DEGRADABLE ANCHOR DEVICE WITH RETAINED GRANULAR MATERIAL

Abstract

Therefore in one aspect, an anchoring device is disclosed, including: a degradable substrate with a first hardness wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness. In certain embodiments, the at least one retaining feature is at least one bump ring. In certain embodiments, the at least one bump ring is at least one segmented bump ring. In certain embodiments, the at least one retaining feature is at least one helical feature. In certain embodiments, the at least one retaining feature is at least one knurled region. In certain embodiments, the degradable substrate includes a leading protrusion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a Continuation-In-Part Application of U.S. Non-Provisional patent application Ser. No. 14/561,523, filed Dec. 5, 2014 which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Disclosure

This disclosure relates generally to degradable slip rings and systems that utilize same for downhole applications.

2. Background of the Art

Wellbores are drilled in subsurface formations for the production of hydrocarbons (oil and gas). Hydrocarbons are trapped in various traps or zones in the subsurface formations at different depths. In many operations, such as fracturing, it is required to anchor devices (such as packers, bridge plugs, etc.) in a downhole location to facilitate production of oil and gas. After such operations, anchoring devices must be removed or destroyed before following operations can begin. Such removal operations may be costly and/or time consuming. It is desired to provide an anchoring device that can provide sufficient anchoring performance while providing desired and predictable degradation characteristics.

The disclosure herein provides controlled degradable slip rings and systems using the same for downhole applications.

SUMMARY

In one aspect, an anchoring device is disclosed, including: a degradable substrate with a first hardness wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness.

In another aspect, a method to anchor a downhole device is disclosed, including: providing a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature; applying a granular gripping material to the outer extent of the degradable substrate and the at least one retaining feature, wherein the granular gripping material has a second hardness greater than the first hardness; and retaining the granular gripping material via the at least one retaining feature.

In another aspect, a downhole system is disclosed, including: a casing string; and an anchoring device associated with the casing string, including: a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness.

Examples of certain features of the apparatus and method disclosed herein are summarized rather broadly in order that the detailed description thereof that follows may be better understood. There are, of course, additional features of the apparatus and method disclosed hereinafter that will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure herein is best understood with reference to the accompanying figures, wherein like numerals have generally been assigned to like elements and in which:

FIG. 1 is a schematic diagram of an exemplary drilling system that includes downhole elements according to embodiments of the disclosure;

FIG. 2 is a schematic diagram of an exemplary downhole device for use in a downhole system, such as the one shown in FIG. 1, according to one embodiment of the disclosure;

FIG. 3A shows a partial view of the substrate of an exemplary anchoring device for use with a downhole device, such as the downhole device shown in FIG. 2 for use with a downhole system, according to one embodiment of the disclosure;

FIG. 3B shows a partial cross sectional view of the anchoring device shown in FIG. 3A;

FIG. 3C shows a partial cross sectional view of the anchoring device shown in FIG. 3A with a granular gripping material;

FIG. 4A shows a partial view of the substrate of another exemplary anchoring device for use with a downhole device, such as the downhole device shown in FIG. 2 for use with a downhole system, according to one embodiment of the disclosure;

FIG. 4B shows a partial view of the substrate of another exemplary anchoring device for use with a downhole device, such as the downhole device shown in FIG. 2 for use with a downhole system, according to one embodiment of the disclosure;

FIG. 4C shows a partial view of the substrate of another exemplary anchoring device for use with a downhole device, such as the downhole device shown in FIG. 2 for use with a downhole system, according to one embodiment of the disclosure; and

FIG. 4D shows a partial view of the substrate of another exemplary anchoring device for use with a downhole device, such as the downhole device shown in FIG. 2 for use with a downhole system, according to one embodiment of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows an exemplary embodiment of a downhole system to facilitate the production of oil and gas. In certain embodiments, system 100 allows for fracturing operations to facilitate production of oil and gas. System 100 includes a wellbore 106 formed in formation 104 with casing 108 disposed therein.

