Analyzing Impacts of Interfacial Instabilities on the Sweeping Power of Newtonian Fluids to Immiscibly Displace Power-Law Materials

Injection of Newtonian fluids to displace pseudoplastic and dilatant fluids, governed by the power-law viscosity relationship, is common in many industrial processes. In these applications, changing the viscosity of the displaced fluid through velocity alteration can regulate interfacial instabilities, displacement efficiency, the thickness of the static wall layer, and the injected fluid’s tendency to move toward particular parts of the channel. The dynamic behavior of the fluid–fluid interface in the case of immiscibility is highly complicated and complex. In this study, a code was developed that utilizes a multi-component model of the lattice Boltzmann method to decrease the computational cost and accurately model these problems. Accordingly, a 2D inclined channel, filled with a stagnant incompressible Newtonian fluid in the initial section followed by a power-law material, was modeled for numerous scenarios. In conclusion, the results indicate that reducing the power-law index can regulate interfacial instabilities leading to dynamic deformation of static wall layers at the top and the bottom of the channel. However, it does not guarantee a reduction in the thickness of these layers, which is crucial to improve displacement efficiency. The impacts of the compatibility factor and power-law index variations on the filling pattern and finger structure were intensively evaluated.</p

Stochastic performance assessment on long-term behavior of multilateral closed deep geothermal systems

Increasing the contribution of geothermal systems to green energy generation requires designing new innovative systems producing a significant amount of thermal power in a sustainable manner. The focus of this study is the performance evaluation of multilateral closed deep geothermal (MCDG) systems as a novel environmentally friendly approach for energy extraction from earth. The investigations on these synthetic systems assume a probabilistic number of borehole sections with several vertical and horizontal wellbores connected through some manifolds and doglegs. To reduce possible thermal losses, the circulated fluid is extracted through only one production wellbore. The findings of this study demonstrated that the heat absorption per meter of MCDG systems is much higher than for simple closed geothermal systems (CDG). Operating with these systems will not necessarily yield better performance. It is also found that the long-term performance of MCDG systems can be predicted as a function of their short-term behavior through stochastic analysis. This correlation is interestingly independent of the number of wellbores and flow rate. By defining specific criteria, the high-performance MCDG systems can be filtered to demonstrate common features as a specific relation between flow rates per vertical and horizontal wellbores. This characterization of MCDG systems should support the design of future high-performance systems

Transport mechanisms of hydrothermal convection in faulted tight sandstones

Motivated by the unknown reasons for a kilometre-scale high-temperature overprint of 270–300 ∘C in a reservoir outcrop analogue (Piesberg quarry, northwestern Germany), numerical simulations are conducted to identify the transport mechanisms of the fault-related hydrothermal convection system. The system mainly consists of a main fault and a sandstone reservoir in which transfer faults are embedded. The results show that the buoyancy-driven convection in the main fault is the basic requirement for elevated temperatures in the reservoir. We studied the effects of permeability variations and lateral regional flow (LRF) mimicking the topographical conditions on the preferential fluid-flow pathways, dominant heat-transfer types, and mutual interactions among different convective and advective flow modes. The sensitivity analysis of permeability variations indicates that lateral convection in the sandstone and advection in the transfer faults can efficiently transport fluid and heat, thus causing elevated temperatures (≥269 °C) in the reservoir at a depth of 4.4 km compared to purely conduction-dominated heat transfer (≤250 °C). Higher-level lateral regional flow interacts with convection and advection and changes the dominant heat transfer from conduction to advection in the transfer faults for the low permeability cases of sandstone and main fault. Simulations with anisotropic permeabilities detailed the dependence of the onset of convection and advection in the reservoir on the spatial permeability distribution. The depth-dependent permeabilities of the main fault reduce the amount of energy transferred by buoyancy-driven convection. The increased heat and fluid flows resulting from the anisotropic main fault permeability provide the most realistic explanation for the thermal anomalies in the reservoir. Our numerical models can facilitate exploration and exploitation workflows to develop positive thermal anomaly zones as geothermal reservoirs. These preliminary results will stimulate further petroleum and geothermal studies of fully coupled thermo–hydro–mechanical–chemical processes in faulted tight sandstones

Enhancement of immiscible two-phase displacement flow by introducing nanoparticles and employing electro- and magneto-hydrodynamics

