Thermite Mixture Research Articles

Numerical investigation of an innovative through-tubing solution to thermal plug and abandonment of oil wells with thermite reactions

Plug and Abandonment (P&A) procedures are mandatory in the oil and gas industry. Conventional well-plugging methods typically involve the laborious and expensive process of cementing, requiring the removal of production tubing. In response to this challenge, a novel approach, known as Thermal Plug and Abandonment (TP&A), has been explored. TP&A proposes the introduction of an exothermic chemical reaction through the production tubing, generating substantial heat to melt the tubing intentionally. The passage formed by the melting process facilitates the traditional insertion of cement, eliminating the need for tubing removal. In this study, the TP&A process is investigated through numerical computations. The oil well structure is approximated as a two-dimensional axisymmetric domain with multiple layers representing different wellbore materials. A numerical code, incorporating chemical kinetics, phase change, and conjugate heat transfer models, was developed in the OpenFOAM® software. The thermite reaction is modeled using a zero-order kinetic model, and the phase change model employs the well-established enthalpy-porosity method to track material melting and solidification. The study primarily focuses on evaluating heat diffusion through the oil well structure during the TP&A process, with a central emphasis on investigating the melting of the production tubing. It was observed that compacting the mixture and diluting it with alumina up to a certain threshold enhanced the tubing’s melting. Reducing the initial mixture porosity from 0.55 to 0.4 has increased the tubing’s melting volume, constrained to the thermite height, from 60 to approximately 91%. Moreover, this study examined how diluting the thermite mixture with inert alumina affectsthe heat transfer and, consequently, the tubing’s melting. The findings indicated that a 20% dilution can enhance the tubing’s melting volume by up to 87%.

Tailoring the Silicon Cementation Applied to P265GH Grade Steel

Increasing the serviceability of industrial components intended for the petrochemical industry is possible through their superficial saturation with silicon (silicon cementation). Obtaining a silicon-rich surface coating results in a considerable increase in corrosion resistance, refractoriness, and wear resistance. One of the most economically convenient options for silicon cementation is pack siliconizing in powdery solid media. This paper presents the possibility of pack siliconizing that contains ferrosilicon (FeSi75C) and a thermite mixture (SiO2 + Al) as active, silicon-providing components, in P265GH grade steel, which is frequently used in the petrochemical industry. The aim of the study was to determine the most suitable active component of the two that were analyzed and at the same time identify the processing conditions in which the siliconized coating has the greatest thickness, is free of porosity, and is in direct contact with the support. The use of experimental programming methods allowed the optimization of the operation to obtain the optimal solution. It was concluded that the thermite mixture is not compatible with pack siliconizing because it results in a superficial saturation predominantly composed of aluminum. When ferrosilicon is used as the active component, it determines the particularly intense formation kinetics of the non-porous siliconized coating with its maximum thickness being reached at high processing temperature values (over 1100 °C) with a proportion of 60% FeSi75 and, simultaneously, with the lowest possible proportion of ammonium chloride (max. 3%), which is the surface activation/cleaning component.

NUMERICAL SOLUTION OF COUPLED HEAT TRANSFER WITH PHASE CHANGE AND THERMITE REACTION

The thermite reaction is a self-sustained exothermic reaction commonly employed in welding processes of railway tracks, material synthesis, pyrotechnics, etc. More recently, this reaction has been assessed to plug depleted oil wells. The investigated geometry is modeled as a two-dimensional axisymmetric domain with a thermite mixture compressed between a polymethylmethacrylate (PMMA) lid and a stainless steel disk. First-order kinetic is assumed for the chemical kinetics model. The governing equations are discretized with the finite-volume approach. Experimental validation is performed by comparing numerical combustion velocities and peak temperatures with the experimental data in the literature. The results demonstrate a remarkable thermal gradient through the longitudinal direction, displaying higher thermal losses next to the thermite-steel interface. These heat losses also affect the melting of species, as a small portion of alumina remains entirely solid during the reaction.