In an exemplary embodiment, a wellbore 106 is drilled from a surface 102 to a downhole location 110. Casing 108 may be disposed within wellbore 106 to facilitate production. In an exemplary embodiment, casing 108 is disposed through multiple zones of production Z1 . . . Zn in a downhole location 110. Wellbore 106 may be a vertical wellbore, a horizontal wellbore, a deviated wellbore or any other suitable type of wellbore or any combination thereof.

To facilitate downhole operations, such as fracturing operations, bridge plugs 116a, packers 116b, or other suitable downhole devices are utilized within casing string 108. In certain embodiments, such downhole devices 116a,b are anchored to casing string 108 via an anchor assembly 118. In certain embodiments, bridge plugs 116a utilize an anchor assembly 118 and frac balls 120 to isolate zones Z1 . . . Zn for fracturing operations. In certain embodiments, frac balls 120 are disposed at a downhole location 110 to obstruct and seal fluid flow in local zone 112 to facilitate flow to perforations 114 in conjunction with bridge plugs 116a. In certain embodiments, packers 116b are utilized in conjunction with anchor assembly 118 to isolate zones Z1 . . . Zn for fracturing operations.

In certain embodiments, frac fluid 124 is pumped from a frac fluid source 122 to a downhole location 110 to flow through perforations 114 in a zone 112 isolated by downhole device 116a,b. Advantageously, fracturing operations allow for more oil and gas available for production.

After desired operations (such as fracturing operations) and before following operations, anchoring devices 118 are often removed or otherwise destroyed to allow the flow of oil and gas through casing 108. In an exemplary embodiment, anchoring devices 118 are configured to anchor against casing 108 of local zone 112 until a predetermined time at which anchoring devices 118 dissolve or degrade to facilitate the production of oil and gas. Advantageously, in an exemplary embodiment, the anchoring devices 118 herein are formed of multiple materials to have predictable and adjustable degradation characteristics while allowing for suitable anchoring characteristics.

FIG. 2 shows a downhole device 216, such as a bridge plug, packer, or any other suitable downhole device, for use downhole systems such as the system 100 shown in FIG. 1. In an exemplary embodiment, downhole system 200 includes downhole device 216 interfacing with casing 208 via anchor assembly 218 to anchor a downhole device 216. In certain embodiments, a frac ball 220 is used with downhole device 216 to isolate frac fluid flow within the wellbore.

In an exemplary embodiment, anchor assembly 218 includes a wedge 224 and a slip ring 228. In certain embodiments, wedge 224 is forced downhole to force slip ring 228 outward against casing 208 to anchor against casing 208. In certain embodiments, slip ring 228 can crack or otherwise separate as it is driven against casing 208. In certain embodiments, wedge 224 is forced via a setting tool, explosives, or any other suitable means. In certain embodiments, downhole device 216 further utilizes a sealing member 226 to seal downhole device 216 against casing 208 and further resist movement. Sealing member 226 may similarly be driven toward casing 208 via wedge 224.

In an exemplary embodiment, a substrate of a slip ring 228 is formed of a degradable material to allow slip ring 228 to dissolve or degrade after a desired anchoring function is performed. In certain embodiments, a secondary material is used in conjunction with the substrate of the slip ring 228 to anchor the slip ring 228 against casing 208. Typically, a secondary material is harder than casing 208 to allow slip ring 228 to partially embed in casing 208. In certain embodiments, the downhole temperature exposure to downhole device 216 and slip ring 228 varies from 100 to 350 degrees Fahrenheit at a particular downhole location for a given area. Advantageously, slip ring 228 as described herein may allow for degradation after a desired time in certain downhole environments, while allowing suitable anchoring performance. In certain embodiments, portions of slip ring 228 can degrade or otherwise not prevent further downhole operations or restrict flow within a wellbore.

