Showing papers by "Abhijit Chaudhuri published in 2020"

Potential of $$\hbox {CO}_{2}$$CO2 based geothermal energy extraction from hot sedimentary and dry rock reservoirs, and enabling carbon geo-sequestration

Abstract: Carbon capture and sequestration (CCS) is necessary to mitigate global warming caused by anthropogenic $$\hbox {CO}_{2}$$ emissions in the atmosphere. However, due to very high storage cost, it is difficult to sustain the CCS industry. The hot sedimentary and dry rock reservoirs with very high temperature can support both geothermal energy production, and carbon geosequestration economically, provided the $$\hbox {CO}_{2}$$ is used as a heat-carrying fluid with proper optimization of injection parameters according to reservoir conditions. In this paper we have reviewed past studies discussing the working mechanisms, pressure management strategies and various advantages of energy extraction from hydrothermal reservoirs by $$\hbox {CO}_2$$ plume geothermal technology and hot dry rock— enhanced geothermal system (EGS) technology. Past studies highlighted that due to very high thermal expansivity and mobility, supercritical $$\hbox {CO}_2$$ can produce more heat than water-EGS. For low enthalpy (around 50 $$^\circ$$C) and shallow (0.5–1.5 km) reservoirs, $$\hbox {CO}_2$$ can fetch more heat than water because of higher heat capacity. Other advantages of CCS and EGS are (i) the production of brine or $$\hbox {CO}_2$$ assisting to manage the reservoir pressure and restrict the fluid interference with neighboring reservoirs, (ii) the fluid loss, which is a significant concern in a water-EGS but for $$\hbox {CO}_{2}$$-EGS it is environmentally friendly, and (iii) higher pressure and cold fluid injection induced geological deformation and microseismicity are relatively less for $$\hbox {CO}_2$$-EGS than water-EGS. In this paper, we have also discussed various challenges of $$\hbox {CO}_2$$-EGS to enable CCS in hydrothermal reservoir and hot dry rock system.

CFD modeling of gypsum scaling in cross-flow RO filters using moments of particle population balance

Abstract: Gypsum scaling over a RO membrane significantly reduces the permeate flux. Since, the phenomenon is linked to concentration polarization; the present study aims to understand the effect of high shear rates over the membrane in reducing gypsum scaling of cross-flow RO filters. We have proposed an integrated CFD and moment-based population balance (MPB) formulation which is less complex than tracking the growth of individual particles. Most of the previous studies on modeling of scaling and permeate flux decline employing MPB formulation were limited to dead-end filters. The present numerical model for cross-flow RO filter has been verified by comparing the precipitate mass and permeate flux decline with the published results for channel filter. This model has been employed for different cross-flow conditions and geometries. We have demonstrated that scaling can be mitigated by increasing the shear rate over the membrane surface. In roto-dynamic RO filters, a 50% increase in the initial permeate discharge can be achieved, and permeate flux decline in time can be restrained if the shear rate is increased by rotating the disk. For a channel of identical membrane area, a similar improvement of permeate discharge requires an approximately two orders of magnitude higher feed discharge. In a channel, gypsum scale formation is significant at larger distances from the inlet. While for roto-dynamic filters, scaling occurs at the stagnation zone near the axis of rotation, the scaling potential decreases with radius. Additionally, we have also discussed some striking differences between fouling and scaling patterns in cross-flow RO filters.

Numerical analysis of viscous fingering and oil recovery by surfactant and polymer flooding in five-spot setup for water and oil-wet reservoirs

Abstract: Surfactant and polymer are used to improve oil recovery. The micro-emulsion phase composition, viscosity and interfacial tension vary with salinity and injection concentration of chemicals. The viscosity contrast which is very large for heavy oil reservoirs, results in various types of viscous instabilities. There is no comprehensive field-scale modelling on the viscous fingering affecting the oil recovery for different types of surfactant-polymer (SP) flooding. We numerically simulated the above phenomena for different types of SP flooding in five-spot wells setup for both water-wet and oil-wet reservoirs. We have observed that many saturation shocks and banks of micro-emulsion, water and polymer are formed. The viscous fingering at the interface of these banks depend on the reservoir wettability, micro-emulsion phase behaviour and injection concentration of chemicals. Fingering can be suppressed by changing the duration of injection and concentration of surfactant and polymer. We have shown that Type II(+) flooding produces more oil than Type II(−) and Type III. But the oil production by Type II(−) can be increased by adopting better injection strategies. We have made a quantitative comparison of output, i.e., oil recovery vs inputs such as injected mass of chemicals, injection duration and pumping energy, which is of interest to industry. The pumping energy requirement is higher for Type II(−) flooding irrespective of wettability. Our results show that short duration injection of surfactant with multistep reduction of polymer concentration suppresses viscous instabilities and produce more than 90% OOIP.

Coupled multiphase flow and geomechanics simulation of hydrate dissociation using FVM-FEM co-located variables arrangement

Abstract: Natural gas hydrates, which are ice like crystalline solids, contain tremendous amount of potential hydrocarbon gas. Gas recovery through hydrate dissociation can be achieved through depressurization, inhibitor injection and thermal stimulation. The hydrate dissociation by depressurization involves significant pressure and temperature gradients as the dissociation process is highly endothermic. The destabilization of solid hydrate into fluid constituents causes loss of cementation which can alter the stress field which in turn changes the porosity and permeability of the hydrate bearing medium causing subsidence. In the present study, a thermohydro-mechanical-chemical (THMC) coupled numerical simulator is developed accounting for the hydrate phase change kinetics, non-isothermal multiphase flow and geomechanics. The point centered or node centered finite volume method is used for space discretization of flow and energy equations while the finite element method is used for stress equilibrium equation. This procedure requires the flow and mechanics variables to be co-located. The finite volumes are constructed around the flow variables defined at nodes while the finite element is defined by the corner nodes. The volumetric strain rate term in the flow equations, which couples the flow and geomechanics equations, is evaluated by interpolating the volumetric strains calculated over the finite elements to the finite volumes. Our simulations show that this procedure results in a stable convergence of the solution without the need for any stabilizing terms due to co-located variable arrangement. Our simulations also show that the iterative coupled approach, where the flow and geomechanics equations are solved separately and sequentially, gives stable convergence without any additional split terms due to sequential but iterative solving of the coupled equations.