Experimental investigation of Al-Fe2O3 thermite reactions for thermal plug and abandonment of oil wells

The use of thermite in the plug and abandonment of wellbores is a promising new method for sealing oil wells. However, the reactants for thermite mixtures are usually in a powder state at ambient conditions, making a perfect homogenization for high heat release a challenging task. In this sense, this study aims to investigate the Fe2O3–Al thermite system prepared through a solvent-based method to maximize homogenization of the mixture and enhance energy release during the exothermic reaction. Tests were conducted to compare the burning velocity, ejected mass percentage, and temperature profiles of the reaction through small steel-tubes, comparing a dry-mixed, stoichiometric composition with a solvent-based mixture. The effect of additives such as Al2O3 and Al were also evaluated. Results showed that the solvent-based process led to higher compactness, higher temperatures on the steel tube's exterior, a more stable reaction, and a 40% decrease in ejected material. Also, Al-rich mixtures had faster reactions, lower temperatures, and more ejected material when compared to the stoichiometric system, while Al2O3-diluted mixtures showed a linear decrease in burning velocity and mass ejection at higher dilution levels, with no significant variation in temperature levels. Mixtures with 40% or higher dilution did not self-propagate. Therefore, a thermite mixture prepared using solvent and diluted with Al2O3 at 20–30% is recommended for the thermal plug and abandonment technology.

Optimal Conditions for Ultrasonic Treatment of Powder Suspensions to Obtain Homogeneous Thermite Mixtures

Optimal Conditions for Ultrasonic Treatment of Powder Suspensions to Obtain Homogeneous Thermite Mixtures

Numerical investigation of the impacts on the primary cement in a new thermal approach for plug and abandonment operations

The advancement of Plug and Abandonments (P&A) procedures is pivotal for reducing the costs associated with current operations. A novel technology concept proposes a heat emitter that will produce enough energy to melt the casing steel without critically affecting the cement layer. However, recent studies concerning this proposal have not given enough attention to the potential impact on the primary cement, which is a crucial material to guarantee the plug's integrity. This study models the heat emitter as a thermite mixture with constant volumetric heat generation, and the oil well structure was approached as a 2-D axisymmetric domain. The finite volume method with a static melting/solidification model is employed to solve the governing equations numerically. A C++ code was developed and compared with the commercial software Ansys® Fluent was performed to verify the present code. The thermal parameters of the heat emitter, including density (1983.6 and 2192.4 kg m−3), specific heat (919.6 and 1016.4 J kg−1 K−1), conductivity (5 and 15 W m−1 K−1), latent heat (1267.79 and 1147.05 kJ kg−1), volumetric heat generation (104.59 and 115.6 MW m−3), and reaction time (71.25 and 78.75 s), are evaluated through a 26 factorial design. The responses analyzed are the maximum melted volume of steel and the volume of cement critically affected. The high variability associated with thermal conductivity indicated a strong dependence on this parameter. Most importantly, this study highlights that melting the casing steel could unintentionally degrade the cement layer, increasing potential leakages paths and integrity problems.

Advanced one-dimensional modeling of thermite reaction for thermal plug and abandonment of oil wells

This paper presents an improved one-dimensional nonstationary model to simulate the reaction propagation of aluminum and iron-oxide in thermite mixtures. This model is motivated by the application of thermite mixtures for thermal plug and abandonment of oil wells. The main improvements of this model include the chemical source term correction in the energy conservation equation, and the imposition of a temperature limit to account for aluminum vaporization. A simplified, first-order, one-step mechanism governed by the Arrhenius relation was assumed, and different pairs of activation energy and pre-exponential factor were analyzed, including some pairs that reproduce the experimental propagation speed reported in the literature. Numerical simulations were done to generate contour plots that map the effects of the kinetics parameters, alumina dilution, and aluminum addition to the initial mixture in the main characteristics of the reaction wave, such as velocity, thickness, ignition delay, and initiation temperature. These simulations indicate that, at alumina dilution of 20% or more, the simulated thermite reaction does not reach the aluminum vaporization temperature and may not present disruption of the system. The model shows that aluminum addition to the initial mixture accelerates the propagation and the numerical results reproduces experimental data from literature. Also, below a burning velocity of 26 mm/s and alumina-dilution higher than 40%, the reaction does not self-propagate.

