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 of preparing a solid surfactant composite may include: coating a liquid water-wetting surfactant on a solid carrier; and drying the solid carrier to produce the solid surfactant composite. A method may include: introducing a spacer fluid into a wellbore, the spacer fluid comprising a solid surfactant composite; and displacing a fluid in the wellbore using the spacer fluid.

A method of preparing a solid surfactant composite may include: coating a liquid water-wetting surfactant on a solid carrier; and drying the solid carrier to produce the solid surfactant composite. A method may include: introducing a spacer fluid into a wellbore, the spacer fluid comprising a solid surfactant composite; and displacing a fluid in the wellbore using the spacer fluid.

A spacer fluid includes an aphron generating component, a polymer, a lost circulation material, and a weighting agent component.

Methods for separating fluids with a barrier pill within a downhole environment are provided. The method includes introducing a barrier pill fluid into the wellbore containing a first fluid to form the barrier pill on top of the first fluid in the wellbore and introducing a second fluid into the wellbore. The barrier pill separates the first fluid and the second fluid. The barrier pill includes a viscoelastic surfactant and an aqueous fluid, such as a brine containing water and about 5 wt % to about 50 wt % of a salt.

Non-aqueous drilling fluids may be removed from a wellbore or tubing nor casing within the wellbore by introducing into the well a biodegradable aqueous fluid comprising banana.

Non-aqueous drilling fluids may be removed from a wellbore or tubing nor casing within the wellbore by introducing into the well a biodegradable aqueous fluid comprising banana.

A spacer fluid comprising: (a) water; and (b) an alkyl polyglycoside derivative, wherein the alkyl polyglycoside derivative is selected from the group consisting of sorbitan fatty acids; functionalized sulfonates, functionalized betaines, an inorganic salt of any of the foregoing, and any combination of any of the foregoing. Preferably, the spacer fluid additionally comprises a solid particulate, such as a weighting agent. A method of displacing an oil-based drilling mud from a portion of a well comprising the steps of: (A) forming the spacer fluid; and (B) introducing the spacer fluid into the well.

A spacer fluid comprising: (a) water; and (b) an alkyl polyglycoside derivative, wherein the alkyl polyglycoside derivative is selected from the group consisting of sorbitan fatty acids; functionalized sulfonates, functionalized betaines, an inorganic salt of any of the foregoing, and any combination of any of the foregoing. Preferably, the spacer fluid additionally comprises a solid particulate, such as a weighting agent. A method of displacing an oil-based drilling mud from a portion of a well comprising the steps of: (A) forming the spacer fluid; and (B) introducing the spacer fluid into the well.

A hydrated inorganic oxide material capable of elongating from a planar shape to a fiber shape along a thickness direction of the planar shape, wherein the fiber shape is at least about 25 times greater in the thickness direction than the planar shape, and wherein during elongating a radial dimension of the hydrated inorganic oxide material changes by less than about 10% may be useful in a plurality of wellbore operations. For example, a method may include introducing a wellbore fluid comprising an aqueous base fluid and a hydrated inorganic oxide material into a wellbore penetrating a subterranean formation; and swelling the hydrated inorganic oxide material by contacting the hydrated inorganic oxide material with a polar amine compound such that the hydrated inorganic oxide material elongates from a planar shape to a fiber shape along a thickness direction of the planar shape.