Brine Composition Research Articles

Physics-Based and Data-Driven Polymer Rheology Model

Summary Polymer flooding is a common enhanced oil recovery (EOR) method used to increase aqueous phase sweep efficiency by increasing viscosity. Estimating polymer viscosity for given reservoir conditions (i.e., oil viscosity, temperature, and brine composition) requires intensive laboratory work. There are existing empirical models to estimate polymer bulk rheology without prior laboratory work; however, they have many coefficients, simple brine composition, and lack physics-based regression boundaries. This study benchmarks the existing polymer empirical and machine learning (ML) models against a new data-driven model with some physics basis for common synthetic polymers. We cover a broad range of polymer concentrations, temperature, salinity, and hardness with an upper limit of 5,000 ppm, 120℃, 290,000 ppm, and 33,000 ppm, respectively. The data were preprocessed through data analytics techniques, and a model was developed with some physics basis by fitting Martin’s equation for Carreau model coefficients. Our regression boundaries obey flexible polymers’ physical and laboratory behavior. We benchmarked the bulk rheological model with existing models in the literature. We used the published models’ coefficients and then tuned their coefficients for our data set for a fair comparison. We then investigated ML as a predictive tool without compromising overfitting the data using the simplest ML model (linear regression) all the way to artificial neural network (ANN) and hybrid ML models. This is the first study that comprehensively benchmarks polymer rheology models and proposes a simple, least number of coefficients, and tunable polymer-rheology model. We provide a predictive bulk rheology model that enables the user to accurately predict polymer viscosity without laboratory measurements and for a wide range of temperatures and brine compositions. Moreover, our study includes the recently common polymer SAV-10 that was not previously studied. We present a simple water viscosity model for a broad brine salinity and temperature range. Our study shows that ML techniques might provide deceptively high accuracy for small data sets, unless due diligence is done to avoid a high-variance model.

A brief overview on geothermal scaling

Hot spring waters are rich in terms of minerals. Since there are dramatic changes in thermodynamic parameters in geothermal power plants, such as a decrease in temperature and pressure, severe precipitation occurs throughout the system components in an uncontrolled manner. There are three main chemistries in deposits: carbonates (mainly calcium carbonates), silicates (metal silicates), and sulphides (antimony sulphide-stibnite). Energy harvesting is remarkably reduced out of the insulating nature of the deposit. Various actions need to be taken to mitigate this undesirable issue of scaling in geothermal systems. Geothermal systems are in fact quite complex, and the composition of brine and, accordingly, the chemistry of the deposit are not identical. Therefore, each system should be studied individually, and a tailor-made remedy should be developed. In this overview, the types of deposits in terms of chemistry and the actions (pH modification or antiscalant dosing) that should be taken to reduce scaling are mentioned, and potential chemistries of antiscalants are given.

The Effect of Natural and Anthropogenic Factors on the Seasonal Ecohydrological Dynamics of the Eastern Basin of the Hypersaline Sakskoe Lake, the Republic of Crimea

Crimean salt lakes have a high resource potential used in various types of human activity, i.e., balneology, chemical industry, and therapy; now, they are attractive tourist sites. A combination of biotic and abiotic factors creates specific conditions for the development and functioning of biota and the formation of unique ionic composition of brine and bottom sediments, which are used in balneology and the production of spa-products. Sakskoe Lake is among the largest coastal salt lakes of Crimea, located on the southwestern coast of the Black Sea. The effect of climate conditions and biota caused the formation of a specific ecosystem in the lake, which has a peculiar ionic composition of brine, changing within the year, and a brine shrimp population. The concentrations of cations and anions in the brine increased in summer because of active evaporation and decreased in winter and spring because of dilution of atmospheric precipitation and snowmelt water. The dynamics of the brine population also showed characteristic seasonal features: the life cycle begins in April, the maximal number of various life stages is recorded in May–June, and the end, in November–December. The artificial regulation of the water–salt regime of the water body through addition of seawater in summer contributed to maintaining optimal conditions, thus ensuring a high vital activity of the biota. The obtained data can reflect the seasonal dynamics of processes in the salt lake, governed by climatic, seasonal, and anthropogenic factors.

