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Collaborating Authors
Gerritsen, Margot
Abstract This paper presents a new workflow for the simulation of in-situ combustion (ISC) dynamics. In the proposed method, data from kinetic cell experiments, depicting the combustion chemistry, are tabulated and graphed based on the isoconversional principle. The tables hold the reaction rates used to predict the production and consumption of chemical species during in-situ combustion. This new method of representing kinetics without the Arrhenius method is applied on one synthetic and two real kinetic cell experiments. In each case, the new method reasonably captures the reaction pathways taken by the reacting species as the combustive process occurs. A data-density sensitivity study on the tabulated rates for the real case shows that only four experiments are required to capture adequately the kinetics of the combustion process. The results are, however, found to be sensitive to the size of the time step taken. The method predicts critical changes in the reaction rates as the experiment is exposed to different temperature conditions, thereby capturing the speed of the combustion front, temperature profile, and fluid compositions of a simulated combustion tube experiment. The direct use of the data ensures flexibility of the reaction rates with time and temperature. In addition, the non-Arrhenius kinetics technique eliminates the need for a descriptive reaction scheme that is typically computationally demanding, and instead focuses on the overall changes in the carbon oxides, oil, water and heat occurring at any time. Significantly, less tuning of parameters is required to match laboratory experiments because laboratory observations are easier to enforce.
- North America > United States > California > San Joaquin Basin > South Belridge Field > Tulare Formation (0.99)
- North America > United States > California > San Joaquin Basin > South Belridge Field > Diatomite Formation (0.99)
- North America > Canada > Alberta > Athabasca Oil Sands > Western Canada Sedimentary Basin > Alberta Basin (0.99)
Summary We demonstrate the effectiveness of a non-Arrhenius kinetic upscaling approach for in-situ-combustion processes, first discussed by Kovscek et al. (2013). Arrhenius reaction terms are replaced with equivalent source terms that are determined by a work flow integrating both laboratory experiments and high-fidelity numerical simulations. The new formulation alleviates both stiffness and grid dependencies of the traditional Arrhenius approach. Consequently, the computational efficiency and robustness of simulations are improved significantly. In this paper, we thoroughly investigate the performance of the non-Arrhenius upscaling method compared with Arrhenius kinetics. We investigate robustness by considering grid effects and sensitivity to heterogeneity. Performance improvements of the new kinetic upscaling approach compared with traditional Arrhenius kinetics are demonstrated through numerical experiments in one and two dimensions for both homogeneous- and heterogeneous-permeability fields.
- Europe (1.00)
- North America > United States > California (0.47)
Abstract History matching with uncertainty quantification has been a topic of great interest over the last 10 years, with many algorithmic approaches developed, and many applications presented. Most of the applications focus on the uncertainty in the petrophysical properties of the reservoir, as that is by far the easiest to parameterise. There are few papers that address the topic of structural uncertainty quantification, yet that is potentially the biggest component of subsurface uncertainty. The principal problem in accounting for structural uncertainty is the difficulty in parameterising subsurface structures, automatically gridding the reservoir model and ensuring that the grid will simulate in a reasonable time. This paper presents a new approach to structural uncertainty quantification. We have adapted the immersed interface method from computational mechanics, used to model fluid flow in domains with moving boundaries, to reservoir simulation. The immersed interface method is used with an extended multipoint flux approximation to completely decouple the parameterisation of structural features from their representation on the grid. Using this new technique, we are easily able to history match a 2D synthetic case where we simultaneously vary the top and bottom surfaces of a reservoir, the location and orientation of faults within the reservoir, and the location and size of pinchouts.
- Europe (0.94)
- North America > United States > Texas (0.46)
- Europe > Norway > Norwegian Sea > Halten Terrace > Njord License > Block 6407/7 > Njord Field > Tilje Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > Njord License > Block 6407/7 > Njord Field > Ile Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > Njord License > Block 6407/10 > Njord Field > Tilje Formation (0.99)
- Europe > Norway > Norwegian Sea > Halten Terrace > Njord License > Block 6407/10 > Njord Field > Ile Formation (0.99)
Abstract Experimental design is a widely used statistical method for understanding the factors that impact an information gathering exercise such as mechanistic simulations. It is used here to gain insight into flow and operating conditions that affect in-situ combustion. Specifically, experimental design was applied to understand in-situ combustion of very heavy oil using a commercial thermal simulator. The design parameters investigated were selected based on combustion laboratory results and literature. These included activation energies of the reaction schemes, oil saturation, air injection rate and pressure control at the producer. A full factorial design was used to create the parametric space considering interactions between the parameters. The degree to which the combustion peak temperature, pressure, combustion front speed, recovery efficiency and coke deposited changed was used to determine the most critical parameters. Results showed the activation energy of the coke deposition reaction had the greatest influence on the combustion process. For the 3-reaction pathway assumed for crude-oil combustion, a slight increase in this activation energy inhibited the combustion reactions. The injection pressure of the system was impacted significantly by the initial oil saturation while the speed at which the front propagated was shown to be primarily a function of the air injection rate. Results also showed that for a given initial oil saturation, a limiting air flux existed below which oil plugging of the linear system occured. Given successful ignition and propagation of the front, optimal recovery was obtained between initial oil saturations of 45-70%. We also observed interaction between the parameters. The effect of the activation energy of the combustion reaction on the recovery was strongly dependent on the amount of oil initially in place. Recovery decreased with increasing activation energy at lower initial saturations, but was independent of activation energy at greater initial saturations. In addition, the velocity profile showed different incremental oil recovery rates with different initial oil saturation.
