Patent Application
20240167368
Wells are often drilled to extract hydrocarbons, such as oil and gas. After drilling a wellbore that traverses a hydrocarbon-bearing formation, a casing string is installed to reinforce portions of the wellbore. A casing string comprises large diameter metal tubulars that are connected end to end, lowered into the wellbore, and cemented in place. The casing string increases the integrity of the wellbore and provides a structure for supporting other wellbore equipment such as production tubing used for producing fluids from one or production zones of the formation to surface. When a production zone is lined with casing, the casing must be perforated in order for formation fluids to enter the wellbore.
Perforating involves creating hydraulic openings that extend through the casing and into the surrounding formation. Typically, perforations are created by lowering a perforating gun string downhole and detonating a series of explosive shaped charges adjacent to the production zone. For safety, perforating guns may be transported to a wellsite in a partially unassembled state to prevent accidental detonation. Once fully assembled at the wellsite, a perforating gun string may be lowered into the cased wellbore on an appropriate conveyance, such as a wireline. An explosive train is then initiated to detonate the shaped charges in a predetermined fashion. The perforating gun string may then be retrieved to the surface.
Modular perforating systems used in wireline applications conventionally utilize a detonation device with an integrated switch. These switches come in different sizes and configurations. Such detonator designs require additional shunt wires to connect between positive and ground connections via a printed circuit board (PCB). This has led to detonators having cumbersome housing and PCBs with soldered connections in order to join together the electrical connections needed to arm the device.
These drawings illustrate certain aspects of some of the example configurations of the present disclosure and should not be used to limit or define the method.
A perforating system and method are disclosed incorporating a self-shunting, clip-on, resistorized detonator in a compact, modular packaging. The disclosure includes a detonator module with a self-shunting clip. The clip includes an arm that makes external contact with an electrically conductive detonator body to effectively shunt the explosive device from unintended electrical currents that might otherwise flow through the detonator and cause an accidental discharge. The clip is automatically un-shunted by separating the arm from the detonator body in response to inserting the detonator into a detonator housing. In its normally shunted state, any inadvertent electrical current will be diverted along the shunted circuit path, bypassing the explosive material inside the detonator. Once un-shunted by insertion of the detonator into the detonator housing, a detonation signal may be transmitted to the detonator along the un-shunted circuit path for initiation of explosive material. The initiation of the explosive material inside the detonator may then trigger a detonation train leading to the firing of perforating charges.
A wellbore casing 34 is cemented within a wellbore 32 by cement 36, which lines and reinforces the wellbore 32. The casing 34 may be perforated for formation fluids to enter the wellbore 32 in the vicinity of the casing 34. The tubular work string 30 may provide various tools involved in perforating, such as a plurality of perforating guns schematically depicted at 40, along with electrical power and signal communication pathways. To perforate the casing 34, the work string 30 may be lowered through casing 34 until the perforating guns 40 are positioned as desired relative to the formation 14. Thereafter, the shaped charges within the string of perforating guns 40 are sequentially fired, either in an uphole to downhole or a downhole to uphole direction. Upon detonation, the liners of the shaped charges form jets that create a spaced series of perforations extending outwardly through the casing 34, cement 36 and into the formation 14. These perforations allow fluid communication between the formation 14 and the wellbore 32.
The detonator 50 includes an electrically conductive detonator body 52 having an outer surface 51 with an outer diameter (OD) and an inner surface 53 having an inner diameter (ID). The detonator body 52 may comprise a ferrous material that provides electrical conductivity and is economical to produce. Alternative configurations also within the scope of this disclosure could incorporate a non-conductive shell (e.g., a plastic or composite material) with electrically conductive circuit paths or traces arranged thereon to provide the electrical conductivity. A resistor initiator 70 is disposed inside the detonator body 52 adjacent an explosive material 56. A insulator cap 58 is provided at an end of the detonator body 52. The insulator cap 58 optionally overlaps with the outer surface 51 (e.g., the OD) and inner surface (e.g., the ID) of the detonator body 52 to provide a tight fit with the detonator body 52. A grounding element 55 inside the detonator body 52 couples the detonator body 52 to a first lead of the resistor initiator 70. An electrically-conductive clip 60 is assembled to the detonator 50 to shunt the detonator 50 as further described below, so that any unexpected electrical phenomena that may apply an electrical current and/or voltage to the detonator body 52 is unlikely to initiate the explosive material 56 inside the detonator body 52.
