Described herein are methods for on the fly mixing of retarded acidizing fluids containing acid, a water-soluble acid retarding agent (RA), and optionally a viscoelastic surfactant (VES), and for on the fly mixing of diversion fluids containing VES and RA in the same equipment. Also described are methods of controlling the preparation of such fluids based on feedback composition analyses.

Embodiments of the present disclosure are directed to a method of producing a viscoelastic surfactant (VES) fluid, the VES fluid comprising desulfated seawater. The method of producing the VES fluid comprises adding an alkaline earth metal halide to seawater to produce a sulfate precipitate. The method further comprises removing the sulfate precipitate to produce the desulfated water. The method further comprises adding a VES and one or more of a nanoparticle viscosity modifier or a polymeric modifier to the desulfated seawater. Other embodiments are directed to VES fluids that maintain a viscosity greater than 10 cP at temperatures above 250 F.

Provided are compositions, methods, and systems that relate to use of viscoelastic surfactant gels in well perforation. A method for well treatment comprising: introducing a viscoelastic surfactant gel into a wellbore; and forming one or more perforation channels in an interval of the wellbore while the viscoelastic surfactant gel is disposed in the wellbore. A method for well treatment comprising: introducing a viscoelastic surfactant gel into a wellbore over an interval of the wellbore to be perforated; disposing a perforating gun into the wellbore such that the viscoelastic surfactant gel is disposed between the perforating gun and a casing of the wellbore; and forming one or more perforation channels in the interval of the wellbore. A downhole perforating system comprising: a perforating gun disposed at a distal end of a work string; and a viscoelastic surfactant gel.

A treatment fluid comprises: a base fluid; a viscoelastic surfactant gelling agent and hydrophobic nanoparticles comprising metallic nanoparticles that are surface modified with C.sub.6-30 aliphatic groups. The treatment fluid is a fracturing fluid, a completion fluid, a gravel pack fluid, a fluid loss pill, a lost circulation pill, a diverter fluid, a foamed fluid, a stimulation fluid and the like.

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.

A method of quantifying a viscoelastic effect of a polymer on residual oil saturation (S .sub.or) including calculating an extensional capillary number (N.sub.ce) using flux, pore-scale apparent viscosity, and interfacial tension to account for the polymer's viscoelastic forces that are responsible for S.sub.or reduction. The polymer is used polymer flooding during enhanced oil recovery. An extensional capillary number is calculated for a plurality of polymer materials, which are then compiled in a database. Also provided is a reservoir simulator for predicting the S.sub.or reduction potential of the viscoelastic polymer, which includes a database of calculated extensional capillary numbers for a plurality of polymers. The database includes a curve generated from the calculated extensional capillary numbers for a plurality of polymers properties, flux rates, formation nature, oil viscosities, and rheological behaviors.

The present invention relates to a carbonate reservoir filtration-loss self-reducing acid fracturing method. The carbonate reservoir filtration-loss self-reducing acid fracturing method comprises the steps: (1) calculating a fracture pressure and a fracture extension pressure of a reconstructed reservoir; (2) injecting an agent A into a stratum under a pressure higher than the stratum fracture pressure, so that fractures are generated on the stratum; (3) injecting an agent B into the stratum under a pressure higher than the stratum fracture pressure, such that the agent B extends the fractures and communicates with a natural fracture net; (4) pumping an acid liquor system agent C with a high etching power into the stratum under a pressure higher than the extension pressure but lower than the fracture pressure to improve the conductivity of the fractures; (5) injecting a displacing liquid agent D under a pressure lower than the stratum fracture pressure to jack acid liquor in a well casing into the stratum; and (6) shutting down a well and performing flow-back. The agent A is a gel acid or VES acid, the agent B is a filtration-loss self-reducing gel acid or filtration-loss self-reducing VES acid, the agent C is closed acid, and the agent D is a displacing liquid. According to the method of the present invention, precipitation type solid filter cakes are formed on wall surfaces of the fractures by utilizing a filtration-loss self-reducing system, so as to perform temporary blocking to reduce the filtration loss. The technology is simple with easy injection, and the filtration-reducing agent is easy to disperse and flow back, and the method is safe and environment-friendly.

Methods and systems for enhancing acid fracture conductivity of acid fracture treatments on subterranean formations are provided. An example method of acid fracture treatment includes initiating fracturing of a subterranean formation in which a wellbore is formed to create a formation fracture, after initiating the fracturing for a period of time, injecting an acidic fluid into the wellbore to etch walls of the formation fracture to thereby create fracture conductivity, introducing a gas into the wellbore to foam fluids in the wellbore, and increasing a foam quality of the fluids with time during the treatment. The foam quality is based on a volume of the introduced gas and a total volume of the fluids in the wellbore.

A three-poly cationic viscoelastic and a clean fracturing fluid containing the three-poly cationic viscoelastic surfactant are provided. N, N-dimethyl-1,3-propanediamine and epichlorohydrin are used to prepare an intermediate A, and then the intermediate A and a fatty acid amidopropyl dimethylamine is used to prepare the three-poly cationic viscoelastic surfactant. The preparation process is simple. The clean fracturing fluid including the three-poly cationic viscoelastic surfactant has excellent temperature and shear resistance, strong suspended sand performance, simple on-site preparation, automatic gel breaking, small damage to formation, low cost and simple preparation process. The clean fracturing fluid including the surfactant also has strong temperature resistance, and the viscosity of the product can be maintained at 42 mPa.Math.s after 80 minutes at 180 C. and 170 s.sup.1, which is higher than the viscosity requirement (>25 mPa.Math.s) of the clean fracturing fluid in on-site construction.

A viscoelastic emulsion formed by combining at least one extended surfactant, a salt (e.g., brine), an oil, such as crude oil, diesel, kerosene, or a vegetable oil, and water, into a mixture comprising an oil-starved Winsor III microemulsion into which excess oil is dispersed. The viscoelastic emulsion may be combined with a proppant to form a fracking fluid. The viscoelastic emulsion may be used in various reservoir applications, such as hydraulic fracturing, or flooding for enhanced tertiary oil recovery, and in other applications such as, but not limited to, environmental remediation, or formation of consumer products.