Precipitation of scale inhibitors
AssigneeShell Oil Company
InventorsJimmie B. Lawson, Robert J. Faircloth, George N. Iken
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Abstract
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.
Claims9
A method to reduce scale deposition in an aqueous phase producing wellbore and surrounding formation, wherein the formation comprises CaSO.sub.4, the method comprising the steps of:
- a) providing a solution comprising an anionic scale inhibitor and a salt having a monovalent cation in a concentration effective to at least about double the solubility of calcium sulfate compared to a scale inhibitor solution in the absence of the salt having a monovalent cation;
- b) injecting the solution into the formation;
- c) precipitating a portion of the anionic scale inhibitor in the formation as a calcium salt of the anionic scale inhibitor;
- and
- d) producing the aqueous phase from the wellbore.
Dependencies are inferred from the claim text.