Shaped charge with limited penetration

Abstract

A shaped charge operable to form a perforation with limited penetration in a borehole, the shaped charge comprising: a housing (60); a main mass explosive material (64) disposed within the housing (60); a liner (62) coupled to the housing (60) and substantially enclosing the main mass explosive material (64) within the housing (60), the liner defining an external bulge (74) forming an apex (72); and an inert jet blocker (48) formed of a solid material cast within the external dome to a predetermined height above the apex (72).

Description

GENERAL STATE OF THE ART

[0001] The present disclosure generally relates to well completions, e.g., for wells used in oil and gas exploration and production. More specifically, embodiments of the disclosure relate to reducing the force of an explosive charge to provide limited penetration into a geological formation or penetration through a limited number of different layers (casing, liner, etc.) disposed within a wellbore.

[0002] Hydrocarbons can be produced through wellbores drilled from a position on the Earth's surface through a variety of producing and non-producing geological formations. A wellbore may be substantially vertical or may contain horizontal and other deviating sections. A wellbore may undergo a variety of maintenance operations after the well is completed. For example, a casing string may be set and cemented in the wellbore to stabilize the geological formation surrounding the wellbore. A liner is provided to extend at least partially within the casing string, and the casing string and / or liner may be perforated by firing a perforating gun or perforating tool.

[0003] Perforation tools may contain explosive charges that can be deployed at an appropriate depth downhole and detonated to perforate one or more of the various casing and liner layers and / or the geological formation surrounding the wellbore. Creating a large perforation in the casing's geological formation is often desirable to increase the permeability of hydrocarbons into the wellbore. In some cases, a limited or controlled explosive charge may be desirable to create perforations that extend through some, but not all, of the casing layers in the wellbore, for example, to promote fluid flow between the annular intermediate regions in the wellbore.

[0004] US 5 753 850 A discloses features falling within the preamble of claim 1. US 2005 / 0 115 448 A1, US 2016 / 0 245 053 A1, US 7 165 614 B1 and US 6 308 634 B1 are further prior art.

[0005] The invention is defined by the independent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The disclosure is described in detail below, purely by way of example, on the basis of the examples illustrated in the accompanying figures, in which: Fig. 1 is a partial cross-sectional side view of a wellbore system incorporating a perforating tool according to the present disclosure; Fig. 2 is an enlarged, partial cross-sectional view of the perforating tool of Fig. 1, which illustrates a shaped charge therein for forming a perforation with limited penetration through some, but not all, casing layers in the wellbore; Fig. 3 is a cross-sectional view of the shaped charge from Fig. 2 in an unmodified configuration for forming a perforation with unlimited penetration, illustrating a casing, an explosive, and a liner defining an apex; Fig. 4 is a cross-sectional view of the shaped charge from Fig. 2 in a modified configuration for forming a perforation with limited penetration, illustrating a jet blocker installed in the apex of the liner; The Fig. 5A to 5E are sequential schematic views illustrating a jet formed by an unmodified shaped charge to form a perforation with unlimited penetration; The Fig. 6A to 6E are sequential schematic views illustrating a jet formed by a modified shaped charge to form a perforation with limited penetration; and Fig. 7 is a schematic view of a procedure for planning, modifying, and discharging a shaped charge to form a limited penetration shaped charge according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0007] For example, the present disclosure includes a shaped charge for use in a perforating tool in a wellbore. The shaped charge includes a jet blocker disposed in an apex of a parabolic or conical casing that limits the velocity or length of a jet formed upon discharge of an explosive within the shaped charge. The jet blocker may comprise an inert material of a castable and curable type, such as an epoxy or flowable plastic, that can be easily introduced into an existing shaped charge to fill the casing to any desired height. The height and material selected for the jet blocker determine the extent to which the penetration achieved by the shaped charge is limited and thus determines which annulus in the wellbore can be penetrated during operation.

