Multicomponent Ion Exchange Research Articles

Research in Industrial Use of Ion Exchange and Simulation

We investigated the industrial use of ion exchange technology as well as the modeling of fixed bed, multicomponent ion exchange processes. In this paper we report on both fields of this research. We have developed a complex technology for the selective separation of the long-live radionuclides and the partial recycling of boric acid from radioactive evaporator bottom residue. A wastewater treatment system has been developed by using a cesium-selective inorganic ion exchanger. The selective separation of 137Cs, 134Cs from high salt concentration and strongly alkaline evaporator bottom residue in Paks NPP has a volume reduction factor of about 3500–6500 at the value of the decontamination factor DF > 100, for the samples of four evaporator bottom residue tanks of the NPP. Some important classes of ion exchangers do possess uniform internal pore structures and bring all parts of the solíd structure into much closer contact with the liquid. Such materials are porous organic resins. For these types of exchangers, we have modified Mansour's multicomponent adsorption model and developed a computer program to describe multicomponent breakthrough, cocurrent, and counter-current elution curves for ion exchangers. In addition, we have developed a subroutine for the calculation of multicomponent ion exchange kinetics according to Nernst-Planck equation and successfully tested it. This subroutine will be added to the multicomponent ion exchange breakthrough and elution simulation program to have a real multicomponent ion exchange simulation program. In this paper we report about these research results too.

Potential for improving the efficiency of terrigenous oil deposits waterflooding with the use of low salinity technology at fields of the Tatarstan Republic

This article is devoted to the review of one of the currently relevant methods of enhanced oil recovery – low-salinity waterflooding (LSW) – on the example of terrigenous Tulian, Bobrikovian and Devonian reservoirs of the Tatarstan Republic fields. The first part of review contains information about the key processes underlying this method, such as swelling and migration of clay particles and wettability alteration, as well as the mechanisms that explain these processes, which include cation exchange, multicomponent ion exchange, electric double layer expansion, etc. Their understanding, in turn, contributes to the identification of the main factors, the presence or absence of which at the field allows us to give a preliminary assessment of LSW application. There are main factors: the presence of clay particles, a significant content of Ca2+ and Mg2+ ions, as well as multivalent ions in formation water, low formation permeability, reduced oil viscosity, an increased content of acidic and especially basic components in oil and, as a result, a hydrophobic type of initial rock wettability. Then, examples of using the method in other fields are given and the results of laboratory studies, including the measurement of the contact angle, core flooding experiments, are briefly highlighted. A preliminary screening is carried out on the basis of geological and field data from several fields of Tatarstan Republic, candidate fields are identified and a preliminary conclusion about LSW application in this region is made. The positive factors for the reservoirs under consideration, identified at the preliminary screening stage, include low formation temperature, high salinity of formation water with a significant content of divalent cations and the potential to shift the pH level from the current slightly acidic level towards increased alkalinity, and an increased content of polar oil components. In addition, the reservoirs of the Tulian and Bobrikovian horizons are characterized by the presence of clay particles, and the Devonian reservoir are characterized by a reduced oil viscosity coupled with an increased oil base number.

A newly proposed isotherm model to predict Cs exchange with crystalline silicotitanate in tank waste simulants

ABSTRACT The Zheng Anthony Miller (ZAM) computer model, a multicomponent ion exchange model used to predict the exchange of Group I metals onto crystalline silicotitanate (CST), has historically been used to predict Cs distribution coefficients from Hanford and Savannah River Site (SRS) tank waste simulants. Comparison of experimentally determined Cs distribution coefficients from tank waste simulants with ZAM isotherm model predictions indicate overprediction of Cs and K distribution coefficients for simple and complex simulants with the engineered form of CST. Additionally, recent changes in chemical composition/manufacturing of IONSIV TM R9140-B have resulted in increased Cs capacity from high-salt, highly alkaline solutions. This work served to assess different isotherm models and refine equilibrium parameters to develop a model that can be applied to Hanford and SRS tank waste Cs removal efforts. Toward this goal, the Campbell Westesen Peterson (CWP) model was developed. This model utilized the experimentally determined Cs capacity, and simplified ZAM equilibria expressions to include only the binary substitution of Cs+ or K+ on the Na+ sites. Equilibrium constants for these equations were refined using experimentally determined distribution coefficients. Overall, the CWP model significantly improved our ability to predict both Cs and K loading capacity from complex matrices.

