Wormholes effect in carbonate acid enhanced oil recovery methods

Acid enhanced oil recovery has been a focus of interest in the oil industry due to its significant results on improved recovery, especially in carbonate reservoirs. However, in carbonate reservoirs, highly conductive pathways called “wormholes” are created when acidic fluids are injected into carbonate rocks. Wormholes could jeopardize the enhanced oil recovery outcome and sweep efficiency leaving a substantial volume of oil in the reservoir unswept. This phenomenon has not been investigated yet. The main objective of this study is to identify the impact of these wormholes on the overall oil recovery during enhanced oil recovery practices. This was achieved by injecting acidic fluid into Indiana limestone at various injection rates to control the creation of wormholes. The injection rates were selected based on a proposed dimensionless phase space that predicts the wormholes development and dissolution phase. Our results show that wormholes have a significant impact on the enhanced oil recovery performance resulting in a decrease in the overall oil recovery by 9.6% for portions of the reservoir that experience wormholing. In real field applications, it is recommended to avoid creating wormholes over large portions of the reservoir affected by acid injection as it may jeopardize the field development outcome leaving an unspecified amount of oil in virgin regions in the reservoir which results in additional operational complications. Wormholes are only beneficial near the wellbore for wellbore cleanup and matrix treatment purposes thus providing easier access to the reservoir. However, care needs to be taken to constrain wormhole formation to skin factor reduction and avoid far-reaching wormholes in the reservoir.Cited as: Alarji, H., Clark, S., Regenauer-Lieb, K. Wormholes effect in carbonate acid enhanced oil recovery methods. Advances in Geo-Energy Research, 2022, 6(6): 492-501. https://doi.org/10.46690/ager.2022.06.0

Entropic Limit Analysis Applied to Radial Cavity Expansion Problems

Analytical solutions of limit analysis design for the simple problem of plane strain expansion of a cylindrical cavity are derived and generalized into entropic extremum principles that allow a fundamental assessment of coupled thermal/hydro/mechanical/chemical (THMC) material instabilities and their effect on the upper and lower bounds of dissipation. The proposed approach integrates a thermodynamically based estimation of uncertainties in coupled deformation processes and an identification of the intrinsic material length/time scales that appear as energy eigenstates of the localization problem. Analytical limit analysis design solutions of the cavity expansion are obtained and upper and lower bound estimates are shown to coincide. This provides a robust framework for adding multiphysics feedbacks. Isothermal conditions are first relaxed and the feedback between shear heating, thermal weakening and thermal diffusion is analyzed. Then the analysis is extended to a full range of THMC localization phenomena which are described with a cascade of characteristic time/length scales derived from instabilities in the governing reaction-diffusion equations. Entropic uncertainties are estimated by alternating system constraints between thermodynamic flux and thermodynamic force on the boundaries

Continental rifts: Complex dissipative patterns from simple boundary conditions

We present numerical models that investigate the development of crustal and mantle detachments during lithospheric extension. Our models, which consider an elasto-visco-plastic lithosphere, explore the relationship between stored and dissipated energies during deformation. We apply the fundamental thermodynamic assumptions of minimization of Helmholtz free energy (i.e. stored energy) and maximization of dissipated energy, and include in the models feedback effects modulated by temperature, such as shear heating, that lead to strain localization. Our models simulate a wide range of extensional systems with varying values of crustal thickness and heat flow, showing how strain localization in the mantle interacts with localization in the upper crust and controls the evolution of extensional systems. Model results reveal a richness of structures and deformation styles as a response to a self-organized mechanism that minimizes the internal stored energy of the system by localizing deformation. Crustal detachments, here referred as low-angle normal decoupling horizons, are well developed during extension of overthickened (60 km) continental crust, even when the initial heat flow is relatively low (50 mW m-2). In contrast, localized mantle deformation is most pronounced when the extended lithosphere has a normal crustal thickness (30–40 km) and an intermediate heat flow (60–70mWm-2). Results show a nonlinear response to subtle changes in crustal thickness or heat flow, characterized by abrupt and sometimes unexpected switches in extension modes (e.g., from diffuse extensional deformation to effective lithospheric-scale rupturing) or from mantleto crust-dominated strain localization. We interpret this nonlinearity to result from the interference of doming wavelengths in the presence of multiple necking instabilities. Disharmonic crust and mantle doming wavelengths results in efficient communication between shear zones at different lithospheric levels, leading to rupturing of the whole lithosphere. In contrast, harmonic crust and mantle doming inhibits interaction of shear zones across the lithosphere and results in a prolonged history of extension prior to continental breakup

The impact of wettability and fluid saturations on multiphase representative elementary volume estimations of micro-porous media

