Study on Viscosity Reduction Mechanism for Offshore Heavy Oil Under the Synergistic Action of Nanocatalyst and Ultrasound

Abstract

Abstract Heavy oil resources are abundant all over the world, but its content of resin and asphaltene is high. Heavy oil has high viscosity and poor fluidity at room temperature, which brings great difficulties to heavy oil recovery and pipeline transportation. At present, the commonly used technologies of heavy oil pipeline transportation are heating transportation, emulsification viscosity reduction transportation and heavy oil mixed with dilute transportation, which have the shortcomings of high energy consumption and poor stability. In this paper, the structure and properties of a blank oil sample from offshore heavy oil and the oil samples dealt with the optimal experimental parameters were characterized by using the methods of ultrasonic alone, nano catalyst alone and synergistic action of nano catalyst and ultrasonic respectively. By means of four-component separation, elemental analysis and full two-dimensional gas chromatography and infrared spectroscopy analysis of light components, the changes of the contents of resins, asphaltenes, trace elements and light components as well as the types of functional groups in oil samples were measured. The results showed that the content of macromolecule such as resin and asphaltene in heavy oil was almost unchanged under the action of ultrasonic alone and the synergistic action of nano catalyst and ultrasonic. The content of saturated hydrocarbon in small molecule decreased to a certain extent, while the content of aromatic component decreased by 5.27% and 6.22% respectively. The peak values of infrared spectra changed slightly under three treatment modes. Among them, the peak values on the left side of the oil sample under the synergistic action of nano catalyst and ultrasonic decreased by 0.24 cm−1, and the peak values on the middle peak changed the most and increased by 0.95 cm−1 under the action of ultrasonic alone. Elemental analysis showed that the sulfur content of oil samples disappeared under the synergistic action of nano catalyst and ultrasonic and the action of ultrasonic alone, and the H/C increased most under the synergistic action of nano catalyst and ultrasonic, from 0.1310 to 0.1457. Two-dimensional gas chromatography showed that aromatic hydrocarbon content decreased, while alkanes (including C7-C40) and holosterols content increased under the synergistic action of nano catalyst and ultrasonic. It could be concluded that the viscosity reduction effect of heavy oil was the best under the synergistic action of nano catalyst and ultrasonic, and the viscosity reduction rate could reach 49.64%. The above experimental results revealed to some extent the mechanism of viscosity reduction of heavy oil under the synergistic action of nano catalyst and ultrasonic, and provided reliable data reference and theoretical basis for submarine heavy oil pipeline transportation technology.