MULTI-PHASE, SINGLE POINT, SHORT GUN PERFORATION DEVICE FOR OILFIELD APPLICATIONS

Abstract

An apparatus for perforating an unconventional subterranean formation includes a charge holder having a passage along a long axis, a detonating device positioned in the passage and a plurality of shaped charges supported by the charge holder and circumferentially distributed along a same plane that is transverse to the long axis. Each shaped charge is formed of at least a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case. All of the shaped charges are directly energetically coupled to the detonating device.

Description

BACKGROUND OF THE DISCLOSURE

1. Field of Disclosure

The present disclosure relates to an apparatus and method for completing a well.

2. Description of the Related Art

Hydrocarbons, such as oil and gas, are produced from cased wellbores intersecting one or more hydrocarbon reservoirs in a formation. These hydrocarbons flow into the wellbore through perforations in the cased wellbore. Perforations are usually made using a perforating gun loaded with shaped charges. The gun is lowered into the wellbore on electric wireline, slickline, tubing, coiled tubing, or other conveyance device until it is adjacent to the hydrocarbon producing formation. Thereafter, a surface signal actuates a firing head associated with the perforating gun, which then detonates the shaped charges. Projectiles or jets formed by the explosion of the shaped charges penetrate the casing to thereby allow formation fluids to flow through the perforations and into a production string.

Conventional perforating tool generate a shot pattern placing tunnels principally along an axial length of a wellbore. The present disclosure proposes non-conventional perforating tools that may enhance completion activity such as hydraulic fracturing.

SUMMARY OF THE DISCLOSURE

In aspects, the present disclosure provides an apparatus for perforating a subterranean formation. The apparatus may include a charge holder having a passage along a long axis; a detonating device positioned in the passage; and a plurality of shaped charges supported by the charge holder and circumferentially distributed along a same plane that is transverse to the long axis. Each shaped charge is formed of at least a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case. All of the shaped charges are directly energetically coupled to the detonating device.

In further aspects, the present disclosure provides a method for perforating an unconventional subterranean formation. The method may include positioning the above-described apparatus in a wellbore and firing the apparatus.

The above-recited examples of features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:

FIG. 1 is a schematic sectional view of a portion of a horizontal well in which are positioned perforating guns according to embodiments of the present disclosure;

FIGS. 2A and 2B illustrate shot patterns obtained by perforating guns shown in FIG. 1;

FIG. 3A is an isometric view of a charge holder made in accordance with one embodiment of the present disclosure;

FIG. 3B is an isometric view of an charge holder made in accordance with one embodiment of the present disclosure;

FIG. 4 is a schematic sectional view of a carrier in accordance with one embodiment of the present disclosure;

FIG. 5 is a schematic sectional view of one embodiment of an apparatus of the present disclosure as positioned within a well penetrating a subterranean formation;

FIG. 6 is a schematic side view of a perforating gun in accordance with one embodiment of the present disclosure that uses one or more scallops;

FIGS. 7A-C illustrate various detonation arrangements for perforating guns made in accordance with embodiments of the present disclosure;

FIGS. 8A, B illustrate segmented cases for perforating guns made in accordance with embodiments of the present disclosure;

FIG. 9 is an exemplary shaped charge that may be used with perforating guns in accordance with embodiments of the present disclosure;

FIG. 10 is schematically illustrates a single detonating device being in energetic contact with a plurality of shaped charges on a single plane in accordance with embodiments of the present disclosure; and

FIG. 11 is schematically illustrates a pocket for receiving a shaped charge in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Aspects of the present disclosure provide methods and related perforating tools for completing unconventional formations, such as hydrocarbon-bearing shale formations. For the present disclosure, an “unconventional” formation is generally a formation that has a permeability that is less than ten millidarcy (mD). Many “unconventional” formations have a permeability between one nano-darcy (nD) and one millidarcy (mD).

