Fundamental study of asphaltene cracking and desorption from rock surface due to microwave radiation: A molecular insight into catalytic effect of minerals and asphaltene chemistry

Abstract

This research aims to investigate the fundamental of asphaltene cracking and desorption during microwave stimulation of an oil well. In this regard, the asphaltene chemistry and the rock mineral type were studied using analytical methods. Two asphaltene samples with different chemistries and origins were adsorbed on the four different rock powders. The asphaltene molecules were characterized using Fourier transform infrared spectroscopy analysis (FTIR), Nuclear magnetic resonance spectroscopy (NMR), Energy-dispersive X-ray (EDS), and elemental analysis. Besides, four different rock powders of carbonate, Bentonite, kaolinite, and sand with identical mesh sizes were used to mimic the various reservoir mineralogy. The rock powders were characterized by FTIR and X-Ray Powder Diffraction (XRD). The asphaltene molecules were adsorbed on the rock powders, and rock sections were provided from the mixture. The molecular changes of asphaltenes on the rock surfaces and desorbed/cracked compounds from the rock surface were respectively addressed by attenuated total reflection spectroscopy (ATR) and Gas chromatography-mass spectrometry (GC-MS). Regarding the ATR technique, the asphaltenes with larger aromatic cores, longer aliphatic chains, and more sulfur compounds had tenser desorption from carbonate and bentonite rock surfaces due to the effect of microwaves. In contrast, the asphaltenes with smaller aromatic cores, and shorter aliphatic chains had tenser desorption from kaolinite and sand rock surfaces. According to the GC-MS analysis, the asphaltene cracking led to producing light aromatic and aliphatic (such as toluene), intermediate aliphatic compounds (such as Hexadecane), and Bis (2-Ethylhexyl) phthalate from the surface of minerals. Based on the ATR spectrums, the microwave radiation of asphaltene-bearing rocks led to the reduction of polar compounds in asphaltenes. This observation achievement was consistent with the contact angle measurements, which showed more hydrophobicity for the microwave-treated rocks.