Examples of novel self-repairing cement-polymer composites and processes of making and using are detailed that address various problems in prior art cements. These matrices, compositions and materials that are more mechanically robust, thermally stable and chemically resistant and demonstrate better bonding to various structures and materials, than other self-healing cements known in the prior art. When in place under preselected conditions (the formulation of the slurry can be modified for optimal effectiveness under various conditions) the organic, cross linking and cement forming portions within the slurry form interconnecting chemical bonds and cures to form a self-repairing and self-re-adhering cement polymer composite matrix in the receiving location.

Examples of novel self-repairing cement-polymer composites and processes of making and using are detailed that address various problems in prior art cements. These matrices, compositions and materials that are more mechanically robust, thermally stable and chemically resistant and demonstrate better bonding to various structures and materials, than other self-healing cements known in the prior art. When in place under preselected conditions (the formulation of the slurry can be modified for optimal effectiveness under various conditions) the organic, cross linking and cement forming portions within the slurry form interconnecting chemical bonds and cures to form a self-repairing and self-re-adhering cement polymer composite matrix in the receiving location.

A method may include: introducing a resin modified cement slurry into a wellbore penetrating a subterranean formation, the subterranean formation comprising a caprock and a carbon dioxide injection zone, the resin modified cement slurry comprising: a resin; a hardener; a hydraulic cement; and water; and setting the resin modified cement slurry to form a set cement wherein the set cement forms a carbonation-resistant barrier in the carbon dioxide injection zone in the subterranean formation.

Embodiments relate to cementing operations and, in certain embodiments, to passivated cement accelerators and methods of using passivated cement accelerators in subterranean formations. An embodiment may comprise a method of cementing comprising: providing a cement composition comprising cement, water, and a passivated cement accelerator; and allowing the cement composition to set.

Cement slurries are provided for use in cementing oil and gas wells. The cement slurry comprises API Class C or Class H Portland cement and a pozzolan selected from the group consisting of pumice and mixtures of pumice and fly ash. Pumice is present in the mixtures in amounts at least about 40 wt % of the pozzolan. The weight ratio of the pozzolan to the cement is from about 35:65 to about 70:30. The novel cement slurries preferably will not comprise any additional lime, including hydrated lime, or other activators.

The invention provides a high temperature resistant Portland cement slurry and a production method thereof. The high temperature resistant Portland cement slurry comprises the following components by weight: 100 parts of an oil well Portland cement, 60-85 parts of a high temperature reinforcing material, 68-80 parts of fresh water, 1-200 parts of a density adjuster, 0.1-1.5 parts of a suspension stabilizer, 0.8-1.5 parts of a dispersant, 3-4 parts of a fluid loss agent, 0-3 parts of a retarder and 0.2-0.8 part of a defoamer. The high temperature resistant Portland cement slurry has a good sedimentation stability at normal temperature, and develops strength rapidly at a low temperature. The compressive strength is up to 40 MPa or more at a high temperature of 350 C., and the long-term high-temperature compressive strength develops stably without degradation. Therefore, it can meet the requirements for field application in heavy oil thermal recovery wells, reaching the level of Grade G Portland cement for cementing oil and gas wells.

Cement slurries are provided for use in cementing oil and gas wells. The cement slurry comprises API Class C or Class H Portland cement and a pozzolan selected from the group consisting of pumice and mixtures of pumice and fly ash. Pumice is present in the mixtures in amounts at least about 40 wt % of the pozzolan. The weight ratio of the pozzolan to the cement is from about 35:65 to about 70:30. The novel cement slurries preferably will not comprise any additional lime, including hydrated lime, or other activators.

A cement slurry including graphene, a cement, and water; the graphene comprises bioderived renewable graphene (BRG). The cement slurry has reduced transient gel formation relative to a same cement slurry absent the graphene. Methods of mitigating transient gels in cement are also provided.

A method may include: introducing a resin modified cement slurry into a wellbore penetrating a subterranean formation, the subterranean formation comprising a caprock and a carbon dioxide injection zone, the resin modified cement slurry comprising: a resin; a hardener, a hydraulic cement; and water; and setting the resin modified cement slurry to form a set cement wherein the set cement forms a carbonation-resistant barrier in the carbon dioxide injection zone in the subterranean formation.

A method may include: introducing a resin modified cement slurry into a wellbore penetrating a subterranean formation, the subterranean formation comprising a caprock and a carbon dioxide injection zone, the resin modified cement slurry comprising: a resin; a hardener; a hydraulic cement; and water; and setting the resin modified cement slurry to form a set cement wherein the set cement forms a carbonation-resistant barrier in the carbon dioxide injection zone in the subterranean formation.