Prediction and programming of microemulsion phase behavior simulation

For multiphase surfactant-oil-brine systems, it was observed that the phase transition of microemulsion phase from lower to middle to upper phase can be phase from lower to middle to upper phase can be achieved by varying any one of the seven variables:emulsifier or surfactant concentration,oil/ brine ratio,surfactant formulation/oil ratiobrine salinity,alcohol concentration,oil chain length, andtemperature. The first three variables show a transition from the middle-phase to upper-phase microemulsion in which the middle-phase microemulsion grows and incorporates the excess oil into the middle phase. The resulting upper-phase microemulsion was found to be water-external. However, for the last four variables, there is a true phase inversion where a middle-phase microemulsion phase inversion where a middle-phase microemulsion inverts into an oil-external microemulsion. It has been established in low surfactant concentration systems that the transition of surfactant-rich phase from lower to upper phase is characterized by a partition coefficient of unity for the surfactant. Similarly for high surfactant concentration systems, we have observed that the phase inversion (i.e., the disappearance of the phase inversion (i.e., the disappearance of the middle-phase microemulsion and formation of oil-external upper-phase microemulsion) occurs at the partition coefficient unity defined as the concentration partition coefficient unity defined as the concentration in the oil phase divided by the concentration of surfactant in the middle and lower phases. This similarity between the effects of salt concentration on low and high surfactant concentration systems supports the view that the middle phase is an integral part of the aqueous phase. Furthermore, a careful examination of the phase-inversion region revealed that as the middle-phase volume decreases, the surfactant concentration in the oil phase increases. We have found also that at the optimal parameters (e.g., salinity, oil chain length, etc.) the surfactant concentration in the excess oil phase approaches that in the excess brine phase. However, the phase inversion occurs when the surfactant concentration in the excess oil phase approaches the concentration in the combined middle and lower brine phase. The results show the similarity between the phase. The results show the similarity between the interfacial tension behavior of low concentration systems and those of high concentration systems. Introduction Systems containing 2 to 10% petroleum sulfonate with or without the addition of alcohol as cosolvent usually exhibit a complicated phase behavior. The surfactant can be predominantly soluble in brine and form a water-external microemulsion in equilibrium with an excess oil phase. On the other hand, if the surfactant has a greater solubility in oil, it can form an oil-external microemulsion in equilibrium with an excess brine phase. The transition of surfactant-rich phase from lower phase (brine phase) to upper (oil phase) generally goes through a region in which a middle phase, which virtually contains most of the surfactant, and remains in equilibrium with an excess oil phase and an excess brine phase. It has been well established that the formation of this middle phase correlates with increased oil displacement efficiency of the process. The development of the multiphase behavior from two-phase with surfactant in the brine phase through three-phase having most of the surfactant in the middle phase to two-phase with the surfactant in the oil phase can be achieved by changing one of the seven parameters in the direction described as follows:increasing the total surfactant concentration in the system,increasing the brine/oil ratio,increasing the surfactant solution/oil ratio,increasing the salinity of the brine,decreasing the hydrocarbon chain length of the oil,increasing the alcohol concentration, anddecreasing the temperature. The first three parameters are controlling the phase behavior in quite the same manner. phase behavior in quite the same manner.

New fully implicit formulations for the multicomponent surfactant-polymer flooding reservoir simulation

