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The microemulsion phase behavior and physicochemical properties of surfactant-water-alcohol-oil systems are the pioneer laboratory study as a function of alcohol, water content and temperature to develop an experimental investigation for a better understanding of the microstructure of a single phase microemulsion and its stability under reservoir condition during hydraulic fracturing to recover the residual trapped oil. Viscosified surfactants are used as an efficient proppant conducting medium in hydraulic fracturing applications. The physicochemical properties of microemulsions are very helpful for characterization of microemulsions to justify their abilities and screening of surfactants. In the study, two branched alcohols, 2-methyl butan-2-ol, 3-methyl butan-1-ol selected as the cosurfactant in the proposed microemulsion system and their effect in tailoring the viscosity of microemulsions were studied. Microemulsion regions elucidated from Winsor's pseudophase model of an oleate surfactant show a signatory distribution pattern of components between different domains with non-polar and asymmetric geometry of cosurfactant directs macromolecular alignments; their alignment contributes to a viscous microemulsions (gel) regime. The effect of surfactant and alkali, and the experimental temperature on the rheological properties of the lamellar mesophase were investigated. Phase transit regions and exact microemulsion and viscous microemulsion magnitudes were elucidated with the help of conductivity and viscosity studies of the ternary system as a function of the aqueous fraction and were in good agreement with Winsor's pseudophase model. Dynamic and steady shear rheological studies showed that the gel is viscoelastic in nature, sustain viscosity and elastic modulus values appropriate for proppant suspension under high shear conditions. The proppant suspension and thermal behavior of ideal gel composition was found to be suitable for Coal Bed Methane and soft rock, clay reservoir stimulation. [ABSTRACT FROM AUTHOR]

Maintaining the optimum viscosity of foam required to create the effective fracture permeability and placing the proppant inside the fracture are difficult because of its poor thermal stability. The objective of this study is to optimize the viscosity of foam by using the Response Surface Methodology (RSM) technique. The Box-Behnken design matrix was selected based on the feasibility, efficiency and simplicity of response surface methodology, which contains 17 number of experiments. Statistical analysis of the model was performed by Analysis of variance (ANOVA), which helps to confirm the robustness of the tested model. The diagnosis of the model was reported with internally studentized residual plots, which proves that the data is authentic with less error value, and the model is significant. The desirability function approach is utilized to analyze the optimized viscosity, followed with a confirmation test, which assists in validating the predicted optimal viscosity results. The input parameters, such as solid particles concentration and foam quality, were set in a range and temperature was set to be at maximizing condition, so that corresponding response, i.e., viscosity was optimized. The optimized viscosity of the foam fracturing fluids systems is in between 36.74 and 74.61 cP at 500 s−1 shear rate. The abovementioned methods and its analysis for the estimation of the optimal viscosity at a high shear rate are very significant and consequently acceptable for the design and development of foam fracturing fluid at the field conditions of unconventional reservoirs. This method is expected to apply for effective designing of foam for fracking of unconventional reservoirs without undergoing rigorous field trials for selecting the correct foam composition. • Optimized viscosity of stabilized foam fracturing fluid at operating shear rate using RSM. • RSM is an essential part of Design of Experiment (DOE). • Applied Analysis of Variance for the testing the significance of the model. • Used Desirability function for the optimization analysis in the RSM. • Model is accurate for predictions of optimal viscosity. [ABSTRACT FROM AUTHOR]

The rheological behavior of a polymer solution is very important for its application in enhanced oil recovery. An experimental study was conducted to examine the effects of salts, alkali, and surfactants on the rheological properties of partially hydrolyzed polyacrylamide (PHPAM) over a wide range of parameters. The experimental results show that addition of ionic species significantly reduces the polymer viscosity by reducing the hydrodynamic size of the polymer. The power-law model was used to describe the rheological properties of the solutions. The flow behavior index, n, of the samples was in the range from 0.232 to 0.275, while the consistency index, K, ranged from (1.45 to 5.76) Pa·sn. The variation of viscosity with temperature was also studied and found to satisfy the Arrhenius equation. [ABSTRACT FROM AUTHOR]