Crude Oil Asphaltenes Studied by Terahertz Spectroscopy

Abstract

Terahertz time-domain spectroscopy (THz-TDS) was used to study the asphaltenes in different crude oils. THz-TDS has a feature of measuring the amplitude and time delay and consequently the refractive index and absorption coefficient spectra simultaneously. Our approach was based on measuring the THz signal from neat crude oil samples and comparing it with the THz signal after removing the asphaltene from the oil samples (maltene). The results show that the differences in the time delay and the peak amplitude between the neat oil and the maltene have a linear relation with the asphaltene content. The refractive index spectra of the asphaltene show variation in the low THz frequencies and comparable spectra in the higher frequencies. The absorption of the asphaltene was mild, and no distinctive absorption feature was observed except for some narrow absorption peaks that we attributed to water molecules adsorbed on the asphaltene.

Effect of Polar Hydrocarbon Contents on Oil–Water Interfacial Tension and Implications for Recent Observations in Smart Water Flooding Oil Recovery Schemes

“…For oil−brine system, eq 5 can be written as (6) In eq 6, the subscripts o and w refer to oil and water, respectively.…”

“…The composition of a crude oil is classified subject to its SARA content (saturates, aromatics, resins, and asphaltenes) where waxes make up around 14%, with branched and cyclical (naphthenic) compounds accounting for 16 and 30%, respectively, while aromatics make up around 30% and asphaltenes and resins 10%. , Consequently, the polar fractions of crude oils have been determined using ambient mass spectrometry and gas chromatography mass spectrometry . The polar components, such as asphaltenes, have also been studied based on Terahertz spectroscopy, which has a feature for measuring the amplitude and time delay and consequently the refractive index and absorption coefficient spectra simultaneously . In light of their nonsolubility in lower-molecular-weight paraffins, the asphaltene content of crude oils has been fractionated using n -hexane. , …”

Industrial Applications of Terahertz Sensing: State of Play

“…A combination of THz spectral data and multivariate statistical methods was used to identify crude oils from different oil fields [138]. Other studies looked at oil content in oil shale [139], at the asphaltene content in crude oil [140], at wax crystals in crude oil [141], and at spectral signatures of coal tar [142].…”

Novel Approach for Improving the Flow of Waxy Crude Oil Using Thermochemical Fluids: Experimental and Simulation Study

“…4 Thus, there are several complexities at different phases of operations in the oil and gas industries. 5,6 Compared to other solids, wax precipitation is a major problem in oil production and transportation facilities. 7−9 The high-molecular-weight paraffin wax (C 20+ ) at reservoir conditions is dissolved in the petroleum fluid.…”

“…Generally, due to changes in thermodynamic intensive properties, viz., pressure, temperature, and composition of hydrocarbon, precipitation of organic flow assurance solids including gas hydrates, asphaltene, and paraffin wax often occurs . Thus, there are several complexities at different phases of operations in the oil and gas industries. , Compared to other solids, wax precipitation is a major problem in oil production and transportation facilities. − The high-molecular-weight paraffin wax (C 20+ ) at reservoir conditions is dissolved in the petroleum fluid. However, as the crude oil flows toward the processing facilities and gradually becomes colder, the solubility of the paraffin molecules reduces and, subsequently, wax deposition and accumulation may occur inside the good completion facilities, surface facilities, and transportation pipelines.…”