Brine Salinity Research Articles

An active molybdenum (polymetallic)-enriching system in foreland basins

Molybdenum (polymetallic)-rich saline brines from the Badain Jaran Desert to the north of the Tibetan Plateau reveal active enrichment of trace metals in the groundwater systems of foreland basins. Molybdenum (polymetallic)-rich brines have salinities of 224–338 g/L and high concentrations of Mo (~3.7 mg/L), Li (~5.8 mg/L), U (~0.65 mg/L), Rb (~2.0 mg/L), Sr (~6.1 mg/L), Mn (~0.62 mg/L), and Ni (~0.52 mg/L). The major ions in the brines are Na+ and Cl−, with small amounts of SO42−. The pH and Eh values are 8.50–8.82 and >200 mV, respectively, with dissolved O contents of >6 mg/L. The δD and δ18O values of these saline brines are −29.2 ‰ to −31.0 ‰ and +0.3 ‰ to +2.8 ‰, respectively, and they exhibit a similar trend to the regional evaporation line, suggesting that the Mo (polymetallic)-rich saline brines originated from evaporation of groundwater in the Badain Jaran Desert. The 3He/4He (R) and R/Ra ratios of the brines are 0.42–2.11 and 0.30–1.51, respectively, and the 38Ar/36Ar and 40Ar/36Ar ratios are 0.194–1.464 and 267.4–360.2, respectively. These results suggest that the Mo-rich saline brines interacted with detrital material in the Badain Jaran Desert and extracted both cosmogenic 3He and radiogenic 4He. We propose that the Mo (polymetallic)-rich saline brines originated from evaporation of groundwater in the Badain Jaran Desert. Regional faults are responsible for the supply of precipitation-derived groundwater to the study area.

Desalination brine effects beyond excess salinity: Unravelling specific stress signaling and tolerance responses in the seagrass Posidonia oceanica.

Desalination has been proposed as a global strategy for tackling freshwater shortage in the climate change era. However, there is a concern regarding the environmental effects of high salinity brines discharged from desalination plants on benthic communities. In this context, seagrasses such as the Mediterranean endemic and ecologically important Posidonia oceanica have shown high vulnerability to elevated salinities. Most ecotoxicological studies regarding desalination effects are based on salinity increments using artificial sea salts, although it has been postulated that certain additives within the industrial process of desalination may exacerbate a negative impact beyond just the increased salinities of the brine. To assess the potential effect of whole effluent brines on P. oceanica, mesocosm experiments were conducted within 10 days, simulating salinity increment with either artificial sea salts or brines from a desalination plant (at 43 psμ, 6 psμ over the natural 37 psμ). Morphometrical (growth and necrosis), photochemical (PSII chlorophyll a fluorometry), metabolic, such as hydrogen peroxide (H2O2), thiobarbituric reactive substances (TBARS) and ascorbate/dehydroascorbate (ASC/DHA), and molecular (expression of key tolerance genes) responses were analyzed in each different treatment. Although with a still positive leaf growth, associated parameters decreased similarly for both artificial sea salt and brine treatments. Photochemical parameters did not show general patterns, although only P. oceanica under brines demonstrated greater energy release through heat (NPQ). Lipid peroxidation and upregulation of genes related to oxidative stress (GR, MnSOD, and FeSOD) or ion exclusion (SOS3 and AKT2/3) were similarly incremented on both hypersalinity treatments. Conversely, the ASC/DHA ratio was significantly lower, and the expression of SOS1, CAT, and STRK1 was increased under brine influence. This study revealed that although metabolic and photochemical differences occurred under both hypersalinity treatments, growth (the last sign of physiological detriment) was similarly compromised, suggesting that the potential effects of desalination are mainly caused by brine-associated salinities and are not particularly related to other industrial additives.

Stainless steel corrosion under anoxic, highly saline and elevated temperature conditions

