An Integrated Review on Asphaltene: Definition, Chemical Composition, Properties, and Methods for Determining Onset Precipitation

Asphaltene is a solid oil component with a wide range of molecular compositions and structures, making it one of oil’s most complicated components. The deposition and precipitation of asphaltene in several places along the oil production line, such as the wellbore, reservoir, flow lines, tubing, and the separation unit at the surface, of the most prevalent flow assurance challenges. Changes in pressure, composition, and temperature cause asphaltene to precipitate out of the oil continuum. Variations in operation condition are caused by various recovery processes (gas injection, natural depletion, and chemical injection) in addition to the creation and blending of various oils during transportation. This paper presents a complete review of asphaltene precipitation (AP) and deposition (AD), which in turn helps in understanding the governing mechanisms and thermodynamic behaviors in this field. This study consists of several stages: analyzing the current state of asphaltene research (asphaltene characteristics, chemical nature, molecular structure, asphaltene crude oil phase behavior, solubility factors, and other factors); describing the phases of asphaltene (from its stability through its deposition in the reservoir pores, facilities, wellbore path in addition to the reasons for their occurrence); clarifying the rheology and asphaltene flow behavior in the reservoir; and finally examining the advantages and disadvantages of most widely used strategies for determining onset AP. In addition, some measured Iraqi asphaltene data are demonstrated and analyzed. This work will contribute to better knowledge of asphaltene and will serve as a reference for future studies on how to properly investigate and simulate asphaltene.