Analyses of Interpolant Ion Effects on Smart Water Core Flooding in Carbonate

Smart water flooding (SWF) is a promising enhanced oil recovery (EOR) technique due to its economic advantages. For this process, wettability alteration is the most accepted controlling effect that leads to increased recovery factors (RFs). The main objective of this work is to investigate how the relative permeability curves’ interpolant affects the SWF mechanisms’ assessment. Wettability alteration is described by shifting these curves in simulations. Numerical simulations of core flooding tests are applied to carbonate at 114.4 °C. A comparison of oil recovery factor (RF), pH and effluent composition is performed for different injection approaches. Mg2+ and SO42− are the interpolant ions and the salinity levels range from 30 to 1 kppm. A simulation of 24 scenarios, 12 for each type of interpolant, is presented. Results show that RF changes significantly, due to salinity and composition, for each interpolant. This has a relevant influence on the interpolant. The greater the dilution, the smaller the effect of the interpolant and brine composition on the recovery estimates. When considering SO42− as an interpolant, the trend is that divalent rich brine (DV) has a higher recovery factor. In contrast, when Mg2+ is the interpolant, DV tends to have a lower recovery. The analysis of ionic exchange and pH variation corroborate the wettability alteration behavior. A pH increase was observed in all scenarios, regardless of the salinity, ion composition or interpolant variation. Also, monitoring the CH3COO-X reduction and SO4-X2 increase equivalent fractions indicated the ion exchange mechanism as being well represented in all simulations. In addition, the results emphasize that even at very low concentrations, SO42− plays a fundamental role in initiating the ion exchange process that culminates in the wettability alteration as a consequence of smart water injection.

Polysulphate: A New Enhanced Oil Recovery Additive to Maximize the Oil Recovery From Carbonate Reservoirs at High Temperature

Summary Seawater (SW) injection is an enhanced oil recovery (EOR) success in the North Sea carbonate reservoirs due to wettability alteration toward a more water-wet state. This process is triggered by the difference in composition between injection and formation water (FW). “Smartwater” with optimized ionic composition can easily be made under laboratory conditions to improve oil recovery beyond that of SW. However, in the field, its preparation may require specific water treatment processes, e.g., desalination, nanofiltration, or addition of specific salts. In this work, a naturally occurring salt called Polysulphate (PS) is investigated as an additive to produce smartwater. Outcrop chalk from Stevns Klint (SK), consisting of 98% biogenic CaCO3, was used to investigate the potential and efficiency of the PS brines to alter wettability in chalk. The solubility of PS in SW and deionized water, and brine stability at high temperatures were measured. Energy dispersive X-ray and ion chromatography were used to determine the composition of the PS salt and EOR solutions, and to evaluate the sulphate adsorption on the chalk surface, a catalyst for the wettability alteration process. Spontaneous imbibition (SI), for evaluating wettability alteration of PS brines into mixed-wet chalk was performed at 90 and 110°C and compared against the recovery performance of FW and SW. The solubility tests showed that the salt was easily soluble in both deionized water and SW with less than 5% solid residue. The deionized PS brine contained sulphate and calcium ion concentrations of 31.5 and 15.2 mM, respectively, and total salinity was 4.9 g/L. This brine composition is very promising for triggering wettability alteration in chalk. The SW PS brine contained 29.6 mM calcium ions and 55.9 mM sulphate ions, and a total salinity of 38.1 g/L. Compared with ordinary SW, this brine has the potential for improved wettability alteration in chalk due to increased sulphate content. Ion chromatography revealed that the sulphate adsorbed when PS brines were flooded through the core, which is an indication that wettability alteration can take place during brine injection. The reactivity was also enhanced by increasing the temperature from 25 to 90°C. Finally, the oil recovery tests by SI showed that PS brines were capable of inducing wettability alteration, improving oil recovery beyond that obtained by FW imbibition. The difference in oil recovery between ordinary SW and SW PS imbibition was smaller due to the already favorable composition of SW. PS brines showed a significant potential for wettability alteration in carbonates and are validated as a potential EOR additive for easy and on-site preparation of smartwater brines for carbonate oil reservoirs. PS salt, added to the EOR solution, provides the essential ions for the wettability alteration process, but further optimization is needed to characterize the optimal mixing ratios, ion compositions, and temperature ranges at which EOR effects can be achieved.