3D microtomographic study of fluid displacement in rock cores

Influence of microemulsion phases on the preparation of fine-disperse emulsions

Polyelectrolyte complexation (PEC) is an associative phase separation process initiated by mixing of two kinds of oppositely charged polyelectrolyte solutions. PEC-based materials have been recognized as ideal prototypes to study membraneless organelles, self-assembled into smart delivery vehicles for nucleotides and proteins, and fabricated into functional devices for purification purposes. Continuous studies have been devoted to understanding thermodynamics, kinetics, morphology, and structures of the polyelectrolyte complexation systems, which were summarized in Chapter 1 of this dissertation. However, a lot of the studies remained qualitative, and the fundamental understanding of the polymer physics involved has not kept pace. Specifically, a precise description of the binodal phase diagram capturing detailed phase behaviors and partitioning of different components into the two respective phases is still lacking. Moreover, joint efforts by experiments and theories are needed to provide an overarching framework with the predictive capacity to control the properties of the PEC-based materials. Accordingly, we have designed a new experimental approach combining salt resistance measurement and thermogravimetric analysis with minimum processing and approximation to produce accurate binodal phase diagrams. Chapter 2 of this dissertation focused on illustrating the phase behaviors of a “clean” polypeptide system, poly(lysine) and poly(glutamic acid) with hydrophilic backbones and matched chain lengths. Essential features of this system were demonstrated, including the screening effect of salt, self-suppression and the change of the volume fraction of the complex phase with addition of salt. Additionally, the salt partitioning into the supernatant phase was found to initially increase and then decrease on increasing the salt concentrations, manifesting as a distinct minimum in the salt partition coefficients. These trends were shown by simulations to be strongly influenced by the excluded volume interactions in the complex phase, which were not accounted for in their entirety in earlier theories. Equipped with the knowledge from the polypeptide system, we have further extended our research to an aliphatic pair of poly(acrylic acid) and poly(allylamine hydrochloride) with hydrophobic backbones in Chapter 3 of the dissertation. While we found the phase behaviors were, to some extent, similar under neutral/basic pHs and followed general expectations of PEC materials, remarkably different behaviors were observed under acidic conditions. Unintuitively, polymer content in the complex phase increased as salt was added, due to the hydrophobicity of aliphatic polymer backbones coupled with hydrogen bonding of unionized monomer units. We systematically investigated both of these specific interactions using turbidimetry, microscopy, and FTIR spectroscopy. These binodal phase diagrams detailed the associative secondary phase assembly from electrostatic complexation, precipitation of an individual polymer, and other noncovalent contributions as a function of pH, polymer concentration, and added salt. Lastly, Chapter 4 of the dissertation has compared the binodal phase behaviors of both polypeptide and aliphatic polyelectrolyte systems to accentuate the effect of solvent quality and chain length. The experimental results could be qualitatively explained by the scaling theory and random phase approximation calculation. The threshold value of Flory-Huggins χ parameter distinguishing complexation disintegration upon salt addition and that remaining stable even at high salt concentrations could be estimated. Additionally, the salt resistance concentration was shown to be proportional to the square root of the polymer chain length.

Purification of Nonionic Alkyl Polyglycolether (CiEj) Surfactants: The “Inverse” 3PHEX Technique

Supervisory control and data acquisition (SCADA) systems are used by many critical infrastructures including electric power production and distribution, water and waste water treatment, rail transportation, and gas and oil distribution. Originally isolated proprietary systems, SCADA systems are increasingly connected to enterprise networks and the Internet and today use commercial hardware and software. As a result SCADA systems now face serious cyber-security threats. The need for testing and evaluation of developed cyber-security solutions presents a challenge since evaluation on actual systems is usually not possible and building complete physical testbeds is costly. This thesis presents the design and development of a water systems simulation for testing and evaluation of cyber-security enhanced field devices. The simulation consists of two main parts: a human machine interface/master terminal unit (HMI/MTU) component and a water treatment and distribution component. The HMI/MTU part supports new security protocols used to communicate with the hardened remote terminal unit (RTU). The water system simulates a water treatment and distribution center. A data acquisition (DAQ) module was used in conjunction with LabVIEWTM to create a water distribution and treatment simulation that could be interfaced with an actual field device. Field device I/Os are wired to the DAQ which then interface with the LabVIEWTM simulation. The simulation supports: selectable polling of I/O, graphical representation of I/O, random water usage, constant water usage, and simulation data collection. The simulation uses a modular design pattern so that it can be easily extended in the future. Initial testing with a hardened RTU prototype confirmed the ability of the simulation to interact with real hardware and identified some minor errors in the prototype’s security protocol implementation. With additional DAQ devices the simulation could be extended to simulate larger water systems.

