A method of reducing lost circulation includes introducing a lost circulation solution comprising Saudi Arabian volcanic ash, a curing agent, and a resin into a subsurface formation through a wellbore, wherein the Saudi Arabian volcanic ash comprises SO.sub.3, CaO, SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, MgO, and K.sub.2O; and allowing the lost circulation solution to thicken within the subsurface formation, thereby forming a barrier between the subsurface formation and the wellbore to reduce lost circulation.

A method of forming a barrier to overcome lost circulation in a subterranean formation. The method includes injecting a polymer-sand nanocomposite into one or more lost circulation zones in the subterranean formation where the polymer-sand nanocomposite is formed from sand mixed with a polymer hydrogel. Further, the polymer hydrogel includes a hydrogel polymer, an organic cross-linker, and a salt. The sand additionally comprises a surface modification. The associated method of preparing a polymer-sand nanocomposite lost circulation material for utilisation in forming the barrier is provided.

According to embodiments disclosed herein, a gel fluid composite may include a nanosilica gel and a plurality of quantum dot tracers. The nanosilica gel may be configured to seal one or more downhole fractures in a wellbore. The plurality of quantum dot tracers may be dispersed in the nanosilica gel. The plurality of quantum dot tracers may each include a semiconductor particle core housed in a silica shell.

Methods and compositions comprising nanoparticle additives for use in drilling and treatment fluid compositions are provided. In some embodiments the present disclosure includes providing a treatment fluid including an aqueous base fluid, a nanoparticle additive, and a viscosifier; introducing the treatment fluid into at least a portion of a subterranean formation to contact at least a portion of the subterranean formation; and allowing the treatment fluid to reduce fluid loss into the subterranean formation.

The present disclosure provides methods that use polymerized alkali silicate gels. An example method comprises: introducing a polymerized alkali silicate gel into a subterranean formation containing a fault, wherein the polymerized alkali silicate gel is introduced the subterranean formation such that at least a leading edge of polymerized alkali silicate gel is placed in the fault or within about 10 miles from the fault.

A method of pumping a fluid and reactive solid into a mineral formation includes the fluid reacting with the mineral formation to produce a nucleation product. The method may be used in shale formations to seal fissures and prevent leakage. The fluid used in this method may comprise CO.sub.2 and the nucleation products may be the products of carbonation reactions. A cement formed by reacting CO.sub.2 with a reactive solid under deep geological formation conditions is also disclosed.

Provided is a loss circulation material that may consist essentially of an acidic nanosilica dispersion and an activator. The acidic nanosilica dispersion may consist of acidic silica nanoparticles, stabilizer, and water, and may have a pH in a range of 3 to 6. The activator may be one or more from the group consisting of sodium bicarbonate, sodium chloride, or an amine salt. A method is provided for controlling lost circulation in a lost circulation zone in a wellbore comprising introducing the loss circulation material and forming a gelled solid from the loss circulation material in the lost circulation zone.

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.

A system includes a casing, a tubing within the casing, a packer, and a colloidal silica gel. The casing inner surface and the tubing outer surface define an annular space, and the packer is within the annular space. The colloidal silica gel which seals a gap. The gap can be a gap between the inner surface of the casing and a surface of the packer, a gap between the outer surface of the tubing and a surface of the packer, and/or a gap extending through the packer. A well can include such a system. A method of sealing a leak in or near a packer present in an annular space between a production casing inner surface and a tubing outer surface includes disposing a composition within the annular space, the composition comprising colloidal silica, water, and an activator. The method also includes allowing colloidal silica to precipitate from the composition to provide a colloidal silica gel within the annular space, wherein the colloidal silica seals a gap that can be a gap between the inner surface of the production casing and a surface of the packer, a gap between the outer surface of the tubing and a surface of the packer, and/or a gap extending through the packer.

According to embodiments disclosed herein, a gel fluid composite may include a nanosilica gel and a plurality of quantum dot tracers. The nanosilica gel may be configured to seal one or more downhole fractures in a wellbore. The plurality of quantum dot tracers may be dispersed in the nanosilica gel. The plurality of quantum dot tracers may each include a semiconductor particle core housed in a silica shell.