FIGS. 3A, 3B and 3C show an exemplary embodiment of slip ring 328. In an exemplary embodiment, slip ring 328 includes a substrate 331 and a granular gripping material 330. In certain embodiments, slip ring 328 is used with downhole devices as shown in FIG. 2 to anchor the downhole devices against a casing. Advantageously, slip ring 328 is a degradable device, allowing slip ring 328 to degrade without any secondary removal or destruction operations.

In an exemplary embodiment, substrate 331 is a degradable material. Advantageously, by forming substrate 331 of slip ring 328 from a degradable material, a downhole device may be anchored by slip ring 328 for the desired period of time, and then the slip ring 328 may be disintegrated to allow further operations without any obstructions. In certain embodiments, substrate 331 is formed from a corrodible metal such as a controlled electrolytic metallic, including but not limited to Intallic. Substrate 331 materials may include: a magnesium alloy, a magnesium silicon alloy, a magnesium aluminum alloy, a magnesium zinc alloy, a magnesium manganese alloy, a magnesium aluminum zinc alloy, a magnesium aluminum manganese alloy, a magnesium zinc zirconium alloy, and a magnesium rare earth element alloy. Rare earth elements may include, but is not limited to scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, and erbium. In certain embodiments, substrate materials 331 are further coated with aluminum, nickel, iron, tungsten, copper, cobalt. In certain embodiments, substrate 331 materials are consolidated and forged. In certain embodiments, the elements can be formed into a powder and a substrate can be formed from pressed powder. In an exemplary embodiment, the material of substrate 331 is selected based on desired degradation characteristics of slip ring 328.

In an exemplary embodiment, substrate 331 forms a generally cylindrical shape with an inner extent 336 and an outer extent 334. In certain embodiments, inner extent 336 has a reducing or reduced radius portion to allow a downhole device to be retained within the slip ring 328. In an exemplary embodiment, the material of substrate 331 is chosen with respect to the relative hardness of the downhole device to prevent damage to the downhole device. In an exemplary embodiment, outer extent 334 of slip ring 328 is configured to interface with a casing. In an exemplary embodiment, outer extent 334 includes granular gripping material 330 designed to interface with casing.

In an exemplary embodiment, slip ring 328 can be configured to break in to several sections when expanded. In certain embodiments, slip ring 328 can be expanded by a wedge as previously shown in FIG. 2. In order to facilitate fracturing of slip ring 328 certain embodiments of slip ring 328 include crack initiation points 332 disposed on outer extent 334. Crack initiation points 332 include, but are not limited to cuts, grooves, slits, perforations, etc. Crack initiation points 332 may serve as a stress concentration point to initiate cracking, fracturing, or separation along the longitudinal axis of slip ring 328 as slip ring 328 is expanded. In certain embodiments, crack initiation points 332 are formed via electrical discharge machining substrate 331.

In an exemplary embodiment, outer extent 334 includes granular gripping material 330 configured to interface with a casing or other suitable anchor medium. In an exemplary embodiment, the material of granular gripping material 330 is selected to be harder than the interfacing casing. In other embodiments, the material of the granular gripping material 330 is the same hardness or softer than the interfacing casing. Casing may have a hardness of approximately 120 ksi. Casing grades may range from L80 to Q125. Advantageously, a relatively harder anchor granular gripping material 330 allows for granular gripping material 330 to firmly anchor the downhole device to casing or other suitable anchor medium. In other embodiments, granular gripping material 330 utilizes friction and casing irregularities to interface with a casing or other suitable anchor medium. In certain embodiments, anchor granular gripping material 330 is formed of a harder material than substrate 331. Advantageously, materials, particularly degradable materials, may not have a suitable hardness to adequately anchor to a casing or other suitable anchor material, requiring the use of a harder anchor granular gripping material 330 as described herein. Materials selected for substrate 331 and granular gripping material 330 may be carefully selected to ensure gripping material 330 embeds further into a casing or anchor medium compared to substrate 331.

