Rheological assessment of crude oils and emulsions under controlled cooling rate: A versatile methodology for flow assurance

Flow assurance in the oil industry aims to prevent flow interruptions in production caused by phenomena such as wax crystallization, emulsion formation, and the development of complex microstructures that alter viscosity and yield stress. The present study implements a standardized methodology to evaluate five crude oils and their corresponding 50/50 (v/v) emulsions with synthetic brine, under controlled cooling rates of 0.8 and 0.08 °C/min. The protocol combines stress ramp and creep tests to obtain the static yield stress, when applicable, and the flow curves to obtain the viscosity function for the other cases. The results revealed Newtonian, shear-thinning, and viscoplastic behaviors, demonstrating the diversity and complexity of the samples analyzed. Differences between crude oils and emulsions indicate that the coexistence of wax crystallization and dispersed droplets can influence the macroscopic rheological response. The discussion explores how these interactions may contribute to the observed behaviors. The proposed approach enables a robust evaluation of flow performance at low temperatures and provides essential data for designing efficient pipeline, pumping, and separation systems, with broad applicability to other complex fluids encountered in flow assurance scenarios.