[0008] Fig. 1 is a partial cross-sectional side view of a wellbore servicing system 10 including a perforating tool 12 according to embodiments of the present disclosure. The wellbore servicing system 10 includes a servicing tower 14 at a position on the earth's surface "S." The servicing tower 14 extends above and around a borehole 16 that penetrates a subterranean geological formation "G." The borehole 16 may be used for the purpose of extracting hydrocarbons, storing hydrocarbons, disposing of carbon dioxide, or the like. The borehole 16 may be drilled into the geological formation "G" using any suitable drilling technique. Although Fig. 1 as extending vertically from the position on the earth's surface "S," in other examples, the borehole 16 may be deviated, horizontal, or curved over at least some portions of the borehole 16. The borehole 16 extends from a position on the earth's surface "S," and in other embodiments, a borehole may extend from a submerged position according to other aspects of the present disclosure.

[0009] Borehole 16, as shown in Fig. 1, is lined with an outer casing 20 and an inner casing 22. The outer casing 20 is secured in place by cement 24, which fills the annular region between the outer casing and the geological formation "G." The inner casing 22 extends within the outer casing 20 to define a target annulus 26 between the inner and outer casings 20, 22. In some embodiments, the perforating tool 12 may be deployed to access the annulus 26 without penetrating the outer casing 20. In other embodiments, a wellbore may be alternately configured, e.g., the wellbore may be open hole, contain tubulars, etc., and other regions in the wellbore may be targeted by the perforating tool 12.

[0010] The perforating tool 12 can be inserted into, retrieved from, rotated within, or otherwise moved within the borehole 16 by a conveyor 30 extending to the position on the earth's surface "S." The conveyor 30 can be a wireline, slickline, coiled tubing, and / or a drill string, as will be appreciated by those skilled in the art. The conveyor 30, the perforating tool 12, and other devices can be coupled together to form a work string 32.

[0011] Fig. Figure 2 is an enlarged, partial cross-sectional view of the perforation tool 12 incorporating a shaped charge 40 therein for forming a perforation with limited penetration. Although the shaped charge 40 is illustrated as a deep penetrating charge, it should be understood that aspects of the present disclosure may be applied to other types of shaped charges, including big-hole or good-hole shaped charges that rely on liner disruption to produce a penetrating jet (see, e.g., Fig. 5E and Fig. 6E).

[0012] An explosion of the shaped charge 40 creates a passageway 44 that extends through the inner casing 22 to the target annulus 26, but not through the outer casing 20. In other embodiments, a passageway could be formed that penetrates all casing and cement layers in a wellbore and extends into the surrounding geological formation "G." The size and / or length of the passageway may be reduced, limited, or controlled by a jet blocker 48 carried by the shaped charge 40.

[0013] The perforating tool 12 includes a carrier body 50 constructed from a cylindrical sleeve. In the illustrated embodiment, the carrier body 50 optionally includes a plurality of radially reduced regions, depicted as scallops or recesses 52. A corresponding one of a plurality of shaped charges 40 is radially aligned with each of the recesses 52, only one of which is in Fig. 2. A discharge end 56 of the shaped charge 40 is arranged adjacent to the recess 52 and an introduction end 58 of the shaped charge 40 is arranged adjacent to a fuse 54 extending through the perforation tool 12. The fuse 54 may be made of an explosive strand, such as Primacord ® , which can be detonated to thereby detonate each of the shaped charges 40 in the perforation tool 12.

[0014] Each of the shaped charges 40 is longitudinally and radially aligned with one of the recesses 52 in the launcher gun body 102 when the perforating tool 12 is assembled. The shaped charges 40 may be arranged in a spatial pattern such that each of the shaped charges 40 is located at its own level or height and is to be detonated individually, such that only one shaped charge 40 is fired at a time. However, it should be understood that alternating arrangements of shaped charges 40 may be used, including cluster-like configurations where more than one shaped charge 40 is located at the same level and detonated simultaneously, without departing from the principles of the present disclosure.

[0015] With reference to Fig. 3 illustrates a shaped charge 40u in an unmodified configuration for forming a perforation with unlimited penetration. The unmodified shaped charge 40u includes a casing 60, a liner 62, and a main mass explosive material 64 disposed between the liner 62 and the casing 60. A booster explosive 68 may be disposed at the inlet end 58 of the shaped charge 40u and may serve to facilitate coupling of the main mass explosive material 64 to the fuse 54 ( Fig. 2) to facilitate.

