A method of using a nanosilica-containing cement in a well cementing operation in a well, the method comprising the steps of pumping a nanosilica-containing cement formulation into the well, wherein the nanosilica-containing cement formulation comprises maltodextrin-coated nanosilica and a cement formulation, where the maltodextrin-coated nanosilica comprises nanosilica particles encapsulated by maltodextrin coating, wherein the pH of the nanosilica-containing cement formulation is between 9 and 14, maintaining a temperature in the well due to a temperature of a formation surrounding the well, wherein the disintegration of the maltodextrin coating is initiated due to the temperature and pH of the nanosilica-containing cement, exposing the nanosilica particles due to the disintegration of the maltodextrin coating from the maltodextrin-coated nanosilica, and reacting the nanosilica particles with the cement formulation such that the transition time is reduced.

A method of using a nanosilica-containing cement in a well cementing operation in a well, the method comprising the steps of pumping a nanosilica-containing cement formulation into the well, wherein the nanosilica-containing cement formulation comprises maltodextrin-coated nanosilica and a cement formulation, where the maltodextrin-coated nanosilica comprises nanosilica particles encapsulated by maltodextrin coating, wherein the pH of the nanosilica-containing cement formulation is between 9 and 14, maintaining a temperature in the well due to a temperature of a formation surrounding the well, wherein the disintegration of the maltodextrin coating is initiated due to the temperature and pH of the nanosilica-containing cement, exposing the nanosilica particles due to the disintegration of the maltodextrin coating from the maltodextrin-coated nanosilica, and reacting the nanosilica particles with the cement formulation such that the transition time is reduced.

A cementitious mixture to make structures with reduction of gas permeability was disclosed. The mixture includes, cementitious materials, and one or more divalent magnesium-iron silicate that in neutral or basic aqueous solutions have the capacity to be a latent hydraulic binder comprising 2% to 99% of divalent magnesium-iron silicate by weight of total hydraulic solid materials. This can be used to produce a cementitious structure for preventing gas transfer between a first region and a second region. A cement slurry was also disclosed.

The present invention relates to the use of a combination of block polymers and particular compositions in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock following the injection thereof, the combination comprises (i) a polymer comprising: —a first block that is adsorbed on at least a portion of the particles; and —a second block, having a composition different from that of the first, and having a weight-average molecular weight of greater than 10 000 g/mol, for example greater than 100 000 g/mol, and that is soluble in the fluid; (ii) particles suitable for providing a gas barrier effect, preferably a latex and/or silica particles.

The present invention relates to the use of a combination of block polymers and particular compositions in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock following the injection thereof, the combination comprises (i) a polymer comprising: —a first block that is adsorbed on at least a portion of the particles; and —a second block, having a composition different from that of the first, and having a weight-average molecular weight of greater than 10 000 g/mol, for example greater than 100 000 g/mol, and that is soluble in the fluid; (ii) particles suitable for providing a gas barrier effect, preferably a latex and/or silica particles.

Described are a self-healing composition, and a preparation method for and an application of the composition. The composition is of a core-shell structure; the core contains a hydrogenated styrenic thermoplastic elastomer polymer and an inorganic filler; the shell contains a hydrophilic polymer; the composition has a density of 1.2-2 g/cm.sup.3, a water contact angle of no more than 90°, and a diesel oil and/or natural gas absorption expansion ratio of 5-15 times. By coating the hydrogenated styrenic thermoplastic elastomer and the inorganic filler with the hydrophilic (surface polarized) polymer, a core-shell structure is formed. When the composition is used for well cementing in an oil/gas field, the composition has a density and compatibility matching cement mortar and thus can form a uniform and stable cement slurry for well cementing in the oil/gas field, and has excellent oil/gas absorption expansion performance and thus can expand after absorbing oil/gas to perform self-healing.

Described are a self-healing composition, and a preparation method for and an application of the composition. The composition is of a core-shell structure; the core contains a hydrogenated styrenic thermoplastic elastomer polymer and an inorganic filler; the shell contains a hydrophilic polymer; the composition has a density of 1.2-2 g/cm.sup.3, a water contact angle of no more than 90°, and a diesel oil and/or natural gas absorption expansion ratio of 5-15 times. By coating the hydrogenated styrenic thermoplastic elastomer and the inorganic filler with the hydrophilic (surface polarized) polymer, a core-shell structure is formed. When the composition is used for well cementing in an oil/gas field, the composition has a density and compatibility matching cement mortar and thus can form a uniform and stable cement slurry for well cementing in the oil/gas field, and has excellent oil/gas absorption expansion performance and thus can expand after absorbing oil/gas to perform self-healing.

The present disclosure relates to downhole fluid additives including a clay, a hydroxylated polymer, a cation, and water. The disclosure further relates to downhole fluids, including drilling fluids, spaces, cements, and proppant delivery fluids containing such as downhole fluid additive and methods of using such fluids. The downhole fluid additive may have any of a variety of functions in the downhole fluid and may confer any of a variety of properties upon it, such as salt tolerance or desired viscosities even at high downhole temperatures.

The present disclosure relates to downhole fluid additives including a clay, a hydroxylated polymer, a cation, and water. The disclosure further relates to downhole fluids, including drilling fluids, spaces, cements, and proppant delivery fluids containing such as downhole fluid additive and methods of using such fluids. The downhole fluid additive may have any of a variety of functions in the downhole fluid and may confer any of a variety of properties upon it, such as salt tolerance or desired viscosities even at high downhole temperatures.

A cement composition is disclosed that includes a cement slurry and an epoxy resin system that includes at least one epoxy resin and a curing agent. The cement slurry has a density in a range of from 65 pcf to 180 pcf and includes a cement precursor material, silica sand, silica flour, a weighting agent, and manganese tetraoxide. The epoxy resin system includes at least one of 2,3-epoxypropyl o-tolyl ether, alkyl glycidyl ethers having from 12 to 14 carbon atoms, bisphenol-A-epichlorohydrin epoxy resin, or a compound having formula (I): (OC.sub.2H.sub.3)—CH.sub.2—O—R.sup.1—O—CH.sub.2—(C.sub.2H.sub.3O) where R.sup.1 is a linear or branched hydrocarbyl having from 4 to 24 carbon atoms; and a curing agent.