Method for prevention of well fouling

A method of cleaning and maintaining a water well penetrating a subterranean formation, said water well including an outer casing having a longitudinal axis extending from an exposed surface of the formation downwardly into the formation and longitudinally spaced perforations for admitting water from the formation into the casing, comprising the steps of recirculating water from the well, adding to the recirculation water an aqueous solution of an anionic polymeric sequesterant in an amount effective to sequester metal cations present in the recirculation water, causing the recirculation water and sequesterant to flow along a liquid flow path through the casing, said perforations and a portion of said formation adjacent to said casing, subsequently adding an effective amount of a biocide to the recirculation water and further recirculating the recirculation water, sequesterant and biocide along said flow path.

A method of cleaning and maintaining a water well penetrating a subterranean formation, said water well including an outer casing which is surrounded by a gravel pack, said casing having a longitudinal axis extending from an exposed surface of the formation downwardly into the formation and longitudinally spaced perforations extending through the outer casing for admitting water from the formation into the casing interior, said perforations including an upper array of perforations longitudinally spaced from a lower array of perforations, comprising the steps of separating said arrays of perforations with a sealing member arranged to divide said casing interior into upper and lower regions respectively containing said upper and lower arrays of perforations, recirculating water from the well, adding to the recirculation water an aqueous solution of a polymeric sequesterant in an amount effective to sequester metal cations, causing the recirculation water and sequesterant to flow along a liquid flow path sequentially through said upper region of said casing, said upper array of perforations, an adjacent portion of said gravel pack, said lower array of perforations, and said lower region of said casing, and then adding and recirculating biocide along said liquid flow path.