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Well drilling and servicing fluids for use in producing formations and methods of removing filter cake therefrom are provided. The methods basically comprise using a drilling or servicing fluid basically comprised of water, a water soluble salt and a particulate solid bridging agent selected from ma

Well drilling and servicing fluids for use in producing formations and methods of removing filter cake therefrom are provided. The methods basically comprise using a drilling or servicing fluid basically comprised of water, a water soluble salt and a particulate solid bridging agent selected from magnesium oxychloride cement, magnesium oxysulfate cement, magnesium potassium phosphate hexahydrate, magnesium hydrogen phosphate trihydrate and magnesium ammonium phosphate hexahydrate. Thereafter, the filter cake deposited by the drilling or servicing fluid is contacted with an aqueous clean-up solution for a period of time such that the bridging agent is dissolved thereby.

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1. A method of removing filter cake from the walls of a well bore penetrating a producing formation deposited therein by a drilling or servicing fluid comprised of water, a water soluble salt and a particulate solid bridging agent comprising the steps of:(a) utilizing as the particulate solid bridgi

1. A method of removing filter cake from the walls of a well bore penetrating a producing formation deposited therein by a drilling or servicing fluid comprised of water, a water soluble salt and a particulate solid bridging agent comprising the steps of:(a) utilizing as the particulate solid bridging agent in said drilling or servicing fluid a chemically bonded ceramic selected from the group consisting of magnesium oxychloride cement, magnesium oxysulfide cement, magnesium potassium phosphate hexahydrate, magnesium hydrogen phosphate trihydrate and magnesium ammonium phosphate hexahydrate which is dissolvable in an aqueous clean-up solution containing a mild organic acid, a hydrolyzable ester, an ammonium salt and one of a chelating agent and an ammonium salt and a chelating agent; and (b) contacting said filter cake with said clean-up solution for a period of time such that said bridging agent is dissolved thereby.