Producing geothermal heat from production water causes cooldown from the reservoir temperature up to 250C at fluid pressures from over 100 bar to 10 bar.During the process degassification of CO2 and methane cause reduction in pH and by that dissolution and precipitation of minerals.At depth, mineral precipitation in the reservoir restricts flow paths through the cyclic system, resulting into injectivity loss, by that higher injection pressures result in additional costs.Due the large number of timesteps,numerically modeling mineralization, accounting for the reaction kinetics, can be computationally expensive. These simulations are less expensive when assuming a local equilibrium between the reactants and reaction-products. As described in Meulenbroek et all. (2020) we present an analytical model for mineral precipitation in a low-enthalpy geothermal reservoir.The three different reaction regimes are (1) fast reactions (2) very slow reactions (3) reaction/transport intermediate zone.We focus on the near-wellbore region in the reservoir, where precipitation can behave as a ‘skin’ and has a more dramatic impact on the injectivity than precipitation further downstream. Our numerical model uses a coupling approach between PHREEQC and COMSOL utilizing the qualification of the different reaction regimes. This methodology was validated by using an analytical solution of a specific mineralization case. In addition it was compared to a field case. @en

1D water oil displacement in porous media is usually described by the Buckley-Leverett equation or the Rapoport-Leas equation when capillary diffusion is included. The rectilinear geometry is not representative for near well oil displacement problems. It is therefore of interest to describe the radially symmetric Buckley-Leverett or Rapoport-Leas equation in cylindrical geometry (radial Buckley-Leverett problem). We can show that under appropriate conditions, one can apply a similarity transformation (r, t) → η= r²/ (2 t) that reduces the PDE in radial geometry to an ODE, even when capillary diffusion is included (as opposed to the situation in the rectilinear geometry (Yortsos, Y.C. (Phys. Fluids 30(10),2928–2935 1987)). We consider two cases (1) where the capillary diffusion is independent of the saturation and (2) where the capillary diffusion is dependent on the saturation. It turns out that the solution with a constant capillary diffusion coefficient is fundamentally different from the solution with saturation-dependent capillary diffusion. Our analytical approach allows us to observe the following conspicuous difference in the behavior of the dispersed front, where we obtain a smoothly dispersed front in the constant diffusion case and a power-law behavior around the front for a saturation-dependent capillary diffusion. We compare the numerical solution of the initial value problem for the case of saturation-dependent capillary diffusion obtained with a finite element software package to a partially analytical solution of the problem in terms of the similarity variable η.

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In this paper, we assess and model new strategies for integration of geothermal energy with gas production in the Oude Leede Gas Field in the Netherlands. We investigate the injection of cooled geothermal water into a gas field located just few kilometers away from the geothermal reservoir in the Netherlands. This synergy type can be considered for economic natural gas production from a gas field in the proximity of a geothermal doublet project and improved energy production in the geothermal reservoir. A 3-D model including a gas trapping mechanism was built to study the possible production potential of the gas field. Water flooding compensates pressure loss by reducing the pore space, however it complicates the process by introducing trapped gas. We studied the effect of injection rate, permeability, saturation condition before flooding and reservoir pressure on the ultimate gas recovery and the residual trapped gas saturation. Injecting water will increase the ultimate recovery factor for higher abandonment pressure. Higher water injection rates will keep the reservoir pressure up, increase the trapped gas saturation, and hence reduce the maximum recovery. The presence of heterogeneity and capillary forces has minor effects on the gas recovery factor. The exergy recovery factor of a water injection process is higher than a gas compression process due to the large amounts of energy required for compression. Considering net present value (NPV) analysis for a higher abandonment pressure, water injection is economically preferable, however not feasible. At a lower abandonment pressure, natural gas depletion can easily compete with the water injection process due to the higher costs of water injection and drilling.@en

This paper develops the theory of liquid-gas filtration combustion, when an oxidizer (air) is injected into porous rock containing two-component liquid fuel. We found a qualitatively new combustion mechanism controlled by the successive vaporization and condensation of the liquid phase sustained by the reaction. Motivated by the problem of recovery of light oil by air injection, as an enhanced oil recovery method, we consider a liquid composed of light and medium pseudo-components. The light part is allowed to oxidize and vaporize, while the medium part is non-volatile and only oxidizes. The liquid mobility depends strongly on its composition, with a small viscosity (high mobility) of the purely light component and a high viscosity for the purely medium (immobile) component. We show that the combined vaporization and condensation in the combustion wave leads to accumulation of the light component in the upstream part of the wave, considerably increasing mobility and, therefore, playing a crucial role in the mechanism of the combustion process. We describe physical implications of this effect, as well as its importance for applications. The results are confirmed by numerical simulations.@en