A fracturing fluid may include a first surfactant and a second surfactant. The first surfactant may have a structure represented by formula (I):

##STR00001##

wherein m is an integer ranging from 2 to 3, and n, o, and k are each, independently, integers ranging from 2 to 10. The second surfactant having a structure represented by Formula (II):

##STR00002##

wherein R.sup.2 is a C.sub.15-C.sub.27 hydrocarbon group or a C.sub.15-C.sub.29 substituted hydrocarbon group, R.sup.3 is a C.sub.1-C.sub.10 hydrocarbon group, and p and q are each, independently, an integer ranging from 1 to 4. Methods of treating a hydrocarbon-bearing formation include injecting the fracturing fluid in the hydrocarbon-bearing formation, the fracturing fluid being configured to transport a proppant in fractures of the hydrocarbon-bearing formation.

A wellbore fluid including a first surfactant, a second surfactant, an activator and an aqueous base fluid is provided. The first surfactant has a structure represented by Formula (I):

##STR00001##

where Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4 are each, independently, a sulfonate, a carboxylate, an ester or a hydroxyl group, m is an integer ranging from 2 to 3, and n, o, and k are each, independently, integers ranging from 2 to 10. The second surfactant has a structure represented by Formula (III):

##STR00002##

where R.sub.2 is a C.sub.15-C.sub.27 hydrocarbon group or a C.sub.15-C.sub.29 substituted hydrocarbon group, R.sub.3 is a C.sub.1-C.sub.10 hydrocarbon group, and p and q are each, independently, an integer ranging from 1 to 4. A method of using the wellbore fluid for treating a hydrocarbon-containing formation is also provided.

The invention concerns synthesized amido-amine-based cationic gemini surfactants with flexible and rigid spacers and different hydrophobic. These gemini surfactants were prepared by modified procedure through amidation of long chain carboxylic acids using 3-(dimethylamino)-1-propylamine followed by treatment with halohydrocarbons and showed excellent thermal stability and surface properties useful for various oilfield applications such as enhanced oil recovery.

Described herein are methods for treating a subterranean formation penetrated by a wellbore with a retarded acidizing fluid containing an acid and an acid retarding agent, the concentrations of which are adjusted based on measured parameter values of the formation. Also described is a method for treating a subterranean formation by introducing an acid to the formation following the introduction of an acid retarding agent to the formation. Also described is a method for acid fracturing a subterranean formation including reducing the concentration of an acid retarding agent contained in a retarded acidizing fluid over the course of the acid fracturing operation.

A method of breaking the viscosity of a treatment fluid comprises: adding hydrophobic nanoparticles to a treatment fluid comprising a base fluid and a viscoelastic surfactant gelling agent, the hydrophobic nanoparticles comprising metallic nanoparticles that are surface modified with C.sub.6-30 aliphatic groups, wherein the hydrophobic nanoparticles are added in an amount effective to decrease the viscosity of the treatment fluid as compared to a treatment fluid absent the hydrophobic nanoparticles.

A fluid including: (i) a continuous aqueous phase, wherein the continuous aqueous phase has total dissolved solids in a concentration of at least 30,000 mg/l; (ii) an alkyl amido quaternary amine; (iii) a polymer, wherein the polymer is water-soluble or water-hydratable; and (iv) a crosslinker for the polymer. The continuous aqueous phase of the fluid can include a water source selected from the group consisting of flowback water, produced water, and any combination thereof. Methods include: (A) forming a fluid according to any of the various embodiments of the disclosure, and (B) introducing the fluid into a well. For example, the fluid can be used as a fracturing fluid for fracturing a treatment zone of a well.

Pumpable process-fluid compositions comprise polyacrylamide, a non-metallic crosslinker and a pH-adjustment material. Such compositions have utility in the context of controlling lost circulation in subterranean wells. Upon entering at least one lost circulation zone, the compositions crosslink, thereby forming a barrier that minimizes or stops fluid flow from the wellbore into the lost circulation zone.

A formation treatment fluid may include a wettability alteration agent, a solvent, an injection gas, and an optional foaming agent. The wettability alteration agent may include a fluorinated surfactant, a silicon-based surfactant, charged nanoparticles partially modified with fluorine containing groups, or combinations thereof. Methods for altering a hydrocarbon-bearing reservoir surface wettability may include providing the formation treatment fluid, injecting the formation treatment fluid into the hydrocarbon-bearing reservoir, and recovering fluids produced from the hydrocarbon-bearing reservoir.

A method for acid treating a carbonate reservoir with an attenuated acid formulation is provided. The method includes mixing an acidic compound with a hygroscopic chemical to form the attenuated acid formulation, and injecting the attenuated acid formulation into a carbonate formation.

A method of treating a subterranean formation penetrated by a well comprises combining an aqueous base fluid, a viscoelastic surfactant gelling agent, two or more types of the following nanoparticles: an alkaline earth metal oxide; an alkaline earth metal hydroxide; a transition metal oxide; or a transition metal hydroxide to form a treatment fluid, and pumping the treatment fluid into the well, wherein the weight ratio of the two or more types of the nanoparticles is selected such that the treatment fluid has an improved fluid efficiency as compared to an otherwise identical reference fluid except for comprising only one type of the nanoparticles selected from an alkaline earth metal oxide; an alkaline earth metal hydroxide; a transition metal oxide; and a transition metal hydroxide.