Mechanistic foam modeling and simulations: gas injection during surfactant-alternating-gas processes using foam-catastrophe theory

The use of foam for mobility control is a promising means to improve sweep efficiency in subsurface applications such as improved/enhanced oil recovery and aquifer remediation. Foam can be introduced into geological formations by injecting gas and surfactant solutions simultaneously or alternatively. Alternating gas and surfactant solutions, which is often referred to as surfactant-alternating-gas (SAG) process, is known to effectively create fine-textured strong foams due to fluctuation in capillary pressure. Recent studies show that foam rheology in porous media can be characterized by foam-catastrophe theory which exhibits three foam states (weak-foam, strong-foam, and intermediate states) and two strong-foam regimes (high-quality and low-quality regimes). Using both mechanistic foam simulation technique and fractional flow analysis which are consistent with foam catastrophe theory, this study aims to understand the fundamentals of dynamic foam displacement during gas injection in SAG processes. The results revealed some important findings: (1) The complicated mechanistic foam fractional flow curves (fw vs. Sw) with both positive and negative slopes require a novel approach to solve the problem analytically rather than the typical method of constructing a tangent line from the initial condition; (2) None of the conventional mechanistic foam simulation and fractional flow analysis can fully capture sharply-changing dynamic foam behavior at the leading edge of gas bank, which can be overcome by the pressure-modification algorithm suggested in this study; (3) Four foam model parameters („¤Po, n, Cg/Cc, and Cf) can be determined systematically by using an S-shaped foam catastrophe curve, a two flow regime map, and a coreflood experiment showing the onset of foam generation; and (4) At given input data set of foam simulation parameters, the inlet effect (i.e., a delay in strong-foam propagation near the core face) is scaled by the system length, and therefore the change in system length at fixed inlet-effect length requires the change in individual values Cg and Cc at the same Cg / Cc. This study improves our understanding of foam field applications, especially for gas injection during SAG processes by capturing realistic pressure responses. This study also suggests new fractional flow solutions which do not follow conventional fractional flow analysis

Pore-scale modeling of viscoelastic flow and the effect of polymer elasticity on residual oil saturation

textPolymers used in enhanced oil recovery (EOR) help to control the mobility ratio between oil and aqueous phases and as a result, polymer flooding improves sweep efficiency in reservoirs. However, the conventional wisdom is that polymer flooding does not have considerable effect on pore-level displacement because pressure forces would not be enough to overcome trapping caused by capillary forces. Recently, both coreflood experiments and field data suggest that injecting viscoelastic polymers, such as hydrolyzed polyacrylamide (HPAM), can result in lower residual oil saturation. The hypothesis is that the polymer elasticity provides several pore-level mechanisms for oil mobilization that are generally not significant for purely-viscous fluids. Both experiments and modeling need to be performed to investigate the effect of polymer elasticity on residual oil saturation. Pore-scale modeling and micro-fluidic experiments can be used to investigate pore-level physics, and then used to upscale to the macro-scale. The objective of this work is to understand the effect of polymer elasticity on apparent viscosity and residual oil saturation in porous media. Single- and multi-phase pore-level computational fluid dynamics (CFD) modeling for viscoelastic polymer flow is performed to investigate the dominant mechanisms at the pore level to mobilize trapped oil. Several interesting results are found from the CFD results. First, the elasticity of the polymer results in an increase in normal stress at the pore-level; therefore, the normal stresses exerted on a static oil droplet are significant and not negligible as for a purely-viscous fluid. The CFD results show that viscoelastic fluid exerts additional forces on the oil-phase which may help mobilize trapped oil out of the porous medium. Second, due to the elasticity of polymer, the viscoelastic polymer has some level of pulling effect; while passing above a dead-end pore it can pull out the trapped oil phase and then mobilize it. However, both CFD modeling and micro-fluidic experiments show the pulling-effect is not likely the main mechanism to reduce oil saturation at pore-level. Third, dynamic CFD simulations show less deformation of the oil phase while viscoelastic polymer is displacing fluid compared to purely viscous fluid. It may justify the hypothesis that polymer elasticity resists against snap-off mechanism. As a result, when viscoelastic polymer displaces the oil ganglia, the oil phase does not snap off, and the oil phase remains connected, and therefore easier to move in porous media compared to disconnected oil. For single phase flow, a closed-form flow equation has been developed based on CFD modeling in converging/diverging ducts representative of pore throats. The pore-level equations were substituted into a pore-network model and validated against experimental data. Good agreement is observed. This study reveals important findings about the effect of polymer elasticity to reduce the residual oil saturation; however, more experiments and simulations are recommended to fully-understand the mobilization mechanisms and take advantage of them to optimize the polymer-flooding process in the field.Petroleum and Geosystems Engineerin