Referring to FIG. 1, there is shown a horizontal section of a wellbore 10 in which are positioned perforating guns 50, 60 in accordance with embodiments of the present disclosure. Each gun 50, 60 includes shaped charges 70. The gun 50 has the shaped charges distributed circumferentially on one plane 72. The gun 60 has the shaped charges distributed circumferentially on two planes 74, 76. The planes 72, 74, 76 of FIG. 1 are transverse to a long axis 11 of the wellbore 10, e.g., the axis along which fluid flows along the wellbore 10.

The number of shaped charges 70 on each plane may be varied to suit a particular situation. A plane may include only one shaped charge 70 or four or more shaped charges 70. In certain situations, two or three shaped charges 70 may be used. While not required, shaped charges 70 are typically evenly distributed along their respective planes; e.g., 180 degrees apart for two shaped charges 70, 120 degrees apart for three shaped charges 70, 90 degrees apart for four shaped charges 70, etc. The maximum number of shaped charges 70 on a particular plane depends, in part, on the dimensions of the shaped charge, the charge holding structure, and the carrier tube.

FIG. 2A illustrates the “shot pattern” 52 that can be obtained by the gun 50 (FIG. 1), assuming four shaped charges 70 are used. In one embodiment, the perforating gun 50 is configured to form a shot pattern 52 that has perforations 80 of limited penetration. For example, the perforations 80 extend through a casing 12 and cement sheath 14, but extend only minimally, if at all, into a surrounding formation 16.

FIG. 2B illustrates the “shot pattern” 62 that can be obtained by the gun 60 (FIG. 1), assuming four shaped charges 70 are used at each plane 74, 76. The shot pattern 62 includes a first set 64 of visible perforations and a second set 66 of hidden perforations 80. It should be noted that the shaped charges 70 of each plane 74, 76 are out of phase by forty-five degrees with one another.

FIG. 3A illustrates one non-limiting embodiment of a charge holder 90 for the gun 50 (FIG. 1). The charge holder 90 may be a cylindrical body that includes cavities 92 in which the shaped charges 70 (FIG. 1) are seated. In one arrangement, the cavities 92 may be pockets formed and circumferentially distributed on an outer surface 91 of the body 93. Each cavity 92 may be defined by an interior seating surface 95 against which the shaped charge 70 (FIG. 1) seats. Certain embodiments may use a cup or conical shape for the seating surface 95. That is, the seating surface 95 may generally follow the curvature or angle of a body of a shaped charge 70 (FIG. 1); i.e., the seating surface 95 is complementary to the body of the shaped charge 70 (FIG. 1). In some embodiments, the seating surface 95 may restrict radially inward and/or lateral movement of the shaped charge 70 (FIG. 1). The charge holder 90 may be formed of steel or be molded of a non-metal material such as plastic. The shaped charges 70 (FIG. 1) may be press fit into the cavities 92 or secured in the cavities 92 using fastening elements (not shown) such as clips, tabs, etc.

For arrangements using four shaped charges 70 (FIG. 1), the charge holder 90 may include four circumferentially distributed cavities 92, which are all arranged along the same plane 72 (FIG. 1). One or more passages 94 may be used to route equipment such as a detonating device (not shown) and/or wiring (not shown). The passage 94 may be an internal bore that extends partially or completely through the body 93. In some embodiments, the charge holder 90 may be formed as a unitary body formed of a metal, plastic, composite, ceramic, and/or other suitable material. In some embodiments, the charge holder 90 may be formed of a material that disintegrates or is consumed upon use.

In embodiments, the body 93 of the charge holder 90 may be a substantially solid cylinder. For the purposes of the present disclosure, a cylinder is considered “solid” if at least twenty five percent of a radius 101 from a center of the passage 94 to the outer surface 91 is formed of a solid material. Other suitable embodiments may have solid material forming at least forty percent, at least fifty percent, or at least seventy five percent of the radius 101. A “solid” cylinder, as referred to in the present disclosure, is in contrast to a “hollow” cylinder. A hollow cylinder has a wall that makes up less than forty percent of the radius 101. A conventional tube or pipe is representative of a hollow cylinder.

