Control of aluminum cross-linked polyacrylamides for sweep improvement
AssigneeThe Standard Oil Company
InventorRobert E. Hammett
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Abstract
A method and fluid for selectively reducing the permeability of an oil-bearing subterranean formation is disclosed, wherein a cross-linkable polymer, a cross-linking agent and a spacer fluid are alternately injected. The spacer, such as sodium citrate, permits repeated injection cycles of the polymer and cross-linking agents without excessive polymer retention at or near the formation face. Such retention filters out polymers and inhibits polymer propagation throughout the formation. The present invention also permits controlled deep penetration of the cross-linked polymer into the formation to increase oil recovery.
Claims9
A method of treating a subterranean formation, comprising the steps of sequentially injecting into the formation:
- (a) an aqueous solution of a cross-linkable polymer;
- (b) an aqueous solution of a cross-linking agent comprising multivalent cations suitable for cross-linking the polymer and sequestering anions;
- and
- (c) an aqueous solution of a salt comprising cations selected from the group consisting of alkali metal cations and sequestering anions.
A method of displacing oil through a subterranean oil-bearing formation having high permeability portions therein, said formation being penetrated by at least one producing well, comprising the steps of sequentially injecting into said formation:
- (a) an aqueous solution of a cross-linkable polymer;
- (b) an aqueous solution of a cross-linking agent comprising multivalent cations and sequestering anions;
- (c) an aqueous solution of a salt comprising alkali metal or ammonium cations and sequestering anions;
- and
- (d) an aqueous fluid into said formation and displacing oil toward said producing well.
Dependencies are inferred from the claim text.