Shell Oil Comapny

Shell Development Company

Gerridina J Torny-Schutte

Feike De Jong

David N Reinhoudt

Arie Van Zon

Reike De Jong

Barium sulfate scale can be removed from remote locations such as those in or around the borehole of a well extending into a subterranean earth formation by contacting the scale with an aqueous solution consisting essentially of water, a monovalent cation salt of a macrocyclic polyether containing at least two nitrogen-linked phosphomethyl groups and enough monovalent basic compound to provide a solution pH of about 8.

Dissolving barium sulfate scale with aqueous solutions of salts of

Barium sulfate scale is dissolved by contacting it with an aqueous solution of: a bicyclic macrocyclic polyether in which the intramolecular cavity or cript is preferentially receptive to the cations of alkaline earth metals, at least a catalytically effective proportion of an alkali metal salt of an organic acid, and enough dissolved alkaline inorganic alkali metal or ammonium compound to provide a solution pH of at least about 8.

Dissolving barium sulfate scale with aqueous solutions of bicyclic

Barium sulfate scale can be removed from remote locations such as those in or around the borehole of a well extending into a subterranean earth formation by contacting the scale with an aqueous solution consisting essentially of water,a monovalent cation salt of a monocyclic macrocyclic polyamine containing at least two nitrogen-linked carboxymethyl groups and enough monovalent basic compound to provide a solution pH of about 8.

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Amsterdam, Netherlands

Gerridina J Torny-Schutte