The clip 60 is optionally a unitary, electrically-conductive structure that is particularly shaped to efficiently and compactly extend from the arm 64, where it externally contacts the detonator body 52, to an end inside the detonator body 52, where the clip 60 couples to the resistor initiator 70. More particularly, the interior portion 62 of the clip 60 is a straight section that extends from the resistor initiator 70 to where it exits the detonator body 52 through the insulator cap 58. After exiting the insulator cap 58, the clip 60 includes a first bend 61 to route the clip 60 close to the insulator cap 58, and a second bend 63 to route the arm 64 of the clip 60 back toward the external surface 51 of the detonator body 52, where the clip 60 electrically contacts the detonator body 52. The clip 60 in this example may comprise a spring-like material, such as a flexible steel that can maintain an elastic stress without yielding to remain biased into electrical contact with the detonator body 52. Alternatively, the clip 60 could be relatively stiff and inflexible and include a spring pivot (schematically indicated at 67 but not required in this example configuration), or the equivalent, to bias the arm 64 into engagement with the detonator body 52. The clip 60 may have sufficient strength and rigidity to also help physically secure the detonator 50 within a detonator housing as discussed below.
The system 100 includes a remote switch 120 that is structurally separated from the detonator 50. For example, the switch 120 may be a circuit located somewhere else in the system 100 such as in another part of a perforating gun assembly, and electrically wired along the system to the detonator receptacle 110. In this example configuration, the switch 120 is not involved in un-shunting the detonator 50 since that function is automatically performed by virtue of insertion of the detonator body 52 into the detonator receptacle 110. Rather, the switch 120 may comprise a circuit that is configured to send electrical power and/or data signals to components of the system 100. In particular, the switch 120 may be used to send a detonation signal to the detonator 50 along a circuit path 122 from the switch 120 to the detonator 50. Accordingly, by plugging the detonator body 52 into the detonator receptacle 110, the detonator is un-shunted as described above as well as placed in electrical communication with the switch 120. When an operator or controller generates a detonation signal 124, the detonation signal 124 may be communicated along the circuit path 122 to the detonator 50 and along the un-shunted circuit path 85 to initiate the explosive material 56 inside the detonator body 52.
The well-perforating system 100 further includes a detonator cord (alternatively referred to as a “det cord”) 130 arranged in proximity to the detonator receptacle 110. The figure shows a side-by-side arrangement of detonator cord 130 to detonator 50, by way of example, but other arrangements such as an end-to-end arrangement of a det cord and detonator are also within the scope of this disclosure. When the detonator 50 is initiated as described above, the detonation cord 130 is energized, which will fire a set of one or more (“N”) perforation charges 144 that are coupled with the detonation cord 130.
Aspects of the disclosure may extend to methods that may be used to perforate a well while avoiding accidental firing of detonators prior to a deliberate well-perforating operation, such as prior to assembly of the well-perforating system components. In one example, a well-perforating safety method involves grounding a first lead of a resistor initiator to an electrically conductive detonator body housing an explosive material adjacent the resistor initiator. A second lead of the resistor initiator is coupled to an electrically-conductive clip electrically contacting an external surface of the detonator body, thereby forming a shunted circuit path bypassing the explosive material. The arm may then be moved away from the detonator body, such as by insertion of the detonator body into a detonator receptacle on a detonator housing, to switch the shunted circuit path to an un-shunted circuit path along the clip to the resistor initiator. This may urge a non-electrically conductive portion of the detonator housing between the detonator body and the clip. Once un-shunted, the detonator may be detonated by transmitting a detonation signal along the un-shunted circuit path to the detonator, thereby initiating the explosive material inside the detonator body. The detonation signal may be generated using an electrical circuit structurally separate from the detonator body.
Thus, the disclosure encompasses various systems and methods for perforating a well, with the safety of shunted circuit path and the ease and convenience of not requiring a bulky PCB to provide the shunting. These system and methods may include any suitable combination of features disclosed herein, including but not limited to the following examples.
Example 1. A detonator for a perforating gun, the detonator comprising: an electrically-conductive detonator body; a resistor initiator inside the detonator body; a grounding element inside the detonator body coupling the detonator body to a first lead of the resistor initiator; and an electrically-conductive clip having an interior portion coupled to a second lead of the resistor initiator inside the detonator body and an arm biased to electrical contact with an external surface of the detonator body to shunt the detonator, wherein the arm is moveable away from the detonator body to un-shunt the detonator.