Role of the injected water salinity and ion concentrations on the oil recovery in carbonate reservoirs

Low salinity water flooding (LSWF) was initially considered using water with a low concentration of dissolved salts and was later extended to include modifying the ionic content of injected brines. This work investigates the effects of changing water salinity and composition along with the concentration of sulfate and iodide ions on oil recovery in carbonate reservoirs during the tertiary recovery stage. An experimental study was carried out using crude oil of 29°API, 8 core samples extracted from the Eocene carbonate reservoir (Egypt), and 6 different water salinities.The results showed additional oil recovery up to 5% of the original oil in place (OOIP) in the tertiary recovery stage with changing water salinity and water composition. Injection of high salinity (HS) and low salinity (LS) brines with high sulfate concentrations increased the incremental oil recovery by a value ranging from 1.7 to 3.8% of the OOIP. On the contrary, injection of HS and LS brines with low sulfate concentrations showed insignificant incremental oil recovery (less than 1% of the OOIP). Furthermore, injection of water with potassium iodide (KI) after injection of water with high sulfate brines showed additional oil recovery of about 1.7% of the OOIP. On the other hand, injection of water with KI after injection of water with low sulfate concentration showed insignificant incremental oil recovery (less than 0.4% of the OOIP).The concentration of sulfate in the injected water appeared to be key parameter to achieve effective waterflooding (WF) projects in carbonate reservoirs. Moreover, the results revealed that the multi-component ion exchange (MIE) mechanism seems to be the primary recovery mechanism for LSWF in carbonate reservoirs. The results and conclusions of this study can be used to develop guidelines for designing waterflooding projects in carbonate reservoirs with optimum salinity.

Atomistic Insight into the Behavior of Ions at an Oil-Bearing Hydrated Calcite Surface: Implication to Ion-Engineered Waterflooding

This research provides an atomistic picture of the role of ions in modulating the microstructural features of an oil-contaminated calcite surface. This is of crucial importance for the rational design of ion-engineered waterflooding, a promising technique for enhancing oil recovery from carbonate reservoirs. Inspired by a conventional lab-scale procedure, an integrated series of molecular dynamics (MD) simulations were carried out to resolve the relative contribution of the major ionic constituent of natural brines (i.e., Na+, Cl–, Mg2+, Ca2+, and SO42–) when soaking an oil-bearing calcite surface in different electrolyte solutions of same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, and deionized water (DW). In all cases, we observed the gradual detachment of polar oil molecules (mimicked by decanoate) already paired to Na+ cations, covering the calcite substrate in such a way that carboxylate groups were in contact with the treating solution. The appearance of such a negatively charged interface in conjunction with the bare calcite/brine surface is a likely nanometric source for the disparity of surface characteristics of oil-bearing rocks reported in the literature. The MD results showed the affinity of divalent cations (Ca2+ or Mg2+) for pairing with negatively charged carboxylate functional groups, thereby facilitating desorption of decanoates. Having a compact solvation shell, Mg2+ was not as effective as Ca2+ cations; however, its performance was enhanced in the presence of sulfate anions. We further figured out the tendency of SO42– anions to shielding Na+ sites over the calcite surface, thus limiting the chance of readsorption of carboxylate compounds. Consistent with lab experiences, sulfate was found to assist the access of magnesium cations to the calcite surface as well. Altogether, the present results provide us with a molecular-level validation for the well-known multicomponent ion exchange mechanism proposed for the wettability alteration of carbonate rocks through enriching the divalent ionic content of the injection brine solution.