In an exemplary embodiment, granular gripping materials 330 are on the outer extent 334 of slip ring 328. In certain embodiments, granular gripping materials 330 are disposed in undercut portion 338. Advantageously, a large portion of slip ring 328 may be covered with granular gripping materials 330 to allow for greater anchoring performance. In certain embodiments, by covering a large portion of slip ring 328 the substrate 331 of slip ring 328 can avoid or mitigate damage. Advantageously, by utilizing granular gripping materials 330, a substrate 331 can be formed with a lower strength material to allow for greater ductility of slip ring 328. In an exemplary embodiment, granular gripping materials 330 can be generally granular form of similar sizes and of regular or irregular shapes. In certain embodiments, granular gripping materials 330a can be relatively larger. In other embodiments, granular gripping materials 330b can be relatively smaller compared to other granular gripping materials 330a. As shown in FIG. 3C the grain size of granular material 330a,330b may vary based on application. In certain embodiments, granular material 330a,330b is applied to slip ring 328 in multiple layers. Advantageously, the use of multiple layers of granular material 330a,330b can prevent damage to substrate 331 by distributing anchor forces and allowing harder materials (or larger granular materials) 330a to interface with casing or anchor medium, while softer granular materials (or smaller granular materials) 330b interface with substrate 331. In certain embodiments, materials 330a interfacing with casing or anchor medium have a granule size of 0.5 to 10 mm. In an embodiment materials 330a interfacing with casing or anchor medium have a granule size of 1 to 5 mm. In certain embodiments, materials 330b interfacing with substrate 331 have a granule size of 1 micron to 2 mm. In an embodiment, materials 330b interfacing with substrate 331 have a granule size of 50 micron to 1 mm. In certain embodiments, the combined thickness of layers 330a,330b ranges from 0.5 to 10 mm. In an embodiment, the combined thickness of layers 330a,330b ranges from 2 to 5 mm. Further, the characteristics and performance of slip ring 328 can be adjusted and designed by altering the layers 330a,b in relation to substrate 331 and casing or anchor medium. Advantageously, granular gripping materials 330 may be configured to be sized and shaped to allow passage through intended flow paths and to allow operations to continue after a substrate 331 has dissolved.

In an exemplary embodiment, granular gripping materials 330 are formed from disintegrable materials that disintegrate into small particulates. Granular gripping materials 330 can be formed of any suitable material, including, but not limited to oxides, carbides, and nitrides. In certain embodiments, granular gripping materials 330 are formed from aluminum oxide, silicon carbide, tungsten carbide, zirconium dioxide, and silicon nitride. In certain embodiments, granular gripping materials 330 can contain ceramic type proppants or other high hardness materials.

In an exemplary embodiment, granular gripping materials 330 are disposed in an undercut portion 338 formed in substrate 331. In certain embodiments, undercut portion 338 has a smaller outside diameter than the remainder of outer extent 334 to allow the inclusion of granular gripping materials 330 while maintaining the same or similar outside diameter as the remainder of outer extent 334. Advantageously, undercut portion 338 may ease the application of granular gripping material 330 and binder 339.

Granular gripping materials 330 may be attached to substrate 331 via a binder 339 or any other suitable adhesive. In certain embodiments, the binder utilizes is degradable. Binders include, but are not limited to toughened acrylics, epoxy, low metal point metals (such as aluminum, magnesium, zinc, and their alloys), etc. In other embodiments, undercut portion 338 can retain granular gripping materials 330 without any additional components. In certain embodiments, various sizes of granular material 330a,b are bound by various binders 339a,b. In certain embodiments, various binders 339a,b can vary based on size of granular material 330a,b as well as relative location within slip ring 328.