FIG. 3B illustrates one non-limiting embodiment of a charge holder 96 for the gun 60 (FIG. 1). The charge holder 96 is similar to that of the charge holder 90 (FIG. 3A). However, the cavities 92 are arranged on two planes 74, 76 (FIG. 1). In this embodiment, the cavities 92 of each plane 74, 76 are out of phase by forty-five degrees with one another.

FIG. 4 illustrates a carrier 100 that may be used with the perforating guns 50, 60 (FIG. 1). The carrier 100 includes a bore 102 for receiving a charge holder, e.g., charge holder 90. Also, a circumferential groove 94 is formed on the outer surface to provide a weakened wall section that allows perforating jets to exit a perforating gun with less loss of energy. The groove 94 extends all the way around the carrier 100. Therefore, there is no need for angular/circumferential alignment between the shaped charges 70 and the circumferential groove 94. Rather, the carrier 100 needs only an internal stop 97 to axially align the shaped charges 70 with the groove 94. By “axially aligned,” it is meant that the shaped charges 70 and the circumferential groove 94 are at the same plane 72 (FIG. 1) that is transverse to the long axis 11 (FIG. 1).

It should be noted that the charge holder 90 may be radially “free-floating” in the bore 102 of the carrier 100. By “free-floating,” it is meant that the charge holder 90 can move laterally, or transverse to the long axis 11 (FIG. 1). The charge holder 90 is only limited in this lateral movement by the inner wall defining the bore 102. There are no structures connected to the charge holder 90 that restrict lateral movement.

Referring to FIG. 3A, the arrangement of multiple shaped charges along one plane may be advantageous during hydraulic fracturing operations. The shaped charges 70 (FIG. 1) form perforations 80 along the same plane 72 (FIG. 1). Thus, hydraulic fracturing fluid 110 flows out of the perforations 80 at the same axial location, but at different circumferential locations. Directing fracturing fluid 110 in this manner may minimize the tortuosity of the “fraccing” event and minimize the pressures required to create formation fractures and allow better proppant placement.

From the above, it should be appreciated that perforating guns according to the present disclosure can be relatively short; e.g., less than one foot. Further, the use of the charge holders 90, 96 may eliminate the need for end plates or other similar structures used to support a conventional charge holding structure.

The above perforating tools may be used to complete a hydrocarbon producing well. Referring to FIG. 5, there is shown a well construction and/or hydrocarbon recovery facility 101 positioned over a subterranean formation of interest 102. The formation 103 is an unconventional formation. As described above, the nature of the unconventional formation 103 is that the rock and earth, which is usually a type of shale, is highly non-permeable; i.e., a permeability that is less than ten millidarcy (mD).

The facility 101 can include known equipment and structures such as a rig 106 and a production structure 108. The production structure 108 can include casing, liners, cement, and other wellbore equipment. A work string 110 is suspended within a wellbore 10 from the rig 106. The work string 110 can include drill pipe, coiled tubing, wire line, slick line, or any other known conveyance means. The work string 110 can include telemetry lines or other signal/power transmission mediums that establish one-way or two-way telemetric communication. A telemetry system may have a surface controller (e.g., a power source) 112 adapted to transmit electrical signals via a suitable cable or signal transmission line.

A perforating gun train 140 is shown in a deviated section 142 of the wellbore 10. The gun train 140 may include one or more guns according to the present disclosure, e.g., guns 50, 60. By deviated, it is meant a section of the wellbore 10 is not vertical. The deviation from a vertical datum can be between one to ninety degrees (horizontal) or greater in some instances. In embodiments, the deviation may be greater than thirty degree, greater than forty five degree, or greater than sixty degrees. By way of reference, a deviation less than ninety degrees would have the section 142 pointed downward and a deviation greater than ninety degrees would have the section 142 pointed upward. By “pointed,” it is meant the direction along which the wellbore 10 was drilled.

