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

Study of geothermal energy potential as a green source of energy with a look at energy consumption in Iran

Regarding disadvantages of fossil fuels, renewables like geothermals can be an eco-friendly source of energy. In Iran, the availability of fossil fuels and poor policies surrounding subsidies (ranked as the first in giving subsidies) caused high energy consumption (1.75 times higher than the global average). Energy is mainly provided by fossil fuels that leads to high CO$_{2}$ emission. This study evaluates the energy consumption trend and potentials of more sustainable resources like geothermals in Iran. The formation of geothermals is tightly linked with geological prerequisites that are partly present within Iran. Adjacency of the metamorphic with volcanic zones, existence of numerous faults and seismic activity of Iran are notable geological characteristics confirming the geothermal potential. In Iran, 18 regions are being explored as the most promising geothermal prospects. To test the potentials of one of these regions, a geothermal power plant with a capacity of 5 MWe is installed in the Sabalan Field. Northwest (where Sabalan Field is located), central (like Mahalat Region) and southeast of Iran (Makran Zone) can be regarded as promising zones for hosting geothermal prospects

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

Implications on large-scale flow of the fractured EGS reservoir Soultz inferred from hydraulic data and tracer experiments

The Enhanced Geothermal System in Soultz-sous-Forêts, located in the geothermal favorable Upper Rhine Graben, is a fracture-controlled reservoir that was highly investigated in the last decades generating a huge geoscientific database. Numerical reservoir models use this database to simulate the operation of the subsurface heat exchanger, yet suffer from simplifications regarding the transfer of experimental into model data, dimensional extension, and computational power and efficiency. The new extensive transient 3D simulations, based on geophysical, geological and hydraulic data, highlight the hydraulic and transport feedback of the Soultz EGS due to convective and advective fluid flow. Developed with the goal of simulating the vast tracer test data during the reservoir-testing phase in 2005, the finite element model is focusing on the main fractured zones, which connect the wells in the deep reservoir. It comprises 13 major hydraulically active faults and fractures in a 13×11 x 5 km extending model domain, as well as open-hole sections of the wells GPK1 to GPK4 and their casing leakages. The simulation of the tracer experiment confirms the strong heterogeneity of the reservoir and highlights the importance of a potential fractured zone, hydraulically separating the reservoir in a northern (GPK1 to 3) and southern section (GPK4). This zone tends to connect the reservoir to the main fault system by hydraulically separating GPK4 from the other wells. The calibration and sensitivity analyses provide a unique, broad understanding of the reservoir flow zones providing information on the extension of the Soultz reservoir in the future and on the fluid pathways in the deep subsurface of the Upper Rhine Graben

Stochastic 3D Navier‐Stokes Flow in Self‐Affine Fracture Geometries Controlled by Anisotropy and Channeling

This study presents a probabilistic analysis of 3D Navier‐Stokes (NS) fluid flow through 30 randomly generated sheared fractures with equal roughness properties (Hurst exponent = 0.8). The results of numerous 3D NS realizations are compared with the highly simplified local cubic law (LCL) solutions regarding flow orientations and regimes. The transition between linear and nonlinear flow conditions cannot be described with a generally valid critical Reynolds number urn:x-wiley:00948276:media:grl62319:grl62319-math-0001, but rather depends on the individual fracture\u27s void geometry. Over 10% reduction in flow is observed for increased global Re (>100) due to the increasing impact of nonlinear conditions. Furthermore, the fracture geometry promotes flow anisotropy and the formation of channels. Flow perpendicular to the shearing leads to increased channeling and fluid flow (∼40% higher) compared to flow parallel to the shearing. In the latter case, dispersed flow and irregular flow paths cause a reduction of LCL validity

Stochastic 3D Navier‐Stokes Flow in Self‐Affine Fracture Geometries Controlled by Anisotropy and Channeling

This study presents a probabilistic analysis of 3D Navier‐Stokes (NS) fluid flow through 30 randomly generated sheared fractures with equal roughness properties (Hurst exponent = 0.8). The results of numerous 3D NS realizations are compared with the highly simplified local cubic law (LCL) solutions regarding flow orientations and regimes. The transition between linear and nonlinear flow conditions cannot be described with a generally valid critical Reynolds number urn:x-wiley:00948276:media:grl62319:grl62319-math-0001, but rather depends on the individual fracture\u27s void geometry. Over 10% reduction in flow is observed for increased global Re (>100) due to the increasing impact of nonlinear conditions. Furthermore, the fracture geometry promotes flow anisotropy and the formation of channels. Flow perpendicular to the shearing leads to increased channeling and fluid flow (∼40% higher) compared to flow parallel to the shearing. In the latter case, dispersed flow and irregular flow paths cause a reduction of LCL validity

Spatial Characterization of Channeling in Sheared Rough‐Walled Fractures in the Transition to Nonlinear Fluid Flow

Accurate quantification of spatially resolved fluid flow within fractures is crucial for successful reservoir development, such as Enhanced Geothermal Systems. This study presents an innovative workflow designed to model and characterize preferential flow paths (channels) within rough-walled shear fractures. A set of 30 rough-walled self-affine fractures, all possessing identical roughness characteristics, is stochastically generated. By solving the nonlinear Navier-Stokes equations in 420 individual realizations, the transition from linear to nonlinear flow regimes and the two extreme flow directions perpendicular and parallel to the shearing are numerically captured. A distinguishing feature of this approach is its comprehensive statistical analysis, which encompasses both the geometric and transport properties of flow paths in the non-simplified three-dimensional fractured void space under typical geothermal flow conditions. In a perpendicular orientation of flow and shearing, fluid flow exhibits pronounced localization, with more than one-third of the volumetric flow concentrated within 15% of the fracture volume. In contrast, parallel to the shearing, a complex pattern of individual tortuous channels emerges, with flow occurring in 22% of the void space. Nonlinear effects primarily manifest outside these channels, suggesting that complex flow phenomena may dominate irregular fracture structures, such as contact zones or asperities. In the parallel case, increased flow rates lead to an amplification of channeling processes resulting in less affected volume and diminished tortuosity of the main flow path, while in perpendicular orientation nonlinear effects are only of minor importance. The small-scale flow regime of both extreme cases tends to converge with increasing flow rates