FIGS. 4A-4D show alternative embodiments of slip ring 428. In an exemplary embodiment, slip ring 428 includes a retaining feature 440 formed in substrate 431. In an exemplary embodiment, retaining feature 440 can be utilized to retain granular gripping material when slip ring 428 is engaged against casing or other suitable surfaces. In certain embodiments, slip ring 428 is used with downhole devices as shown in FIG. 2 to anchor against a casing.

In an exemplary embodiment, outer extent 434 of slip ring 428 includes at least one retaining feature 440 formed in substrate 431. Retaining feature 440 can be formed to retain a granular gripping material to prevent the unwanted migration of the material, particularly in high pressure and high temperature environments. In certain embodiments, retaining feature 440 can retain granular gripping material when the granular gripping material is subjected to shear forces and other forces during engagement. Advantageously, retaining feature 440 provides additional surface area for a binder associated with the granular gripping material as well as features to resist sliding of the granular gripping material. Retaining features 440 can include, but are not limited to protrusions, grooves, surface irregularities, finishes, surface scratches, threading, holes, angled portions, etc. Retaining features 440 can be continuous, discontinuous, patterned, random, etc.

Referring to FIG. 4A, in an exemplary embodiment, retaining feature 440 is at least one bump ring to prevent the sliding of granular gripping material. Bump rings can be raised protrusions or grooves circumferentially disposed along the outer extent 434 of slip ring 428. In certain embodiments, bump rings can be of any suitable height, number, pattern, etc. In certain embodiments, bump rings can be disposed at any suitable location.

Referring to FIG. 4B, in an exemplary embodiment, retaining feature 440 is at least one segmented bump ring to prevent the sliding of granular gripping material. Segmented bump rings can be raised protrusions or grooves circumferentially disposed along the outer extent 434 of slip ring 428. In certain embodiments, segmented bump rings can be of any suitable height, number, pattern, etc. In certain embodiments, segmented bump rings can be disposed at any suitable location. In certain embodiments, segments of bump rings can be randomly disposed.

Referring to FIG. 4C, in an exemplary embodiment, retaining feature 440 is helical feature to prevent the sliding of granular gripping material. Helical feature can be raised protrusions or grooves circumferentially disposed along the outer extent 434 of slip ring 428. In certain embodiments, helical bump feature can be of any suitable height, number, pattern, etc. In certain embodiments, helical features can a continuous helical shape or a segmented helical shape be disposed at any suitable location along outer extent 434 of slip ring 428. In certain embodiments, segments of helical features can be randomly disposed.

Referring to FIG. 4D, in other embodiments, retaining feature 440 is a knurled or rough surface portion disposed along outer extent 434 of slip ring 428. In certain embodiments, a knurled, rough, or other treatment portion can be formed in substrate 431 and disposed circumferentially, axially, etc. In certain embodiments, surface treatments can be of any suitable width, depth, pattern, roughness, etc. In certain embodiments, retaining feature 440 can include either bump rings or surface treatments in multiple locations, a combination of retaining features 440, or any other suitable retaining feature 440 to retain the granular gripping material.

In an exemplary embodiment, retaining feature 440 can be integrally formed in substrate 431. Retaining feature 440 can be formed via casting, machining, or any other suitable forming technique. In certain embodiments, retaining feature 440 can be formed after other portions of slip ring 428 are formed.

In certain embodiments, slip ring 428 includes a leading protrusion 442 formed in substrate 431. Leading protrusion 442 may be disposed on the outer extent 434 of a downhole edge of slip ring 428. During operation, a cone or other suitable device can impart a force upon inner extent 436 to expand slip ring 428 along crack initiation points 432. Advantageously, leading protrusion 442 can limit expansion and travel of slip ring 428 during use by contacting the inner walls of the casing before other portions of slip ring 428. The expansion and travel of slip ring 428 can be modified by adjusting the radius, width, and other parameters of leading protrusion 442. In certain embodiments, leading protrusion 442 can further be utilized to retain granular gripping material either alone, or in conjunction with retaining feature 440.

