# US 12,601,231 B2 · Dissolvable ballast for untethered downhole tools

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- Number: US 12,601,231 B2
- Document ID: US12601231B2
- Status: Granted
- Kind: B2
- Application number: 18/989,597
- Filed: 2024-12-20
- Published: 2025-04-24
- Granted: 2026-04-14
- Earliest claimed: 2022-05-24
- Assignees: Saudi Arabian Oil Company
- Applicants: Saudi Arabian Oil Company; Aramco Services Company
- Inventors: Huseyin Rahmi Seren; Max Deffenbaugh; Mohamed Larbi Zeghlache
- Web page: https://patentgrep.com/patent/US12601231B2

## CPC

- E21B 23/00: Apparatus for displacing, setting, locking, releasing or removing tools, packers or the like in boreholes or wells (setting of casings, screens or liners E21B43/10)
- 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

A method involves mixing metallic particles and a liquefied polymer to form a mixture, placing the mixture within a mold, placing a magnet in the vicinity of the mixture within the mold, thereby causing the metallic particles to position themselves in a self-assembly formation within the mixture in response to a magnetic field generated by the magnet, and solidifying the liquefied polymer, such that a polymer matrix is formed. The metallic particles are distributed and secured in the self-assembly formation throughout the polymer matrix, thereby forming a ballast for an untethered downhole tool configured to be lowered into a well formed in a subterranean formation. The polymer matrix is configured to dissolve in response to being exposed to downhole fluid within the well at specified downhole conditions.

## Claims

### Claim 1

A method comprising:
mixing metallic particles and a liquefied polymer to form a mixture;
placing the mixture within a mold;
placing a magnet in the vicinity of the mixture within the mold, thereby causing the metallic particles to position themselves in a self-assembly formation within the mixture in response to a magnetic field generated by the magnet; and
solidifying the liquefied polymer, such that a polymer matrix is formed, wherein the metallic particles are distributed and secured in the self-assembly formation throughout the polymer matrix, thereby forming a ballast for an untethered downhole tool;
coupling the ballast to the untethered downhole tool; and
lowering the untethered downhole tool with the ballast into a well formed in a subterranean formation, wherein the polymer matrix is configured to dissolve in response to being exposed to downhole fluid within the well at specified downhole conditions.

### Claim 2 (depends on 1)

The method of claim 1, comprising placing a separator between the magnet and the mixture, such that the magnet does not come into physical contact with the mixture before solidifying the liquefied polymer.

### Claim 3 (depends on 1)

The method of claim 1, wherein the metallic particles comprise particles of at least one of tungsten, copper, iron, steel, nickel, cobalt, iron oxide, ferrite, silicon, tantalum, molybdenum, or lead.

### Claim 4 (depends on 3)

The method of claim 3, wherein the metallic particles comprise ferromagnetic particles configured to provide soft magnetic properties to the ballast, and the ferromagnetic particles have a relative magnetic permeability greater than 10 and a non-zero magnetic coercivity that is less than 1 kiloamperes per meter (kA/m).

### Claim 5 (depends on 1)

The method of claim 1, wherein the polymer matrix is water-dissolvable and comprises at least one of polylactic acid (PLA), polyvinyl alcohol (PVA), polyglycolide (PGA), starch, cellulose, lipids, collagen, or chitin.

### Claim 6 (depends on 1)

The method of claim 1, comprising coating at least a portion of an external surface of the ballast with a coating having a thickness in a range of from about 1 micrometer (μm) to about 100 μm.

### Claim 7 (depends on 6)

The method of claim 6, wherein the coating comprises at least one of polytetrafluoroethylene (PTFE), parylene, diamond, silicon nitride, or silicon carbide.