The occurrence of multi-phase flows in porous media is a complex phenomenon that involves multiple scales, ranging from individual pores to larger continuum scales. Upscaling frameworks have emerged as a response to the need for addressing the disparity between micro-scale processes and macroscopic modelling. Determination of the representative elementary volume is important for understanding fluid dynamics in micro-porous materials. The size of the representative elementary volume for multiphase flow in porous media is significantly affected by wettability and fluid saturations. Previous studies have overlooked this aspect by conducting simulations under conditions of constant medium wettability and fluid saturations. This study uses finite volume simulations with a volume of fluid approach for two distinct asymptotic homogenization methods, namely hydrodynamic bounds of relative permeability and thermodynamic bounds of entropy production. Strong wetting conditions with high wetting phase saturation were found to require a smaller sample size to establish representative elementary volume, while mixed-wettability scenarios necessitate the largest sample sizes. These findings improve our understanding of multiphase fluid flow behaviour in micro-porous materials and aid in enhancing techniques for scaling up observations and predictive modelling in engineering and environmental fields.Document Type: Short communicationCited as: Hussain, S. T., Regenauer-Lieb, K., Zhuravljov, A., Hussain, F., Rahman, S. S. The impact of wettability and fluid saturations on multiphase representative elementary volume estimations of micro-porous media. Capillarity, 2023, 9(1): 1-8. https://doi.org/10.46690/capi.2023.10.0

Asymptotic hydrodynamic homogenization and thermodynamic bounds for upscaling multiphase flow in porous media

This paper presents a novel technique for upscaling multiphase fluid flow in complex porous materials that combines asymptotic homogenization approach with hydrodynamicand thermodynamic bounds. Computational asymptotic homogenization has been widely utilised in solid mechanics as a method for analysing multiscale expansion and convergence coefficients in heterogeneous systems. Computations are performed over several volumes by increasing the size until convergence of the material parameters under different load scenarios is achieved. It works by simplifying the problem with a homogenization method and is ideally suited for estimating the representative elementary volume of microporous material by expanding algorithms. The validity of the method to include complex multiphase hydrodynamic processes and their interaction with the matrix structure of porous media lacks a sound theoretical foundation. To overcome this problem, a variational thermodynamic approach is used. Upper and lower bounds of entropy production are proposed to provide effective material properties with uncertainties. This allows multiple possibilities to address dynamics via thermodynamically linked processes. This work utilizes volume of fluid approach to model multiphase porous media flow in models based on micro-computerized tomography x-ray data of Bentheimer sandstone and Savonnieres carbonate. It is found that the representative elementary volume sizes obtained by the conventional asymptotic homogenization methods do not satisfy thermodynamic bounds which consistently require larger representative elementary volume sizes. For the Savonnieres carbonate the entropic bounds have not converged fully questioning the reliability of the effective properties obtained from the classical method.Document Type: Original articleCited as: Hussain, S. T., Regenauer-Lieb, K., Zhuravljov, A., Hussain, F., Rahman, S. S. Asymptotic hydrodynamic homogenization and thermodynamic bounds for upscaling multiphase flow in porous media. Advances in Geo-Energy Research, 2023, 9(1): 38-53. https://doi.org/10.46690/ager.2023.07.0

Petrography, petrology and mineralogy of eclogite nodules from the Jwaneng Diamond Mine, Botswana. An approach documented by mantle metasomatism, kimberlite emplacement and finally by super sonic uplift of the diamondiferous host rocks

Scientific contributions and therein geochemical datasets applied to mantle xenoliths collected from the Jwaneng Diamond Mine in Botswana are very rare, because of the problematic accessibility of the mine and additionally the strong alteration of the xenoliths nodules itself. In this study we present a unique and detailed petrographical, petrological and mineralogical dataset applied to these very extraordinary eclogite nodules from the Jwaneng Diamond Mine. Our results show, for the first time strong evidence for mantle metasomatism in the studied area and additionally we calculated the duration of the mantle metasomatic event, which last ∼100 Ma, based on Mg diffusion profiles in garnet. Furthermore, the outcome of our survey show, that the investigated eclogite nodules, has been affected by a mixture of Group I and Group II kimberlites. The formation of Group I kimberlite was caused by the depleted mantle and the development of the later Group II kimberlite by the enriched mantle. The source of the enriched mantle was probably from a megalith, a remnant of a former oceanic crust related to the eastward subduction from the Scotia arc during Jurassic eras. Emplacement of the later mica rich Group II kimberlite leads finally to the explosive eruption kinetics of the kimberlite and consequently to the supersonic uplift of the diamond bearing host rocks. At this point, our results indicates, that supersonic uplift from the Earth´s mantle to the Earth´s surface of the diamondiferous host rocks took place with an velocity of up to ∼1200 km/h (333 m/s) after mantle metasomatism took place. This outcome is based on OH diffusion profiles around totally embedded cracks in garnet. We corroborate this high estimate through velocities expected from viscous laminar flow driven by the pressure gradient. We also evaluate the velocity given by the conversion of gravitational potential energy into kinetic energy, which gives an upper kinetic limit and implies high velocities through the drag coefficients needed to support the dense diamond bearing rock fragment in the melt. This robust evidence for near-accoustic wave speed velocity challenges our understanding of the basic mechanisms that can generate deep and fast cracks within the Earth. The inferred speed of extraction shows that extreme mechanisms must be at work, which potentially starts as a melt filled propagating elastic crack at depth and during ascent accelerates through bubble feedback into its final explosive state

