# US 10,119,358 B2 · Degradable wellbore isolation devices with varying degradation rates

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- Number: US 10,119,358 B2
- Document ID: US10119358B2
- Status: Granted
- Kind: B2
- Application number: 14/651,750
- Filed: 2014-08-14
- Published: 2016-09-22
- Granted: 2018-11-06
- Earliest claimed: 2014-08-14
- Assignees: Halliburton Energy Services, Inc.
- Applicants: Halliburton Energy Services, Inc.
- Inventors: Zachary William Walton; Michael Linley Fripp; Zachary Ryan Murphree; John Todd Broome
- Web page: https://patentgrep.com/patent/US10119358B2

## CPC

- E21B 33/1285: {by fluid pressure}
- E21B 33/12: Packers; Plugs (used for cementing E21B33/134, E21B33/16)
- E21B 33/1204: {permanent; drillable}
- E21B 33/1208: {characterised by the construction of the sealing or packing means (E21B33/1277 takes precedence)}
- E21B 33/1293: {with means for anchoring against downward and upward movement (E21B33/1291, E21B33/1295 take precedence)}
- E21B 33/134: Bridging plugs
- E21B 33/16: using plugs for isolating cement charge; Plugs therefor {(stage cementing E21B33/146; spacer compositions C09K8/424)}
- E21B 43/26: by forming crevices or fractures
- E21B 2200/08: Down-hole devices using materials which decompose under well-bore conditions
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

An example downhole tool includes a wellbore isolation device that provides a plurality of components including one or more first components and one or more second components. Each component is made of a degradable material that degrades when exposed to a wellbore environment, and the one or more first components degrades at a first degradation rate while the one or more second components degrades at a second degradation rate that is slower than the first degradation rate.

## Claims

### Claim 1

A downhole tool, comprising:
a wellbore isolation device that provides a plurality of components including one or more first components, one or more second components, and one or more third components, wherein the one or more third components anchor the downhole tool, each component is made of a degradable material that degrades when exposed to a wellbore environment, and the one or more third components degrade to detach the downhole tool, and
wherein the one or more first components degrades at a first degradation rate, the one or more second components degrades at a second degradation rate that is slower than the first degradation rate, and the one or more third components degrades at a third degradation rate that is slower than the second degradation rate to degrade the one or more second components to a state of lost integrity prior to the detachment of the downhole tool due to the degradation of the one or more third components.

### Claim 2 (depends on 1)

The downhole tool of claim 1, wherein the wellbore isolation device is selected from the group consisting of a frac plug, a frac ball, a bridge plug, a wellbore packer, a wiper plug, a cement plug, and any combination thereof.

### Claim 3 (depends on 1)

The downhole tool of claim 1, wherein the one or more first components includes a frac ball, the one or more second components includes a body the one or more third components includes an anchoring mechanism, and the anchoring mechanism is actuatable to anchor the body within the wellbore.

### Claim 4 (depends on 1)

The downhole tool of claim 1, wherein the degradable material is selected from the group consisting of borate glass, polyglycolic acid, polylactic acid, a degradable polymer, a degradable rubber, a galvanically-corrodible metal, a dehydrated salt, a dissolvable metal, a blend of dissimilar metals that generates a galvanic coupling, and any combination thereof.

### Claim 5 (depends on 1)

The downhole tool of claim 1, wherein the degradable material includes an accelerant that is releasable during degradation to accelerate degradation of at least one of (i) the one or more first components or (ii) the one or more second components.

### Claim 6 (depends on 1)

The downhole tool of claim 1, further comprising a sheath disposed on all or a portion of at least one of (i) the one or more first components or (ii) the one or more second components.

### Claim 7 (depends on 6)

The downhole tool of claim 6, wherein the sheath is a material selected from the group consisting of a TEFLON® coating, a wax, a drying oil, a polyurethane, an epoxy, a crosslinked partially hydrolyzed polyacrylic, a silicate material, a glass, a polymer, polylactic acid, polyvinyl alcohol, polyvinylidene chloride, a hydrophobic coating, paint, and any combination thereof.

### Claim 8 (depends on 1)

The downhole tool of claim 1, wherein all or a portion of an outer surface of at least one of (i) the one or more first components or (ii) the one or more second components is treated with a treatment to slow degradation of the degradable material.

### Claim 9 (depends on 8)

The downhole tool of claim 8, wherein the treatment is selected from the group consisting of an anodizing treatment, an oxidation treatment, a chromate conversion treatment, a dichromate treatment, a fluoride anodizing treatment, a hard anodizing treatment, and any combination thereof.

### Claim 10

A method, comprising:
introducing a wellbore isolation device into a wellbore, the wellbore isolation device providing a plurality of components including one or more first components, one or more second components, and one or more third components, wherein each component is made of a degradable material that degrades when exposed to a wellbore environment;
anchoring the wellbore isolation device within the wellbore at a target location via the one or more third components;
performing at least one downhole operation via the one or more first components;
degrading the one or more first components at a first degradation rate;
degrading the one or more second components at a second degradation rate that is slower than the first degradation rate; and
degrading the one or more third components at a third degradation rate to detach the wellbore isolation device, wherein the third degradation rate is slower than the second degradation rate to degrade the one or more second components to a state of lost integrity prior to the detachment of the wellbore isolation device via the degradation of the one or more third components.