Use of AI tools to understand and model surface-interaction based EOR processes

Enhanced Oil Recovery (EOR) is as a key tertiary recovery strategy that aims at enhancing the oil recovery from the earth's subsurface of existing oilfields. One such EOR process that is dependent on multiple variables of complex surface interactions between the formation brine, injected brine, hydrocarbon and rock surface is different composition water flood. This specific EOR technique has been gaining wide focus in research due to its ease of implementation both in terms of logistic and cost albeit the complex interactions that leads to its success is still not clear. Due to the variables of the different phases playing a prominent role in the outcome of this EOR technique, the resulting complexity necessitates the need for Artificial Intelligence (AI) tools to be able to understand, model and screen this EOR technique. There are numerous AI tools based on supervised, unsupervised and reinforcement strategies that can be used in understanding the prominence of different parameters of this surface-interaction based EOR process. In this research work several data analysis methods followed by use of machine learning methods (a subset of AI) are used to analyse the different parameters and their impact on the outcome of the EOR process. Based on these AI tools the prominent parameters are discerned and their correlation with respect to the success of the EOR process is determined. This is followed by evaluation of the AI tools for screening of the EOR process prior to making investment decisions involving commitment to huge capital, resources, and time. This research determines that the key parameters of brine composition, salinity at initial and final conditions, oil API and initial recovery achieved which is a function of the wettability are key for the success of this EOR process. Through this work findings, the industry has a valuable tool to make early decisions that ensure greater probability of success of screening and selecting this EOR technology before commitment of resources for detailed design and implementation.

Inhibition of calcium carbonate scale under severe conditions

Despite extensive works have been devoted to study the scale inhibition behavior, the performance of inhibitors is still not fully understood. In this paper, we present a laboratory study to elucidate the impact of water composition on the performance of some commonly used phosphonate and polymeric calcium carbonate scale inhibitors, in highly supersaturated brines at high temperature. Calcium tolerance inhibitor chemicals with various molecular structures are studied using dynamic scale loop test method at 150 °C. Brine composition is varied by changing the non-stoichiometry of scaling lattice ions, e.g., ( Ca 2 + ) / ( CO 3 2 − ) ratio, over a wide range. Test results indicate that the effectiveness of inhibitors can be significantly changed by the scaling ion ratio. In general, the efficacy of inhibitors decreases significantly with calcium concentration in the test brine even at constant supersaturation state and temperature, and also the performance ranking of the different inhibitor chemistries can be changed with brine composition. This could be caused by the alternations of interactions between inhibitor molecules and the surface of calcium carbonate scale crystals. Findings from this study suggest that the effect of scaling ion ratio must be considered in scaling risk assessment and for the optimization of inhibitor treatment programs.

Impact of Wettability Alteration on the Front Instability of Immiscible Displacement in Porous Media

AbstractWettability alteration that occurs as a result of changing the brine composition or using chemicals that lower the interfacial tension can significantly alter the mobility of nonaqueous liquid (NAPL)/water phases. Here, we show that including dynamic wettability alternation (moving from non‐water‐wet to water‐wet) or interpolating between two sets of relative permeability curves may create an unstable displacement of the residence‐fluid by the injected fluid. The instability occurs due to not only the viscosity ratio but also the new shape of relative permeability curves and their end‐point values. We perform a full factorial design on Corey relative permeability parameters to determine the most destabilizing factors when the viscosity ratio is one. The observations indicate that instability proliferates when the end‐point relative permeability to the NAPL phase of modified salinity brine increases, and their corresponding exponents decrease compared with high salinity brine (seawater or formation water). Besides, numerical simulations of such a displacement demonstrate that modified salinity water (MSW)'s breakthrough is accelerated by wettability change toward water‐wet compared with a non‐fingering analytical solution. This may result in a delayed mobilization of the NAPL phase in porous media. We also discuss the role of capillary pressure, heterogeneity, and secondary and tertiary injection of MSW in stabilizing the shock front.

