Geopolymer cement slurries, cured geopolymer cements, and methods of making cured geopolymer cement and methods of using geopolymer cement slurries are provided. The geopolymer cement slurry comprises cement precursor material, Saudi Arabian volcanic ash, and an aqueous solution. 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.

Geopolymer cement slurries, cured geopolymer cements, and methods of making cured geopolymer cement and methods of using geopolymer cement slurries are provided. The geopolymer cement slurry comprises cement precursor material, Saudi Arabian volcanic ash, and an aqueous solution. 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.

A composition of a cement additive material to improve durability of cementitious structures, was disclosed. The cement additive composition includes an admixture of one or more of divalent magnesium metal silicates with capacity to act as a latent hydraulic binder in said composition activated by a hydration process under aqueous conditions, and in particular the divalent metal silicate is magnesium-dominated silicate, preferably comprising mineral groups of olivines, orthopyroxenes, amphiboles, and serpentines or mixtures thereof. The composition also includes chloride ions or brine.

A composition of a cement additive material to improve durability of cementitious structures, was disclosed. The cement additive composition includes an admixture of one or more of divalent magnesium metal silicates with capacity to act as a latent hydraulic binder in said composition activated by a hydration process under aqueous conditions, and in particular the divalent metal silicate is magnesium-dominated silicate, preferably comprising mineral groups of olivines, orthopyroxenes, amphiboles, and serpentines or mixtures thereof. The composition also includes chloride ions or brine.

A method of reducing lost circulation in a wellbore includes introducing an activation solution including an aqueous solution, Na.sub.2SiO.sub.3, NaOH, and one or both of CaCO.sub.3 or Mn.sub.3O.sub.4 into the wellbore. The method further includes introducing Saudi Arabian volcanic ash into the wellbore. 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. The method further includes allowing the Saudi Arabian volcanic ash to contact the activation solution in the wellbore, thereby forming a geopolymer barrier between the wellbore and a subsurface formation to reduce lost circulation in the wellbore.

A method of reducing lost circulation in a wellbore includes introducing an activation solution including an aqueous solution, Na.sub.2SiO.sub.3, NaOH, and one or both of CaCO.sub.3 or Mn.sub.3O.sub.4 into the wellbore. The method further includes introducing Saudi Arabian volcanic ash into the wellbore. 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. The method further includes allowing the Saudi Arabian volcanic ash to contact the activation solution in the wellbore, thereby forming a geopolymer barrier between the wellbore and a subsurface formation to reduce lost circulation in the wellbore.

The present invention disclosed a cross-linked plugging agent stimulated by high density brine which comprises main agent: 10 wt %-90 wt %, gelling agent: 0.5 wt %-9 wt % and pure water; wherein the main agent is selected from the group consisting of a Dipotassium phosphate (K.sub.2HPO.sub.4), a Tripotassium phosphate (K.sub.3PO.sub.4) and a Potassium pyrophosphate (K.sub.4P.sub.2O.sub.7), a Potassium Dihydrogen Phosphate (KH.sub.2PO.sub.4), a Sodium dihydrogen phosphate (NaH.sub.2PO.sub.4); the gelling agent is selected from the group consisting of a Xanthan gum and a kappa carrageenan. The gelling time is controlled within 0.5-12 h under an experiment temperature of 90 C.-160 C. The final gelling strength is controlled within D-H. The density is controlled within 1.0-1.55 g/cm.sup.3. The plugging agent is able to be applied in well completion and workover under high temperature, high pressure, multi-pressure series of strata oil and gas environment when temporary blockage and leak proof is required, protection of reservoir near perforations and water plugging.

The present invention disclosed a cross-linked plugging agent stimulated by high density brine which comprises main agent: 10 wt %-90 wt %, gelling agent: 0.5 wt %-9 wt % and pure water; wherein the main agent is selected from the group consisting of a Dipotassium phosphate (K.sub.2HPO.sub.4), a Tripotassium phosphate (K.sub.3PO.sub.4) and a Potassium pyrophosphate (K.sub.4P.sub.2O.sub.7), a Potassium Dihydrogen Phosphate (KH.sub.2PO.sub.4), a Sodium dihydrogen phosphate (NaH.sub.2PO.sub.4); the gelling agent is selected from the group consisting of a Xanthan gum and a kappa carrageenan. The gelling time is controlled within 0.5-12 h under an experiment temperature of 90 C.-160 C. The final gelling strength is controlled within D-H. The density is controlled within 1.0-1.55 g/cm.sup.3. The plugging agent is able to be applied in well completion and workover under high temperature, high pressure, multi-pressure series of strata oil and gas environment when temporary blockage and leak proof is required, protection of reservoir near perforations and water plugging.

Some embodiments of the present invention comprise a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising remediated coal ash, hydraulic cement, and water; and allowing the settable composition to set. Other embodiments comprise a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising remediated coal ash, calcium hydroxide (lime), and water; and allowing the settable composition to set. Other embodiments comprise a settable composition comprising: remediated coal ash, hydraulic cement, calcium hydroxide, natural pozzolan and water; and allowing the composition to set. Other embodiments comprise a settable composition comprising remediated coal ash and any combination of hydraulic cement, calcium hydroxide, slag, fly ash, and natural or other pozzolan.

Some embodiments of the present invention comprise a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising remediated coal ash, hydraulic cement, and water; and allowing the settable composition to set. Other embodiments comprise a method of cementing comprising: placing a settable composition into a well bore, the settable composition comprising remediated coal ash, calcium hydroxide (lime), and water; and allowing the settable composition to set. Other embodiments comprise a settable composition comprising: remediated coal ash, hydraulic cement, calcium hydroxide, natural pozzolan and water; and allowing the composition to set. Other embodiments comprise a settable composition comprising remediated coal ash and any combination of hydraulic cement, calcium hydroxide, slag, fly ash, and natural or other pozzolan.