US 12,227,697 B2
Methods for delaying in situ acid generation for acid delivery to a site
Desmond E. Schipper, Houston, TX (US); Amy J. Cairns, Houston, TX (US); and Katherine L. Hull, Houston, TX (US)
Assigned to SAUDI ARABIAN OIL COMPANY, Dhahran (SA)
Filed by Saudi Arabian Oil Company, Dhahran (SA)
Filed on Aug. 5, 2021, as Appl. No. 17/394,547.
Claims priority of provisional application 63/061,840, filed on Aug. 6, 2020.
Prior Publication US 2022/0041922 A1, Feb. 10, 2022
Int. Cl. E21B 43/27 (2006.01); C09K 8/60 (2006.01); C09K 8/70 (2006.01); C09K 8/72 (2006.01)
CPC C09K 8/72 (2013.01) [C09K 8/602 (2013.01); C09K 8/706 (2013.01); E21B 43/27 (2020.05)] 17 Claims
 
1. A method for delivering an acid to a site within a rock formation, the method comprising:
introducing one or more aqueous fluids to the formation thereby contacting the site with the one or more aqueous fluids comprising an ammonium salt, an oxidizing agent, and a surfactant; and
generating an acid at the site at a rate that is less than the rate of acid generation when the surfactant is absent;
wherein the surfactant is selected from the group consisting of a phosphonate-based surfactant, a sulfonate-based surfactant, and combinations thereof, and
wherein the sulfonate-based surfactant is or is derived from one or more selected from methanesulfonate, trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, perfluorobutanesulfonate, octanesulfonate, dodecanesulfonate, dodecylbenzene sulfonate, or petroleum sulfonate,
wherein the surfactant is configured to delay a reaction between the oxidizing agent and the ammonium salt such that acid generation is delayed,
wherein a molar ratio of the surfactant to the ammonium salt or to the oxidizing agent is 1:1 or less.