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Carbonate reservoirs in Western China are characterized by deep burial, high temperature, and strong heterogeneity. In this paper, based on the physical properties of high-temperature carbonate reservoirs, the authors have developed an autogenic acidic fracturing fluid suitable for high-temperature carbonate reservoirs. The performance of the new acidic fluid has been experimentally evaluated. The results show that the fluid demonstrates satisfactory viscosity-temperature performance, and after continuous shear tests at 140°C for 2 h the viscosity of the fluid remains about 100 mPa∙s. At room temperature (RT), the pH value of the fluid is neutral, and the titratable acid concentration could reach 15.49% at 90°C. When subjected to high temperatures, the fluid is characterized by a high acid concentration, low acid generation rate, and moderate corrosion inhibition rate. The static rock corrosion rates of the fluid at room temperature and 140°C are 0.00009125 and 0.009575 g/min, respectively. The corrosion rate is slow, and the effective action distance of the fluid can be five times higher than that of a thickened acid and three times higher than that of a cross-linked acid. The experimental results verify the acid's ability to transform high-temperature carbonate reservoirs and good applicability in high-temperature carbonate reservoirs. The proposed autogenic acidic fracturing fluid system provides essential technical support for the efficient development of high-temperature carbonate reservoirs. [ABSTRACT FROM AUTHOR]

Rectangular cavity filled with a non-Newtonian shear-thinning nanofluid was investigated considering varied fin geometry under a vertical magnetic field. Irreversibility and entropy generation mechanisms were investigated by finite element method. The effect of geometry parameter (a), Hartmann number (Ha), nanoparticles volume fraction (φ) and nanoparticles type (Fe3O4, CuO and Al2O3) on the Nusselt numbers, entropy generations and Bejan numbers were investigated by the response surface methodology (RSM). Increasing a leads to an increase in both local and average Nusselt numbers and increment in different terms of entropy generation, while it reduces the Bejan number. Fe3O4 nanoparticle shows the highest Nusselt number compared to other nanoparticles. RSM analysis revealed that a = 0.29 and φ = 0.04 are the optimized values for the goal of maximum Nusselt number and minimum Bejan number. [ABSTRACT FROM AUTHOR]