Pore-scale simulation of wettability and interfacial tension effects on flooding process for enhanced oil recovery

For enhanced oil recovery (EOR) applications, the oil/water flow characteristics during the flooding process was numerically investigated with the volume-of-fluid method at the pore scale. A two-dimensional pore throat-body connecting structure was established, and four scenarios were simulated in this paper. For oil-saturated pores, the wettability effect on the flooding process was studied; for oil-unsaturated pores, three effects were modelled to investigate the oil/water phase flow behaviors, namely the wettability effect, the interfacial tension (IFT) effect, and the combined wettability/IFT effect. The results show that oil saturated pores with the water-wet state can lead to 25–40% more oil recovery than with the oil-wet state, and the remaining oil mainly stays in the near wall region of the pore bodies for oil-wet saturated pores. For oil-unsaturated pores, the wettability effects on the flooding process can help oil to detach from the pore walls. By decreasing the oil/water interfacial tension and altering the wettability from oil-wet to water-wet state, the remaining oil recovery rate can be enhanced successfully. The wettability-IFT combined effect shows better EOR potential compared with decreasing the interfacial tension alone under the oil-wet condition. The simulation results in this work are consistent with previous experimental and molecular dynamics simulation conclusions. The combination effect of the IFT reducation and wettability alteration can become an important recovery mechanism in future studies for nanoparticles, surfactant, and nanoparticle–surfactant hybrid flooding process

A simple and versatile protocol for the preparation of functionalized heterocycles utilizing 4-benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione

<div><p>The reaction of ethyl benzoylpyruvate with phenyl isothiocyanate in alkaline medium yields 4-benzoyl-5-phenylamino-2,3-dihydrothiophene-2,3-dione (<b>1</b>). Reaction of the intermediate <b>1</b> with primary aromatic amines such as aniline derivatives, benzidine and secondary aliphatic amines, namely diethylamine, piperidine, morpholine and piperazine afforded the corresponding thiophene <b>2a–2g</b> and amide <b>3a–3d</b> derivatives. Compound <b>1</b> reacts with <i>N,N</i>′- and <i>N,O</i>-dinucleophiles such as 1,2-diaminoalkanes, 2-aminoethanol, 1-aminoguanidine, guanidine, urea, 1,2-phenylenediamine and 2-amino-4-methylphenol to form the heterocylic compounds <b>4–10</b>.</p></div

Testing of Snorre Field Foam Assisted Water Alternating Gas (FAWAG) Performance in New Foam Screening Model

Eclipse Functional Foam Model was used in order to provide a guideline for the history matching process (Gas-Oil Ratio (GOR), oil and gas production rates) to the Foam Assisted Water Alternating Gas method in the Snorre field, Norway, where the surfactant solution was injected in two slugs to control gas mobility and prevent gas breakthrough. The simulation showed that the first short slug was not efficient while significant GOR decrease and incremental oil production was obtained after the second longer slug in some periods. This study shows that the Eclipse foam model is applicable to the planning of water and gas injections, the testing of various surfactant properties, and the evaluation of the efficiency of the method at the field scale