Showing papers on "Viscous fingering published in 2022"

An improved multicomponent pseudopotential lattice Boltzmann method for immiscible fluid displacement in porous media

Abstract: Immiscible fluid displacement in porous media occurs in several natural and industrial processes. For example, during petroleum extraction from porous rock reservoirs, water is used to displace oil. In this paper, we investigate the primary drainage and imbibition in a heterogeneous porous medium using an improved numerical model based on the multicomponent pseudopotential lattice Boltzmann method. We apply recent developments from the literature and develop new pressure boundary conditions. We show that the proposed model is able to simulate realistic viscosity ratios, and it allows independent tuning of surface tension from viscosity. Moreover, the model suppresses a nonphysical behavior of previous schemes, in which trapped fluid volumes significantly change with time. Furthermore, we show that the developed model correctly captures the underlying physical phenomena of fluid displacements. We simulate oil–water flows and verify that the measured values of irreducible water and residual oil saturations are realistic. Finally, we vary the wetting conditions of the porous medium to represent different wettability states. For the different scenarios, we show that the simulations are in good agreement with the experimental results.

The Role of Immiscible Fingering on the Mechanism of Secondary and Tertiary Polymer Flooding of Viscous Oil

Abstract: Abstract Immiscible viscous fingering in porous media occurs when a low viscosity fluid displaces a significantly more viscous, immiscible resident fluid; for example, the displacement of a higher viscosity oil with water (where μ o > > μ w ). Classically, this is a significant issue during oil recovery processes, where water is injected into the reservoir to provide pressure support and to drive the oil production. In moderate/heavy oil, this leads to the formation of strong water fingers, bypassed oil and high/early water production. Polymer flooding, where the injected water is viscosified through addition of high molecular weight polymers, has often been applied to reduce the viscosity contrast between the two immiscible fluids. In recent years, there has been significant development in the understanding of both the mechanism by which polymer flooding improves viscous oil recovery, as well as in the methodologies available to directly simulate such processes. One key advance in modelling the correct mechanism of polymer oil recovery in viscous oils has been the development of a method to accurately model the “simple” two-phase immiscible fingering (Sorbie in Transp Porous Media 135:331–359, 2020). This was achieved by first choosing the correct fractional flow and then deriving the maximum mobility relative permeability functions from this. It has been proposed that central to the polymer oil recovery is a fingering/viscous crossflow mechanism, and a summary of this is given in this paper. This work seeks to validate the proposed immiscible fingering/viscous crossflow mechanism experimentally for a moderately viscous oil ( μ o = 84 mPa.s at 31 °C; μ w = 0.81 mPa.s; thus, ( μ o / μ w ) ~ 104) by performing a series of carefully monitored core floods. The results from these experiments are simulated directly to establish the potential of our modified simulation approach to capture the process (Sorbie, et al., 2020). Both secondary and tertiary polymer flooding experiments are presented and compared with the waterflood baselines, which have been established for each core system. The oil production, water cut and differential pressure are then matched directly using a commercial numerical reservoir simulator, but using our new “fractional flow” derived relative permeabilities. The use of polymer flooding, even when applied at a high water cut (80% after 0.5 PV of water injection), showed a significant impact on recovery; bringing the recovery significantly forward in time for both tertiary and secondary polymer injection modes—a further 13–16% OOIP. Each flood was then directly matched in the simulator with excellent agreement in all experimental cases. The simulations allowed a quantitative visualisation of the immiscible finger propagation from both water injection and the banking of connate water during polymer flooding. Evidence of a strong oil bank forming in front of the tertiary polymer slug was also observed, in line with the proposed viscous crossflow mechanism. This work provides validation of both polymer flooding’s viscous crossflow mechanism and the direct simulation methodology proposed by Sorbie et al. (Transp Porous Media 135:331–359, 2020). The experimental results show the significant potential for both secondary and tertiary polymer flooding in moderate/heavy oil reservoirs.

Electrically controlled self-similar evolution of viscous fingering patterns

Abstract: A controlling protocol for the traditional viscous fingering instability is presented. By coupling time-dependent injection rates with time-varying electric currents, it is shown via boundary integral simulations that the strategy allows control of the self-similar regime (delay, promote, or suppress) and the relative finger instability size without altering the system's physical parameters.

