Maximal oil recovery by simultaneous condensation of alkane and steam

This paper deals with the application of steam to enhance the recovery from petroleum reservoirs. We formulate a mathematical and numerical model that simulates coinjection of volatile oil with steam into a porous rock in a one-dimensional setting. We utilize the mathematical theory of conservation laws to validate the numerical simulations. This combined numerical and analytical approach reveals the detailed mechanism for thermal displacement of oil mixtures discovered in laboratory experiments. We study the structure of the solution, determined by the speeds and amplitudes of the several nonlinear waves involved. Thus we show that the oil recovery depends critically on whether the boiling-point of the volatile oil is around the water boiling temperature, or much below or above it. These boiling-point ranges correspond to three types of wave structures. When the boiling point of the volatile oil is near the boiling point of water, the striking result is that the speed of the evaporation front is equal or somewhat larger than the speed of the steam condensation front. Thus the volatile oil condenses at the location where the steam condenses too, yielding virtually complete oil recovery. Conversely, if the boiling point is too high or too low, there is incomplete recovery. The condensed volatile oil stays at the steam condensation location because the steam condensation front is a physical shock.GeotechnologyCivil Engineering and Geoscience

Modeling of wettability alteration during spontaneous imbibition of mutually soluble solvents in mixed wet fractured reservoirs (poster)

Mutually-soluble solvents can enhance oil recovery both in mixed-wet fractured reservoirs. When a partially waterwet matrix is surrounded by an immiscible wetting phase in the fracture, spontaneous imbibition is the most important production mechanism. Initially, the solvent moves with the imbibing brine into the core. However, upon contact with oil, as the chemical potential of the mutual solvent is different in both phases, diffusion occurs and the solvent is transported in the oleic phase. Through the migration of the mutually soluble component from the aqueous phase into the oleic phase, oil properties and/or rock-fluid interactions are modified. The hypothesis in this work is that a mutually-soluble solvent improves the ultimate recovery and the imbibition rate in mixed-wet cores. The main recovery mechanisms are the wettability change of the mixed-wet cores, oil swelling and oil viscosity reduction. In this paper the numerical modeling of spontaneous imbibition of Mutually soluble solvent in mixed-wet cores in presented. We implemented the wettability alteration, the oil swelling mechanism, the oil viscosity reduction mechanism, the IFT reduction, and the density reduction mechanisms in the numerical model. Our numerical studies show that the most important production mechanism in the mixed-wet systems are the oil swelling and the wettability alteration and the second most important mechanism is the oil viscosity reduction. The effect of the IFT reduction and the density reduction in the oil production is not significant. The numerical results show an improvement of 27%.Geoscience & EngineeringCivil Engineering and Geoscience

Modeling of non-equilibrium effects in solvent-enhanced spontaneous imbibition in fractured reservoirs (poster)

In fractured reservoirs, much of the oil is stored in low permeable matrix blocks that are surrounded by a high permeability fracture network. Therefore, production from fractured reservoir depends on the transfer between fracture and matrix, which is critically dependent on their interaction. COMSOL Multiphysics® was implemented to model the process of penetration of the aqueous phase into an oil-filled core due to both capillary and gravity forces. The theoretical imbibition production curve is faster than the experimental production curve, which implies that the imbibition is occurring much faster than in the experiment. This indicates delayed imbibition, which can in principle be modelled using dynamic capillary pressure and relative permeability effects.Geoscience & EngineeringCivil Engineering and Geoscience

Modeling of nonequilibrium effects in the gravity driven countercurrent imbibition (excerpt)

Geoscience & EngineeringCivil Engineering and Geoscience

Analysis of model equations for stress-enhanced diffusion in coal layers. Part I: Existence of a weak solution

GeotechnologyCivil Engineering and Geoscience

Modeling of Non-equilibrium Effects in the Gravity Driven Countercurrent Imbibition

Geoscience & EngineeringCivil Engineering and Geoscience

Process-based upscaling of reactive flow in geological formations

Recently, there is an increased interest in reactive flow in porous media, in groundwater, agricultural and fuel recovery applications. Reactive flow modeling involves vastly different reaction rates, i.e., differing by many orders of magnitude. Solving the ensuing model equations can be computationally intensive. Categorizing reactions according to their speeds makes it possible to greatly simplify the relevant model equations. Indeed some reactions proceed so slow that they can be disregarded. Other reactions occur so fast that they are well described by thermodynamic equilibrium in the time and spatial region of interest. At intermediate rates kinetics needs to be taken into account. In this paper, we categorize selected reactions as slow, fast or intermediate. We model 2D radially symmetric reactive flow with a reaction-convection-diffusion equation. We show that we can subdivide the PeDaII phasespace in three regions. Region I (slow reaction); reaction can be ignored, region II (intermediate reaction); initially kinetics need to be taken into account, region III (fast reaction); all reaction takes places in a very narrow region around the injection point. We investigate these aspects for a few specific examples. We compute the location in phase space of a few selected minerals depending on salinity and temperature. We note that the conditions, e.g., salinity and temperature may be essential for assigning the reaction to the correct region in phase space. The methodology described can be applied to any mineral precipitation/decomposition problem and consequently greatly simplifies reactive flow modeling in porous media.Mathematical PhysicsPetroleum Engineerin

