An improved oil or gas well cement for penetrating, sealing and plugging wells to be abandoned. The cement fill includes (a) a cement component including a calcium sulfoaluminate cement and a Portland cement having a ratio by weight of Portland cement to calcium sulfoaluminate cement ranging from 1/19 to ⅕ and (b) an aggregate component with gradation spanning 1,200 microns to 5 microns. Further an improved oil or gas well microcellular cement for penetrating sealing and completely filling wells to be abandoned that includes (a) a cement component including a calcium sulfoaluminate cement and a Portland cement having a ratio by weight of Portland cement to calcium sulfoaluminate cement ranging from 1/19 to ⅕ and (b) an aggregate component with gradation spanning 200 microns to 5 microns and (c) a foaming agent.

Disclosed herein is a method of servicing a wellbore penetrating a subterranean formation, comprising: placing a cementitious composition of the type disclosed herein into the wellbore. The cementitious composition comprises a cement blend and water, wherein the cement blend comprises Portland cement and pozzolan, wherein the Portland cement is present in an amount of from equal to or greater than about 0.01 wt. % to equal to or less than about 25.0 wt. % based on the total weight of the cement blend.

A method of cementing may include preparing a cement composition comprising: cementitious components comprising: a cement; a supplementary cementitious material; and nanoparticulate boehmite; and water; and introducing the cement composition into a subterranean formation.

A method of cementing may include preparing a cement composition comprising: cementitious components comprising: a cement; a supplementary cementitious material; and nanoparticulate boehmite; and water; and introducing the cement composition into a subterranean formation.

A carbonation-resistant cementitious blend containing cement, an expandable agent present, a dispersion agent, a fluid loss additive, a defoamer, and an olive waste. Concrete samples made therefrom and methods of producing such concrete samples are also specified. The addition of olive waste provides enhanced durability (carbonation resistance) and maintains mechanical strength (e.g. compressive strength, tensile strength) after exposure to CO.sub.2 and/or brine. The resulting concretes are suitable cementing material for oil and gas wells as well as wellbores for geologic carbon sequestration.

The effectiveness of expansive cement systems may be diluted when, during a well cementing operation, commingling takes place between the cement slurry and a spacer fluid, a drilling fluid, or both. Incorporating expansive agents in the spacer fluid or drilling fluid may reduce or negate the loss of expansion at the cement slurry/spacer interface or the cement slurry/drilling fluid interface, thereby promoting zonal isolation throughout the cemented interval.

A method may include providing a cement composition comprising ground vitrified clay, hydrated lime, and water; and introducing the cement composition into a subterranean formation.

The effectiveness of expansive cement systems may be diluted when, during a well cementing operation, commingling takes place between the cement slurry and a spacer fluid, a drilling fluid, or both. Incorporating expansive agents in the spacer fluid or drilling fluid may reduce or negate the loss of expansion at the cement slurry/spacer interface or the cement slurry/drilling fluid interface, thereby promoting zonal isolation throughout the cemented interval.

The effectiveness of expansive cement systems may be diluted when, during a well cementing operation, commingling takes place between the cement slurry and a spacer fluid, a drilling fluid, or both. Incorporating expansive agents in the spacer fluid or drilling fluid may reduce or negate the loss of expansion at the cement slurry/spacer interface or the cement slurry/drilling fluid interface, thereby promoting zonal isolation throughout the cemented interval.

A variety of methods and compositions are disclosed, including, in one embodiment a method a cementing in a subterranean formation comprising: providing a set-delayed cement composition comprising water, pumice, hydrated lime, and a set retarder; foaming the set-delayed cement composition; activating the set-delayed cement composition; introducing the set-delayed cement composition into a subterranean formation; and allowing the set-delayed cement composition to set in the subterranean formation. Additional methods, foamed set-delayed cement composition, and systems for cementing are also provided.