun stack. The initiator circuits 302, 304, 306, 308, 310 are configured as described for the initiator circuit 202 of FIG. 2, with the feedthrough switches 302a, 304a, 306a, 308a, 310a initially in a disabled state. The control system 314 is communicatively connected to the stack and provides power to the stack. The first initiator circuit 302 (IC1) powers up and sends its status, including its address, to the control system 314. The control system 314 registers the address of IC1 302 and instructs IC1 302 to enable its passthrough switch 302a and then go to sleep. With the IC1 passthrough switch 302a enabled and IC1 302 in a sleep state, the second initiator circuit 304 (IC2) powers up and sends its status, including its address, to the control system 314. The control system 314 compares the address of IC2 304 to the registered address of IC1 302. If the IC2 304 address is a duplicate of the IC1 302 address, the control system 314 assigns and registers a new address for IC2 304 and instructs IC2 304 to enable its passthrough switch 304a and then go to sleep. If the IC2 304 address is distinct from the IC1 302 address, the control system 314 registers the address of IC2 304 and instructs IC2 304 to enable its passthrough switch 304a and then go to sleep. With the IC1 and IC2 passthrough switches 302a, 304a enabled and IC1 302 and IC2 304 each in a sleep state, the third initiator circuit 306 (IC3) powers up and sends its status, including its address, to the control system 314. The control system 314 compares the address of IC3 306 to the registered addresses of IC1 302 and IC2 304. If the address of IC3 306 is a duplicate of either of the previously registered addresses, the control system 314 assigns and registers a new address for IC3 306 and instructs IC3 306 to enable its passthrough switch 306a and then go to sleep. If the IC3 306 address is distinct from the previously registered addresses, the control system 314 registers the address of IC3 306 and instructs IC3 306 to enable its passthrough switch 306a and then go to sleep. This process continues until the last initiator circuit 310 (ICn) is associated with an address distinct from all other initiator-circuit addresses in the stack.

Through this address-deduplication process, the control system ensures that each gun in the stack is associated with an address unique in the stack. Thus, it is possible to ensure unique addressing for factory-addressed initiator circuits while using a relatively small number of bits for the address. For example, if it is determined that the gun stack will not have more than 256 addressable circuits, then an 8-bit address is sufficient. In some embodiments, certain addresses may be reserved for certain tools. For example, a perforating-gun stack may be run with a release tool or a setting tool or a safety sub, each also using an addressable switch/circuit and addresses may be reserved for these tools and thus would not be appropriate for a gun IC. In such a circumstance, the address- deduplication process would ensure that no gun IC is assigned a reserved address, assigning a new address if the factory address is one of the reserved addresses.

FIG. 4 depicts an exemplary address-deduplication algorithm 400 for a gun stack comprising n initiator circuits. The stack is powered up 401 and the address of the first initiator circuit (IC₁) is read and stored 402 as ADD₁. The feedthrough switch of IC₁ is then enabled and IC₁ is placed in a sleep state 403. The system then loops through the remaining n-1 initiator circuits to read, deduplicate, and store the addresses: A loop 404 of IC index i from i=2 to n is established 404, 405 and the address of IC_i (ADD) is read and stored 406. For each ICi, a loop of IC index j (j=1 to i-1) is established 408, 409 and ADD_i is compared to each address (ADD_j) of each previously read initiator circuit (IC_j) in the stack 410. If there is a duplicate, a new address is assigned and recorded for IC_i 412. Once ADD has been compared to each of the previously recorded addresses (j=i at step 409) the feedthrough switch of IC_i is enabled and IC enters a sleep state 407 and the process continues to the next IC in the stack. Once all initiator circuits have been processed (i=n+1 at step 405) the deduplication process is complete 414 and the stack is ready for operation.

FIG. 5 depicts an exemplary address-deduplication algorithm 500 for a multi-gun stack. The stack is powered up 501 and the address of the first initiator circuit (IC₁) is read and stored 502 as ADD₁. The system then continues through the initiator circuits (IC_i) to read, deduplicate, and store until all the initiator circuits have been processed: The feedthrough switch of IC₁ is enabled, IC₁ is placed in a sleep state, and an IC index i is set to 2 503. The address ADD_i of the next IC in the stack is read and stored 504 and then compared to the set of previous addresses [ADD₁, . . . , ADD_i-1] 506. If the address ADD_i is a duplicate of any of the previous addresses, a new address is assigned and recorded for IC_i 508. If there are any remaining ICs in the stack 510, the feedthrough switch of IC_i is enabled, IC_i is placed in a sleep state, the IC index i is incremented 511, and the deduplication process continues for the next IC in the stack 504. Once the last IC has been processed 510 the deduplication process is complete 512 and the stack is ready for operation.