Electrokinetic Mechanisms and Synergistic Effect on Ion-Tuned Wettability in Oil-Brine-Rock Systems

Wettability alteration has been recognized as the dominant mechanism of ion-tuned waterflooding, where the ionic composition of injecting brine is modified to improve oil recovery. Yet mechanisms of ion-tuned wettability have not been fully understood, and there are ongoing debates over the effectiveness and relative contribution of each mechanism. In this paper, ion-tuned wettability in variable oil-brine-rock (OBR) systems over a wide range of ionic compositions is theoretically investigated, with focuses on two electrokinetic mechanisms, double layer expansion (DLE) and multicomponent ion exchange (MIE). Results indicate that the qualitative features of ion-tuned wettability in terms of DLE and MIE in various OBR systems with different surface properties can be divided into two typical types, depending on the electrical double layer (EDL) interaction being repulsive or attractive. With attractive EDL force, both DLE and MIE do not contribute to the water-wetness. While with repulsive EDL force, DLE only takes effect at relatively high concentration and MIE has a significantly larger impact at a low percentage of divalent cation. In addition, DLE and MIE can have a synergistic effect, where one mechanism alone has a negligible effect on wettability but two mechanisms combined have a big impact.

Explicit continuum scale modeling of low-salinity mechanisms

Understanding the influence of injection water composition on the displacement efficiency has been a long-standing issue in reservoir engineering; a reduction of the injection water salinity can lead to additional oil production, which is considered a low-cost and environmentally friendly method for enhanced oil recovery. Several underlying chemical mechanisms have been identified; however, the identification of the governing mechanisms remains difficult and specific to the chemical setting of the reservoir and injection water composition. In this work, we implement two potential mechanisms, namely, double layer expansion and multicomponent ion exchange, to achieve an explicit description of low-salinity effects in the open-source continuum-scale flow simulator DuMuX, with the goal of designing and interpreting experiments, and upscaling the results. By assuming sets of input parameters, we show that there is a minimum required core length dependent on the dispersion of the chemical flooding front dominated by sample heterogeneity. Above this length scale, the saturation profile is fully developed, and the chemical effluent analysis is conclusive, which both is required to calibrate continuum scale models. The change in the chemical water composition shows a characteristic fingerprint for both investigated mechanisms and therefore allows the identification of the leading low-salinity mechanism. The model is publicly available.

Effect of different low salinity flooding schemes and the addition of alkali on the performance of low-salinity waterflooding during the recovery of heavy oil from unconsolidated sandstone

Low salinity waterflooding (LSW) is a promising enhanced oil recovery process. The LSW advantage has been associated to changes in rock wettability toward a more water wet state. This study evaluated the effect of different flooding schemes on the performance of LSW in terms of production rate and incremental oil recovery from sand-pack systems. This work also investigated the main mechanism prompting sand wettability changes during LSW.Flooding Scheme-1 consisted of high salinity waterflooding, low salinity waterflooding, alkali aided low salinity waterflooding, and low salinity waterflooding. Flooding Scheme-2 consisted of low salinity waterflooding, alkali aided low salinity waterflooding, and low salinity waterflooding. Flooding Scheme-3 consisted of alkali aided low salinity flooding and low salinity waterflooding. The main mechanism causing wettability reversal was verified employing contact angle analysis, inductively coupled plasma spectrometry, and scanning electron microscopy.This new study reveals in a straightforward manner the effect of low salinity waterflooding schemes on both production rate and incremental oil recovery. LSW in secondary mode, as conducted in FS-2, expedited the oil production rate by 15% and increased the overall oil recovery by 20% relative to flooding schemes FS-1 and FS-3. Furthermore, this study determined that multi-component ionic exchange was the dominant mechanism for the reversal of sand wettability to a more water wet state.This paper provides new insights for heavy oil producers on the relevance of the flooding schemes during LSW and on the dominant mechanism for wettability alteration during the recovery of heavy oil from unconsolidated sands.

Experimental study of combined low salinity and surfactant flooding effect on oil recovery