[0016] The casing 60 serves to protect the internal explosive materials 64, 68 during handling and storage of the shaped charge 40u and provides a mass against which the explosion can react during operation. The casing 60 may, for example, be constructed of steel or another suitable material. The liner 62 may be attached to the casing 60 by an adhesive bead or other mechanical mechanism defined between a liner skirt 70 and the casing 60. The liner 62 may be constructed of any suitable material, including metallic materials such as brass, copper, steel, aluminum, zinc, lead, and tungsten (or combinations of these and other suitable materials). The liner 62 is generally parabolic or conical in shape such that an apex 72 is defined at the innermost end of the external recess 74 of the shaped charge 40u.The shaped charge 40u may generally rely on rupturing the liner 62 to produce a high-velocity jet for creating tunnels or passageways in the geological formation “G” (. Fig. 1) during a perforation event. Often, unmodified shaped charges 40u are provided with at least a portion of the liner 62 constructed of a dense material present in this high-velocity jet. The energy thus transferred to the dense material can be more effectively concentrated to promote deeper tunnels.

[0017] Fig. Figure 4 is a cross-sectional view of the limited penetration shaped charge 40 formed from the unmodified configuration ( Fig. 3) by installing the jet blocker 48. In some embodiments, the jet blocker 48 is a solid plastic or metal billet that is machined to a suitable size and shape and then secured within the recess 74. The jet blocker 48 may be constructed from a material similar to or different from the material of the liner 62. In some embodiments, the jet blocker 48 may be constructed from a castable and curable type material, such as adhesive, epoxy, acrylic, RTV, silicone, or a similar material, which may be cast into the apex 72 of the liner 62 to any desired height "H." As described in more detail below, the height "H" may be predetermined to limit the force generated by the shaped charge 40 during detonation.Thus, a specific target annulus 26 (. Fig. 2) without penetrating a casing layer or other structure surrounding the target annulus 26. In some embodiments, the height "H" may be less than about half of a total height ("TH") defined by the external recess 74.

[0018] The jet blocker 48 can mold itself into the shape of the liner crest 72 without the need for machining and can then cure to bond to the liner 62. An adhesive bond can be created between the jet blocker 48 and the liner 62 either due to the curing of the castable and curable material or through an additional adhesive, if necessary. The jet blocker 48 can thus be secured in place without the need for an additional cover, which could interfere with the operation of the shaped charge. Preferably, the jet blocker 48 can generally comprise lightweight materials so that the susceptibility of the shaped charge 40 to vibration damage when the perforating tool 12 ( Fig. 1) is operated in borehole 16.

[0019] The liner 62 includes a jet production region 76 between the jet blocker 48 and the discharge end 56 of the shaped charge 40. The jet production region 76 of the liner 62 is substantially free of jet blocker material. As described below (see Fig. 6C), the jet production region 76 can break apart upon itself during detonation to produce a jet.

[0020] The Fig. 5A to 5E are sequential schematic views illustrating a jet 80 formed by an unmodified shaped charge 40u to form a perforation with unlimited penetration. Initially or immediately after detonation ( Fig. 5A), the casing 60 and the liner 62 are generally intact. A blast wave propagates through the main mass explosive 64 from the ignition end 58 toward the discharge end 56. When the wave reaches the apex 72 of the liner 62, the liner 62 ruptures radially inward, forming an initial jet ( Fig. 5B) 82. After a time interval, e.g., 20 microseconds, has elapsed after the detonation ( Fig. 5C and Fig. 5D), the liner 62 breaks apart further and the casing 60 begins to disintegrate into fragments 84. After a longer time interval, e.g., 50 microseconds, the liner 62 has completely broken apart and the complete jet 80 can extend along a length “L” towards the geological formation “G” ( Fig. 1) or extend into them. The jet 80 can move at a relatively high speed, e.g., 20,000 ft / s, through casing, cement, and geological layers, forming perforations and passages therein.