Towards a Self Consistent Plate Mantle Model that Includes Elasticity: Simple Benchmarks and Application to Basic Modes of Convection

One of the difficulties with self consistent plate-mantle models capturing multiple physical features, such as elasticity, non-Newtonian flow properties, and temperature dependence, is that the individual behaviours cannot be considered in isolation. For instance, if a viscous mantle convection model is generalized naively to include hypo-elasticity, then problems based on Earth-like Rayleigh numbers exhibit almost insurmountable numerical stability issues due to spurious softening associated with the co-rotational stress terms. If a stress limiter is introduced in the form of a power law rheology or yield criterion these difficulties can be avoided. In this paper, a novel Eulerian finite element formulation for visco-elastic convection is presented and the implementation of the co-rotational stress terms is addressed. The salient dimensionless numbers of visco-elastic plastic flows such as Weissenberg, Deborah and Bingham numbers are discussed in a separate section in the context of Geodynamics. We present an Eulerian formulation for slow temperature dependent, visco-elastic-plastic flows. A consistent tangent (incremental) formulation of the governing equations is derived. Numerical and analytical solutions demonstrating the effect of visco-elasticity, co-rotational terms are first discussed for simplified benchmark problems. For flow around cylinders we identify parameter ranges of predominantly viscous and visco-plastic and transient behavior. The influence of locally high strain rates on the importance of elasticity and non-Newtonian effects is also discussed in this context. For the case of simple shear we investigate in detail the effect of different co-rotational stress rates and the effect of power law creep. The results show that the effect of the co-rotational terms is insignificant if realistic stress levels are considered (e.g. deviatoric invariant smaller than 1/10 of the shear modulus say). We also consider the basic convection modes of stagnant lid, episodic resurfacing and mobile lid convection as applicable to a cooling planet. The simulations show that elasticity does not have a significant effect on global parameters such as the Nusselt number and the qualitative nature of the basic convection pattern. Our simple benchmarks show, however, also that elasticity plays a significant role for instabilities on the local scale of an individual subduction zone

Modeling episodic fluid-release events in the ductile carbonates of the Glarus thrust

The exposed Glarus thrust displays midcrustal deformation with tens of kilometers of displacement on an ultrathin layer, the principal slip zone (PSZ). Geological observations indicate that this structure resulted from repeated stick-slip events in the presence of highly overpressured fluids. Here we show that the major characteristics of the Glarus thrust movement (localization, periodicity, and evidence of pressurized fluids) can be reconciled by the coupling of two processes, namely, shear heating and fluid release by carbonate decomposition. During this coupling, slow ductile creep deformation raises the temperature through shear heating and ultimately activates the chemical decomposition of carbonates. The subsequent release of highly overpressurized fluids forms and lubricates the PSZ, allowing a ductile fault to move tens of kilometers on millimeter-thick bands in episodic stick-slip events. This model identifies carbonate decomposition as a key process for motion on the Glarus thrust and explains the source of overpressured fluids accessing the PSZ

The formation of micro diamonds in decompression cracks out of equilibrium controlled by the C:O:H ratio in the kimberlitic melt

Diamonds are supposed to be formed in the diamond window under high-pressure conditions due to the polymorph graphite/diamond phase transition. In this study we present for the first time, that natural diamonds can be formed by C:O:H bearing volatiles during the uplift of the kimberlitic melt in eclogites from the Roberts Victor mine, South Africa. Our results give evidence that the kimberlitic melt acts like a catalyst, and therefore the C:O:H ratio in the kimberlite changes through the uplift of the kimberlite permanently, caused by the formation of hydrous and carbonatitic minerals within the kimberlitic melt. This catalytic process leads to the growth of light carbon bearing molecules and under favorable thermodynamic, stoichiometric and kinetic conditions micro diamonds can be formed, even under lower pressure conditions outside of the diamond window. High-spatial-resolution synchrotron based FT-IR has been used to detect C:O:H-bearing volatiles around planar defect structures in garnet. In micro diamond bearing planar defect structures, a correlation between C:O:H-bearing volatiles could be identified whereas in micro diamond free planar defect structures no correlation of the different C:O:H containing volatiles is visible. The conclusions from our study proves that C:O:H-bearing volatiles, and their distribution pattern around the studied micro cracks, are suggestive of the formation of micro diamonds in natural eclogites