When fired, the perforating gun train 140 creates one or more openings as shown in FIGS. 2A and/or 2B.

It should be understood that the teachings of the present disclosure are susceptible to numerous variants and embodiments. Non-limiting variants are described below.

As noted above, the present disclosure is not limited to any particular number of shaped charges per plane. A plane may include only one shaped charge, two shaped charges, three shaped charges, or four or more shaped charges. Also as discussed above, while not required, shaped charges may be evenly distributed along their respective planes; e.g., 180 degrees apart for two shaped charges, 120 degrees apart for three shaped charges, 90 degrees apart for four shaped charges, etc.

Referring to FIG. 6, in certain embodiments, a carrier 100 may include one or more scallops 160 to reduce a wall thickness. The scallop 160 is contrasted from the circumferential groove 94 (FIG. 4) in that the scallop 160 is a localized reduction in wall thickness of the carrier 100. The shaped charge(s) 70 may be aligned with the scallop(s) 160 using a key 162 fixed to the charge holder 90 that seats within a groove or keyway 164 formed along an inner surface of the carrier 100. Thus, when the key 162 seats within the keyway 164, there is circumferential alignment between the shaped charge(s) 70 and the scallop(s) 160. When the charge holder 90 abuts the internal stop 97, the scallop(s) 160 are axially aligned with the shaped charges 70. It should be understood that the key 162 and keyway 164 are merely illustrative of the alignment members that may be used to circumferentially align the shaped charge(s) 70 with the scallops(s) 160. Other alignment members may use snap rings/slots, pins/bores, etc.

Referring to FIGS. 7A-C, there are shown different arrangements for detonating shaped charges 70. In these arrangements, it should be appreciated at a single detonating device detonates all of the shaped charges 70 in a common plane. Further, in these arrangements, all of the shaped charges 70 are directly energetically coupled to a detonating device. By “directly energetically coupled,” it is meant that the detonation energy from a detonating device is transmitted to the shaped charges 70. The shaped charges 70 may or may not be in physical contact with the detonating device, but are sufficiently close enough that the energy released by the detonating device detonates the shaped charges 70. Thus, in a direct energetic coupling, no intervening energetic element external to the shaped charge is used transfer a detonation from a detonating device to the shaped charges.

In FIG. 7A, the shaped charges 70 are detonated directly by a detonating cord 170. The detonating cord 170 may be detonated by a detonator 172, that is directly or indirectly activated by a signal sent from the surface. In FIG. 7B, the shaped charges 70 include booster charges 176, which are detonated by the detonating cord 170. The booster charge 176 may be internal to the shaped charge 70 and not a separate element. In FIG. 7C, the shaped charges 70 are detonated directly by the detonator 172, which may be directly or indirectly activated by a remote signal. Optionally, the shaped charges 70 may include internal booster charges 176. Thus, it should be appreciated that a detonating device is any device that releases sufficient energy (e.g., thermal energy, shock waves, pressure wave, etc.) capable of detonating a plurality of shaped charges 70, all of which are on a common plane via a direct energetic coupling.

FIGS. 8A and B illustrate embodiments of a charge holder 90 that is segmented segments. Referring to FIG. 8A, the charge holder 90 may be a cylindrical body that includes three body segments 190. In one arrangement, each body segment 190 is “pie shaped;” i.e., generally defined by two radii from a center and an arc. The surfaces aligned with each radii may be considered radial surfaces. The radial surfaces of each body segment 190 are contiguous with one another such that, when assembled, the body segments 190 form a solid cylindrical body. Each body segment 190 has a cavity 192, which may be a pocket, formed on an outer surface 194 of the body segment 190. Each cavity 192 may be defined by an interior seating surface 196 against which the shaped charge 70 (FIG. 1) seats, which may be the same as the seating surface 95 (FIG. 3A) described previously. The segmented charge holder 90 includes a central passage 200 for receiving the device that detonates the shaped charges 70 (FIG. 1), e.g., detonating cord, booster charge, bi-directional booster charge, detonator, a device providing a high-order detonation, etc.

