An Improved Model for the Oxidation Processes of Light Crude Oil

doi:10.1205/026387697523859

Chemical Engineering Research and Design

Volume 75, Issue 4, May 1997, Pages 392-400

https://doi.org/10.1205/026387697523859 Get rights and content

The oxidation kinetics of a light Australian crude oil were studied experimentally using an evolved gas analysis technique. Mixtures of sand, water and an 824 kg m^-3 crude oil were heated at a controlled rate with a constant flow of an oxidizing gas. The effluent gas was continually analysed for its oxygen, carbon monoxide and carbon dioxide contents. The oxidation behaviour was found to be substantially different to that previously observed for heavier crudes. An improved mathematical model is proposed that allows the oxidation kinetics of the oil to be modelled by considering three competing and overlapping classes of reactions. The model allows the kinetic parameters for each class of reaction to be estimated. The effects on the kinetic parameters of variables such as pressure, sand grain size and carbon dioxide content of the injection gas were also investigated experimentally.

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Cited by (24)

The role of reservoir fluids and reservoir rock mineralogy on in-situ combustion kinetics
2023, Geoenergy Science and Engineering
In-situ combustion (ISC) is a complex process with great potential. This study aims to simplify some of the complications associated with the reaction kinetics of ISC and investigate the impact of reservoir rock composition and crude oil fractions on the reaction kinetics of ISC.
Sixty-six reaction kinetics experiments were conducted using Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) on two heavy crude oil samples and two types of porous media (clays and carbonates). In these experiments, a 5 °C/min heating rate was used to simulate the low-temperature-oxidation (LTO) region, and a 20 °C/min heating rate was used for the high-temperature-oxidation (HTO) region. The role of crude oil composition on the reaction kinetics of combustion was also investigated through saturates, aromatics, resins, and asphaltenes (SARA) fractionation. The two crude oils were first separated into their SARA fractions, and then the reaction kinetics of individual fractions and their two and three component pseudo-blends were studied.
‘To understand the contribution of aquathermolysis reactions, the crude oils and their SARA fractions were mixed with water, and the reaction kinetics tests were repeated in the presence of water. The chemical reactions occurring in the presence and absence of water in crude oil and their fractions were discussed using control experiments conducted on known simple hydrocarbons: n-decane (C₁₀H₂₂), n-decanal (C₁₀H₂₀O), n-decanol (C₁₀H₂₂O), and decanone (C₁₀H₂₀O). Additionally, the reactivity of the mineralogy of the porous media was examined, and both clay and carbonates were tested. All experiments were analytically modeled to obtain reaction kinetics parameters in terms of activation energy (E_a) and heat generation (ΔH).
The results show that while emulsified water decreases the effectiveness of the combustion process, the presence of initial water increases it. This is due to the increase in heat generation and decrease in activation energy, which is mainly caused by the interaction between water and aromatics fractions (aquathermolysis reaction) at elevated temperatures. The amount of clay in the reservoir is critical for the success of the ISC process. If the reservoir has a higher clay content than a certain threshold, the combustion performance will be compromised. Resins fractions have a higher tendency to interact with carbonates during ISC in the HTO region.
Overall, this study provides simplified analytical approaches based on experimental results to better understand the ISC chemical reaction kinetics for different types of crude oil and reservoir rocks.
Thermal enhanced oil recovery in deep heavy oil carbonates: Experimental and numerical study on a hot water injection performance
2020, Journal of Petroleum Science and Engineering
Citation Excerpt :
The flow of the fire moves, whereas the front moves a mixture of hot combustion gasses, steam, and hot water. It leads to a reduction of oil viscosity and the displacement of oil toward production wells (Bousaid and Ramey, 1968; Gutiérrez et al., 2012; Kisler and Shallcross, 1997; Moore et al., 1996; Moore et al., 2007; Xu et al., 2001; Yang et al., 2017; Yang and Gates, 2009; Yang and Chen, 2016). In hot water flooding, to decrease the viscosity of heavy oil, a significant amount of hot water is injected into the wells to decrease the viscosity and subsequently displace the oil more easily towards oil production wells (Alajmi et al., 2009; Pwaga et al., 2010).
Currently, thermal methods of enhanced oil recovery are based on the use of heat transfer mediums (steam, hot water) and in-situ combustion, which are the most efficient methods in the development of heavy oil reservoirs. In this study, experimental and numerical modeling was carried out to estimate the efficiency of hot water injection to engage in the active development of high-viscosity oil reserves in a deep carbonate reservoir. There is a limited amount of published experimental studies on carbonates, in comparison with sandstones, shale, or oil sands. Oil-bearing formations at depths of 1100–1500 m require technology that can achieve sufficiently high fluid temperature (250–300 °C) in the bottom-hole zone to be successful. The performance of the implemented technique on a field greatly depends on the quality of the experimental data and numerical simulation. Particularly, the hydrodynamic model, reaction kinetics, and operational parameters are crucial parameters for future upscaling.
The hot water injection experiment was conducted using a medium pressure combustion tube assembly on the reservoir rock model made of consolidated carbonate samples. Moreover, a new numerical model was constructed to simulate the experiment with a reproduction of the fluid models, properties of the oil and rock samples, and full geometry of the core holders where chemical interactions occur. What makes this model authentic is the calibration of reaction kinetics called “aquathermolysis” to hot water injection process, which replicate the most prevalent thermal process during the interaction of hot water and hydrocarbons.