Engineering the rheology and IFT behavior of mixed formulations of anionic and non-ionic surfactants with added silica nanoparticles

Tertiary enhanced oil recovery (EOR) is one of the feasible exploitable fossils fuel to meet global energy consumption. The conventional EOR chemical approach has many disadvantages over the nano-EOR due to many unforeseen issues and loss of chemicals in the porous medium, affecting the techno-economic of the projects. The nano-EOR approach can augment and modify the rock-fluid interaction and mobility. It is a promising approach at the nanoscale to provide a unique platform to revolutionize the EOR process for ultimate oil gain. The other critical parameters, such as IFT, wettability, capillary pressure, and rheology, can also influence the rock-fluid interaction at the interface. The author has focussed mainly on the impact of IFT, surface tension, and rheology of nano silica-surfactant formulation (Alkyl benzene sulfonate-triton-x-100) in the presence of 3 wt% brine, synthetic formation water (SFW) and paraffin oil. The critical micellar concentration (CMC) value of the above composition was estimated at around 50 mg/lt. The IFT has been observed around 12.21mN/m against 3 wt% brine-surfactant composition at room temperature and 8.25mN/m at higher temperatures (∼60 °C). In the case of SFW, the IFT of 14.95mN/m at room temperature and 8.55mN/m at a higher temperature. The studies have also been conducted with nano silica-surfactant-3 wt% brine composition and found the IFT of 2.85mN/m at room temperature and 1.20mN/m at higher temperatures (∼60 °C). Whereas in the case of nano silica-surfactant-SFW formulation, it was found 4. 24mN/m at room temperature and<2.0mN/m at a higher temperature. The declining trends of IFT of the above systems will modify the rock-fluid interface properties and enhance mobility under in-situ conditions. The rheological studies also confirmed that 0.10 wt% of nano silica-surfactant with base fluid composition is an optimum and desired concentration for achieving favorable rheology and better techno-economics of nano-EOR applications.

Polymer enhanced foam for improving oil recovery in oil-wet carbonate reservoirs: A proof of concept and insights into the polymer-surfactant interactions

The feasibility of polymer enhanced foam (PEF) for enhanced oil recovery (EOR) in a strongly oil-wet and heterogeneous carbonate reservoir with medium temperature (131 °F) and high salinity was experimentally investigated. An Alkyl Poly-Glycoside (APG) surfactant was firstly selected because of its prominent foam behavior in oil-wet carbonates. The effect of polymer type, flow rate and brine composition on foam strength and stability were systematically investigated, aiming to understand how the interactions between polymer and surfactant could influence the transport behavior and performance of PEF in porous media. It was found that, with either an associative polymer or a nonionic polymer (PAM), the foam strength and foam stability could be largely enhanced, both in the absence and in the presence of oil. A significant improvement in oil recovery efficiency was obtained for PEF with an associative polymer, approximately 5% higher than that achieved for conventional polymer-free foam. The PEF behavior is intimately dependent on the interactions between the polymer and the surfactant. It is hypothesized that the increased foam strength by adding polymer at oil-wet conditions may be resulted from an increase of aqueous phase viscosity, the wettability alteration from oil-wet to less oil-wet, the generation of a highly viscoelastic film and (or) the creation of a more stable pseudo-emulsion film. This study provides a robust approach for PEF mobility control and reservoir conformance in oil-wet and heterogeneous carbonate reservoir under analogous reservoir conditions.

How Brine Composition Affects Fly Ash Reactions: The Influence of (Cat-, An-)ion Type

