The present disclosure relates to spacer fluids for use in subterranean operations and, more particularly, in certain embodiments, to spacer fluids that include a spacer additive comprising a solid scouring material and a biopolymer gum while being essential free of clay. An example method may comprise spacer fluid comprise water and a spacer additive. The spacer additive may comprise a solid scouring material and a biopolymer gum, wherein the solid scouring material comprises crystalline silica in an amount of about 5 wt. % or less, and wherein the spacer fluid is essentially free of clay. The example method may further comprise and introducing the spacer fluid into a wellbore to displace at least a portion of a first fluid in the wellbore.

A method of treating a well comprising introducing a well treatment fluid into the well, and a well treatment fluid, are provided. The well treatment fluid comprises an aqueous base fluid, sepiolite clay, and a polymer component selected from the group of an acryloylmorpholine polymer, a polyvinylpyrrolidone polymer, and mixtures thereof. In one embodiment, for example, the method is a method of drilling a well. In this embodiment, the well treatment fluid is a drilling fluid.

According to one or more embodiments of the present disclosure, a spacer fluid includes an aqueous fluid, a weighting agent, and a clay stabilizer consisting of one or more polyethylene polyamines having a first structure H.sub.2NCH.sub.2CH.sub.2(NHCH.sub.2CH.sub.2).sub.xNH.sub.2, where x is an integer greater than or equal to 3. The amount of the clay stabilizer may be from 0.1 wt. % to 10 wt. % relative to the total weight of the spacer fluid. The average molecular weight of the polyethylene polyamines in the spacer fluid having the first structure may be from 200 g/mol to 400 g/mol. All of the polyethylene polyamines in the spacer fluid having the first structure may be encompassed in the clay stabilizer. Methods for cementing a casing in a wellbore using the spacer fluid are also disclosed.

A method of treating a subterranean formation can include: introducing a first fluid into a wellbore penetrating the subterranean formation; introducing a second fluid into the wellbore after introduction of the first fluid, wherein the second fluid comprises: a base fluid comprising water; a viscosifier; and a stabilizer, and wherein the second fluid has a rheological 3-rpm dial reading to 300-rpm dial reading ratio in the range of 1:1 to 1:3; and introducing a third fluid into the wellbore after introduction of the second fluid, wherein the second fluid inhibits or prevents the first fluid from mixing with the third fluid. The second fluid can be a liquid plug that substantially inhibits or prevents the first fluid from mixing with the third fluid. The first fluid can be a drilling mud or spacer fluid. The third fluid can be a spacer fluid or a cement composition.

A method of servicing a wellbore may comprise providing a treatment fluid comprising a carrier fluid and hollow particles, wherein the hollow particles may comprise an outer wall that encapsulates a gas. The method may further comprise introducing the treatment fluid into a wellbore annulus and trapping at least a portion of the treatment fluid in the wellbore annulus. The carrier fluid may degrade the outer wall of the hollow particles in the wellbore annulus and release the encapsulated gas.

A solid surfactant composition includes a water-wetting surfactant and a plant fiber carrying agent. A process includes forming a solid surfactant composition comprising a water-wetting surfactant and a plant fiber carrying agent and injecting the solid surfactant composition into a wellbore.

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.

Wellbore synthesis techniques are disclosed suitable for use in geothermal applications. Embodiments are provided where open hole drilled wellbores are sealed while drilling to form an impervious layer at the wellbore/formation interface. The techniques may be chemical, thermal, mechanical, biological and are fully intended to irreversibly damage the formation in terms of the permeability thereof. With the permeability negated, the wellbore may be used to create a closed loop surface to surface geothermal well operable in the absence of well casing for maximizing thermal transfer to a circulating working fluid. Formulations for the working and drilling fluids are disclosed.

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 treatment fluid can be provided for controlling annular pressure-buildup in a wellbore. The treatment fluid can include a base fluid and a pozzolanic material that can be dispersed within the base fluid. The pozzolanic material can cause the treatment fluid to controllably consolidate in an annulus of the wellbore for controlling annular pressure-buildup in the wellbore.