Formation of the phase composition of cast intermetallic alloys of the Fe—Al system by self-propagating high-temperature synthesis

The technology for producing cast intermetallic alloys of the Fe—Al system by self-propagating high-temperature synthesis from precursors in the form of a composition consisting of aluminum wire pressed with a thermite coating mixture of iron minium and aluminum powder is considered. The features of the phase composition of the obtained specimens with various aluminum contents are established. Keywords intermetallic compound, aluminum, iron, iron oxide, remelting, self-propagating high-temperature synthesis, thermite mixture

High-speed optical imaging technique for combusting metal nanopowders

This paper discusses a technique for studying laser initiation and combustion of high-energy materials in real time using a two-channel video recording system. Traditional high-speed imaging is used as one channel, and a brightness-amplified laser projection system (laser monitor) is used as the second channel. The synchronization of laser ignition and high-speed imaging of the flame and the sample surface is considered in detail. The relationship between the propagation of the flame glow and the change in the surface of the nanoAl + MnO2 thermite mixture during combustion has been established. A method of simultaneous high-speed recording of images of a laser monitor by two cameras with different recording frame rates is proposed to provide the possibility of studying the initial stage of combustion and the entire combustion process of the same nanopowder sample with different temporal and spatial resolutions. Imaging of the surface of nanoAl + MnO2 thermite mixtures at a recording frame rate of 20,000fps has been implemented using a laser monitor. The possibility of determining the propagation velocity of the combustion wave on the surface of the sample is demonstrated to be up to 85 mm/s. The influence of the exposure time of a high-speed camera on the image quality of a laser monitor is investigated. It is demonstrated that the image quality is almost the same for the images formed by 1–9 emission pulses of the brightness amplifier.

DEVELOPMENT OF TITANIUM-THERMITE MIXTURE FOR WELDING

The influence of reducing metals on the metallurgical processes of thermite welding has been studied. Iron scale and powdery materials were used as starting materials for the metallothermic mixture: titanium powder PTS according to TU 15‒1958, aluminum powder PA-2 according to GOST 6058‒73. Aluminum gas purification dust was introduced into the composition of the metallothermic mixture. The chemical composition of the metal was determined by the atomic emission method using the DFS-71 spectrometer according to GOST RISO 14284‒2009, the slag composition was determined by the X-ray fluorescence method on the Shimadzu XRF-1800 spectrometer according to GOST 28033‒89. The composition of the titanothermite mixture has been developed, which ensures the production of dense metal. The addition of a small amount of aluminum powder to the composition of the titanium-thermite mixture ensures the completeness of the interaction and reduction of iron scale, at the same time, the amount of molten metal increases. The introduction of aluminum gas purification dust into the thermite mixture as a flux reduces gas emission during thermal processes. In addition, the addition of a carbon-fluorine-containing flux additive increases the carbon content in the resulting metal and improves its mechanical properties.

The production of corrosion alloy by self-propagating high-temperature synthesis

The subject of research: Self-propagating high-temperature synthesis (SHS) is an energetically low-cost method for obtaining materials with desired properties.
 The purpose of research: Development and approbation of the method of self-propagating high-temperature synthesis.
 Methods and objects of research: For the synthesis of a corrosion-resistant material, a thermite mixture of Al (75 %) and Fe2O3 (25 %) and the addition of MoO3 with a variable mass fraction of 10 %, 15 %, 20 %, 25 % of thermite were taken. The composition and structure of the synthesized material were determined by XRD and metallography methods. Based on the properties of the physical properties of the obtained material (porosity, electrical conductivity) and its phase composition (MoO2, Al2O3, FeMoO4), samples obtained with a 15 % addition of MoO3 were selected for testing for corrosion resistance.
 Results of research: The paper presents the results of approbation of obtaining a corrosion-resistant material by the SHS method. Conducted tests for corrosion resistance established: the rate of continuous corrosion of the synthesized material (MoO3 15 %) was 0.2 mm / year, which is close in value to corrosion-resistant steels; high resistance of the synthesized material to technical salt when tested for 14 days with a concentrated solution of the reagent 0.18 ml * eq / l. The listed properties of the synthesized material confirm the possibility of obtaining corrosion-resistant materials by the SHS method, including those for operation in the Arctic.