Abstract Hypersaline brines can be solidified and stabilized via the hydraulic and pozzolanic reactions between fly ash(es) and calcium-based additives. Although recent work has examined fly ash reactivity in single-salt (“simple”) hypersaline brines (ionic strength, Im &amp;gt; 1 mol/L), the effects of mixed-salt solutions on fly ash reactivity remain unclear. Herein, the reactivity of a Class C (calcium oxide [CaO]-rich) or Class F (CaO-poor) fly ash mixture with calcium hydroxide is reacted in solutions bearing sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium sulfate (Na2SO4), or combinations thereof for 1.5 ≤ Im ≤ 2.25 mol/L, from 1 week until 24 weeks. Expectedly, sulfate anions promote the formation of sulfate phases (i.e., ettringite, monosulfoaluminate, U-phase), while chloride anions induce the formation of Cl-AFm compounds (i.e., Kuzel’s and Friedel’s salt). Although the Class C fly ash’s reactivity is similar across different anions (for a fixed cation and Im), Class F fly ash shows a small change in reactivity depending on the anion present. NaCl suppresses (Class C and Class F) fly ash reactivity by up to 30 % as compared to neat CaCl2 and MgCl2-based brines. Thermodynamic modeling reveals that NaCl induces a considerable increase in pH—up to 13.7, where many hydrated phases of interest cease to be the major phase expected—as compared to CaCl2 and MgCl2 brines (pH &amp;lt; 13). In mixed-salt brines, anion immobilization is competitive: sulfate achieves a greater level of incorporation into the hydrates, as compared to chloride. These results offer new understanding of how the brine composition affects solidification and stabilization and thereby yield new insight into improved approaches for wastewater disposal.

Theoretical and Experimental Study of Fine Migration During Low-Salinity Water Flooding: Effect of Brine Composition on Interparticle Forces

Summary The majority of sandstone reservoirs contain clay particles. When clay is exposed to low-salinity water, fine detachment and migration occur due to multi-ion exchange and electrical double layer (EDL) expansion. Fine migration due to low-salinity water enhances oil recovery while damaging injection and production wells. This research investigates the effect of clay particles' weight percentage (wt%), ionic strength, total dissolved solids, and the injection rate of the low-salinity water on fine migration. The interparticle forces of kaolinite-kaolinite and kaolinite-quartz systems in various mediums were determined. Ten quartz sandpacks containing 2, 5, and 10 wt% of kaolinite were made to simulate clay-rich sandstone reservoirs. Afterward, different brines (10 and 50 mM solutions of NaCl, CaCl2, MgCl2, and Na2SO4 salts as well as seawater and its diluted samples) were injected into these sandpacks with different scenarios. It was observed that the interparticle forces for both systems in the presence of 10 mM solutions of NaCl, Na2SO4, and also 50 mM NaCl are repulsive. Therefore, even by injecting the low flow rate of these samples (0.1 cm3/min), the total fine migration was observed leading to intense permeability reduction in high clay-rich sandstones. However, in the case of low clay-containing sandpacks, the magnitude of permeability starts to rise a while after getting imposed to fine migration. In the presence of brines containing 50 mM MgCl2 and CaCl2, seawater, and its five-times diluted sample, the interparticle forces were an attraction, and fine migration occurred under no condition. However, using other samples of low-salinity water, the interparticle forces in the kaolin-kaolin system were repulsive and attractive in the kaolin-quartz system. Therefore, the phenomenon of partial fine migration occurs while flooding. So, in low-clay sandpacks, fines migrated only in high rate injection. However, the fine migration was evident for sandpacks containing 10 wt% of clay particles even by low flow rate injection. In general, there is a trade-off between the intensity of fine migration and divalent cations concentration in flooding water. Eliminating these cations or using them at 10 mM concentration may result in total fine migration, which is beneficial for low clay-containing media but damages clay-rich ones strongly. A high concentration of these cations prevents fines from movement, eradicating low-salinity flooding advantages. However, using medium concentrations results in partial fine migration, and the intensity, in this case, depends on clay concentration and flooding rate.

Electrodialysis for the Concentration of Lithium-Containing Brines-An Investigation on the Applicability.