Horizontal miscible displacements through porous media: the interplay between viscous fingering and gravity segregation

Abstract: Abstract We consider miscible displacements in two-dimensional homogeneous porous media where the displacing fluid is less viscous and has a different density than the displaced fluid. We find that the dynamics evolve through nine possible regimes depending on the viscosity ratio, strength of density variations and the strength of the background flow, as characterized by the Péclet number. At early times the interface is dominated by longitudinal diffusion before undergoing a transition to a slumping regime where vertical flow is important. At intermediate times, vertical flow and diffusion can be neglected and there are three different limiting solutions: a fingering limit; an injection-driven gravity-current limit; and a density-driven gravity-current limit. Finally at late times, transverse diffusion becomes important and there is a transition from an apparent shutdown regime to a viscously enhanced Taylor-slumping regime. In each of the regimes, the dominant scalings are identified and reduced-order models for the evolution of the concentration field are developed. Lastly, three case studies are considered to illustrate the dominant physical balances in the geophysically relevant setting of geological $\textrm {CO}_2$ storage.

Fabrication of meso sized structures through controlled viscous fingering in Lifting Plate Hele-Shaw Cell with holes and slots

Abstract: Lifting plate Hele-Shaw cell involves a high viscous fluid sandwiched between two parallel plates. The low viscosity fluid (air) enters from the periphery when one of the plates is lifted away from another plate. The air penetrates a high viscous fluid at various points from the periphery. This penetration causes the formation of a tree-branch-like structure called viscous fingering. Due to this insertion, sandwiched fluid changes its structure. This structural change is known as instability. The viscous fingers generated through this flow are highly random and unstable. This study presents methods to control the instabilities. The study reports control techniques by providing anisotropies (holes and slots) on any one of the plates. The study further presents the effect of size, position, and the orientation of these holes and slots on the viscous fingering exhaustively. Deployment of these control techniques leads to the emergence of new fabrication techniques with the potential to develop meso-sized finger patterns spontaneously without expensive setup as otherwise required in the lithography process. To demonstrate the capability of this proposed fabrication technique, various net-shaped patterns available in nature are mimicked. These developed miniature patterns can be used in various applications such as micro-mixers, micro-heat exchangers, etc.

Nanofibers Fabrication by Blown‐Centrifugal Spinning

Abstract: Here, a new, simple, and effective fabrication method of random and aligned nanofibers by utilizing centrifugal spinning and solution blowing is shown. This process, termed blown-centrifugal spinning (BCS), capitalizes on a rotating reservoir and uses high velocity expanding gas to extrude fibers. The polymer solution is injected from the orifice of the reservoir and is brought in contact with the airflow on the reservoir's surface. The fiber morphology bears a relationship with airflow rate, solution viscosity, surface tension, and solvent evaporation rate. Fiber formation in the flowing stream is controlled by dynamic pressures, surface tension, and viscous forces.

Immiscible Viscous Fingering: The Simulation of Tertiary Polymer Displacements of Viscous Oils in 2D Slab Floods

Abstract: Immiscible viscous fingering in porous media occurs when a high viscosity fluid is displaced by an immiscible low viscosity fluid. This paper extends a recent development in the modelling of immiscible viscous fingering to directly simulate experimental floods where the viscosity of the aqueous displacing fluid was increased (by the addition of aqueous polymer) after a period of low viscosity water injection. This is referred to as tertiary polymer flooding, and the objective of this process is to increase the displacement of oil from the system. Experimental results from the literature showed the very surprising observation that the tertiary injection of a modest polymer viscosity could give astonishingly high incremental oil recoveries (IR) of ≥100% even for viscous oils of 7000 mPa.s. This work seeks to both explain and predict these results using recent modelling developments. For the 4 cases (µo/µw of 474 to 7000) simulated in this paper, finger patterns are in line with those observed using X-ray imaging of the sandstone slab floods. In particular, the formation of an oil bank on tertiary polymer injection is very well reproduced and the incremental oil response and water cut drops induced by the polymer are very well predicted. The simulations strongly support our earlier claim that this increase in incremental oil displacement cannot be explained solely by a viscous “extended Buckley-Leverett” (BL) linear displacement effect; referred to in the literature simply as “mobility control”. This large response is the combination of this effect (BL) along with a viscous crossflow (VX) mechanism, with the latter VX effect being the major contributor to the recovery mechanism.

