Inhibition of silica precipitation
AssigneeUnion Oil Company of California
InventorDarrell L. Gallup
Life of this patent
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Abstract
A method for controlling fouling of a flashing vessel or heat-exchange surface exposed to a high-enthalpy geothermal brine tending to form silicon-containing scale. The method adds a silicon-complexing amount of fluoroborate species to the brine to form a fluid mixture that does not produce substantial amounts of the scale when the temperature of the fluid mixture is reduced. The addition does not significantly increase corrosion rates of mild steel heat-exchanger materials of construction.
Claims37
A method for inhibiting the formation of a silicon-containing precipitate from an aqueous brine solution derived from a geothermal reservoir said method comprising:
- adding a fluoroborate species to said brine solution comprising a silicon-containing component to inhibit the formation of silicon-containing precipitate at a pH of said brine solution above 4.0, said fluoroborate species comprising tetrafluoroborate. BF.sub.3 OH.sup.- and any species in solution comprising boron and fluorine which comprises or is in equilibrium with tetrafluoroborate ions or BE.sub.3 OH.sup.-.
A method for controlling the fouling of a solid, heat exchange surface when exposed to a high-enthalpy geothermal fluid having less than a saturated concentration of silicon-containing components that are capable of producing a silicon-containing precipitate, said method comprising:
- adding an amount of a fluoroborate species to said geothermal fluid to produce a fluid mixture, said fluoroborate species comprising tetrafluoroborate, BF.sub.3 OH.sup.- and any species in solution comprising boron and fluorine which comprises or is in equilibrium with tetrafluoroborate ions or BF.sub.3 OH.sup.- ;
- and
- flowing said fluid mixture in contact with said heat exchange surface at a pH of said fluid mixture above 4.0 wherein the formation of silicon-containing precipitate is inhibited.
A method for inhibiting the precipitation of silicon-containing scale from a hot pressurized geothermal fluid having a pH from about 4.0 to about 6.0 and dissolved silicon-containing components capable of forming a silicon-containing precipitate when sufficient thermal energy is removed from said geothermal fluid, said method comprises the following steps:
- (1) flashing said geothermal fluid to produce steam and an aqueous liquid brine solution containing said dissolved silicon-containing components;
- (2) contacting said aqueous liquid brine solution with a source of tetrafluoroborate ions to form a fluid mixture containing soluble silicon-containing components;
- (3) flowing said fluid mixture in contact with a surface of a geothermal heat-exchanger to reduce the temperature of said fluid mixture;
- and
- (4) flowing said fluid mixture obtained from step (3) without forming a substantial amount of said precipitate prior to contact with a solid surface contained in a subterranean reservoir.
Dependencies are inferred from the claim text.