The importance of lithium as a raw material is steadily increasing, especially in the growing markets of grid energy and e-mobility. Today, brines are the most important lithium sources. The rising lithium demand raises concerns over the expandability and the environmental impact of common mining techniques, which are mainly based on the evaporation of brine solutions (Salars) in arid and semiarid areas. In this case, much of the water contained in the brine is lost. Purification processes lead to further water losses of the ecosystems. This calls for new and improved processes for lithium production; one of them is electrodialysis (ED). Electrodialysis offers great potential in accessing lithium from brines in a more environmentally friendly way; furthermore, for the recovery of lithium from spent lithium-ion batteries (LIB), electrodialysis may become a vital technology. The following study focused on investigating the effect of varying brine compositions, different ED operation modes, and limiting factors on the use of ED for concentrating lithium-containing brine solutions. Synthetic lithium salt solutions (LiCl, LiOH) were concentrated using conventional ED in batch-wise operation. While the diluate solution was exchanged once a defined minimum concentration was reached, the concentrate solution was concentrated to the respective maximum. The experiments were conducted using a lab-scale ED-plant (BED1-3 from PCCell GmbH, Germany). The ion-exchange membranes used were PCSK and PCSA. The treated solutions varied in concentration and composition. Parameters such as current density, current efficiency, and energy requirements were evaluated. ED proved highly effective in the concentration of lithium salt solutions. Lithium chloride solutions were concentrated up to approximately 18-fold of the initial concentration. Current efficiencies and current densities depended on voltage, concentration, and the composition of the brine. Overall, the current efficiencies reached maximum values of around 70%. Furthermore, the experiments revealed a water transport of about 0.05 to 0.075% per gram of LiCl transferred from the diluate solution to the concentrate solution.

Role of salinity concomitant with asphaltene and resin on the interfacial tension of ionic liquid from imidazolium family

Imidazolium-based ionic liquids have been considered environmentally friendly surfactants with display high performance in the interfacial tension (IFT) reduction. On the other hand, adjusting/tuning ions composition of the aqueous media (such as SO4−, Ca2+, and Mg2+) is an important feature in the smart water-enhanced oil recovery process. Since oil composition (particularly asphaltene and rein fractions) demonstrates the remarkable impact on the interfacial behavior of crude oil/aqueous solution, the synergetic effect between [C12mim][Cl] IL and active ions in the seawater on the IFT of various synthetic oils were evaluated. The structural properties of asphaltene and resin fraction of two crude oil with API gravity of 32.3 (oil A) and 27.5 (oil B) (through preparing six synthetic oils) and tuning ion composition (through preparing five aqueous media) at an ionic strength of seawater (IS = 0.8 M) on the performance of the IL were evaluated. The results showed a lower IFT value of synthetic oils prepared by oil A than those prepared by oil B in the presence of all studied electrolyte solutions, due to the presence of more polar heteroatoms in the structure of asphaltene and resin extracted from oil A, indicates the dominant effect of the nature of oil type on the [C12mim]Cl surface activity compared to the effect of ion type (composition of brine).

Seasonal alteration of environmental condition-driven shift in microbiota composition, physicochemical attributes and organic compound profiles in aged Paocai brine during intermittent back-slopping fermentation

The aim of this study was to investigate the seasonal alterations in microbial composition and quality parameters of Paocai brine during back-slopping fermentation. With relatively constant reducing sugar levels across seasons, higher titratable acidity and lower pH was observed in summer and autumn. Organic compound analysis revealed higher production of lactic acid, acetic acid and γ-aminobutyric acid (GABA), and less free amino acids in summer. As for bacterial composition, Lactobacillus gradually flourished across winter, spring, summer and autumn, accompanied by decline of Pediococcus abundance. For fungal composition, Kazachstania and Pichia were dominant genera, with Pichia flourishing in spring and summer. Pearson's correlation analysis illustrated that, through driving microbial succession, jar temperature was the primary factor influencing quality of Paocai brine during back-slopping fermentation. Understanding the quality fluctuation of fermented vegetables across seasons along with ambient difference would be helpful for developing targeted technology to obtain products with stable and reproducible quality.

Influence of brine compositions on wetting preference of montmorillonite in rock/brine/oil system: An in silico study

In this paper, we investigated dependency of thin brine film stability confined between rock and hydrocarbon layer on brine solution properties in terms of salinity and anionic components. Molecular Dynamics simulation was used to investigate behavior of the system at rock/brine and brine/oil interfaces to characterize thin brine film. Here, montmorillonite, a thin water film containing different salinities (low salinity water, 5,000 ppm, and high salinity water, 70,000 ppm) of NaCl and Na2SO4, and organic components constituting 3:1 M mixture of decane and sodium decanoate were considered to represent rock, brine, and oil, respectively. High salinity brine makes the thin film more stable. Extensive repulsive electrostatic forces between Cl− anions distributed in brine film and carboxylate functional groups at the brine/oil interface impede penetration of oil components into the brine film and then their adsorption onto the clay surface. Low salinity Na2SO4 showed the most stable brine film, in which distribution of anions at the brine/oil interface prevents intrusion of oil components into the brine film. However, high salinity Na2SO4 showed strong potential in forming ionic aggregations comprising Na+ cations and anions. These ionic aggregations act as bridging agents to adhere oil constituents onto the clay slab.