FIG. 8A shows a charge holder 90 with three body segments 190 whereas FIG. 8B depicts an arrangement that has four body segments 202. The body segments 190, 202 may be molded of a non-metal, such as plastic. The body segments 190, 202 may be held together in a cylinder by any suitable means. For example, an O-ring may be fitted into one or more grooves 205 formed on the body segments, e.g., body segment 202. Additionally or alternatively, other retaining members, such as clips, fasteners, adhesives, etc. may be used to secure the body segments 190, 202 to one another.

Additionally, in some embodiments, the body segments 190, 202 may be a casing of a shaped charge; i.e., an energetic material (not shown) may be disposed in the cavity 192, which is then enclosed by a suitable liner (not shown). It should be appreciated in such embodiments, a perforating tool eliminates a charge holder; i.e., the shaped charges are self-supporting in a carrier. By “self-supporting,” it is meant that the shaped charges structurally can support one another to maintain a desired relative orientation.

It is emphasized that the perforating tools of the present disclosure is not limited to any particular shaped charge design or configuration. Merely for better understanding, there is illustrated in FIG. 9, one suitable shaped charge 70 that may be used with the above-described perforating tools. The shaped charge 70 may have a frusto-conical charge case 224. The charge case 224 is open at the outer end 230. Disposed within the interior of the case 224 is a liner 228 having a generally conical or frusto-conical configuration. Disposed between the liner 228 and interior wall 226 of the casing 224 is an explosive material 234. The charge case 224 has an apex 236 at a closed end 238. A detonating device 240 for detonating the explosive 234 is positioned adjacent to the apex 236. In this configuration, it should be noted that the apex 236 does not enclose the detonating device 240. As seen in FIG. 10, the apex 236 is shaped to be sufficiently narrow to allow a plurality of shaped charges 70 to be circumferentially arrayed on the same plane around the detonating device 240. Thus, in one aspect, the detonating surface may be defined by an outer surface. All of the shaped charges 70 have an energetic coupling with this outer surface. While the outer surface may define a circumferential body, the outer surface may also define other geometric shapes such as squares, rectangles, ovals, triangles, etc. Regardless of the geometric shape, there are multiple energetic couplings to such an outer surface. While the apex 236 is shown as a concave surface, the apex 236 may also be flat or have any other geometry.

It should be noted that for the FIGS. 8A, B embodiments, a shaped charge 70 as configured in FIG. 9 may modified as previously described. That is, the body segment 190, 202 (FIGS. 8A,B) is the charge case 224 (FIG. 9), in such case they may be referred to as charge case segments. Because the assembly of charge case segments 190, 202 form a cylindrical body of shaped charges that can be directly inserted into a carrier 100 (FIG. 4), a separate structure for holding the shaped charges, such as a charge tube or strip, is not required. That is, the shaped charges are considered self-supporting in the carrier 100 (FIG. 4).

A non-limiting embodiment of a perforating tool having self-supporting shaped charges may include a carrier, a shaped charge assembly disposed in the carrier, and a detonating device disposed in the carrier. The shaped charge assembly may include a plurality of shaped charges. Each shaped charge may include a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case. The shaped charges may be circumferentially disposed around the detonating device such that all of the shaped charges are on the same plane, the plane being transverse to a long axis of the carrier. Additionally, each charge case has a radial surface substantially contiguous with a radial surface of an adjacent shaped charge. The charge cases are arranged to form a solid cylindrical body. Optionally, a retaining member may be disposed around the shaped charges to secure the shaped charges to one another. Optionally, the shaped charges may have a direct energetic coupling to the detonating device.