A close correlation between experimental and numerical results was obtained in terms of cumulative water and oil recovery and temperature profiles. The developed numerical model reflects the dynamics of oil displacement at different rates of water injection. According to experimental and numerical simulations, thermal effects reduce viscosity with a proportionate increase in oil recovery. The achieved recovery factor for the experiment was 63%. Lastly, a good match of cumulative gases (CH₄, H₂, H₂S, CO₂, and HMWG) was obtained for the hot water injection experiment. Adapted fluid model, relative permeability, kinetic model, and operational parameters are necessary for the upscaling to the field. The improved efficiency of oil displacement at this site is confirmed by numerical simulation.
Impact of asphaltenes and clay interaction on in-situ combustion performance
2020, Fuel
The increased surface area of reservoir rock due to the presence of clays and the catalytic impact of clays are known to enhance the in-situ combustion (ISC) performance. But the basics behind these mechanisms are still unknown. Six one-dimensional (1-D) combustion tube experiments were conducted on three different crude oil samples. Each crude oil was evaluated with two combustion tube runs; sand-oil and sand-clay-oil mixtures to study the effect of clay on combustion performance. Then, Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) was run at isothermal conditions by ramping up the temperature using the combustion tube temperature. The activation energy and the heat of combustion were calculated empirically. The quality of the produced oil samples was determined through viscosity measurement and saturates, aromatics, resins, and asphaltenes (SARA) fractionation. To better understand the fuel formation mechanism, the compositional variations in SARA fractions have been analyzed through Fourier Transform Infrared (FTIR). Further, asphaltenes surfaces were visualized by Scanning Electron Microscope (SEM) and the Energy Dispersive Spectroscopy (EDS). The combustion tube experimental result shows that saturates fractions have been decreased in displaced oil since saturates are consumed as an ignitor during ISC. The aromatics fraction has been significantly increased in produced oil, which helps to increase the mobility of displaced oil through viscosity reduction. Moreover, the amount of asphaltenes in produced oil decreased due to fuel formation reactions. In the presence of clays, the cribriform structures were formed on asphaltenes surface and aid the combustion process by increasing the surface area of asphaltenes.
Rice husk combustion evolved gas analysis experiments and modelling
2015, Biomass and Bioenergy
Citation Excerpt :
The kinetic parameters such as reaction order, activation energy and pre-Arrhenius constant are then calculated for each of the reaction groups or reaction regimes [21–23]. In this work the oxidation model proposed earlier [20,23] will be modified and applied to study the combustion characteristics of rice husk. The predicted oxygen consumption model shall be validated with the actual EGA experimental data of oxygen consumption.
Rice husk is a major agricultural waste which could be a major source of fuel for boilers and furnaces if its calorific value could be realized efficiently. The oxidation kinetics of rice husks combustion were investigated using an evolved gas analysis technique. Rice husk samples were heated from 100 °C to 500 °C at a constant rate inside a small pressurised reactor. An oxygen-containing gas was passed through the reactor at a controlled flow rate and the evolved gas was continually analysed for its oxygen, carbon monoxide and carbon dioxide contents after moisture had been removed. A model for the oxidation of the rice husks samples is proposed that considers that the many simultaneous and competing oxidation reactions may be adequately represented by grouping them into three overlapping and competing reaction regimes in which CO₂, CO and H₂O are the only reaction products. The activation energies, and peak oxygen consumption temperatures were all found to be linear functions of the oxygen partial pressure in the reactor. Increasing the oxygen partial pressure decreased the temperatures at which peak oxygen consumption occurred. The total system pressure had no effect on the combustion behaviour other than through the oxygen partial pressure. At a heating rate of 80 K h⁻¹ and a system pressure of 500 kPa values for E/R for the low temperature, medium temperature and high temperature oxidation reactions are 14.7, 19.2 and 17.4 respectively.
The spontaneous ignition potential of a super-light crude oil
2001, Fuel
The spontaneous ignition potential of a super-light crude oil was investigated employing adiabatic, packed-bed reactors. Various process parameters such as initial reactor temperature, oxidant gas flux, oxygen concentration in the oxidant gas, initial oil and water saturations and reactor pressure were varied to determine the set of conditions that would cause the sand–oil mixture to ignite spontaneously. All attempts to ignite the oil failed even when very favorable ignition conditions were tested including 174°C initial temperature, 7340 kPa reactor pressure, 40% oxygen in the oxidant gas and 26 h of oxidation time. Failure of the super-light crude to self-ignite was thought to be due to its low content of unsaturates, mainly aromatics and asphaltenes.
Distinguishing between overlapping low temperature and high temperature oxidation data obtained from a pressurized flow reactor system using consolidated core material
2000, Fuel
A flow reactor operated at high pressure has been used to study the oxidation kinetics of selected North Sea light crude oils. Real consolidated reservoir rocks impregnated with oil were tested. A simple approach based on oxidation reaction kinetics was adopted throughout the course of this study to decouple the low temperature (LTO) and high temperature (HTO) reaction regimes and to determine the boundary between them. Reaction kinetic results for low temperature oxidation region are presented in this paper.

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Chemical Engineering Research and Design

References (17)

Fireflood ignition devices and methods

In Situ

Screening of oils for in situ combustion at reservoir conditions by accelerating rate calorimetry

SPE Reservoir Engineering

Reaction kinetics of in situ combustion: Part 2 – modelling

Soc of Pet Eng J

Modifying in situ combustion performance by the use of water-soluble additives

SPE Reservoir Eng

Cited by (24)

The role of reservoir fluids and reservoir rock mineralogy on in-situ combustion kinetics

Thermal enhanced oil recovery in deep heavy oil carbonates: Experimental and numerical study on a hot water injection performance

Impact of asphaltenes and clay interaction on in-situ combustion performance

Rice husk combustion evolved gas analysis experiments and modelling

The spontaneous ignition potential of a super-light crude oil

Distinguishing between overlapping low temperature and high temperature oxidation data obtained from a pressurized flow reactor system using consolidated core material