[0021] The Fig. 6A to 6E are sequential schematic views illustrating a jet 90 formed by a modified shaped charge 40 to form a perforation with limited penetration. Initially or immediately after detonation ( Fig. 6A), the housing 60, the liner 62, and the jet blocker 48 are generally intact. When the blast wave propagates to the apex 72 ( Fig. 6B), the liner 62 breaks apart and envelops the jet blocker 48 such that a relatively low-density plug 92 is formed within the breaking-apart liner material. The jet blocker 48 prevents the formation of an initial jet 94 of the liner material until a time interval, e.g., 20 microseconds, has elapsed after detonation ( Fig. 6C). The jet 94 does not form until the lining material breaks apart upon itself between / behind the plug 92. The lining 62 breaks apart further and the housing 60 breaks into fragments 96 ( Fig. 6D). After a longer time interval, e.g., 50 microseconds, and after the liner 62 has completely broken apart, the beam 90 may travel along a reduced length “e” compared to the length “L” of the beam 80 ( Fig. 5E). The jet 90 may also travel at a relatively low speed compared to the jet 80. Because the jet 90 is slower and shorter than the jet 80, the jet 90 produces a reduced penetration effect. For example, the jet 90 may impart a relatively low energy to the inner casing 22 ( Fig. 2) so that the jet 90 penetrates only a specific predetermined number of casing layers in the wellbore 16. For example, the jet 90 may penetrate only the inner casing 22 without penetrating the outer casing 20 to form a passage 44 that extends only to the target annulus 26.

[0022] Fig.7 is a schematic view of a procedure 100 for planning, modifying, and discharging a shaped charge 40 to form a limited-penetration shaped charge 40 according to embodiments of the present disclosure. Initially, the procedure 100 begins in step 102 by determining a height "H" for a jet blocker 48 that will produce an expected specific limited penetration effect. The height "H" may be determined empirically. For example, various modified shaped charges 40 with different liner materials and configurations may be tested by detonating a modified shaped charge alongside reference casing coupons to determine the penetration characteristics of the various shaped charges 40. The height "H" of the jet blocker 48 may be varied and tested, and the specific material of the jet blocker 48 may also be varied and tested.For example, different jet blocker materials with different densities, ductility, or other material properties can be tested. Intermediate values ​​can be interpolated and / or estimated based on the empirical tests. A data set of the limited penetration effects of various modified shaped charges 40 can thus be compiled.

[0023] Next, in step 104, if an actual application arises that requires a limited penetration perforation, the actual required limited penetration effect is identified. For example, the exact casing scenario may be evaluated and a target annulus 26 may be identified. The procedure 100 then proceeds to decision 106, which determines whether the data set assembled in step 102 includes the limited penetration effect identified in step 104. If no beam blocker 40 has been tested that would produce the required limited penetration effect, the procedure 100 may return to step 102, where additional testing may be performed.For example, a greater height "H" of a beam blocker 48 may be tested when less force is required, and a lower height "H" may be tested when greater force is required than previously tested test blockers 48 were determined to provide.

[0024] If a jet blocker 10 has been tested that would produce the required limited penetration effect, the procedure proceeds to step 108. An unmodified shaped charge 40u may be provided that includes a liner 62 defining a crest 72. The unmodified shaped charge 40u may, for example, be a commercially available shaped charge with known or documented penetration characteristics.

[0025] Subsequently, these known or documented penetration characteristics may be limited or reduced in step 110 by forming a jet blocker 48 in the internal recess 74 of the unmodified shaped charge 40u. In some embodiments, the jet blocker 48 is formed by first forming a billet of the solid material remote from the shaped charge 40 and securing the billet in the external recess 74 to form the jet blocker 48. The billet may be formed, for example, by machining a metal or plastic blank to have a suitable height "H," and thereafter, the billet may be secured in the recess 74 by an adhesive or other mechanism.