A new generation improved oil recovery methods comes from combining techniques to make the overall process of oil recovery more efficient. One of the most promising methods is combined Low Salinity Surfactant (LSS) flooding. Low salinity brine injection has proven by numerous laboratory core flood experiments to give a moderate increase in oil recovery. Current research shows that this method may be further enhanced by introduction of surfactants optimized for lowsal environment by reducing the interfacial tension. Researchers have suggested different mechanisms in the literature such as pH variation, fines migration, multi-component ionic exchange, interfacial tension reduction and wettability alteration for improved oil recovery during lowsal injection. In this study, surfactant solubility in lowsal brine was examined by bottle test experiments. A series of core displacement experiments was conducted on nine crude oil aged Berea core plugs that were designed to determine the impact of brine composition, wettability alteration, Low Salinity Water (LSW) and LSS flooding on Enhancing Oil Recovery (EOR). Laboratory core flooding experiments were conducted on the samples in a heating cabinet at 60 °C using five different brine compositions with different concentrations of NaCl, CaCl2 and MgCl2. The samples were first reached to initial water saturation, Swi, by injecting connate water (high salinity water). LSW injection followed by LSS flooding performed on the samples to obtain the irreducible oil saturation. The results showed a significant potential of oil recovery with maximum additional recovery of 7% Original Oil in Place (OOIP) by injection of LS water (10% LS brine and 90% distilled water) into water-wet cores compared to high salinity waterflooding. It is also concluded that oil recovery increases as wettability changes from water-wet to neutral-wet regardless of the salinity compositions. A reduction in residual oil saturation, Sor, by 1.1–4.8% occurred for various brine compositions after LSS flooding in tertiary recovery mode. The absence of clay swelling and fine migration has been confirmed by the stable differential pressure recorded for both LSW and LSS flooding. Aging the samples at high temperature prevented the problem of fines production. Combined LSS flooding resulted in an additional oil recovery of 9.2% OOIP when applied after LSW flooding. Surfactants improved the oil recovery by reducing the oil-water interfacial tension. In addition, lowsal environment decreased the surfactant retention, thus led to successful LSS flooding. The results showed that combined LSS flooding may be one of the most promising methods in EOR. This hybrid improved oil recovery method is economically more attractive and feasible compared to separate low salinity waterflooding or surfactant flooding.

Selective exchange of alkali metal ions on EAB zeolite

EAB zeolite exhibits higher selectivities to Na + and K + ions than to Li + ions, especially in multicomponent competitive ion exchange condition. • EAB zeolite exhibits high selectivities to Na + and K + ions than Li + ions in independent and competitive ion exchange. • In competitive ion exchange, the selectivities b(Na/Li) and b(K/Li) increase with the initial concentrations. • Na + and K + ions tend to replace Li + ions out from EAB framework spontaneously in competitive ion exchange. EAB zeolite was successfully prepared and applied to selective adsorption of Li + , Na + and K + ions. The physical and chemical properties of the adsorbent were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM) and thermogravimetry (TG) methods. The ion exchange behaviours for Li + , Na + and K + ions in monomcomponent and multicomponent solutions were studied. In independent ion exchange, the ion exchange capacities ratios α (Na/Li) and α (K/Li) were 3.8 and 6.2, respectively. In competitive ion exchange, the selectivities β (Na/Li) and β (K/Li) increased with the initial concentrations and reached 409 and 992 when the initial concentrations was 100 mmol/L. The thermodynamic study results showed that Gibbs free energy change (Δ G Θ ) of ion exchange reaction between Li-EAB and K + was −34.96 kJ/mol, indicating that ion exchange of K + ions was more energetically favourable than Li + ions. The calculation results showed that the energy barriers of ion exchange increased in the order K + < Na + < Li + . The study shows that EAB zeolite is potential to be used in the separation of alkali ions.

Application of Low-Salinity Waterflooding in Carbonate Cores: A Geochemical Modeling Study

Waterflooding is the most widely applied improved oil recovery technique. Recently, there has been growing interest in the chemistry and ionic composition of the injected water. Low-salinity waterflooding (LSWF) is a relatively recent enhanced oil recovery technique that has the ability to alter the crude oil/brine/rock interactions and improve oil recovery in both clastics and carbonates. In this paper, the increase in the recovery factor during LSWF was modeled based on the exchange of divalent cations (Ca2+ and Mg2+) between the aqueous phase and the carbonate rock surface. Numerical simulations were performed using laboratory coreflood data, and oil recovery and pressure drop from experimental works were successfully history matched. The ion exchange equivalent fractions, effluent ions concentrations, changes in mineral moles, and pH have also been examined. Besides, an investigation of multi-component ionic exchange as a mechanism responsible for wettability alteration during LSWF in heterogeneous low-permeability carbonate cores is presented. The results show that wettability alteration is responsible for the increase in oil recovery during LSWF, as reflected by the shift in the crossover points of the relative permeability curves. A sensitivity study done on many key parameters (e.g., timing of LSWF injection, injection rate and temperature) and the mechanistic modeling method revealed that they all have huge effects on the process.