Compared with conventional reservoirs, shale reservoirs are more difficult to develop due to their characteristics of self-generation and self-storage and tightness. Based on the experience accumulated in production practice, the technical method of improving shale oil development through shut-in is put forward. The literature research on shale reservoirs shows that there is a lack of microscopic study on imbibition, the essence of oil–water exchange is not clear enough, and there is a lack of the systematic summary and induction of theoretical knowledge. This article starts from the background of shut-in stimulation of Gulong shale oil, conducts literature research on the related knowledge of shut-in of shale oil from three aspects: characterization of fracture network, shut-in mechanism, and oil and water distribution state, and summarizes the law of shut-in of shale oil in a microscopic aspect. On this basis, a dual-porosity numerical simulation model is established according to the geological and fluid characteristics of the Gulong shale oil reservoir. Through the simulation of a numerical simulation model, the water saturation and pressure maps of the matrix and lamellation-fracture system in the process of shut-in were obtained. It was found that the matrix system basically did not participate in the oil–water exchange in the process of shut-in, so in the subsequent characteristic curve analysis, only the lamellation-fracture system was mapped and analyzed. The water saturation and pressure curves of different distances of the main fracture at different times were made, and it was found that the water saturation and pressure in the main fracture and near fracture areas were higher, and the change was more obvious than that in the far. Thus, the pressure drop curves of the near fracture were used to analyze the flow stage of the fluid. The single variable method is used to analyze the influencing factors from two aspects: the fracture density and permeability of the stimulated zone. The results will give a better understanding of the oil and water distribution during shut-in and guide the duration of shut-in in shale oil reservoirs.

Surfactant feedstock for surfactant-polymer (SP) flooding field applications is commonly delivered as a blend of surfactant mixtures with a distribution of molecular weight (MW), rather than as a pure component. Moreover, two or more synthetic commercial surfactants with their own MW distributions are often injected simultaneously. In order to design an effective SP flooding process it is important to predict phase behavior of complex surfactant mixtures with changing formulation variables, such as temperature, pressure, oil EACN, brine salinity, and surfactant composition. The main challenges to model phase behavior of surfactant mixtures include distinct optimum conditions for each type of surfactant, limited information about the distribution of the surfactants in the commercial blends, different partitioning of surfactants in the excess phases and microemulsion phases, and dynamically altered surfactant composition due to selective adsorption, degradation, or differing partition coefficients. In this paper, we present new mixing rules for our recently developed equation of state model to predict phase behavior of surfactant mixtures with changing compositions of two or more synthetic commercial grade surfactants. The model is based on the hydrophilic-lipophilic difference (HLD), net-average curvature (NAC), and mole fraction weighted ratios of surfactant blends (in terms of both multiple synthetic surfactants and their individual distributions). Significant chromatographic separation of surfactant mixture may occur as a result of distinct adsorption isotherms for different surfactant components. These composition changes can have a critical impact on the phase behavior of the mixture and the ultimate oil recovery. Fish plots are constructed for varying water-oil ratios and surfactant compositions that show significant sensitivity to water-oil ratio and surfactant composition. When the injected chemicals do not separate (e.g. there is no selective adsorption, degradation, or selective partitioning), fish plots for a water-oil ratio of 1.0 are symmetric with surfactant concentration because the surfactant blend behaves as a pure surfactant pseudocomponent. For water-oil ratios not equal to 1.0, the surfactant blend can still be modeled as one pseudocomponent, as long as surfactant composition remains fixed, but the fish plot becomes asymmetric. Fish plots, however, are always asymmetric when surfactant composition changes. In such cases, the surfactants must be represented by multiple components with different characteristics and distributions. The results are illustrated using ternary and quaternary diagrams based on measured experimental data in the literature. The new model is included in our in-house compositional simulator PennSim, which shows that simulations of a surfactant flood with different adsorption isotherms can significantly change recovery.