[0026] Alternatively, to form the jet blocker 40, a castable and hardenable material may be poured into the external recess 74 to cover the apex 72 and to the height "H" predetermined in step 102. The castable and hardenable material may be allowed to harden and bond to the liner 62, thereby forming the jet blocker 48. The jet blocker 48 may then support itself within the liner 62 without significantly reshaping the unmodified shaped charge 40u. The jet blocker 48 may be supported vertically within the external recess while the castable and hardenable material hardens.

[0027] The resulting shaped charge 40 can then be lowered into a wellbore 16 to a location in the wellbore adjacent to a target annulus (step 112). The shaped charge 40 can then be detonated in the wellbore 16 to penetrate the target annulus 26 without penetrating the outer casing 20 surrounding the target annulus 26.

[0028] The aspects of the disclosure described below are provided to describe, in a simplified form, a selection of concepts described in more detail above. This section is neither intended to identify central or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0029] In one aspect, the disclosure is directed to a shaped charge operable to form a limited-penetration perforation in a wellbore. The shaped charge includes a casing, a main mass explosive material disposed within the casing, and a liner coupled to the casing and substantially enclosing the main mass explosive material within the casing. The liner defines an external recess forming an apex. The shaped charge also includes a jet blocker formed from a solid material and extending to a predetermined height above the apex within the external recess.

[0030] In one or more embodiments, the beam blocker may be constructed from a curable material that is poured into the external recess and cures within the external recess. The beam blocker may include at least one of the group of materials consisting of adhesive, epoxy, acrylic, RTV, and silicone. In some embodiments, the liner comprises a metal material that forms the external recess into a conical shape.

[0031] In some embodiments, a bond between the jet blocker and the lining material is established by curing the curable material. A jet-forming portion of the lining may be substantially free of the solid material forming the jet blocker. In some embodiments, the predetermined height is less than about half a total height of the external recess. In some embodiments, the shaped charge further includes a booster explosive disposed at an inlet end of the shaped charge.

[0032] In another aspect, the disclosure is directed to a method of modifying a shaped charge to create a limited penetration perforation in a wellbore. The method includes (a) providing a shaped charge having a casing, a bulk explosive, and a liner defining an external recess, and (b) forming a jet blocker by securing a solid material within the external recess to fill a predetermined height of the external recess such that a jet-forming portion of the liner is substantially free of the solid material forming the jet blocker.

[0033] In some embodiments, the method further includes curing a castable and hardenable material within the external recess of the solid jet blocker material. The method may also include bonding the castable and hardenable material to the liner by curing the castable and hardenable material to form a self-supporting jet blocker in the external recess. In some embodiments, the method further includes forming a billet of the solid material remote from the shaped charge and securing the billet in the external recess to form the jet blocker.

[0034] In one or more embodiments, the method further includes determining the height by detonating modified shaped charges adjacent to reference casing coupons and empirically determining the penetration characteristics of various modified shaped charges.

[0035] Empirically determining the penetration properties of various modified shaped charges may involve detonating shaped charges with jet blockers of different heights, densities, and ductilities.

[0036] The method may further include lowering the shaped charge into a wellbore and detonating the shaped charge adjacent to a target annulus. In some embodiments, detonating the shaped charge adjacent to the target annulus includes penetrating the target annulus without penetrating an outer member surrounding the target annulus. In some embodiments, detonating the shaped charge includes fracturing the liner around the jet blocker to form a plug and further fracturing the liner to form a limited-length, limited-velocity jet of the liner material. In another aspect, the disclosure is directed to a perforation tool system for forming a limited-penetration perforation in a wellbore.The perforation tool includes a carrier body constructed from a cylindrical sleeve, a plurality of shaped charges disposed within the carrier body, each of the shaped charges having a casing, a main mass explosive, and a liner defining an external recess, and a jet blocker formed in the external recess of each shaped charge, the jet blocker being formed from a solid material filled to a predetermined height in the external recess such that a jet forming portion of the liner is substantially free of jet blocker material.

[0037] In some embodiments, the perforation tool system further includes a detonating cord extending through the carrier body and coupled to each of the shaped charges. The perforation tool system may also include a conveyor coupled to the carrier body, the conveyor operable to lower the carrier body into a wellbore.