Filtration efficiency of particle-laden flows for thermal plug and abandonment of oil wells using turbulence modeling in porous media

In this work, the process of filtration of particles carried out by turbulent flows is investigated. The applied mathematical framework considers turbulent flow regime in the clear region and within the filter. The motivation for this work is to get insight on possible use of filters to separate thermite mixtures from a carrier phase and their use in thermal plug and abandonment of oil wells. Axisymmetric simulations are performed using the finite volume method. A macroscopic k-ε model is applied to handle turbulence. Pressure drop, stream function and turbulence field are computed. Using correlations in the literature, filter efficiencies are estimated based on calculated flow and pressure fields. Reynolds numbers varied from 2.3 × 103 to 4.6 × 104 for different permeabilities K ranging from 3.47 × 10−9 m2 to 8.89 × 10−9 m2, corresponding to filter particle diameters dp = 1.0 × 10−2 m and 1.0 × 10−3 m and different porosities (0.5 to 0.8). The results showed that pressure drop is strongly affected by porosity, permeability and Reynolds number; the stream function maps indicated wider stagnant zones for filters with larger particle diameters (higher permeabilities); turbulence fields showed slight generation of turbulence inside the filtration zone. The results for efficiency illustrated that, in case of filtrating thermite, higher inlet velocities, filters with particles of size 1.0 × 10−3 m and lower porosity filters favor the collection mechanism.

Synchronized Two-Camera Laser Monitor for Studying Combusting Powder Systems

In this paper, we offer a laboratory facility for in situ visualization of the combustion of ultrafine metal powders, which combines laser initiation and simultaneous high-speed recording of images of the flame of a burning material and a surface covered by a flame. Visualization of the surface through the flame is realized using a laser monitor—an optical projection system with brightness amplification. The proposed imaging system makes it possible to get more detailed information about the combustion process, in particular, to study the change in the surface through the flame in the area of laser initiation, and the propagation of heating and combustion waves over the sample, as well as to study the change in the surface reflectance during combustion. To study the area of laser initiation, it is proposed to simultaneously record images of a laser monitor with two cameras. The symmetry of the combustion wave front propagation and the combustion products’ formation during laser initiation of the nanoAl + Fe3O4 thermite mixture was demonstrated. The nature of propagation in the form of a ring is a consequence of the symmetry of the properties of the system under study, at the micro and macro levels.

Effect of Carbon Content on the Combustion and Chemical Transformation of Thermite Mixtures Based on Co3O4/Cr2O3/Nb2O5 with Al

Effect of Carbon Content on the Combustion and Chemical Transformation of Thermite Mixtures Based on Co3O4/Cr2O3/Nb2O5 with Al

Role of multi-layered graphene as an additional fuel on energy release of Al/MoO3 nano-thermite

ABSTRACT Al/MoO3 nano-thermite is successfully reinforced with MLG (multi-layered graphene) using physical mixing synthesis technique, assisted with ultrasonication. MLG nanoplatelets in the nano-thermite (Al/MoO3) are utilised as an additional fuel to replace the conventional fuel, i.e. Al nanoparticles. The chemical composition and stability of samples are analysed by XRD (X-ray diffraction) and Raman techniques. The FESEM (field-emission scanning electron microscopy) and HR-TEM (high-resolution transmission electron microscopy) analysis revealed the morphology, uniform distribution of MoO3 (metal oxide) and Al, MLG (fuels) and also the contact between constituents of the thermite mixture. DSC (Differential scanning calorimetry) results showed that the exothermic behaviours are affected by the gradual replacement of Al by MLG as a fuel and achieved the maximum energy release of 1220 J/g, which is three times higher than 451 J/g, i.e. energy release in the case of Al/MoO3 conventional nano-thermite.

