Classification Method of Heavy Oil Based on Chemical Composition and Bulk Properties

Abstract

Heavy oil resources in the world are extremely abundant, and viscosity is currently the main reference index for heavy oil classification. However, the diversification of practical issues in heavy oil exploitation, and the refinement of processing and utilization urgently require the support of heavy oil classification with more reference indexes. In this study, the macroscopic properties of typical heavy oils in China were analyzed, and the semi-quantitative analysis of the molecular composition of different heavy oils was completed based on high-resolution mass spectrometry. The results show that heavy oils with similar viscosities can exhibit huge differences in macroscopic properties and chemical composition. According to the evaluation of the chemical composition and macroscopic properties of typical Chinese heavy oils, 12 types of compounds belonging to saturates, aromatics, resins, and asphaltenes (SARA) were identified, establishing a connection between the macroscopic fractions and molecular compositions of heavy oils. By summarizing the comparative results, a new classification criterion for heavy oils was established, focusing on the main parameters of H/C ratio and total acid number (TAN), with sulfur content as a supplementary indicator. H/C is the embodiment of the degree of molecular condensation in the macroscopic properties, reflecting the structural characteristics of the main molecules of the heavy oil. Chinese heavy oil is generally characterized by high TAN, which corresponds to the composition of petroleum acids, and it is also an important reference index for the exploitation and processing of heavy oils. Most Chinese heavy oils have a very low sulfur content, but the presence of sulfur compounds in high-sulfur heavy oils can lead to significant differences in the distribution of compound types among the SARA. This new classification method for heavy oil combines the characteristics of chemical composition of heavy oils, which is expected to provide valuable support for the extraction and processing of heavy oil.