[0038] The Summary of Disclosure is intended solely to provide the United States Patent and Trademark Office and the public at large with a means of quickly determining, through cursory examination, the nature and substance of the technical disclosure and merely represents one or more examples.

[0039] Although various examples have been presented in detail, the disclosure is not limited to the examples shown. A person skilled in the art may make modifications and adaptations to the above examples. Such modifications and adaptations are included within the scope of the disclosure.

Claims

[1] A shaped charge operable to form a perforation with limited penetration in a borehole, the shaped charge comprising: a housing (60); a main mass explosive material (64) disposed within the housing (60); a liner (62) coupled to the housing (60) and substantially enclosing the main mass explosive material (64) within the housing (60), the liner defining an external bulge (74) forming an apex (72); and an inert jet blocker (48) formed of a solid material cast within the external dome to a predetermined height above the apex (72). [2] A shaped charge according to claim 1, wherein the jet blocker (48) is constructed of a hardenable inert material which is poured into the external dome and hardens within the external dome. [3] The shaped charge of claim 2, wherein the jet blocker (48) comprises at least one of the group of materials consisting of adhesive, epoxy, acrylic, RTV, and silicone, and optionally wherein the liner comprises a metal material forming the external bulge in a cone shape. [4] A shaped charge according to claim 2, wherein a bond between the jet blocker (48) and the lining material is made by hardening the hardenable material. [5] A shaped charge according to any one of the preceding claims, wherein a jet forming portion of the liner is substantially free of the solid material forming the jet blocker (48). [6] A shaped charge according to any one of the preceding claims, wherein the predetermined height is less than about half a total height of the external bulge. [7] A shaped charge according to claim 1, further comprising a booster explosive disposed at an inlet end of the shaped charge. [8] A method of modifying a shaped charge to create a limited penetration perforation in a wellbore, the method comprising: Providing a shaped charge having a casing (60), a main mass explosive (64) and a liner (62) defining an external bulge of the shaped charge; and Forming a jet blocker (48) by securing a solid material in the external bulge to fill a predetermined height of the external bulge by pouring the material such that a jet forming portion of the liner is substantially free of the solid material forming the jet blocker. [9] The method of claim 8, further comprising curing a castable and hardenable material within the external dome of the solid jet blocker material, and optionally further comprising bonding the castable and hardenable material to the liner by curing the castable and hardenable material to form a self-supporting jet blocker in the external dome. [10] The method of claim 8 or claim 9, further comprising forming a billet of the solid material remote from the shaped charge and securing the billet in the external bulge to form the jet blocker. [11] The method of any one of claims 8 to 10, further comprising determining the height by detonating modified shaped charges adjacent to reference casing coupons and empirically determining the penetration characteristics of different modified shaped charges, and optionally wherein empirically determining the penetration characteristics of different modified shaped charges includes detonating shaped charges with jet blockers having different heights, densities and ductilities. [12] A method according to any one of claims 8 to 10, further comprising lowering the shaped charge into a borehole and detonating the shaped charge adjacent to a target annulus. [13] A method according to claim 12, wherein either (i) detonating the shaped charge adjacent the target annulus comprises penetrating the target annulus without penetrating an external member surrounding the target annulus, and / or (ii) detonating the shaped charge comprises rupturing the liner around the jet blocker to form a plug and further rupturing the liner to form a jet of liner material of finite length and velocity. [14] A perforation tool system for forming a limited penetration perforation in a wellbore, the perforation tool comprising: a support body (50) constructed from a cylindrical sleeve; a plurality of shaped charges (40) disposed within the carrier body (50), each of the shaped charges (50) having a casing (60), a main mass explosive (64), and a liner (62) defining an external bulge; and a jet blocker (48) formed in the external bulge of each shaped charge, the jet blocker (48) being formed from a solid material cast into the external bulge to a predetermined height such that a jet forming portion of the liner is substantially free of jet blocker material. [15] The perforating tool system of claim 14, further comprising either (i) a detonating cord extending through the carrier body and coupled to each of the shaped charges, and / or (ii) a delivery means coupled to the carrier body, the delivery means operable to lower the carrier body into a wellbore.

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