Abstract: A method of reducing fluid loss into a highly conductive formation interval during drilling and completion of a well through such an interval wherein a foamed cement slurry, including an acid or oil soluble component, is injected into the well and forced into the conductive portions of the formation zone, which may comprise a fractured or rubblized formation portion. The cement is allowed to harden or set at a porosity of at least 15%, followed by resuming drilling and, in completing the well, dissolving the soluble component to increase the permeability of or disintegrate the cement to permit production of formation fluids into the well.

Abstract: Gas leakage from oil wells through casing thread connections and other small leakage spaces is reduced or eliminated by injecting into the lift gas flowstream a sealant composition comprising a carrier liquid, such as diesel fuel or water, an ethoxylated phenol surfactant and particulate silica and/or Gilsonite. A liquid sealant composition is injected into oil wells on artificial gas lift comprising arctic diesel fuel, a surfactant and solubilized Gilsonite in a weight ratio of about 10:1 diesel fuel to Gilsonite and diesel fuel to surfactant, respectively. Effective reduction in leakage flow rates is obtained over a relatively short time period (one to ten hours).

Abstract: Spacer fluids providing an effective buffer between drilling fluids and cement slurries during well completion. The spacer fluids comprise a sulfonated styrene copolymer dispersant and one or more additional components such as surfactants, viscosifiers and weighting materials to form a rheologically compatible fluid between the drilling fluid and the cement slurry.

Abstract: A method and a treating mixture for controlling lost circulation of fluid from a wellbore to a formation wherein the treating mixture is flowed down the wellbore to block flow into the formation. The mixture is comprised of a non-aqueous carrier liquid (e.g. diesel) and particles of compressed sponge) which expands upon contact with an aqueous liquid in the formation. The mixture may also contain a second lost circulation material (e.g. unhydrolyzed polyacrylamide) which hydrates to bridge and plug any voids or spaces left between the expanded sponge particles. When used to control lost of an aqueous liquid, e.g. water-based mud, a non-aqueous liquid (e.g. diesel) is used ahead and behind the treating mixture to separate it from aqueous liquids. When used to control loss of an oil-based liquid, water is pumped behind the treating mixture to provide the aqueous liquid necessary for expanding the sponge particles once they are in place.

Abstract: Spacer fluids providing an effective buffer between drilling fluids and cement slurries during well completion. The spacer fluids comprise a sulfonated styrene copolymer dispersant and one or more additional components such as surfactants, viscosifiers and weighting materials to form a rheologically compatible fluid between the drilling fluid and the cement slurry.