Compositions and method for controlling precipitation when acidizing sour wells
AssigneeHalliburton Company
InventorsWalter R. Dill, Michael L. Walker
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Abstract
A precipitation control additive composition, an acidizing composition for treating a sour well and a method of treating a sour well are provided. An iron sequestering agent and a sulfide modifier are added to a treating solution. The iron sequestering agent combines with iron present in the solution while the sulfide modifier combines with sulfides present in the solution. By combining with both iron and sulfides present in the solution, the combination of an iron sequestering agent and a sulfide modifier effectively inhibits precipitation of ferric hydroxide, ferrous sulfide and free sulfur from the solution. As a result, formation and other serious damage is prevented.
Claims7
A method of treating a sour well penetrating a subterranean formation comprising:
- introducing into said well a treating fluid comprising an acid solution having a pH below 1.9, an iron sequestering agent comprising at least one compound selected from the group consisting of aminopolycarboxylic acids, hydroxycarboxylic acids, cyclic polyethers and derivatives of said acids and ethers, present in an amount of from about 0.25 to about 5 percent by weight of the acid solution, and a sulfide modifier comprising at least one compound selected from the group consisting of an aldehyde, acetal, hemiacetal and any other compound capable of forming aldehydes in the acid solution, present in an amount of from about 0.25 to about 5 percent of the acid solution;
- and
- treating said subterranean formation with said treating fluid whereby said fluid spends to a pH above about 1.9 while substantially preventing precipitation of ferrous hydroxide, ferrous sulfide and free sulfur within said formation from said spent acid solution.
Dependencies are inferred from the claim text.