- Africa > Nigeria > Gulf of Guinea > Niger Delta > Niger Delta Basin > OPL 217 > Agbami-Ekoli Field > Agbami Field (0.99)
- Africa > Nigeria > Gulf of Guinea > Niger Delta > Niger Delta Basin > OPL 216 > Agbami-Ekoli Field > Agbami Field (0.99)
- Information Technology > Modeling & Simulation (0.68)
- Information Technology > Data Science > Data Mining (0.34)
Abstract The gas mobility control aspects of foamed gas make it highly applicable for improved oil recovery. Gas bubble size, often termed as foam texture, determines gas flow behavior. A population balance model has been developed previously for modeling foam texture and flow in porous media. The model incorporates pore-level mechanisms of foam bubble generation, coalescence, and transport. Here, we propose a simplified foam model to reduce computational costs. The formulation is based on the assumption of local equilibrium of foam generation and coalescence and is applicable to high and low quality foams. The proposed foam model is compatible with a standard reservoir simulator. It provides a potentially useful, efficient tool to predict accurately foam flows at the field scale for designing and managing foamed-gas applications. There are three main contributions of this paper. First, the population balance representation of foam generation by gas-bubble snap off is modified to extend the capability of the population balance approach to predict foam flow behaviors in both the so-called high-quality and low-quality regimes. Second, a simplified population-balance model is developed and implemented with the local-equilibrium approximation. Third, foam displacement experiments in a linear sandstone core are conducted to verify the proposed model. A visualization cell is employed to measure the effluent foam bubble sizes for a transient flow as well as to estimate the in-situ foam bubble sizes along the length of the core during steady flow. Additionally, the evolution of aqueous phase saturation is monitored using X-ray computed tomography (CT) and the pressure profile is measured by a series of pressure taps. Good agreement is found between the experimental results and the predictions of the simplified model, with a minor mismatch in the entrance region. Introduction Foam is a dispersion of a gas within a continuous liquid. Foamed gas has attracted tremendous research interest and effort because of its significantly reduced mobility in comparison to continuous gas mobility. The unique flow properties of foamed gas make foam highly applicable as a gas mobility control agent for enhanced oil recovery (EOR). EOR by steam or carbon dioxide injection, for example, sometimes exhibit poor sweep efficiency, gravity override, and channeling of gas through the most permeable zones of the reservoir (Green and Willhite, 1998; Lake, 1989). Foaming the injected gases increases the gas-phase resistance dramatically, thereby providing mobility control to improve the sweep efficiency and oil production. Enhanced/improved oil recovery by the use of foam has been employed during field steam-foam pilots in the late 1980's and several nonthermal applications of foam in the mid 1990's. For instance, the Mecca and Bishop steam-foam pilots in the Kern River field (Patzek and Koinis, 1990) show major oil response after 2 years of foam injection, and yield incremental oil recovery of 8.5% - 18% of the original oil in place (OOIP) over a five year period.
- North America > United States > California > Kern County (0.87)
- Europe > United Kingdom > Irish Sea > East Irish Sea > Liverpool Bay (0.24)
- Research Report > New Finding (0.46)
- Research Report > Experimental Study (0.46)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.47)
- North America > United States > California > San Joaquin Basin > South Belridge Field > Tulare Formation (0.99)
- North America > United States > California > San Joaquin Basin > South Belridge Field > Diatomite Formation (0.99)
- North America > United States > California > San Joaquin Basin > Midway-Sunset Field > Webster Formation (0.99)
- (14 more...)
