US 12,291,673 B2
Polyester diverting agents for low-temperature oil wells
Douglas Kip Hillshafer, Western Springs, IL (US); and Sarah Wolek, Arlington Heights, IL (US)
Assigned to STEPAN COMPANY, Northfield, IL (US)
Filed by Stepan Company, Northbrook, IL (US)
Filed on Dec. 27, 2023, as Appl. No. 18/396,909.
Application 18/396,909 is a division of application No. 17/617,729, granted, now 11,898,096, previously published as PCT/US2020/037782, filed on Jun. 15, 2020.
Claims priority of provisional application 62/863,404, filed on Jun. 19, 2019.
Prior Publication US 2024/0141225 A1, May 2, 2024
Int. Cl. C09K 8/68 (2006.01); C09K 8/72 (2006.01); C09K 8/88 (2006.01)
CPC C09K 8/725 (2013.01) [C09K 8/68 (2013.01); C09K 8/885 (2013.01); C09K 2208/18 (2013.01)] 14 Claims
 
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 comprises at least one agent selected from the group consisting of:
(i) ethylene glycol succinates;
(ii) acid-terminated ethylene glycol succinates;
(iii) acid-terminated polyglycolic acids;
(iv) acid-terminated polylactic acids; and
(v) mixtures of any of (i) through (iv) with a half acid ester,
wherein “acid-terminated ethylene glycol succinates” means a reaction product with a cyclic anhydride or dicarboxylic acid that generates a carboxylic acid end group from a hydroxyl end group, and “half acid ester” means a reaction product of an alcohol or a polyol with a cyclic anhydride or a dicarboxylic acid,”
and wherein the diverting agent comprises an acid-terminated polyglycolic acid made from a cyclic anhydride and polyglycolic acid having a number-average molecular weight within the range of 400 to 2,000 g/mol.