Experimental And Theoretical Investigation Of Natural Convection In CCS: Onset Time, Mass-Transfer Rate, Capillary Transition Zone, And Heat Of Dissolution

We study the enhanced mass transfer of CO2 in water for a CO2 saturated layer on top of a water saturated porous medium, experimentally and theoretically. A relatively large experimental set-up with a length of 0.5 m and a diameter of 0.15 m is used in pressure decay experiments to minimize the error of pressure measurement due to temperature fluctuations and small leakages. The experimental results were compared to the theoretical result in terms of onset time of natural convection and rate of mass transfer of CO2 in the convection dominated process. In addition, a non-isothermal multicomponent flow model in porous media, is solved numerically to study the effect of the heat of dissolution of CO2 in water on the rate of mass transfer of CO2. The effect of the capillary transition zone on the rate of mass transfer of CO2 is also studied theoretically. The simulation results including the effect of the capillary transition zone show a better agreement with experimental results compared to the simulation result without considering a capillary transition zone. The simulation results also show that the effect of heat of dissolution on the rate of mass transfer is negligibleGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Petroleum Engineerin

Geothermal energy combined with CO2 sequestration: An additional benefit

In this transition period from a fossil-fuel based society to a sustainable-energy society, it is expected that CO2 capture and subsequent sequestration in geological formations plays a major role in reducing greenhouse gas emissions. An alternative for CO2 emission reduction is to partially replace conventional-energy for heating and cooling buildings (e.g., cogeneration units) with geothermal energy. A mixture of CO2 with cold return water injected into geothermal reservoirs can be the integration of geothermal-energy production and subsurface CO2 storage. In this process, mixed CO2-water is injected, while hot water is simultaneously produced from the production well. The process may end when CO2 either in the aqueous phase or in the CO2-rich phase breaks through. It depends on the function of the CO2 as being a stored medium or being a source for gasdrive water production. In this study, we discuss the influence of various CO2 injection volumes on low-enthalpy production mechanisms/storage of CO2 in relation to the production of hot water from the geothermal aquifer systems. Furthermore, we provide injection-screening conditions for optimal geothermal recovery, maximal storage of CO2 and/or re-use of a CO2-water cycle. For any energy source, one important attribute is the recovery efficiency, i.e., how much energy can be extracted from this source with respect to the amount of energy invested during the process of energy extraction. In this work, we estimate the total amount of energy invested for mixed CO2-water injection into the geothermal reservoir, using an “effectiveenergy” analysis. Furthermore, we provide a cursory evaluation of the economics of the proposed project assuming that we can relate the energy balance to an economic analysis. In such a conversion, the notion intensity of embodied energy plays a central role. We also introduce a plot of the heat-energy extraction and the storage capacity, which can be used to locate optimal in-situ conditions. These results, which are plotted in a heat-energy/storage-capacity diagram, are discussed in detail. Aspects regarding specific geoand technical infrastructure are ignored.Geoscience & EngineeringCivil Engineering and Geoscience

Negative Saturation Approach for Non-Isothermal Compositional Two-Phase Flow Simulations

This article deals with developing a solution approach, called the non-isothermal negative saturation (NegSat) solution approach. The NegSat solution approach solves efficiently any non-isothermal compositional flow problem that involves phase disappearance, phase appearance, and phase transition. The advantage of the solution approach is that it circumvents using different equations for single-phase and two-phase regions and the ensuing unstable procedure. This paper shows that the NegSat solution approach can also be used for non-isothermal systems. The NegSat solution approach can be implemented efficiently in numerical simulators to tackle modeling issues for mixed CO2–water injection in geothermal reservoirs, thermal recovery processes, and for multicontact miscible and immiscible gas injection in oil reservoirs. We illustrate the approach by way of example to cold mixed CO2–water injection in a 1D geothermal reservoir. The solution is compared with an analytical solution obtained with the wave-curve method (method of characteristics) and shows excellent agreement. A complete set of simulations is carried out, which identifies six bifurcations. The two main bifurcations are (1) when the most downstream compositional wave is replaced by a compositional shock and (2) when an extra Buckley–Leverett rarefaction appears. The plot of the useful energy (exergy) versus the CO2 storage capacity shows a Z-shape. The top horizontal part represents a branch of high exergy recovery/relatively lower storage capacity, whereas the bottom part represents a branch of lower exergy recovery/higher storage capacity.Geoscience & EngineeringCivil Engineering and Geoscience