FIG. 6 depicts an exemplary address-deduplication algorithm 600 for a multi-gun stack. The stack is powered up and an IC index i is set to 1 601. The system then reads and records the addresses of the initiator circuits (IC_i) in the stack: The address ADD of the i^th IC in the stack is read and stored 602. If there are any remaining ICs in the stack 604, the feedthrough switch of IC_i is enabled, IC_i is placed in a sleep state, the IC index i is incremented 605, and the read-and-record process continues for the next IC in the stack 602. Once the address of the last initiator circuit has been read 604 the number of ICs in the stack is recorded 606 and the addresses are deduplicated: An IC index i is set to 2 608 and the address of IC (ADD_i) is compared to the set of recorded addresses of the other ICs ADD=[ADD_j, j≠i] 610. If the address ADD_i is a duplicate of any of the other addresses, a new address is assigned and recorded for IC_i 612. If there are any remaining ICs to be deduplicated 614, the feedthrough switch of IC_i is enabled, IC_i is placed in a sleep state, and the IC index i is incremented 615 and the deduplication process continues for the next IC in the stack 610. Once the last IC has been processed 614 the deduplication process is complete 616 and the stack is ready for operation.

In the address-deduplication process, a new address to be assigned and recorded for an initiator circuit may be randomly selected from the set of available address. The set would consist of the available bit combinations less addresses known to be in the stack less any reserved addresses. Such a process has the added benefit of generating an address set for the perforating-gun stack that is likely to be unique to the stack. Such an address set may be useful in identifying the job in a post-job processing or presentation of information.

While the foregoing description is directed to the preferred embodiments of the invention, other and further embodiments of the invention will be apparent to those skilled in the art and may be made without departing from the basic scope of the invention. And features described with reference to one embodiment may be combined with other embodiments, even if not explicitly stated above, without departing from the scope of the invention. The scope of the invention is defined by the claims which follow.

Claims

1. A perforating system comprising:

(a) a first perforating gun having an addressable circuit with a preassigned first-gun address;

(b) at least one additional perforating gun, each additional perforating gun having an addressable circuit with a preassigned additional-gun address;

(c) a control system comprising a processor configured to deduplicate the additional-gun addresses.

2. The perforating system of claim 1 wherein the control-system processor is configured to deduplicate the addresses of the additional perforating guns by:

(a) communicating with the first perforating gun to determine and record the first-gun address; and

(b) for each additional perforating gun: communicating with the additional perforating gun to determine and record its additional-gun address, determining whether this additional-gun address is in the set of addresses comprising the first-gun address and any previously recorded additional-gun addresses, and, if so, assigning and recording a new additional-gun address for the additional perforating gun.

3. The perforating system of claim 1 wherein the control-system processor is configured to deduplicate the addresses of the additional perforating guns by:

(a) communicating with the first perforating gun to determine and record the first-gun address;

(b) for each additional perforating gun: communicating with the additional perforating gun to determine and record its additional-gun address;

(c) determining whether there are any duplicate addresses in the set of addresses comprising the first-gun address and the additional-gun addresses; and

(d) assigning and recording a new additional-gun address for at least a subset of the additional guns that have a duplicate address so that each additional-gun has an additional-gun address that is distinct from all other additional-gun addresses and from the first-gun address.

4. The system of claim 1 wherein the control-system processor is configured to randomly assign an available address to at least one of the additional perforating guns in order to deduplicate the additional-gun addresses.

5. A method for operating a perforating system comprising a first perforating gun and at least one additional perforating gun, the method comprising:

(a) reading and recording a first-gun address associated with the first perforating gun;

(b) for each additional perforating gun, reading and recording an additional-gun address associated with the additional perforating gun;

(c) deduplicating the additional-gun addresses.

6. The method of claim 5 wherein the step of deduplicating is performed sequentially on a gun-by-gun basis as each additional-gun address is read and before proceeding to read and record the next additional-gun address.

7. The method of claim 5 wherein the step of deduplication is performed after the first-gun address and all the additional-gun addresses have been read and recorded.

8. The method of claim 5 wherein the deduplicating step includes assigning and recording a new additional-gun address selected randomly from the set of available addresses.