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: What is disclosed is a method of accelerating the set of a retarded cement. The cement may range from a drilling fluid containing dispersants or retarders that will slow down the set of the drilling fluid when cementitious fluid is added thereto, through overwashing, or treating a retarded primary or remedial cement that may have been injected into fractures or areas within a well to overwashing a plug or any volume of retarded cement that needs to be set in a well.The specific uses are discussed.

Abstract: A method of accelerating the set of retarded cement characterized by contacting the retarded cement slurry with a solution containing an effective amount of a compatible accelerator. The compatible accelerator is selected from the group consisting of triethanolamine, diethanolamine and monoethanolamine. This may be employed in overwashing operations, treating retarded cement that is injected into open areas in the well or treating the set of a plug of retarded cement in a well to effect acceleration and/or viscosification of the cement. Also disclosed are specific uses.

Abstract: A method of cementing in a wellbore penetrating subterranean formations characterized by mixing a predetermined quantity of Portland Cement containing at least 2 percent by weight of tricalcium aluminate; at least 2 percent by weight of gypsum; and 0.3-2.0 percent by weight of polyvinyl alcohol with enough water to form a pumpable slurry; pumping the slurry to a desired location in the wellbore and allowing the slurry to harden to a solid mass. Also disclosed is the composition. These methods and composition provide a cementing that has many advantages and beneficial results as delineated in the specification.

Abstract: What is disclosed is a method of accelerating the set of a retarded cement. The cement may range from a drilling fluid containing dispersants or retarders that will slow down the set of the drilling fluid when cementitious fluid is added thereto, through overwashing, or treating a retarded primary or remedial cement that may have been injected into fractures or areas within a well to overwashing a plug or any volume of retarded cement that needs to be set in a well.The specific uses are discussed.

Abstract: Wellbores are cemented with a cement composition formed from drilling fluid occupying the wellbore by circulating a quantity of drilling fluid mixed with a cement material and a dispersant such as a sulfonated styrene copolymer with or without an organic acid into the wellbore to displace the drilling fluid and to continuously convert the drilling fluid into the cement composition. The cement composition may be recirculated through the space in the wellbore to completely evacuate any drilling fluid not converted to cement so as to minimize any faults in the cement composition occupying the wellbore. A preflush composition containing the dispersant and being rheologoically compatible with both the drilling fluid and the drilling fluid converted to cement slurry may be used as a displacement fluid.

Abstract: A well cementing composition and method are shown in which a hydraulic cement, water, and a heat actuated matrix control admix are mixed together to provide a cement slurry composition having improved cementing characteristics over a broad temperature range. The admix contains a polyvinyl acetate-polyvinyl alcohol polymer which is insoluble in the slurry composition at ambient temperatures and which has greater than about 95% acetate groups converted to hydroxyl groups. As the circulating temperature rises in the range from about 90.degree. to 140.degree. F., the polymer begins to solubilize and gradually thickens the slurry to combat thermal thinning, fluid loss and settling. A companion cellulosic fluid loss material can be utilized, which is soluble in the slurry at ambient temperatures, to provide initial fluid loss control.