A method for reducing lost circulation in a subterranean formation. The method includes providing a treatment fluid comprising a base fluid and a lost circulation material comprising brown mud. The treatment fluid is introduced into a wellbore within the subterranean formation such that at least a portion of the brown mud bridges openings in the subterranean formation to reduce loss of fluid circulation into the subterranean formation.

The invention provides a carbon dioxide-resistant hydraulic cement composition. The inventive composition comprises a Portland cement, Class C fly ash and water. The Class C fly ash is present in the composition in an amount in the range of from about 5% to less than about 30% by weight based on the total weight of the cementitious components in the composition. In another aspect, the invention provides a method of cementing in a carbon dioxide environment. In yet another aspect, the invention provides a method of enhancing the recovery of a hydrocarbon fluid from a subterranean formation.

The invention provides a carbon dioxide-resistant hydraulic cement composition. The inventive composition comprises a Portland cement, Class C fly ash and water. The Class C fly ash is present in the composition in an amount in the range of from about 5% to less than about 30% by weight based on the total weight of the cementitious components in the composition. In another aspect, the invention provides a method of cementing in a carbon dioxide environment. In yet another aspect, the invention provides a method of enhancing the recovery of a hydrocarbon fluid from a subterranean formation.

A colored cementitious composition is provided that is composed of hydraulic cement and a liquid coloring suspension. The liquid coloring suspension for cementitious compositions contains polycarboxylate dispersant, pigment, and a polysaccharide thixotropic additive. The liquid coloring suspension has improved viscosity consistency, improved shelf-life, anti-settling and anti-sludging properties, and decreased polycarboxylate dispersant requirements.

A colored cementitious composition is provided that is composed of hydraulic cement and a liquid coloring suspension. The liquid coloring suspension for cementitious compositions contains polycarboxylate dispersant, pigment, and a polysaccharide thixotropic additive. The liquid coloring suspension has improved viscosity consistency, improved shelf-life, anti-settling and anti-sludging properties, and decreased polycarboxylate dispersant requirements.

A carbonation-resistant cementitious blend containing cement, an expandable agent present, a dispersion agent, a fluid loss additive, a defoamer, and an olive waste. Concrete samples made therefrom and methods of producing such concrete samples are also specified. The addition of olive waste provides enhanced durability (carbonation resistance) and maintains mechanical strength (e.g. compressive strength, tensile strength) after exposure to CO.sub.2 and/or brine. The resulting concretes are suitable cementing material for oil and gas wells as well as wellbores for geologic carbon sequestration.

A carbonation-resistant cementitious blend containing cement, an expandable agent present, a dispersion agent, a fluid loss additive, a defoamer, and an olive waste. Concrete samples made therefrom and methods of producing such concrete samples are also specified. The addition of olive waste provides enhanced durability (carbonation resistance) and maintains mechanical strength (e.g. compressive strength, tensile strength) after exposure to CO.sub.2 and/or brine. The resulting concretes are suitable cementing material for oil and gas wells as well as wellbores for geologic carbon sequestration.

The present invention provides dry mixes for skim coat mortars having improved pot life and workability while reducing cellulose ether dosage comprising a white cement, one or more fillers having a sieve average particle size of from 15 to 60 microns, from 0.25 to 0.5 wt. % of one or more gel-like crosslinked cellulose ethers containing polyether groups, preferably, a mixed cellulose ether having polyoxypropylene dioxyethylene ether crosslinks, and from 1 to 2.5 wt. % of one or more polymer redispersible powders (RDP). At least one gel-like crosslinked cellulose ether has a crossover point as measured by oscillation rheometry, at which storage modulus (G′) and loss modulus (G″) intersect and are identical, of 1.0ω or less. The present invention also provides methods of using the dry mixes.

Cement slurries, cured cements, and methods of making cured cement and methods of using cement slurries have, among other attributes, an extended thickening time, leading to improved retardation, flowability, and pumpability and may be used, for instance, in the oil and gas drilling industry. The cement slurry includes water, microfine cement material, and bisphenol-F diglycidyl ether resin.

Cement slurries, cured cements, and methods of making cured cement and methods of using cement slurries have, among other attributes, an extended thickening time, leading to improved retardation, flowability, and pumpability and may be used, for instance, in the oil and gas drilling industry. The cement slurry includes water, microfine cement material, and bisphenol-F diglycidyl ether resin.