Experimental investigation on the complex chemical reactions between clay minerals and brine in low salinity water-flooding

This paper presents a dynamic effect of clay types and content on low salinity water-flooding (LSF) based on coreflooding experiments. The EDL (electrical double layer) expansion, MIE (multicomponent ion exchange), local pH increase between clay minerals and brine are investigated to get a better understanding on the complexity of role of clay in LSF. The results of coreflooding experiments using unconsolidated core sample show that the incremental oil recovery of kaolinite is higher than that of illite at the same clay content. Kaolinite and illite have a positive effect on MIE, EDL expansion, and local pH increase. The incremental oil recovery was proportional to the local pH increase in both core samples. Especially, more MIE and EDL expansion occur in kaolinite core samples. Therefore, the wettability is further changed to the water-wet condition in kaolinite sample. The results of correlation coefficient analysis show the kaolinite content has a strong correlation with MIE, EDL expansion, local pH increase, and oil recovery. On the other hand, the correlations between oil recovery and chemical reactions in illite samples are relatively low compared to the kaolinite samples excepting local pH increase. Therefore, the sandstone reservoir containing kaolinite is more suitable for the LSF.

Numerical investigation of optimum ions concentration in low salinity waterflooding

Injecting low saline water is one of the practices used to improve hydrocarbon production that has recently significantly grown due to its advantages over seawater and chemical flooding. Although many theories and mechanisms have been provided on how additional oil recovery has been achieved utilizing low salinity waterflooding, the principle fundamentals of the mechanism(s) are still ambiguous. This article investigates the potential use of low salinity waterflooding (LSWF) to improve oil production from a sandstone formation. A 3D field-scale model was developed using Computer Modeling Group ( generalized equation-of-state model simulator) based on a mature oil field data. The developed model was validated against actual field data where only 8% deviation was observed. Simulation analysis indicated that multi-component ion exchange is a key factor to improve oil production because it alters rock wettability from oil-wet to water-wet. Simulation sensitivity studies showed that low salinity water flooding provided higher oil production than high water salinity flooding. Moreover, simulation showed early breakthrough time of low salinity water injection can provide high oil recovery up to 71%. Therefore, implementing LSWF instantly after first stage production provides recovery gains up to 75%. The determined optimal injected brine composition concentration for Ca 2+ , Mg 2+ and Na + are 450, 221, and 60 ppm, respectively. During LSWF, a high divalent cations and low monovalent cations’ concentration can be recommended for injected brine and formation aquifer for beneficial wettability alteration. Simulation also showed that reservoir temperature influenced the alteration of ion exchange wettability during LSWF as oil recovery increased with temperature. Therefore, high temperature sandstone reservoirs can be considered as a good candidate for LSWF. Cited as : Ben Mahmud, H., Mahmud, W.M., Arumugam, S. Numerical investigation of optimum lons concentration in low salinity waterflooding. Advances in Geo-Energy Research, 2020, 4(3): 271-285, doi: 10.46690/ager.2020.03.05

Case study: the impact of Low Salinity Waterflooding on Sandstone Reservoirs at Egypt’s Western Desert

Surface chemistry has a great effect in enhancing oil recovery (EOR). For oil-wet sandstone reservoirs, low salinity waterflooding (LSWF) is effective as it can alter rock wettability and reduce the oil/water interfacial tension. LSWF application is related to the rock’s clay content and type. Clay hydrocarbon bonding can be formed through many mechanisms such as van deer forces and ionic bridge. LSWF effect is to weaken these bonds through two main mechanisms, Double Layer Expansion (DLE) and Multicomponent Ionic Exchange (MIE). This research figure out the impact of LSWF application through a comparsion between two fields (S & D), in Egypt’s Western Desert, which have depleted strongly oil-wet reservoirs with similar rock & fluid Properties. Field (S) is flooded by low salinity water (LSW), while field (D) is flooded by high salinity water (HSW). Fortunately, the LSWF application was with no extra desalination cost as the water source for field (S) flooding is a LSW aquifer zone, which has a salinity +/- 5000 ppm as total dissolved solids (TDS). Water Susceptibility for Field (S) rock showed good compatibility between the injected LSW, formation water and rock minerals. XRD and SEM for field (S) indicate calcareous cementation with detrital clays content around 5% which is mainly kaolinite. This composition helps to activate the LSWF effect. For field (S), the estimated ultimate recovery (EUR) is 46%, while EUR for field (D) is 39%. One of the main causes of this increase in field (S) is the successful LSWF application.

