Shell Oil Comapny

George Neal Iken

Jimmie B Lawson

Robert J Faircloth

A scale inhibitor solution composition comprising water; an organophosphorous scale inhibitor selected from the group consisting of nitrilotri(methylene phosphonic acid), diethylenetriaminepenta-(methylene phosphonic acid) and salts thereof with monovalent cations; and sodium chloride in a concentration of between about 12 and about 14% by weight of the scale inhibitor solution.

Precipitation of scale inhibitors

A method to place anionic scale inhibitors in formations containing CaSO.sub.4 is provided. The solution dissolves CaSO.sub.4 when injected into the formation containing CaSO.sub.4 causing calcium salts of the scale inhibitor to precipitate at a rate and to an extent that exceeds that resulting when an inhibitor solution not containing the salt is used. Precipitation of the calcium salt of scale inhibitor is maximized because salt reduces its solubility.

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Houston, TX, United States of America

George Neal Iken