Coupling Chemical Kinetics and Flashes in Reactive, Thermal and Compositional Reservoir Simulation
Kristensen, Morten Rode (Tech. U. of Denmark) | Gerritsen, Margot (Stanford University) | Thomsen, Per G. (Technical University of Denmark) | Michelsen, Michael L. (Tech. U. of Denmark) | Stenby, Erling Halfdan (Tech. U. of Denmark)
Abstract Phase changes are known to cause convergence problems for integration of stiff kinetics in thermal and compositional reservoir simulations. We propose an algorithm for detection and location of phase changes based on discrete event system theory. The algorithm provides a robust way for handling the switching of variables and equations required when the number of phases changes. We extend the method to handle full phase equilibrium described by an equation of state. Experiments show that the new algorithm improves the robustness of the integration process near phase boundaries by lowering the number of convergence and error test failures by more than 50% compared to direct integration without the new algorithm. To facilitate the algorithmic development we construct a virtual kinetic cell model. We use implicit one-step ESDIRK (Explicit Singly Diagonal Implicit Runge-Kutta) methods for integration of the kinetics. The kinetic cell model serves both as a tool for the development and testing of tailored solvers as well as a testbed for studying the interactions between chemical kinetics and phase behavior. A comparison between a Kvalue correlation based approach and a more rigorous equation of state based approach to phase equilibrium shows that phase behavior may significantly impact the reaction paths. Introduction In this paper we discuss the development of efficient algorithms for the integration of the stiff chemical reactions in In-Situ Combustion (ISC) processes. ISC processes have a strong multi-scale character. Physical sub-processes such as mass and heat transport have associated temporal, and often also spatial, scales that are typically much larger than those for kinetics. Operator splitting methods, such as those developed in Younis and Gerritsen [1], are attractive for solving processes with such disparate temporal scales. They allow sub-processes to be essentially decoupled so that each subprocess can be solved using tailored numerical methods and time steps. For example, stiff kinetics is best treated by implicit methods and requires relatively small time steps, whereas convective transport can often be integrated explicitly with much larger time steps. In this work, we assume that the ISC process is solved using an operator splitting method. In a reaction substep, each grid block is then effectively treated as a small kinetic cell with homogeneous pressure and temperature and well mixed fluids. We focus on the design of efficient numerical integration of the stiff kinetics. High computational efficiency is very desirable as a typical simulation may involve millions of reaction substeps. Phase behavior, that is the transfer of components between phases, adds further complexity to compositional and thermal processes. In lack of better alternatives we shall assume thermodynamic equilibrium conditions. How to numerically treat the interaction of phase behavior with kinetics is, as yet, not fully understood. We expect that predictions are very sensitive to the approach chosen, because phase behavior and kinetics both affect the amount and composition of the combustion fuel, the heat released and the combustion gases produced.
Abstract We propose a time-stepping methodology for in-situ combustion simulation that is designed specifically to accommodate the various physical sub-processes, including conduction, advection, and kinetics, that have widely varying time-scales. The approach combines operator splitting with fractional time-stepping. The method is applied to a scaled form of the governing equations. We derived seven independent scaling parameters in the in-situ combustion process, representing ratios of heat capacity, mass transfer and heats of reaction. We provide a proof of concept for one particular splitting and fractional step method that we found to be intuitive. In each time-step of this scheme, we solve the pressure equation semi-implicitly. Conservative accumulation treatment is assured by elimination at the Jacobian level. This is followed by an explicit solve for temperature, where a second elimination is performed to de-couple accumulation terms from the remaining concentration equations. The concentration equations are then integrated in a fractional-step, additive-splitting fashion. This means that reactions are separated numerically from the concentration advection-reaction equations. The overall solution for concentrations is obtained by performing a sequence of solves for reactions alternating with pure advection. A local fractional time-step size for either sub-process is introduced, and may be varied according to the local physics. Finally the global time-step solution is composed in an accurate fashion out of the sub-process solves. To test the method a couple of test problems were designed for which the parameters are given in full detail so that it can be used for inter-code comparisons. Introduction Substantial underutilized hydrocarbon resources exist within the United States in the form of so-called heavy oil (10 to 20 ºAPI) and conventional oil (greater than 20 ºAPI) that remain after secondary waterflood and primary pressure depletion operations. Thermal oil recovery, and in particular In-Situ Combustion (ISC), may be well suited to unlock these resources. Essentially, ISC is the process of injecting air into an oil reservoir to oxidize a small fraction of the hydrocarbons present. The oxidation process produces heat and steam that aid oil production. Heating reduces the high oil viscosity of heavy oils and thus substantially improves recovery efficiency. Likewise, heating induces thermal expansion and vaporization of conventional oils. Thermal conduction allows heat to sweep areas of the reservoir not directly contacted by hot fluid. In the broadest terms, the purpose of our research is to improve our predictive capabilities of the physically and mathematically very complex ISC process. In this paper in particular, we suggest a computational framework that has promise in addressing the temporal multi-scale character of the various physical processes that play a role in ISC. The multiscale ISC process In-Situ Combustion (ISC) processes are physically complex. In addition to strongly coupled phase behavior, compositional transport, and flow, such processes also involve thermal effects and chemical reactions. The characteristic time-scales associated with each of these sub-processes can vary substantially over the duration of a combustion process as well as over the reservoir domain. This implies that throughout the life of a combustion process, the set of dominant physics that influences behavior the most can vary as well. For example, it is clear that conductive and convective heat transport dictate the recovery until reactions dominate. On the other hand, the fashion by which the reservoir is heated, and associated transients, can dictate if and how a sustainable front develops. This operational dependency is thought to be related to the chemical properties of the system. Once combustion starts off, reactive and convective transport tend to dominate, and the sustainability of a front and its dynamics will then depend on relative timescales between sub-reaction steps and species transport.
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.54)
- Geology > Geological Subdiscipline (0.48)