A Novel Oil-Tolerant and Temperature-Resistant Self-Generating Foam for Drag Reduction in Heavy Oil Pipelines

Summary This study presents, for the first time, a synergistically enhanced AAXT (1.5 g/L AOS + 1.0 g/L AES + 3.0 g/L XG + 2.0 g/L TD) microfoam system capable of self-foaming through the addition of gas-generating reagents, enabling drag reduction in heavy oil pipeline transportation without the need for external gas sources or injection equipment. Such a foaming system demonstrates promising application prospects in offshore heavy oil transportation. The microstructure, rheological properties, drag reduction performance, and drainage kinetics of the resulting self-generating foams are characterized. The foaming process exhibits a progressive increase in foam quality through three distinct stages as reaction time increases. In the first stage, foam quality increases slowly; in the third stage, bubble size increases dramatically, while quantity ceases to increase. The foam quality, reached at the end of the second stage, approaches the jamming gas fraction of 64%, exhibiting both favorable foamability and stability. Based on the experimentally observed drainage characteristics, an improved logarithmic model is proposed to predict drainage kinetics. The foam rheological behavior was found to follow the Carreau-Yasuda fluid model, where the apparent viscosity decreases below 80 mPa·s at shear rates above 100 s−1. Flow experiments with heavy oil and the self-generating foams show that the maximum drag reduction rate reaches 77%, and the required proportion of foam solution is relatively low, which holds promise for improving the efficiency of heavy oil transportation.