Abstract. Several countries consider hosting a deep geological repository for high-level nuclear waste (HLW) in salt rock. In the unexpected case of solution access to the emplacement caverns during the long-term evolution of such a repository, metallic containers will be exposed to highly saline brines. In this study, corrosion experiments under conditions expected to be representative of HLW disposal in salt rock have been performed with stainless steel, a material typically used to construct containers containing vitrified HLW. Experiments were performed in closed vessels under anoxic and highly saline conditions at 90 ∘C. Polished stainless steel coupons were suspended in 5 mol L−1 NaCl or 3.4 mol L−1 MgCl2 at their natural pH. At the end of the experiments (up to 294 d), vessels were cooled down to room temperature, pH and Eh were measured in situ, the ultra-centrifuged contacting brines were analyzed by (HR)ICP-MS (high-resolution inductively coupled plasma mass spectrometry) and the formed corrosion products were identified. In all corrosion experiments, pHm and Eh hardly changed with exposure time, and the nature of the salt had no significant effect. The overall corrosion rates were low, and the quantities of dissolved metal ions revealed the formation of only sparingly soluble corrosion products. The formation of a passivation layer mostly made of Cr(III) (hydr)oxide was evidenced, but no localized surface attack could be detected. The coupon corroded in 5 mol L−1 NaCl was embedded in resin and cross-cut for further analyses, using synchrotron-based techniques with a small beam footprint (X-Ray fluorescence (μXRF), X-Ray diffraction (μXRD), and X-ray absorption near-edge structure (μXANES)). Element distribution maps revealed the presence of a very thin (<1 µm) layer of corrosion products, with regions enriched either in Cr or in Fe and Ni. X-ray diffractograms identified the presence of spinel-type compounds (Fe3O4 and NiFe2O4) and Cr2O3, which was corroborated by recording μXANES at the Cr, Fe and Ni K-absorption edges. The additional presence of layered double hydroxides in addition to NiO and Ni(OH)2 was also evidenced. Overall, results point to a corrosion layer having a duplex structure, with an inner layer mostly of chromium (hydr)oxides and an outer layer made of Fe- and Ni-based spinel compounds admixed with nickel (hydr)oxides.

Experimental performance analysis for reverse osmosis pilot plant subjected to different brackish salinity spectrum

The main obstacles to reverse osmosis desalination processes are high energy intensity and long-term continuity. Temperature and pressure have the greatest and most significant effects on energy use. The main objectives of the current study are to determine the pressure and temperature-dependent optimal operating parameters for a membrane desalination unit. To determine the ideal operating settings for a membrane unit, the impact of changing pressure and temperature on its performance was investigated. These two elements are closely connected to the energy consumption per cubic meter under various operating situations. The present work is experimentally carried out in a research laboratory for capacity building and future research studies in the desalination field established in the National Center of Water Research – Egypt. This laboratory is Egypt’s first multi-functional Desalination Research Station for seawater, brackish water, and related water treatment areas. The plant is equipped with online instrumentation and Data Acquisition System and 13 sensors for most physical parameters which economically affect membrane performance and desalination processes. These parameters, particularly pressure and temperature, are measured, evaluated and analyzed. According to the findings in this study, feed salinity and feed pressure both have significant impacts.At 13 bar pressure, the maximum salt rejection was 98.8%. When feed pressure is increased from 5 to 13 bars, there is a 73.3% decrease in permeate salinity. Additionally, applying a 13 bar feed pressure to water with a salinity of 1000 ppm results in the best water quality of 12 ppm. The relationship between feed pressure, brine salinity, and membrane water recovery appeared to be approximately linear and positive. More crucially, it was discovered that feed pressure, salinity, and water recovery are all constants for water permeability. A prototype for the maximum pressure (ranges from 15.6 to 10.8) and temperature (ranges from 21 to 35) at which the optimal recovery of the laboratory occurred was developed. Moreover, the developed prototype includes the corresponding permeate TDS and a specific energy for each optimal point.

Experimental study on nanoparticles-assisted low-salinity water for enhanced oil recovery in asphaltenic oil reservoirs

The purpose of this research is to look into the augmentation of silica nanoparticles (NPs) with low salinity (LowSal) brine for EOR. A series of analyses, including oil/water interfacial tension (IFT) and rock wettability tests were undertaken to determine an optimal dispersion to flood into a porous carbonate core with a defined pore size distribution. At 60 °C and 14.5 psi, the maximum drop (i.e., roughly 12.5 mN/m) in oil/water IFT by 0.3 wt.% brine occurred, but when 0.08 wt.% silica was added to the brine, the IFT reduced to 14.51 mN/m at 60 °C and 14.5 psi. The wettability analysis revealed a significant reduction in contact angle, from 142° to 72° and 59°, using 0.04 and 0.08 wt.% silica in LowSal brine, but the extent reduced by brine alone was insufficient. The results of rock pore size characterization were discussed in terms of the accomplishment of operating EOR in the porous medium in the presence of NPs. The addition of 0.08 wt. % silica to the injected brine resulted in an additional oil recovery of 16.3% OOIP as well as a significant shift in the endpoints/cross-points of the oil/water relative permeability curves. The findings of this research might help improve oil recovery from asphaltenic oil reservoirs or, more environmentally friendly, remediate petroleum crude-oil polluted soil.