Anisotropic Approach to Control Viscous Fingering Pattern Generated in Lifting Plate Hele-Shaw Cell

Abstract: Stability is one of the important aspects of life, our everyday systems — the permanence of things. When this stability gets disturbed, instability is produced. Sometimes this instability is desirable, and sometimes not. In the crude oil extraction process, fluid instability is observed. Saffman and Taylor explored the concept of the Hele-Shaw cell to study these instabilities. The Hele-Shaw cell involves a high viscous fluid sandwiched between two parallel plates, and the low viscosity fluid enters from the periphery. Insertion of low viscous fluid into a high viscous fluid generates a pattern that is a resemblance to a finger. This phenomenon is called viscous fingering. In this paper, the authors control the instabilities and mimic patterns available in nature. These instabilities can be controlled by controlling one of the fluids in the cell. Here authors control the low viscous fluid (air) by providing anisotropies. Anisotropy means providing holes and slots on any plate of the cell. This anisotropy guides air to interact with high viscous fluid at some desired location. The authors further studied the effect of size, position, the orientation of these holes and slots on the viscous fingering exhaustively.

Enhanced thermal fingering in a shear-thinning fluid flow through porous media: Dynamic pore network modeling

Abstract: Thermal-viscous fingering instability in porous media is a common phenomenon in nature as well as in many scientific problems and industrial applications. Despite the importance, however, thermal transport in flow of a non-Newtonian fluid in porous media and the resulting fingering has not been studied extensively, especially if the pore space is heterogeneous. In this paper, we propose a pore network model with full graphics processing unit-parallelized acceleration to simulate thermal transport in flow through three-dimensional unstructured pore networks at centimeter scale, containing millions of pores. A thermal Meter equation is proposed to model temperature- and shear stress-dependent rheology of the non-Newtonian fluids. After comparing the simulation results with an analytical solution for the location of the thermal front in a spatially uncorrelated pore network, thermal transport in flow of both Newtonian and non-Newtonian fluids is studied in the spatially uncorrelated and correlated pore networks over a range of injection flow rates. The simulations indicate that the injection flow rate, the shear-thinning rheology, and the morphological heterogeneity of the pore space all enhance thermal-viscous fingering instability in porous media, but with distinct patterns. In spatially correlated networks, the average temperature and apparent viscosity at the breakthrough point in flow of a shear-thinning fluid exhibit non-monotonic dependence on the injection flow rate. An analysis of the fractal dimension of thermal patterns at the breakthrough point supports the conclusion. The results highlight the importance of designing optimal flow conditions for application purposes.

Immiscible Viscous Fingering: Modelling Unstable Water–Oil Displacement Experiments in Porous Media

Abstract: Abstract Viscous fingering in porous media occurs when the ( miscible or immiscible ) displacing fluid has a lower viscosity than the displaced fluid. For example, immiscible fingering is observed in experiments where water displaces a much more viscous oil. Modelling the observed fingering patterns in immiscible viscous fingering has proven to be very challenging, which has often been identified as being due to numerical issues. However, in a recent paper (Sorbie et al. in Transp. Porous Media 133:331–359, 2020) suggested that the modelling issues are more closely related to the physics and formulation of the problem. They proposed an approach based on the fractional flow curve, $${f}_{w}^{*}$$ f w ∗ , as the principal input, and then derived relative permeabilities which give the maximum total mobility. Sorbie et al . were then able to produce complex, well-resolves immiscible finger patterns using elementary numerical methods. In this paper, this new approach to modelling immiscible viscous fingering is tested by performing direct numerical simulations of previously published experimental water/oil displacements in 2D sandstone porous media. Experiments were modelled at adverse viscosity ratios ( $${\mu }_{o}/{\mu }_{w}$$ μ o / μ w ), with oil viscosities ranging from μ o = 412 to 7000 cP, i.e. for a viscosity ratio range, ( $${\mu }_{o}/{\mu }_{w}$$ μ o / μ w ) $$\sim$$ ∼ 400–7000. These experiments have extensive production data as well as in situ 2D immiscible fingering images, measured by X-ray scanning. In all cases, very good quantitative agreement between experiment and modelling results is found, providing a strong validation of the new modelling approach. The underlying parameters used in the modelling of these unstable immiscible floods, the $${f}_{w}^{*}$$ f w ∗ functions, show very consistent and understandable variation with the viscosity ratio, ( $${\mu }_{o}/{\mu }_{w}$$ μ o / μ w ).