Referring to FIGS. 3A and 9, as described previously the seating surface 95 may generally follow the curvature or angle of an outer surface 250 of the charge case 224 of the shaped charge 70. The seating surface 95 may be contiguous for some or all of the outer surface 250. For example, in some embodiments, the seating surface 95 may be contiguous with the seating surface 95 for at least twenty five percent of a linear distance 252 between the base 230 and the apex 232. In other embodiments, the contiguous distance between the base 230 and the apex 232 may be at least forty percent, at least fifty percent, or at least seventy five percent. In other embodiments, the seating surface 95 is completely contiguous and only disrupted by an opening (not shown) through which at least the apex 236 is positioned in the passage 94 or passage 200 (FIG. 8A). By “contiguous,” it is meant that the seating surface 95 generally follow the curvature of the outer surface 250. Continuous physical contact is not required. Similar percentages for contiguous distance may be used for the interior seating surface 196 illustrated in FIG. 8A.

FIG. 11 illustrates the seating surface 95 associated with the pockets 92, 192 described above. The seating surface 95, 196 terminates at an opening 193 through which the apex 236 (FIG. 9) enters the passage 94 or passage 200 as described previously.

In the context of the present disclosure, a detonation is a supersonic combustion reaction, which can create shock waves and release thermal energy. High explosives (RDX, HMX, etc.) are materials that will detonate. A detonator is a device used to trigger an explosive material, such as the explosive material in a shaped charge or a detonating cord. Detonators can be mechanically or electrically initiated.

The foregoing description is directed to particular embodiments of the present disclosure for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope of the disclosure. Thus, it is intended that the following claims be interpreted to embrace all such modifications and changes.

Claims

1. An apparatus for perforating a subterranean formation, comprising:

a charge holder having a passage along a long axis;

a detonating device positioned in the passage; and

a plurality of shaped charges supported by the charge holder and circumferentially distributed along a same plane that is transverse to the long axis, wherein each shaped charge is formed of at least a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case, and wherein all of the shaped charges are directly energetically coupled to the detonating device.

2. The apparatus of claim 1, wherein the charge holder is solid.

3. The apparatus of claim 1, wherein the charge holder includes a plurality of circumferentially distributed pockets formed on an outer surface of the charge holder, and wherein each pocket receives one shaped charge of the plurality of shaped charges.

4. The apparatus of claim 3, wherein each pocket has a seating surface complementary to a body of the shaped charge received therein.

5. The apparatus of claim 1, wherein at least fifty percent of a radius from a center of the passage to the outer surface is formed of a solid material.

6. The apparatus of claim 1, wherein the charge holder includes a plurality of body segments.

7. The apparatus of claim 6, wherein a body segment of each segment is the charge case of each of the plurality of shaped charges.

8. The apparatus of claim 1, wherein the detonating device is a detonator responsive to a surface signal.

9. The apparatus of claim 1, wherein the detonating device is one of: (i) a booster charge, and (ii) a detonating cord.

10. The apparatus of claim 1, further comprising a carrier having a bore receiving the charge holder, the carrier having a circumferential groove extending fully around an outer surface, the circumferential groove being axially aligned with the plurality of shaped charges.

11. A method for completing an unconventional subterranean formation, comprising:

positioning a perforating tool in a section of the wellbore that intersects the unconventional formation, wherein the wellbore is deviated from a vertical datum, the perforating tool including: a charge holder having a passage along a long axis; a detonating device positioned in the passage; and a plurality of shaped charges supported by the charge holder and circumferentially distributed along a same plane that is transverse to the long axis, wherein each shaped charge is formed of at least a charge case, an explosive material disposed in the charge case, and a liner enclosing the explosive material in the charge case, and wherein all of the shaped charges are directly energetically coupled to the detonating device; and

firing the perforating tool to form at least one opening in the unconventional formation.

12. The method of claim 11, further comprising:

fracturing the formation by pumping a fracturing fluid through the at least one opening.

13. The method of claim 11, wherein the deviation is at least forty five degrees from the vertical datum.

14. The method of claim 11, wherein the unconventional formation has a permeability that is less than ten millidarcy (mD).