Example 2. The detonator of Example 1, wherein the arm of the electrically-conductive clip is automatically moved away from the detonator body in response to insertion of the detonator body into the detonator housing.
Example 3. The detonator of Example 2, wherein the arm is biased toward the detonator body to secure the detonator body to the detonator housing in response to insertion of the detonator body into the detonator housing.
Example 4. The detonator of any of Examples 1 to 3, further comprising: a insulator cap closing an end of the detonator body, wherein the clip extends through the insulator cap to the resistor initiator.
Example 5. The detonator of Example 4, wherein the insulator cap overlaps with an outer diameter and inner diameter of the detonator body.
Example 6. The detonator of any of Examples 1 to 5, wherein the grounding element comprises a grounding body frictionally engaging an inner diameter of the detonator body and a grounding lead extending from the grounding body to the first lead of the resistor initiator.
Example 7. The detonator of any of Examples 1 to 6, wherein the clip is a unitary structure from the arm to an end where the clip is coupled to the second lead of the resistor initiator.
Example 8. A well-perforating system, comprising: a charge carrier for removably carrying a plurality of perforating charges; a detonator housing securable to an end of the charge carrier and including a detonator receptacle; and a detonator including an electrically-conductive detonator body receivable within the detonator receptacle of the detonator housing, a resistor initiator inside the detonator body, a grounding element inside the detonator body coupling the detonator body to a first lead of the resistor initiator, and an electrically-conductive clip electrically coupled to a second lead of the resistor initiator inside the detonator body and including an arm biased toward electrical contact with an external surface of the detonator body to shunt the detonator, wherein the arm is moveable away from the detonator body to un-shunt the detonator.
Example 9. The well-perforating system of Example 8, further comprising: a switch physically separated from the detonator body but electrically coupled to the detonator body when the detonator body is received within the detonator receptacle.
Example 10. The well-perforating system of Example 8 or 9, further comprising: a detonator cord in proximity to the detonator receptacle; and an explosive material inside the detonator body that initiates in response to an un-shunted electrical current from the clip through the resistor initiator to the explosive material.
Example 11. The well-perforating system of any of Examples 8 to 10, wherein the detonator housing comprises a non-electrically conductive portion that urges the electrically-conductive clip away from the detonator body in response to the receiving of the detonator body into the detonator housing to un-shunt the detonator.
Example 12. The well-perforating system of Example 11, wherein the arm is biased toward the detonator body to help secure the detonator to the detonator housing in response to insertion of the detonator body into the detonator housing.
Example 13. The well-perforating system of any of Examples 8 to 12, further comprising: a insulator cap closing an end of the detonator body, wherein the clip extends through the insulator cap to the resistor initiator.
Example 14. The well-perforating system of Example 13, wherein the insulator cap overlaps with an outer diameter and inner diameter of the detonator body to provide a tight fit.
Example 15. The well-perforating system of any of Examples 8 to 14, wherein the grounding element comprises a grounding body frictionally engaging an inner diameter of the detonator body and a grounding lead extending from the grounding body to the first lead of the resistor initiator.
Example 16. The well-perforating system of any of Examples 8 to 15, wherein the clip is a unitary structure from the arm to an end where the clip is coupled to the second lead of the resistor initiator.
Example 17. A well-perforating safety method, comprising: grounding a first lead of a resistor initiator to an electrically conductive detonator body housing an explosive material adjacent the resistor initiator; coupling a second lead of the resistor initiator to an electrically-conductive clip including an arm electrically contacting an external surface of the detonator body, thereby forming a shunted circuit path bypassing the explosive material; and
moving the arm away from the detonator body to switch the shunted circuit path to an un-shunted circuit path along the clip to the resistor initiator.
Example 18. The method of Example 17, further comprising: transmitting a detonation signal along the un-shunted circuit path to the detonator, thereby initiating the explosive material inside the detonator body.
Example 19. The method of Example 18, wherein transmitting the detonation signal comprises generating the detonation signal using an electrical circuit structurally separate from the detonator body.
Example 20. The method of any of Examples 17 to 19, wherein moving the arm away from the detonator body comprises inserting the detonator body into a detonator housing to urge a non-electrically conductive portion of the detonator housing between the detonator body and the clip.
For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.
Therefore, the present embodiments are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present embodiments may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual embodiments are discussed, all combinations of each embodiment are contemplated and covered by the disclosure. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present disclosure.