A dynamic network model for the action of low salinity on two-phase flow

Experimental evidence shows that decreasing the salinity of the injection water during the oil recovery process can lead to an increase in the amount of oil recovered. While the ion-exchange reactions which cause this effect are well understood in an industrial setting, there is a limited understanding of how to quantitatively describe the macroscale low salinity effect in terms of the microscale mechanisms. In this paper, we derive a dynamic network model for the salinity-dependent two-phase flow of oil and water through a porous medium in which the salinity of the water affects the thickness of the thin water layer separating the oil phase from the solid surface through the multicomponent ionic exchange mechanism, which results in a salinity-dependent slip condition on the effective oil-solid interface. We solve the network model numerically for a drainage stage followed by waterflood stage on a 30 × 30 network with random pore and throat radii distributions, and present results averaged over multiple simulations. Low-salinity waterflooding is compared with high-salinity waterflooding in both secondary and tertiary mode. Our model is able to reproduce the low salinity effect observed experimentally, in which the amount of oil produced increases as the salinity of the injection brine decreases.

Effect of salinity on oil production: review on low salinity waterflooding mechanisms and exploratory study on pipeline scaling

The past decades have witnessed a rapid development of enhanced oil recovery techniques, among which the effect of salinity has become a very attractive topic due to its significant advantages on environmental protection and economical benefits. Numerous studies have been reported focusing on analysis of the mechanisms behind low salinity waterflooding in order to better design the injected salinity under various working conditions and reservoir properties. However, the effect of injection salinity on pipeline scaling has not been widely studied, but this mechanism is important to gathering, transportation and storage for petroleum industry. In this paper, an exhaustive literature review is conducted to summarize several well-recognized and widely accepted mechanisms, including fine migration, wettability alteration, double layer expansion, and multicomponent ion exchange. These mechanisms can be correlated with each other, and certain combined effects may be defined as other mechanisms. In order to mathematically model and numerically describe the fluid behaviors in injection pipelines considering injection salinity, an exploratory phase-field model is presented to simulate the multiphase flow in injection pipeline where scale formation may take place. The effect of injection salinity is represented by the scaling tendency to describe the possibility of scale formation when the scaling species are attached to the scaled structure. It can be easily referred from the simulation result that flow and scaling conditions are significantly affected if a salinity-dependent scaling tendency is considered. Thus, this mechanism should be taken into account in the design of injection process if a sustainable exploitation technique is applied by using purified production water as injection fluid. Finally, remarks and suggestions are provided based on our extensive review and preliminary investigation, to help inspire the future discussions.

Thermodynamic modeling of the temperature impact on low-salinity waterflooding performance in sandstones

Low-salinity waterflooding has emerged as an innovative technique to improve oil recovery. Extensive research has been devoted to providing a better understanding of the mechanisms involved and to optimize its performance. Among those mechanisms, multi-component ion exchange mechanism explains the coordination of surface complexes in a way that highlights the essence of low-salinity waterflooding. However, the impact of temperature on low-salinity waterflooding is still poorly understood. We used surface complexation modeling to study both the oil/brine and mineral/brine interfaces up to a temperature of 150 ∘C. Given the heterogeneity of the oil interface, we studied three oil interfaces with varying total base number to total acid number ratios. It was determined that temperature is a critical factor in estimating the performance of low-salinity waterflooding. While temperature reduces the pH range at which low-salinity waterflooding yields positive effect for basic oil, it shifts the pH window at which low-salinity waterflooding has potentially negative results to lower pH values for neutral oil. In addition, the temperature magnifies the ability of low-salinity waterflooding to enhance surface potential. Our results support the need for conducting experimental work at the relevant reservoir temperature to evaluate the performance of low-salinity waterflooding.