Therefore in one aspect, an anchoring device is disclosed, including: a degradable substrate with a first hardness wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness. In certain embodiments, the at least one retaining feature is at least one bump ring. In certain embodiments, the at least one bump ring is at least one segmented bump ring. In certain embodiments, the at least one retaining feature is at least one helical feature. In certain embodiments, the at least one retaining feature is at least one knurled region. In certain embodiments, the degradable substrate includes a leading protrusion. In certain embodiments, the leading protrusion limits an engagement depth of the anchoring device. In certain embodiments, the leading protrusion retains the granular gripping material.

In another aspect, a method to anchor a downhole device is disclosed, including: providing a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature; applying a granular gripping material to the outer extent of the degradable substrate and the at least one retaining feature, wherein the granular gripping material has a second hardness greater than the first hardness; and retaining the granular gripping material via the at least one retaining feature. In certain embodiments, the at least one retaining feature is at least one bump ring. In certain embodiments, the at least one bump ring is at least one segmented bump ring. In certain embodiments, the at least one retaining feature is at least one helical feature. In certain embodiments, the at least one retaining feature is at least one knurled region. In certain embodiments, the degradable substrate includes a leading protrusion.

In another aspect, a downhole system is disclosed, including: a casing string; and an anchoring device associated with the casing string, including: a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness. In certain embodiments, the at least one retaining feature is at least one bump ring. In certain embodiments, the at least one bump ring is at least one segmented bump ring. In certain embodiments, the at least one retaining feature is at least one helical feature. In certain embodiments, the at least one retaining feature is at least one knurled region. In certain embodiments, the degradable substrate includes a leading protrusion.

The foregoing disclosure is directed to certain specific embodiments for ease of explanation. Various changes and modifications to such embodiments, however, will be apparent to those skilled in the art. It is intended that all such changes and modifications within the scope and spirit of the appended claims be embraced by the disclosure herein.

Claims

1. An anchoring device, comprising:

a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature;

a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness.

2. The anchoring device of claim 1, wherein the at least one retaining feature is at least one bump ring.

3. The anchoring device of claim 2, wherein the at least one bump ring is at least one segmented bump ring.

4. The anchoring device of claim 1, wherein the at least one retaining feature is at least one helical feature.

5. The anchoring device of claim 1, wherein the at least one retaining feature is at least one knurled region.

6. The anchoring device of claim 1, wherein the degradable substrate includes a leading protrusion.

7. The anchoring device of claim 6, wherein the leading protrusion limits an engagement depth of the anchoring device.

8. The anchoring device of claim 6, wherein the leading protrusion retains the granular gripping material.

9. A method to anchor a downhole device, comprising:

providing a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature;

applying a granular gripping material to the outer extent of the degradable substrate and the at least one retaining feature, wherein the granular gripping material has a second hardness greater than the first hardness; and

retaining the granular gripping material via the at least one retaining feature.

10. The method of claim 9, wherein the at least one retaining feature is at least one bump ring.

11. The method of claim 10, wherein the at least one bump ring is at least one segmented bump ring.

12. The method of claim 9, wherein the at least one retaining feature is at least one helical feature.

13. The method of claim 9, wherein the at least one retaining feature is at least one knurled region.

14. The method of claim 9, wherein the degradable substrate includes a leading protrusion.

15. A down hole system, comprising:

a casing string; and

an anchoring device associated with the casing string, comprising:

a degradable substrate with a first hardness, wherein an outer extent of the degradable surface includes at least one retaining feature; and

a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness.

16. The downhole system of claim 15, wherein the at least one retaining feature is at least one bump ring.

17. The downhole system of claim 16, wherein the at least one bump ring is at least one segmented bump ring.

18. The downhole system of claim 15, wherein the at least one retaining feature is at least one helical feature.

19. The downhole system of claim 15, wherein the at least one retaining feature is at least one knurled region.

20. The downhole system of claim 15, wherein the degradable substrate includes a leading protrusion.