Exploration of the Difference in Molecular Structure of n-C₇ and CO₂ Induced Asphaltenes

Abstract

Determination of the molecular structure of asphaltenes, especially in their native environment, is a formidable challenge in petroleum chemistry. Here we demonstrate that a combination of different spectroscopy and imaging based experimental techniques can be utilized to determine structures of asphaltenes, which have precipitated out of a crude oil, in an environment similar to real field conditions. A high pressure–high temperature quartz crystal microbalance (HPHT-QCM) setup can be used to detect asphaltene onset at oil production conditions. HPHT-QCM can also simulate CO2 injection conditions mimicking gas injection methods used to enhance oil recovery from depleted oil reservoirs. In this paper, we present the first compositional and structural research study on the QCM asphaltene deposits under gas injection conditions and compare it to n-C7 asphaltenes from the same crude oil precipitated in the laboratory. This study combines the use of Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray (EDX) analysis. Furthermore, deposits collected from chemically treated fluids were also studied. The HPHT-QCM asphaltene deposits from parent crude oil are richer in oxygen species, such as the O x and R–OH polar groups, relative to the n-C7 asphaltenes. The results of this study provide high-pressure information that leads to better understanding of asphaltene precipitation and deposition phenomena and could be taken into account when designing prevention strategies to avoid asphaltene problems throughout the oil production process.

Study of Asphaltene Deposition in the Presence of a Hydrophobic Deep Eutectic Solvent Using XDLVO Theory

“…Thus, hydrogen bonding between asphaltene and HDES could be proposed as a dominant mechanism responsible for stabilizing asphaltene particles in the oleic medium. It must be noted that the molecular structure of asphaltene depends on the precipitation agents, e.g., gas or light n -alkanes . In this regard, various molecular structures could potentially affect the inhibition process using the newly introduced inhibitor.…”

“…It must be noted that the molecular structure of asphaltene depends on the precipitation agents, e.g., gas or light n-alkanes. 43 In this regard, various molecular structures could potentially affect the inhibition process using the newly introduced inhibitor. Therefore, the results of this study would only be valid for the light n-alkane induced asphaltenes.…”

Experimental investigation of dynamic asphaltene adsorption on calcite packs: The impact of single and mixed‐salt brine films

“…On the other hand, the instability of a thin water film leads to its rupture which in turn results in an increase in asphaltene adsorption . Asphaltene at the oil‐brine interface is able to penetrate into an unstable water film and adsorb on the solid surface . The stability of water film depends on its pH and ionic strength .…”

Effect of Polyethylene-Vinyl Acetate Pour Point Depressants on the Flow Behavior of Degassed Changqing Waxy Crude Oil before/after scCO2 Extraction

“…The existence of a larger amount of solvation liquids in the precipitates before scCO 2 extraction results in the large blocks in Figure a,c. However, the scCO 2 extraction can stepwise extract nonpolar and light polar components from an asphaltene micelle, which is disadvantage of protecting asphaltenes from precipitation. − Thus, the morphology of the precipitates after scCO 2 extraction is flocculated asphaltene particles (around 1 μm) because of the less solvation liquids.…”