Surfactant mediated enhanced oil recovery techniques such as surfactant-polymer (SP), and alkaline-surfactant-polymer (ASP) flooding, have received increased attention in the past decade due to their ability to reduce capillary forces at the pore-scale to ultra-low values and mobilize oil. In order to improve the economics of such processes, a better understanding of the interaction of surfactant-oil-brine systems is needed. Recently, an equation-of-state (EoS) has been developed that significantly improves microemulsion phase behavior prediction based on coupling of the HLD-NAC equations with a new correlation of optimum conditions, and an updated hydrophilic-lipophilic difference (HLD) model that includes pressure (Ghosh and Johns 2014, 2016). The new EoS accounts for gradients in key formulation properties relevant for reservoir-scale processes in a robust and noniterative framework. One common assumption of all existing microemulsion phase behavior models is the assumption of pure excess phases, which says that the surfactant component can only be present in the microemulsion phase. The focus of this paper is to allow for surfactant partitioning into both the water and oil excess phases, and then relate the relevant surfactant partitioning coefficients to the HLD state function so that K-values, and potentially phase behavior, can be predicted. This paper derives important relations of the surfactant partition coefficient between relevant phases based on a chemical potential description of the HLD, which measures the deviation from optimum conditions. In particular, we calculate the surfactant partition coefficients from numerous experiments in the literature and show that the surfactant partitioning coefficient has a linear scaling with HLD for a wide variety of formulation variables. Surfactant K-values between excess phases from all experiments examined collapse onto the same linear relationship so that once HLD is known (based on formulation variables such as salinity) the K-values are explicitly determined. The estimation of surfactant partition coefficients can be used to aid the design of surfactant formulations for EOR processes.

The phase behavior of systems containing minimum amounts of sodium bis (2-ethylhexyl) sulfosuccinate with equimolar ratio of tetra ethyl ammonium chloride were studied as a function of salt concentration and alkane carbon number at ambient temperature. Visual inspection as well as cross polarizers were used to detect anisotropy. Solubilization ratios for oil and brine in the middle phases were measured and used to calculate the interfacial tension. Ultra-low interfacial tension values were predicted for the systems containing heptane, octane and nonane as model oil. Different phase behavior was observed for systems with higher alkane number.

A special combination of alcoholic precipitation and salting out of proteins was described as three-phase partitioning [1]. Proteins are accumulated in a coherent middle phase in the partitioning system composed of tert-butanol, ammonium sulphate and water. The mechanical properties of the middle phase were determined in model systems using bovine serum albumin (BSA) or ovalbumin. The stressdeformation relationship obtained by uniaxial compression showed the elastic behaviour of the middle phase. It was found that the elastic modulus of the protein gel changed with stress. The middle phase became harder upon compression, possibly owing to some change in structure. The viscoelastic properties were determined by measuring the deformation as a function of time. The BSA gels showed higher elastic and viscous deformation and lower viscosity than the ovalbumin gels. The rheological behaviour of protein gels is consistent with the previous results obtained from the analysis of middle-phase components, which indicate that the middle phase formed in three-phase partitioning is an emulsion gel.

Saturation distributions exhibiting unphysical "checkerboard" patterns, time-step size sensitivity, and slow convergence in certain instances are observed in a fully implicit surfactant simulator that is based on an industry-wide accepted formulation. In this paper, we discuss methods to address each of the above conditions and hereby achieve a robust algorithm with favorable convergence characteristics. The proposed remedies are result of in-depth studies of the physics of micro-emulsion appearance and disappearance as well as detailed analysis of the numerical convergence difficulty. Our method considers wide ranges of solution variables in a typical surfactant flood simulator and critical key parameters identified by flash algorithm [Han, et al. 2017] and general non-linear solver. The details of the improved formulation are provided and should enable readers to replicate all these results. Identifying grid cells in a reservoir model where and when the micro-emulsion phase appears is a key capability in the modeling of surfactant phase behavior. The Critical Micelle Concentration (CMC) is the commonly accepted triggering criterion for forming the micro-emulsion phase. We have observed unphysical "checkerboard" saturation patterns for several cases where water mobility is greater than oil mobility when using the conventionally accepted CMC calculation method. We have analyzed the reasons for this unphysical solution and propose a new CMC definition to ensure physically consistent simulation results. Typical CMC values for surfactant flood are in the range of 10-5 to 10-3. This requires surfactant concentration to be solved more accurately relative to other component concentrations as it directly affects micro-emulsion phase disappearance. The simulation results may vary with time-step sizes not only from the time-truncation errors but, more importantly, from the accuracy of the solved surfactant concentration for each time-step. Special treatments are introduced to reduce the time-step size sensitivity in our simulator. For cases with cation exchange, slow convergence is observed as the corresponding governing equations form an ill-conditioned matrix for cells with small surfactant concentration. An extra term is introduced into the formulation to speed up the convergence rate without changing the model behavior.

