Oxidation Behavior of Light Crude Oil and Its SARA Fractions Characterized by TG and DSC Techniques: Differences and Connections

Abstract

This research is intended to reveal the difference and connection of oxidation behavior between crude oil and its SARA fractions. Thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques were used to characterize oxidation behavior. The results showed that the oxidation behavior of individual SARA components exhibited an obvious difference. Saturates showed a weak high-temperature oxidation (HTO) region. Asphaltenes generated more heat in HTO than in the low-temperature oxidation (LTO) region. Aromatics showed intense exothermic activity in both LTO and HTO regions. Heat release and mass loss showed a good correspondence in the HTO region for all SARA fractions, which means heat release and mass loss were caused by the same reaction mechanism that is believed to be the coke combustion as it is the only significant reaction in the HTO region. However, the good correspondence did not exist in the LTO interval where the reactions are more complicated and a multiple-step mechanism should be considered. In addition, it is not quite reasonable to determine the reactivity of SARA fractions only by TG data as little mass loss does not mean reactants are inactive. Kinetic parameters of LTO and HTO reactions were determined by Friedman and Ozawa–Flynn–Wall isoconversional methods. In general, for the crude oil and each fraction, the activation energies of HTO were higher than that of LTO. The additivity of DSC data could be applied quite well in the LTO region. However, the predicted curve seriously deviated from the actual situation after 350 °C, which implies the exothermic reaction process of individual components was influenced by the presence of other components. Nevertheless, the total heat release of the measured and predicted values was similar, which makes it possible to predict the heat effect of crude oil from individual SARA components.

The Oil-Bearing Strata of Permian Deposits of the Ashal’cha Oil Field Depending on the Content, Composition, and Thermal Effects of Organic Matter Oxidation in the Rocks

“…For the successful implementation of thermal and steam-thermal effects on the formation, it is necessary to know and determine the thermal effects caused by the material composition of the rocks and to be able to determine and select the optimal conditions for the implementation of technological processes of influence on the formation, namely, temperature and pressure. To solve these problems, thermal methods are used, in particular, thermogravimetry and differential scanning calorimetry (TG/DSC) [23,34,[43][44][45][46][47][48][49][50][51].…”

“…Using the example of oil and bitumen samples that were examined above from the Permian deposits of the Ashal'cha oil field, differing in the mineral composition of rocks, OM content, yields, and group composition of extracts (Table 4), phase transitions were determined using highpressure differential scanning calorimetry (DSC) [43][44][45] and the magnitudes of thermal effects resulting from oxidation reactions of various components of OM of oilcontaining rocks. The study was carried out in air in the temperature range from 30 to 600°С at a pressure in the reaction system of 5 MPa [47]. Pressure of 5 MPa was used 9 Geofluids due to the following factors: firstly, to eliminate the evaporation of crude oil in an unsealed crucible; secondly, to ensure complete oxidation of oil without unburned coke; and thirdly, to simulate the state of the reservoir.…”

“…On DSC curves of the studied rock samples (Figures 9 and 10), three main areas of manifestation of thermal effects can be identified. According to the literature [43,45,47], the first region from 20 to 200°C corresponds to the evaporation of light hydrocarbons and the removal of constitutional water present in clay minerals. The second and third areas in the temperature range of 200-600°C reflect the heat that is released as a result of oxidation reactions of various petroleum components contained in the rock.…”

Quantification of low‐temperature oxidation of light oil and its SAR fractions with TG‐DSC and TG‐FTIR analysis

“…The weight loss of each fraction is summed according to its content in crude oil to obtain the cumulated weight loss, and the same method is used to obtain the cumulated heat flow. The same calculation method is applied in reference . The relationship between the cumulated and measured weight loss and heat flow is illustrated in Figure .…”

“…However, both the main components involved in the LTO reaction and the differences associated with the oxidation characteristics among different components have not been well understood. To quantify the oxidation characteristics of crude oils, thermal analysis such as thermogravimetric analysis and differential scanning calorimetry (TG‐DSC), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis coupled with Fourier transform infrared spectrometer (TG‐FTIR) have been applied to investigate the oxidation properties of crude oil and its SARA fractions, as summarized in Table . Also, this table tabulates the reaction modes and characteristics during the combustion of light and heavy oils, the kinetics and thermochemical parameters of each reaction mode, the differences of oxidation characteristics between light, medium, and heavy oils, the oxidation relationship of crude oil and SARA fractions during the combustion process, and the combustion process of asphalt binder and its SARA fractions, respectively.…”