Explosive Burning of a Mechanically Activated Al and CuO Thermite Mixture

The results of experiments to determine the role of structural schemes for the ignition of a mechanically activated thermite mixture Al–CuO and the formation of its combustion flame are presented. The reaction initiated in the bulk of the experimental assembly transforms into torch combustion in an open space. The dynamics of the volume of the flame reaction region was determined. The stage of flame formation has a stochastic character, determined by the random distribution of the reaction centres in the initial volume of the components. A high-speed camera, a pyrometer and electro contact sensors were used as diagnostic tools. The ultimate goal of the study was to optimize the conditions for the flame formation of this mixture for its effective use with a single ignition of various gas emissions.

Numerical simulation of solid-phase chemical transformations in thermite mixtures under shock-wave loading

Shock-wave loading of a steel cylindrical ampoule that contained an aluminum-copper oxide(Al/CuO) thermite mixture is simulated in three-dimensional space using the SPH method.The chemical reaction starts after the performance of the criterion on temperature or pressure.Thechemical reaction equations are integrated using the first-order Euler method.The elastic-plastic flow is calculated using the variational formulation.The numerical study of solid-phase chemical transformations in the Al/CuO thermite mixture under shock-wave loading shows that the initiation of reactions in the shock wave,further development,and completion depends significantly on the amplitude and duration of the shock wave.Sub-critical pressure pulse can lead to an incomplete reaction or incompletely compacted final product.

Structure and mechanical characteristics of the materials of castings obtained by aluminothermic remelting of tungsten-oxide-containing compositions

Inoculation of the iron-carbon base melt with ferrotungsten is one of the stages of commercial production of wear-resistant-steel castings. The energy- and resource-intensive process of obtaining this component, as well as non-uniform distribution of tungsten-rich ores in the lithosphere necessitate the search for alternative methods of commercial manufacture of wear-resistant steels and articles made therefrom. The high temperature inherent in tungsten remelting processes is reached through exothermic oxidation-reduction reaction occurring in mixtures containing ore concentrate. Scale and aluminum swarf, which are technogenic formations difficult to dispose of, are used as the principal components of such thermite mixtures. Scheelite concentrate may be used as the ore component. Thus, the process under design is aimed at solving the problems of recycling waste generated by the metallurgical and mechanical engineering industries, as well as at ensuring energy- and material efficiency of the process of manufacturing castings from wear-resistant steels. The lack of information on the structure- and property-formation processes for wear-resistant steels obtained by aluminothermic remelting of scheelite concentrate-containing compositions has necessitated the conduct of a set of experiments. The paper presents the results of the experiment in determination of the impact of the reductant and scheelite concentrate content in thermites on the structure and mechanical properties of the samples of wear-resistant iron-carbon alloys.

Синтез композиционных материалов на кобальтовой и никелевой основе методом центробежной СВС-металлургии

This paper discusses the synthesis regularities of new composite materials via combustion processes and their features of physicochemical transformations for task of a modern technology. In early studies, the authors showed the possibility of synthesizing composite materials via centrifugal SHS metallurgy, in which the combustion of thermite mixtures and the chemical transformations were studied. The compositions, structures and mechanical properties of the synthesized materials were also investigated

Al-CuOx multilayer nanostructures: formation features and thermal properties of new type of local heat source

In this work, multilayer nanostructured thermite materials are considered - a new type of local heat sources. Aluminium and copper oxide were chosen as components of the thermite mixture. The formation of multilayer structures was carried out on the surface of the substrate by the method of magnetron sputtering. The features of the deposition process as well as the energy properties of the formed materials have been investigated. The results obtained confirm the prospects of using this class of materials as local heat sources.