# US 11,898,096 B2 · Polyester diverting agents for low-temperature oil wells

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,898,096 B2
- Document ID: US11898096B2
- Status: Granted
- Kind: B2
- Application number: 17/617,729
- Filed: 2020-06-15
- Published: 2022-08-11
- Granted: 2024-02-13
- Earliest claimed: 2019-06-19
- Assignees: Stepan Company
- Applicants: Stepan Company
- Inventors: Douglas Kip Hillshafer; Sarah Wolek
- Web page: https://patentgrep.com/patent/US11898096B2

## CPC

- C09K 8/725: {Compositions containing polymers}
- C09K 8/68: containing organic compounds
- C09K 8/70: characterised by their form or by the form of their components, e.g. foams
- C09K 8/885: {obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds}
- C09K 2208/18: Bridging agents, i.e. particles for temporarily filling the pores of a formation; Graded salts
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A hydraulic fracturing method for recovering oil from a low-temperature subterranean oil formation is disclosed. Before, during, or after inducing hydraulic fracturing within the formation, a particulate, degradable polyester diverting agent is introduced into the formation in an amount effective to improve oil production from the formation. The diverting agent is allowed to degrade, and oil is recovered. The diverting agent has a melting point greater than the average temperature of the formation and is selected from: (i) ethylene glycol succinates; (ii) acid-terminated ethylene glycol succinates; (iii) acid-terminated polyglycolic acids; (iv) acid-terminated polylactic acids; (v) mixtures of any of (i) through (iv) with a half acid ester; and (vi) mixtures of polylactic acids or polyglycolic acids with a half acid ester. These easily synthesized classes of particulate polyester diverting agents degrade more effectively than polylactides under the conditions present in low-temperature wells and should help to enhance well productivity.

## Claims

### Claim 1

A hydraulic fracturing method for recovering oil from a low-temperature subterranean oil formation, wherein low-temperature means an average temperature within the range of 80° F. to 180° F., the method comprising: (a) before, during, or after inducing hydraulic fracturing within the formation, introducing into the formation a particulate, degradable polyester diverting agent in an amount effective to improve oil production from the formation; (b) allowing the diverting agent to degrade; and (c) recovering oil from the formation;
wherein the diverting agent has a melting point greater than the average temperature within the formation; and
wherein the diverting agent is a mixture of polylactic acids or polyglycolic acids with a half acid ester, wherein half acid ester means a reaction product of an alcohol or a polyol with a cyclic anhydride or dicarboxylic acid.

### Claim 2 (depends on 1)

The method of claim 1 wherein the diverting agent is a mixture of polyglycolic acid having a number-average molecular weight within the range of 400 to 5,000 g/mol and 1 to 15 wt. %, based on the amount of diverting agent, of a half acid ester.

### Claim 3 (depends on 2)

The method of claim 2 wherein the half acid ester is a reaction product of phthalic anhydride and diethylene glycol.

### Claim 4 (depends on 1)

The method of claim 1 wherein the formation has an average temperature within the range of 90° F. to 150° F.

### Claim 5 (depends on 1)

The method of claim 1 wherein the formation has an average temperature within the range of 100° F. to 130° F.

### Claim 6 (depends on 1)

The method of claim 1 wherein the diverting agent has a melting point at least 30 Fahrenheit degrees greater than the average temperature of the formation.

### Claim 7 (depends on 1)

The method of claim 1 wherein the diverting agent can degrade within the formation at temperatures less than 150° F. to lose at least 10% of its mass within 14 days.

### Claim 8 (depends on 1)

The method of claim 1 wherein the diverting agent can degrade within the formation at temperatures less than 130° F. to lose at least 20% of its mass within 14 days.