Oxidation and Ignition Behaviour of Saturated Hydrocarbon Samples With Crude Oils Using TG/DTG and DTA Thermal Analysis Techniques

Abstract

This research is aimed at providing a better understanding of the oxidation behaviour of fractions of crude oil, and to then develop an approach to improve ignition for air injection processes. In this research, Thermogravimetric and Differential Thermal Analysis (TG/DTA) techniques were used to investigate oxidation behaviour using thermal fingerprinting effects on pure paraffin samples and mixtures of pure components with crude oil. The results demonstrated that each paraffin sample shows different oxidation behaviours at low temperatures and high temperatures. The fractions lighter than C16 distill before they reach a temperature where oxidation reactions are significant. Only low temperature exothermic activities are apparent for the fractions between C16 and C26. The heavier fractions show both low and high temperature exothermic activities. The lower molecular weight samples show lower onset temperatures for oxidation reactions. With increasing molecular weight, the exothermic peak temperatures both in the low and high temperature regions shift to higher temperatures and increased energy release. When low activity Oil B and the more reactive Oil C were mixed with a small amount of paraffin sample heavier than C26, both crude oils showed intensified low temperature oxidation behaviour, with a greater magnitude of heat evolution. The addition of heavier paraffins offers the potential to accelerate reactions and improve ignition. Introduction High Pressure Air Injection (HPAI) has been proven as a potential and viable process for improving oil recovery from several light oil reservoirs. When air is injected into an oil reservoir, the oxygen contained in the air can potentially react with the oil in place by various oxidation reaction schemes. Success of such a process depends mainly on the crude oil properties and rock properties, as well as operating conditions. The oxidation behaviour and the conditions typically favouring auto-ignition of crude oils are of the utmost importance for light oil air injection. However, because of the low initial temperature of many of the formations, and the poor reactivity of some crude oils, the magnitude of timedelay is often so great that spontaneous ignition is not economically attractive. Chemical ignition is one of the options to improve ignition(1, 2). Unfortunately, little research has been documented. The potential for using thermal analysis techniques to investigate oxidation behaviour of crude oils during combustion has been realized. Thermal analysis techniques include Thermogravimetric (TG) and Differential Thermal Analysis techniques (DTA) or Differential Scanning Calorimetry (DSC). In TG, a small amount of a sample of crude oil, with or without sand, is heated in the presence of flowing air and the change in weight of the sample is recorded as a function of temperature. In DTA or DSC, the difference in temperature or energy input/output during hemical or physical transitions based on the differences between the sample and a reference material is recorded as a function oftemperature or time.

Research on oxidation kinetics of tight oil from Wolfcamp field

“…Figure 3a shows the TG/DTG curves of oil in dynamic air purge under different heating rates condition, and Figure 3b on the other hand, illustrates the DSC curves of oil in dynamic air purge under different heating rates condition, In Figure 3a, it is observed that the TG pattern of heating rate at 15°C/min is different with heating rates are 5 and 10°C/min. For 5 and 10°C/min, as the heating rates increase, the curve slightly shifts to a higher temperature region and this phenomenon is in consistence with Downloaded by [University of Sussex Library] at 08:00 28 June 2016 Thomas (2001), Sonibare et al (2003), and Li et al (2004). Also, in Figure 3b it is observed that the exothermic peaks shift from a lower temperature region to a higher temperature region along with the incLensement of heating rates.…”

“…The success of an air injection process (AIP) process depends mainly on the crude oil and rock properties as well as the operational conditions (Li et al, 2004). Theoretically, the combustion of oil can be initiated whenever oxygen comes in contact with fuel.…”

Recovery of light oil by air injection at medium temperature: Experiments

“…The authors conclude that high oxygen injection rates are required to stimulate the scission reactions. Germain et al [20] describe combustion tube tests with light oil in heterogenous low permeability (1 − 100 mD) reservoirs using pressures of 40 − 45 bars and leading to combustion temperatures between 260 • C and 370 • C. Low pressure thermal gravity and differential scanning calorimetry test results [36] show that distillation is a dominant process for the recovery of light and medium oils at elevated temperatures. This may indicate that pressure effects need to be taken into account.…”

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

“…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.…”