From Atoms to Pre-salt Reservoirs: Multiscale Simulations of the Low-Salinity Enhanced Oil Recovery Mechanisms

The goal of this review paper is two-fold: bringing an updated survey on the literature of the proposed mechanisms behind the low-salinity enhanced oil recovery (EOR) and propose ways to model them based on simulations coupling atomic to reservoir scales. The low salinity water injection (LSWI) presents some advantages over other EOR techniques since it is a cost-effective method, has no inherent environmental damage and does not affect the subsequent stages of crude oil treatment and refinement. The LSWI is particularly interesting for exploration and production on pre-salt carbonate reservoirs. We couple the LSWI mechanisms with molecular modeling methodologies, addressing their use to describe the EOR via LSWI. From the molecular modeling, one can obtain parameters for the large-scale reservoir simulators, thus, improving their accuracy. Therefore, the molecular modeling approaches are complementary tools to optimize the EOR via LSWI. Among all the involved mechanisms on the LSWI, the wettability alteration is pointed out by several authors as the fundamental one, to explain the EOR. However, there are controversies related to its cause: salting-in effect, multi-component ionic exchange, pH alteration, electric double layer expansion, fines migration, limited release of particles and osmotic pressure are among the main proposals. In this sense, several molecular modeling techniques have been explored to foster theories that explain the possible mechanisms and optimize the oil production combining the molecular dynamics simulations and Ab initio calculations with reservoir simulators.

Prediction of multicomponent ION exchange equilibria by using the e-NRTL model for computing the activity coefficients in solution

The e-NRTL model for computing the activity coefficients in solution of electrolytes was used for the first time, as the best of our knowledge, together with the Wilson's equation for evaluating the non-ideal behavior of the resin phase, in the prediction of multicomponent ion exchange equilibria. For this purpose, experimental data for the binary systems Ni2+/Na+ and Zn2+/Na+ and the ternary system Ni2+/Zn2+/Na+ using Amberlite IR-120 reported by Franco et al. [1] were considered. The results obtained showed that the major impact over the equilibrium modelling was caused by the inclusion of the Wilson's equation demonstrating the predominant effect of the non-ideality of the resin phase. No significant differences in the results (for the systems and ionic concentrations explored here) were observed when Bromley, Pitzer and e-NRTL equations were used to predict the activity coefficients in solution. Regarding the prediction of the multicomponent equilibria, it can be said that the most complex models: Pitzer's and e-NRTL ones, yield the best results. Again, the major impact in the improvement of the prediction was the inclusion of the Wilson's parameters. Finally, since the e-NRTL model allows to indistinctly work with both electrolytes and non-electrolytes, it could be possible to design modules for simulating the ion exchange operation in process simulations software like Aspen Plus®.

An efficient three-dimensional rhizosphere modeling capability to study the effect of root system architecture on soil water and reactive transport

AimsThe objective of this research was to develop a three-dimensional (3D) rhizosphere modeling capability for plant-soil interactions by integrating plant biophysics, water and ion uptake and release from individual roots, variably saturated flow, and multicomponent reactive transport in soil.MethodsWe combined open source software for simulating plant and soil interactions with parallel computing technology to address highly-resolved root system architecture (RSA) and coupled hydrobiogeochemical processes in soil. The new simulation capability was demonstrated on a model grass, Brachypodium distachyon.ResultsIn our simulation, the availability of water and nutrients for root uptake is controlled by the interplay between 1) transpiration-driven cycles of water uptake, root zone saturation and desaturation; 2) hydraulic redistribution; 3) multicomponent competitive ion exchange; 4) buildup of ions not taken up during kinetic nutrient uptake; and 5) advection, dispersion, and diffusion of ions in the soil. The uptake of water and ions by individual roots leads to dynamic, local gradients in ion concentrations.ConclusionBy integrating the processes that control the fluxes of water and nutrients in the rhizosphere, the modeling capability we developed will enable exploration of alternative RSAs and function to advance the understanding of the coupled hydro-biogeochemical processes within the rhizosphere.