In this study, two-component displacement of a time-dependent non-Newtonian fluid by a Newtonian fluid in a two-dimensional inclined channel is simulated. Using a special multi-component model of the lattice Boltzmann method that is called He-Chen-Zhang, made it possible to do the simulations for non-uniform density and very high viscosity ratios. The main focus of this study is altering the flow pattern and displacement efficiency by Applying Electro- and magneto-hydrodynamic fields, using added nanoparticles and heating the channel walls. Displacement efficiency in different cross-sections, thickness of the static wall layer at the top and bottom of the channel, development of interfacial instabilities, magnitude of generated forces and, temperature distribution in the simulation environment are analyzed comprehensively to fully control the fingering structure. Investigation of injected fluid movement in the other one and displacement efficiency showed that enhancement in the power of the electric field is associated with displacement efficiency alteration in various longitudinal sections of the channel. However, removing the residual layer at the top and bottom of the fingering structure doesn't cause the total efficiency of displacement (Mt) to change significantly since the axial motion of the invading fluid is weakened. In contrast, applying magnetic field, increasing the Hartmann number and changing the rotation angle of the coordinate system (to 180), enhances the axial velocity and displacing ability of this fluid. Furthermore, for Ha = 10 and θ = 0, with the transverse velocity rising, displacement efficiency for longitudinal sections close to the channel axis decreases and the occurrence of interfacial instabilities is inevitable.</p

Analyzing impacts of interfacial instabilities on the sweeping power of Newtonian fluids to immiscibly displace power-law materials

Injection of Newtonian fluids to displace pseudoplastic and dilatant fluids, governed by the power-law viscosity relationship, is common in many industrial processes. In these applications, changing the viscosity of the displaced fluid through velocity alteration can regulate interfacial instabilities, displacement efficiency, the thickness of the static wall layer, and the injected fluid’s tendency to move toward particular parts of the channel. The dynamic behavior of the fluid–fluid interface in the case of immiscibility is highly complicated and complex. In this study, a code was developed that utilizes a multi-component model of the lattice Boltzmann method to decrease the computational cost and accurately model these problems. Accordingly, a 2D inclined channel, filled with a stagnant incompressible Newtonian fluid in the initial section followed by a power-law material, was modeled for numerous scenarios. In conclusion, the results indicate that reducing the power-law index can regulate interfacial instabilities leading to dynamic deformation of static wall layers at the top and the bottom of the channel. However, it does not guarantee a reduction in the thickness of these layers, which is crucial to improve displacement efficiency. The impacts of the compatibility factor and power-law index variations on the filling pattern and finger structure were intensively evaluated.</p

Impact of thermosiphoning on long-term behavior of closed-loop deep geothermal systems for sustainable energy exploitation

Circulation of working fluid in closed geothermal loops is an alternative environmentally friendly approach to harvest subsurface energy compared to open hole geothermal doublet systems. However, the rapid decline of production temperature, low generated thermal power, and difficulties in deepening the system are major limitations. Herein, synthetic studies are presented to investigate the system's performance and improve its longevity for better use of this clean baseload power. The investigations are conducted by implementing appropriate equations of state to model state-of-the-art thermal and hydraulics processes in wellbores and considering various geometrical configurations to adopt proper design strategies. They provide insight for maximizing the generated thermal power, decreasing pumping energy, and avoiding production temperature drawdown. The results indicate that a stable thermal condition could be reached in which not only the temperature breakthrough is avoidable, but also the generated thermal power and production temperature continuously enhance over the project lifetime of one century. Analysis of the thermosiphon effect in the designed systems revealed that even with the pressure loss of 900 kPa at surface installations, the triggered natural flow rate is larger than 11 L/s. This thermosiphon flow rate yields the thermal power production of 2 MW and Cumulative extracted energy of 15 PJ over the project lifetime of 100 years. Restriction of this flow rate to 5 L/s leads to an average extraction temperature of 80 °C. It is also found that a change in the subsurface temperature gradient does not affect the optimal 2 km isolation length of the production well.</p

Stochastic performance assessment on long-term behavior of multilateral closed deep geothermal systems

Increasing the contribution of geothermal systems to green energy generation requires designing new innovative systems producing a significant amount of thermal power in a sustainable manner. The focus of this study is the performance evaluation of multilateral closed deep geothermal (MCDG) systems as a novel environmentally friendly approach for energy extraction from earth. The investigations on these synthetic systems assume a probabilistic number of borehole sections with several vertical and horizontal wellbores connected through some manifolds and doglegs. To reduce possible thermal losses, the circulated fluid is extracted through only one production wellbore. The findings of this study demonstrated that the heat absorption per meter of MCDG systems is much higher than for simple closed geothermal systems (CDG). Operating with these systems will not necessarily yield better performance. It is also found that the long-term performance of MCDG systems can be predicted as a function of their short-term behavior through stochastic analysis. This correlation is interestingly independent of the number of wellbores and flow rate. By defining specific criteria, the high-performance MCDG systems can be filtered to demonstrate common features as a specific relation between flow rates per vertical and horizontal wellbores. This characterization of MCDG systems should support the design of future high-performance systems