Shell Oil Comapny

Robert J Faircloth

Jimmie B Lawson

Gerald C Adams

George Neal Iken

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 is provided to fracture a subterranean formation along with a fracturing fluid useful in this method, the method comprising the steps of: a) providing a fracturing fluid, the fracturing fluid is an aqueous solution having an initial pH greater than about 8 and comprising a polysaccharide, a source of borate in an amount that is effective to crosslink the polysaccharide at a pH greater than 8, an oxidative breaker, and a precursor that hydrolyzes in an amount that is effective to lower the pH of the fracturing fluid after a time period that is greater than about one half hour and less than about two days; b) injecting the fracturing fluid into the formation at a pressure the is effective to fracture the formation and force at least a portion of the fracturing fluid into the fracture; and c) permitting the precursor to hydrolyze and thereby lowering the pH of the fracturing fluid to a pH that is less than about 8.

Formation fracturing

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.

Scale inhibitors are precipitated in a formation by injection in an acidic solution comprising a base generating component and a chelating agent. The inhibitor is preferably a calcium salt of an organic phosphonate. The chelating agent prevents iron ions from causing premature hydrolysis of the base generating component.

Precipitation of scale inhibitors in subterranean formations

Scale inhibitors are precipitated in a formation by injection in an acidic solution comprising a base generating component. The inhibitor is preferably a calcium salt of an organic phosphonate.

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Houston, TX, United States of America

Robert J Faircloth