Compositions and methods for diverting injected fluids to achieve improved hydrocarbon fluid recovery
View Patent ↗The present disclosure is directed to compositions and methods that may be used for enhanced oil recovery, for modifying the permeability of subterranean formations and for increasing the mobilization and/or recovery rate of hydrocarbon fluids present in the formations. The compositions may include, for example, expandable cross linked polymeric microparticles having an unexpanded volume average particle size diameter of from about 0.05 to about 5,000 microns and a cross linking agent content of from about 100 to about 200,000 ppm of hydrolytically labile silyl ester or silyl ether crosslinkers and from 0 to about 300 ppm of non-labile crosslinkers.
1. A method for improving recovery of hydrocarbon fluids from a subterranean formation comprising conditions of temperature and pH, the method comprising
injecting into the subterranean formation a composition comprising highly cross linked expandable polymeric microparticles, the microparticles having an unexpanded volume average particle size diameter that is smaller than the pores of the subterranean formation and a crosslinking agent content of from 0 to about 300 ppm of non-labile crosslinking agents and from about 100 to about 200,000 ppm of labile crosslinking agents, wherein the labile crosslinking agents comprise one or more hydrolytically labile silyl ether or silyl ester crosslinkers, and wherein the particle size is constrined by cross-linking with said labile and non-labile crosslinkers and wherein the hydrolytically labile crosslinkers break under the conditions of temperature and pH in the subterranean formation to form expanded microparticles; and
recovering hydrocarbon fluids from the subterranean formation.
2. The method of claim 1 , wherein from about 100 ppm to about 10,000 ppm of the composition, based on polymer actives, is injected into the subterranean formation.
3. The method of claim 1 , wherein the composition is added to injection water as part of a secondary or tertiary process for the recovery of hydrocarbon fluids from the subterranean formation.
4. The method of claim 1 , wherein the composition is used in a carbon dioxide and water tertiary recovery project.
5. The method of claim 1 , wherein the composition is used in a tertiary oil recovery process, one component of which constitutes water injection.
6. The method of claim 1 , wherein the subterranean formation is a sandstone or carbonate hydrocarbon reservoir.
7. The method of claim 1 wherein the particle size of the polymeric microparticles before expansion is selected based on the calculated pore size of the highest permeability theif zone.
8. The method of claim 1 wherein the expanded polymeric microparticles impede the flow of an injected fluid in the pores of the subterranean formation.