Abstract: The present invention provides improved methods of combating lost drilling fluid circulation in wells, particularly in wells penetrating vugular and naturally fractured formations such as geothermal wells. The methods basically comprise the steps of forming a quick set cementitious composition which when drilled after setting produces cuttings compatible with the drilling fluid being used, introducing the cementitious composition into the drilling fluid thief zone in the well, allowing the composition to set into a cementitious plug in the thief zone and then continuing the drilling of the well bore through and below the cementitious plug.

Abstract: Improved hydraulic cement compositions and methods for cementing wells drilled through low temperature earth formations wherein the cement is subjected to freeze-thaw cycling are provided. The compositions are comprised of a hydraulic cement, gypsum cement, fly ash, an alkali metal halide, water, and an alcohol freezing point depressant.

Abstract: The present invention provides methods of cementing a well with a cementing composition utilizing a portion of the fluid used to drill the well as a component of the cementing composition. The methods basically comprise forming a cementing composition, consisting essentially of a cementing precursor composition and a set-activator introducing the cementing composition into the well and permitting the cementing composition to set into a hard mass therein; wherein the cementing precursor composition is the fluid used to drill the well.

Abstract: The present invention provides fly ash cementing compositions and methods which are useful in any cementing application, and are particularly suitable for cementing in subterranean zones penetrated by well bores. The cementing compositions can include a portion of the drilling fluid used to drill a well bore as a component thereof. Also, drilling fluid can be disposed of by combining it with the fly ash cementing composition whereby it solidifies in a disposal location.

Abstract: The present invention provides methods of cementing a well with a cementing composition utilizing a portion of the drilling fluid used to drill the well as a component of the cementing composition. The methods basically comprise forming a cementing composition, consisting essentially of a cementing precursor composition, a set-activator, and a portion of the drilling fluid, introducing the cementing composition into the well and permitting the cementing composition to set into a hard mass therein.

Abstract: Improved hydraulic cement compositions and methods for cementing wells drilled through low temperature earth formations wherein the cement is subjected to freeze-thaw cycling are provided. The compositions are comprised of a hydraulic cement, gypsum cement, fly ash, an alkali metal halide, water, and an alcohol freezing point depressant.

Abstract: Improved liquid fluid loss reducing additives, well cement compositions containing the additives and methods of using the compositions are provided by this invention. The liquid fluid loss reducing additives are basically comprised of water, polyethylene imine, an alkali metal salt of alkylbenzene sulfonic acid and an alkali metal salt of naphthalene sulfonic acid condensed with formaldehyde.

Abstract: The present invention provides methods of cementing a well with a cementing composition utilizing a portion of the drilling fluid used to drill the well as a component in the cementing composition. The methods basically comprise forming a set-activated cementing composition comprised of water, silica fume, a dispersing agent, a set-activator, a set delaying additive and a portion of the drilling fluid, introducing the resulting set-activated cementing composition into the well and permitting the cementing composition to set into a hard mass therein.

Abstract: Retarded acid soluble well cement compositions which set into hard substantially impermeable masses and methods of using such compositions for forming removable cement plugs or seals in subterranean zones are provided. The compositions are comprised of magnesium oxychloride cement and a set retarder comprised of a water soluble borate and a sugar.

Abstract: Retarded acid soluble well cement compositions which set into hard substantially impermeable masses and methods of using such compositions for forming removable cement plugs or seals in subterranean zones are provided. The compositions are comprised of magnesium oxychloride cement and a set retarder comprised of a water soluble borate and a sugar.

Abstract: A dispersant for cement slurries is provided comprised of a copolymers of sodium vinylsulfonate and either acrylic acid or acrylamide. Salt cement slurries and method of use in cementing in subterranean wellbores are also provided.

Abstract: Liquid water loss reducing additives for use in cement slurries are provided comprised of aqueous solutions of low molecular weight carboxymethylhydroxyethyl-cellulose polymers. Methods of using the additives are also provided.

Abstract: Salt water cement slurries having low water loss when in contact with water permeable earth formations and additives for reducing water loss from salt water cement slurries are provided. The additives are comprised of very low molecular weight carboxymethylhydroxyethylcellulose polymers. Methods of using the additives are also provided.

Abstract: Liquid water loss reducing additives for use in cement slurries are provided comprised of aqueous solutions of low molecular weight carboxymethylhydroxyethylcellulose polymers. Methods of using the additives are also provided.