Experimental study on the role of polymer addition in Saffman-Taylor instability in miscible flow displacement

Abstract: The role of nonlinear rheology of polymeric fluids in finger formation and the ensuing morphology of the patterns in miscible flow displacement is examined experimentally. The poly(ethylene oxide) (PEO) is introduced in either displaced or displacing fluid. The PEO solutions exhibit shear-thinning viscosity as well as normal stresses. As viscous fingering is primarily caused by the viscosity contrast between two miscible fluids, the zero-shear viscosities of the two fluids are controlled mainly by their composition. The contribution of rheological behaviour in fingering is studied by varying the molecular weight of the polymer. The development of fingering patterns in PEO solutions are observed to be more complex showing more branches and tip-splitting vis-\`a-vis Newtonian fluid even for the same value of effective viscosity contrast regardless of polymer addition in either fluids. Particularly, flow displacement with displaced PEO solution exhibits significantly intensified patterns such that a fractal-like growth is observed when PEO solution of either high concentration or high molecular weight is being displaced. The additional non-linear behavior, side-branching, tip-splitting, and shielding, is attributed to the inhomogeneity in fluid viscosity and normal stresses (or, elasticity) due to local flow behaviour. While shear-thinning behaviour promotes the longitudinal growth of fingers leading to shielding effect, the presence of normal stresses inhibits longitudinal growth of fingers promoting fingers in the transverse direction that imparts tip-splitting. Overall, the nonlinear rheology of the fluids gives rise to the effects, in addition to the viscosity modifications, and hence is crucial for determining the morphology of the fingering instability.

Competition of gravity and viscous forces in miscible vertical displacement in a three-dimensional porous medium

Abstract: When viscosity and density contrast exist in the vertical miscible displacement in porous media between two fluids, the interplay between the viscous force and gravity determines the interface stability. Two stability criteria are derived to determine the interface stability. Hill's and Dumore's stability criteria are used to determine the interface stability of the sharp and diffused interface, respectively. In this study, we visualized the crossover between unstable displacement and stable displacement for a vertical displacement in porous media using microfocused x-ray computed tomography. The experiments were divided into four possible configurations: (1) unconditionally stable (gravitationally stable-viscously stable), (2) unconditionally unstable (gravitationally unstable-viscously unstable), (3) conditionally stable (gravitationally stable-viscously unstable), and (4) conditionally stable (gravitationally unstable, viscously stable). The structure of the displacement interface was visualized for the critical velocity ratio (V/Vc) in the range of 0.5–11.9. In the conditionally stable configurations 3 and 4, a crossover between stable and unstable displacements was observed. We found that Dumore's stability criterion is more appropriate for predicting interface stability than Hill's stability criterion. Viscous fingering occurs in configuration 3 when V/Vc is higher than Dumore's critical velocity, whereas gravity fingering occurs in configuration 4 when V/Vc is lower than Dumore's critical velocity. Similar events in two-dimensional experiments, such as tip-splitting, shielding, and coalescence, were also observed three-dimensionally. The significant changes in the mixing length and sweep efficiency signify the crossover between the stable and unstable displacements.

Heavy Oil Recovery by Alkaline-Cosolvent-Polymer Flood: A Multiscale Research Using Micromodels and Computed Tomography Imaging

Abstract: Summary For reservoirs containing oil with a high total acid number, the alkali-cosolvent-polymer (ACP) flood can promote the formation of microemulsion rather than viscous macroemulsion and achieve good mobility control. The enhanced oil recovery (EOR) performance of ACP flood has been studied at core and reservoir scale in detail; however, the effect of ACP flood on residual oil still lacks enough research. In this paper, a micromodel with a single channel is used to clarify the dynamic effects of alkali-cosolvent (AC) and ACP solutions on the residual oil after waterflood. Based on this, medical computed tomography (Medical-CT) scan and microcomputed tomography (Micro-CT) scan are used in combination to visualize microscale flow and reveal the mechanisms of residual oil reduction during ACP flood. The heterogeneous core plugs containing two layers of different permeabilities are used for coreflood experiments to clarify the EOR performance of ACP flood in heterogeneous reservoirs. The oil saturation is monitored by Medical-CT. Then, two core samples are drilled in each core plug that is used in the coreflood experiment. The decrease of residual oil saturation caused by ACP flood is further quantified by Micro-CT imaging. Results show that ACP flood is 14.5% oil recovery higher than AC flood (68.9%) in relative high permeability layers (HPLs) and 17.9% higher than AC flood (26.3%) in relative low permeability layers (LPLs). Compared with AC flood, ACP flood shows a more uniform displacement front, which implies that the injected polymer effectively weakened the viscosity fingering. This is similar to the experimental results demonstrated visually in the micromodel experiments. ACP solution first generates an oil bank by the mobility ratio improvement to mobilize residual oil and then dissolve and emulsify residual oil under ultralow interfacial tension (IFT) conditions. Moreover, a method that can calculate the ratio of oil/water distribution in each pore is developed to establish the relationship between the residual oil saturation of each pore and its pore size, and concluded that they follow the power-law correlation.