Method Measures Effective Scale-Inhibitor Concentration at Low Detection Limit

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209503, “A Fast and Accurate Method for Scale-Inhibitor Effective Concentration Measurement With Low Detection Limit,” by Xin Wang, Rice University; Zhaoyi Dai, SPE, China University of Geosciences; and Saebom Ko, Rice University, et al. The paper has not been peer reviewed. _ The accurate measurement of residual scale-inhibitor concentration in produced brine is essential for scale prevention. However, these scale inhibitors are effective at substoichiometric concentrations in most production conditions. It is difficult to measure such low inhibitor concentration with traditional methods, especially for non- or low-phosphorous polymeric scale inhibitors. In the complete paper, an assay method is developed to determine effective scale-inhibitor concentration. The presented assay method is quick, robust, and accurate, with a relative error of less than 10% even at 1 mg/L of inhibitor. Experimental Setup and Methods Brine Chemistry Inhibitor (BCIn) Continuous-Stirred-Tank Reactor (CSTR) Method. The schematic of the BCIn CSTR testing apparatus is shown in Fig. 1. The original supersaturated solution (OSS) with a designated barite scale inhibitor is injected into the reaction vial with no head space. This OSS may contain zero or a certain amount of scale inhibitor, and it will be stirred continuously and kept at room temperature during the whole test period. At Time 0, the cation titrant solution (TC) and the anion titrant solution (TA) start to be pumped continuously into the reaction vial with the same flow rate by using two syringe pumps. A green laser beam (with a wavelength of 532 nm) is shone through the reaction vial; light intensity is recorded continuously as current by using a multimeter with a photodiode detector in real time. The time between Time 0 and the solution turbidity change, which is detected as current drop, is defined as the critical time. Without the supply of scale inhibitor from the TC and TA solutions, the inhibitor concentration in the reaction vial decreases exponentially and the inhibitor concentration at Time t can be calculated. With continuous dilution of the inhibitor and continuous supply of the barite supersaturated solution in the reaction vial by TC and TA solution, the small nuclei and crystals begin to accumulate in the reaction vial, resulting in a turbidity change detected by the laser at the critical time. Because of the exponential decrease of the scale inhibitors, it is observed that, with the same solution composition and residence time, critical time increases linearly with the initial concentration of inhibitor. A series of tests is designed to match the composition of target brine with different amounts of scale inhibitors. The standard curve can then be developed. For the brine with an unknown amount of scale inhibitor, the inhibitor concentration can be calculated from the measured critical time. The known-additions method also can be used to determine the unknown inhibitor concentration in a sample. This process, and its associated equations, is provided in the complete paper, as is sample pretreatment.

Stable Phase Equilibria in the Quaternary Systems LiBr–NaBr–SrBr2–H2O and LiBr–KBr–SrBr2–H2O at 288.15 K

Aiming at the composition of underground brines in the Sichuan Basin of China, stable phase equilibria in quaternary systems LiBr–NaBr–SrBr2–H2O and LiBr–KBr–SrBr2–H2O at 288.15 K are studied using the isothermal dissolution equilibrium method. The solubilities of salts in the quaternary systems listed above are measured, and the corresponding equilibrium solid phases are identified using X-ray powder diffraction. As a result, the corresponding phase diagrams of the two quaternary systems are plotted, respectively. In the two stable phase diagrams, there is no solid solution or complex salt at 288.15 K. For the quaternary system LiBr–NaBr–SrBr2–H2O, there are two invariant points, five univariate curves, and four solid crystallization regions, which are LiBr·2H2O, NaBr, NaBr·2H2O, and SrBr2·6H2O, respectively, of which LiBr·2H2O has the smallest crystallization field, indicating that its solubility is the largest and it is the hardest to be precipitated from the saturated solution. There are one invariant point, three univariate curves, and three solid crystallization fields, corresponding to LiBr·2H2O, KBr, and SrBr2·6H2O in the quaternary system LiBr–KBr–SrBr2–H2O, respectively. The experimental results show that the solubilities of salts KBr, NaBr, and SrBr2 in the saturated solution decrease with the increasing concentration of LiBr, which indicates that LiBr has a strong salting out effect on KBr, NaBr, and SrBr2 in the solution.