### Claim 11 (depends on 10)

The method of claim 10, wherein the one or more first components includes a frac ball, the one or more second components includes a body, the one or more second third components includes an anchoring mechanism, and the anchoring mechanism is actuatable to anchor the body within the wellbore, the method further comprising:
degrading the degradable material of the body faster than the degradable material of the anchoring mechanism.

### Claim 12 (depends on 10)

The method of claim 10, wherein the degradable material is selected from the group consisting of borate glass, polyglycolic acid, polylactic acid, a degradable polymer, a degradable rubber, a galvanically-corrodible metal, a dehydrated salt, a blend of dissimilar metals that generates a galvanic coupling, and any combination thereof.

### Claim 13 (depends on 10)

The method of claim 10, further comprising:
releasing an accelerant as (i) the one or more first components or (ii) the one or more second components degrades; and
accelerating the degradation of at least one of (i) the one or more first components or (ii) the one or more second components with the accelerant.

### Claim 14 (depends on 10)

The method of claim 10, further comprising slowing a degradation of at least one of (i) the one or more first components or (ii) the one or more second components with a sheath disposed on all or a portion of (i) the at least one of the one or more first components or (ii) the one or more second components.

### Claim 15 (depends on 10)

The method of claim 10, further comprising slowing a degradation of at least one of (i) the one or more first components or (ii) the one or more second components with a treatment applied on all or a portion of (i) the at least one of the one or more first components or (ii) the one or more second components.

### Claim 16

A hydraulic frac plug, comprising:
a mandrel having a central flow passage defined therethrough;
a mule shoe secured to the mandrel;
a frac ball disposed at an upper end of the mandrel;
one or more packer elements disposed about the mandrel and expandable to seal against a wellbore;
an upper slip wedge and a lower slip wedge each disposed about the mandrel on opposing sides of the one or more packer elements; and
an upper slip and a lower slip each disposed about the mandrel on opposing sides of the one or more packer elements and actuatable to anchor the hydraulic frac plug within the wellbore, wherein at least the mandrel, the mule shoe, the frac ball, the upper and lower slip wedges, and the upper and lower slips are each made of a degradable material that degrades when exposed to a wellbore environment, and the upper and lower slip wedges, or the upper and lower slips degrade to detach the hydraulic frac plug,
wherein the degradable material of the mule shoe and the frac ball degrades at a first degradation rate,
wherein the degradable material of the mandrel degrades at a second degradation rate that is slower than the first degradation rate, and
wherein the degradable material of at least one of the upper and lower slip wedges, or the upper and lower slips degrades at a third degradation rate that is slower than the second degradation rate to degrade the mandrel to a state of lost integrity prior to the detachment of the hydraulic frac plug due to the degradation of the at least one of the upper and lower slip wedges, or the upper and lower slips.

### Claim 17 (depends on 16)

The hydraulic frac plug of claim 16, wherein the degradable material is selected from the group consisting of borate glass, polyglycolic acid, polylactic acid, a degradable polymer, a degradable rubber, a galvanically-corrodible metal, a dehydrated salt, a blend of dissimilar metals that generates a galvanic coupling, and any combination thereof.

### Claim 18 (depends on 16)

The hydraulic frac plug of claim 16, wherein the degradable material includes an accelerant that is releasable during degradation to accelerate degradation of at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips.

### Claim 19 (depends on 16)

The hydraulic frac plug of claim 16, further comprising a sheath disposed on all or a portion of at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips.

### Claim 20 (depends on 16)

The hydraulic frac plug of claim 16, wherein all or a portion of an outer surface of at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips is treated with a treatment to slow degradation of the degradable material.

### Claim 21 (depends on 16)

The hydraulic frac plug of claim 16, wherein paint is applied to outer surfaces of the mandrel, the upper and lower slips, and the upper and lower slip wedges, and degradation of the degradable material commences at the central flow passage.

### Claim 22

A method, comprising:
introducing a hydraulic frac plug into a wellbore, the hydraulic frac plug including a mandrel having a central flow passage defined therethrough, a mule shoe secured to the mandrel, a frac ball disposed at an upper end of the mandrel, an upper slip wedge and a lower slip wedge each disposed about the mandrel, and an upper slip and a lower slip each disposed about the mandrel, wherein the mandrel, the mule shoe, the frac ball, the upper and lower slip wedges, and the upper and lower slips are each made of a degradable material that degrades when exposed to a wellbore environment;
actuating the upper and lower slips and thereby anchoring the hydraulic frac plug within the wellbore at a target location;
performing at least one downhole operation via the frac ball;
degrading the degradable material of the mule shoe and the frac ball at a first degradation rate;
degrading the degradable material of the mandrel, at a second degradation rate that is slower than the first degradation rate; and
degrading the degradable material of at least one of the upper and lower slip wedges, or the upper and lower slips at a third degradation rate to detach the hydraulic frac plug, wherein the third degradation rate is slower than the first second degradation rate to degrade the mandrel to a state of lost integrity prior to the detachment of the hydraulic frac plug due to the degradation of the at least one of the upper and lower slip wedges, or the upper and lower slips.

### Claim 23 (depends on 22)

The method of claim 22, further comprising:
releasing an accelerant as at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips degrades; and
accelerating the degradation of the at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips with the accelerant.

### Claim 24 (depends on 22)

The method of claim 22, further comprising slowing a degradation of at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips with a sheath disposed on all or a portion of the at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips degrades.

### Claim 25 (depends on 22)

The method of claim 22, further comprising slowing a degradation of at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips with a treatment applied on all or a portion of the at least one of the mandrel, the upper and lower slip wedges, or the upper and lower slips degrades.