초록 ▼

A water permeability contrast correction process to improve the sweep efficiency of waterflooding which involves the sequential injection of (1) an optional aqueous preflush slug to adjust connate water salinity, (2) an aqueous thickened slug comprising a sequestered polyvalent metal cation such as

A water permeability contrast correction process to improve the sweep efficiency of waterflooding which involves the sequential injection of (1) an optional aqueous preflush slug to adjust connate water salinity, (2) an aqueous thickened slug comprising a sequestered polyvalent metal cation such as aluminum citrate and a gelable polymeric viscosifier such as polyacrylamide, (3) carbon dioxide to decrease the pH of the polymer slug which triggers the delayed in-situ gelation of said thickened slug to preferentially decrease water permeability in highly permeable thief zones, and (4) an aqueous drive fluid.

대표청구항 ▼

A method for treating an underground formation which comprises: (A) injecting effective permeability control proportions of an in-situ gelable composition comprising effective ratios of: (a) water, (b) at least one polymer capable of gelling with a crosslinking agent within a gelation pH range, (c)

A method for treating an underground formation which comprises: (A) injecting effective permeability control proportions of an in-situ gelable composition comprising effective ratios of: (a) water, (b) at least one polymer capable of gelling with a crosslinking agent within a gelation pH range, (c) at least one polyvalent metal cation, and (d) at least one sequestering anion; and thereafter (B) injecting carbon dioxide, thereby causing gelation in-situ.