The strontium isotope fingerprint of phosphate rocks mining

High concentrations of metal(loid)s in phosphate rocks and wastewater associated with phosphate mining and fertilizer production operations pose potential contamination risks to water resources. Here, we propose using Sr isotopes as a tracer to determine possible water quality impacts induced from phosphate mining and fertilizers production. We utilized a regional case study in the northeastern Negev in Israel, where salinization of groundwater and a spring have been attributed to historic leaking and contamination from an upstream phosphate mining wastewater. This study presents a comprehensive dataset of major and trace elements, combined with Sr isotope analyses of the Rotem phosphate rocks, local aquifer carbonate rocks, wastewater from phosphate operation in Mishor Rotem Industries, saline groundwater suspected to be impacted by Rotem mining activities, and two types of background groundwater from the local Judea Group aquifer. The results of this study indicate that trace elements that are enriched in phosphate wastewater were ubiquitously present in the regional and non-contaminated groundwater at the same levels as detected in the impacted waters, and thus cannot be explicitly linked to the phosphate wastewater. The 87Sr/86Sr ratios of phosphate rocks (0.707794 ± 5 × 10−5) from Mishor Rotem Industries were identical to that of associated wastewater (0.707789 ± 3 × 10−5), indicating that the Sr isotopic fingerprint of phosphate rocks is preserved in its wastewater. The 87Sr/86Sr (0.707949 ± 3 × 10−6) of the impacted saline groundwater were significantly different from those of the Rotem wastewater and the background saline groundwater, excluding phosphate mining effluents as the major source for contamination of the aquifer. Instead, the 87Sr/86Sr ratio of the impacted water was similar to the composition of brines from the Dead Sea, which suggests that the salinization was derived primarily from industrial Dead Sea effluents with distinctive Sr isotope and geochemical fingerprints.

Coreflooding and Steady-State Principles Determine Reaction Kinetics

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209380, “Reaction Kinetics Determined From Coreflooding and Steady-State Principles for Stevns Klint and Kansas Chalk Injected With MgCl2 Brine at Reservoir Temperature,” by Pål Østebø Andersen, Reidar Inge Korsnes, and Andre Tvedt Olsen, University of Stavanger, et al. The paper has not been peer reviewed. A methodology is presented for determining reaction kinetics from coreflooding. A core is flooded with reactive brine at different compositions with injection rates varied systematically. Each combination is performed until steady state, when effluent concentrations no longer change significantly with time. The authors also propose shut-in tests where brine reacts statically with the core for a defined period and then is flushed out. The residence time and produced brine composition is compared with the flooding experiments. This design allows characterization of the reaction kinetics from a single core. The steady-state method allows computationally efficient matching even with complex reaction kinetics. Introduction The complete paper presents a methodology to interpret reactive flow experiments. The main principle is to focus on the steady-state data collected when effluent concentrations do not change further with time for given injected composition, injection rate, core properties, temperature, and pressure. Such measurements depend only on the dynamic equilibrium between reactions, advection, and to some extent dispersion, while transient events and mechanisms can be ignored. The authors hypothesize that, by measuring such data under different injected compositions, injected rates, and temperatures, characterization of reaction kinetics is possible with great detail. This is demonstrated by performance of reactive flow experiments on chalk cores at varied conditions with the purpose of collecting steady-state data. A key advantage from the interpretation perspective is that complicated reactive transport equations can be simplified by ignoring the changes in time and only simulating and matching the steady state. The experimental setup is detailed in the complete paper, as is a general description of advection-dispersion-reaction systems, a description of steady states in an advection-dispersion-reaction system and an advection-reaction system, and a theoretical description of a magnesium chloride (MgCl2)/calcite system.