The oil recovery effectiveness of a chemical flood has been shown to be related to the phase behavior of the brine-oil-surfactant system. In particular, it is advantageous to formulate the system particular, it is advantageous to formulate the system so that middle phases are formed. There are, however, an infinite number of surfactant cosurfactant (alcohol) combinations which will give the desired phase behavior. The selection of the preferred system out of this infinity of possible systems is an optimization problem and is the subject of this paper. problem and is the subject of this paper. An extensive study of the interfacial tension of dodecyl ortho xylene sulfonate sodium salt, as a function of salinity, alcohol and hydrocarbon molecular weight has been conducted. The results reveal that certain formulations may be preferred since the interfacial tension of some systems at optimum conditions is smaller than others. Indeed, conditions giving a global interfacial tension minimum were found. It is also known that for enhanced oil recovery, it is desirable to maintain miscibility between the chemical slug and the reservoir fluids as long as possible. This means that the height of the possible. This means that the height of the multiphase region should be minimized. This study show that the height can be minimized by a proper formulation. Introduction A correlation relating the variables deft optimum systems for improved oil recovery has be reported. This equation gives the optimum salinity, S*, as a function of the alkane carbon number of the oil, ACN, the alcohol and a parameter, sigma, which is characteristic of the surfactant as follows: (1) where K is a constant equal to 0.16 for all alkylaryl sulfonates and f(A) is a function of alcohol type and concentration known for alcohols heavier than C5. The dots indicate that other variables, such as the water-oil ratio (WOR) and the temperature, have been omitted since they are not considered in this work. Equation 1 applies if WOR = 4 and T = 25 degrees C. The ratio sigma/K has been called the EPACNUS and is the extrapolated preferred alkane carbon number at unit salinity and preferred alkane carbon number at unit salinity and without alcohol, since f(A) is defined so that it vanishes as the alcohol concentration goes to zero. Equation 1 represents a plane in the space in S,ACN and f(A) as shown in Figure 1, and any point on this plane is an optimum system in the following sense. For a given oil and surfactant system, a middle phase will be observed over a range of salinities and the midpoint of this salinity range will be called the optimum salinity. Furthermore, the surfactant system is said to be an optimum one. This implies that a series of experiments in which a property important to improved oil recovery, such property important to improved oil recovery, such as interfacial tension or amount of surfactant needed to solubilize certain volumes of water and oil, will yield a minimum value of the property when a point on the plane is reached. Thus, a series of interfacial tension measurements will reveal a minimum value at the point where line 4 shown in Figure 1 pierces the plane. (Perhaps, it would be more pierces the plane. (Perhaps, it would be more precise to assert that the minimum will occur in the precise to assert that the minimum will occur in the vicinity of the plane rather than on it. This point is further clarified in a subsequent section.) If the experiment is repeated at a different salinity or alcohol concentration or both, then the minima of the properties in question will be found at the new point at which a vector parallel to line 4 intersects the plane. If the values of the minima are different at the two points, then one point on the plane may be preferred to the other with regard to plane may be preferred to the other with regard to efficiency of oil recovery. Thus, it is appropriate to ask if all points on the optimum plane are equivalent with regard to oil recovery. This is the question addressed in this paper.

Chapter 7 - Surfactant Flooding