An investigation of factors affecting Low Tension Gas process for enhanced oil recovery in carbonate reservoirs

Laboratory scale experiments have established LTG (Low Tension Gas) flooding to be a promising EOR method in low permeability and high salinity carbonate reservoirs for both tertiary and secondary recovery. In this work, three important factors that strongly influence the performance of LTG process are investigated: (i) wettability, (ii) injection gas type, and salinity variation. LTG flooding was investigated for the first time for low permeability carbonate cores, which had been aged for over five weeks after being oil flooded at residual water saturation (aged cores), and high formation brine salinity hardness. Hydrocarbon gas from the field was tested as a candidate for co-injection with surfactant solution to generate foam during LTG flooding. This eliminates the need for importing gas from an external source. Another innovation in the LTG process design is that the need for freshwater or treating the produced water from the field was removed by using the re-purposed high salinity produced water for all stages of the LTG flood. LTG floods in aged cores was observed to give oil recovery similar to non-aged cores under same conditions. LTG flood in aged cores resulted in a residual oil saturation of 11% compared to 19.4% using secondary WAG injection.

Modified ceramic membranes for the treatment of highly saline mixtures utilized in vacuum membrane distillation

Membrane Distillation processes could enable the treatment of highly saline solutions and facilitate minimal (MLD) or zero liquid discharge (ZLD) applications. Ceramic membranes can be a robust alternative to polymeric membranes if they are chemically modified to exhibit hydrophobic qualities to prevent wetting, particularly for vacuum membrane distillation (VMD). This study found that the thin top layer of asymmetrically structured ceramic membranes is robust enough for highly saline and abrasive suspensions and that TiO2 membranes outperform Al2O3 membranes in respect to the mass transport due to their larger support pore size and lower thermal conductivity. A maximum permeate flux of 35 kg/(m2 h) with exceptionally high rejections were measured in VMD using a saline brine with a concentration of 350 g NaCl per kg H2O. Furthermore, a VMD mass transfer model was successfully adopted (based on the Dusty Gas Model) to facilitate the calculation of the mass transfer through asymmetrically structured TiO2 membranes. Model deficiencies such as the underestimation of polarization effects were discussed, and correction factors integrated accordingly. This was done to establish a mass transfer modelling fundament for asymmetrical ceramic membranes used in MD that can be extended in future works and possibly serve as a tool for membrane optimization.

Economical, Simple‐to‐Prepare, and Salt‐Resistant Evaporator Based on Porous Activated Carbon for Sustainable Solar Evaporation

Interfacial solar vapor evaporation is expected to be an emerging technology to solve the scarcity of freshwater due to its sustainability and high efficiency. However, the present application of evaporators is mainly limited by the complex preparation process, expensive cost of raw material, and poor structure. Herein, based on coconut shell activated carbon (CSC) and ultrahigh molecular weight polyethylene (UHMWPE), a cost‐effective and robust CSC/UHMWPE (CSC/PE) evaporator is prepared through sintering in a mold. Benefiting from high light absorptance (≈90%) and excellent thermal localization, the CSC/PE evaporator exhibits an evaporation rate of 1.340 kg m−2 h−1 and an evaporation efficiency of 80.57% in 3.5 wt% brine under 1 sun irradiation. Moreover, by regulating the component ratios, the CSC/PE evaporator achieves superhydrophilicity and proper water transportation rate, and shows long‐term stability with an average evaporation rate of 1.309 kg m−2 h−1 in natural seawater for 10 h. Specifically, the high porosity CSC/PE facilitates the salt resistance in high salinity brine (15 wt%). Importantly, the cost‐effectiveness of CSC/PE is 53.43 g h−1 $−1, which is economical compared to other reported evaporators. Therefore, the economical, simple‐to‐prepare, and durable CSC/PE evaporator has enormous potential in interfacial solar vapor evaporation for freshwater production.

An experimental and numerical investigation on mechanical behavior of sandstone specimens saturated in brine

The mechanical behavior of reservoir rock saturated in brine is of great interest to scientists and engineers for geological CO2 sequestration in deep saline aquifers. However, the mechanical behavior of brine-saturated sandstone under triaxial compression has not been fully investigated, particularly with numerical simulations. In this study, an experimental study and numerical simulation were carried out on brine-saturated sandstone specimens to explore the mechanical properties in sandstones subjected to various brine salinities. Laboratory uniaxial compression tests were conducted on the brine-saturated sandstone specimens, and enhancements in strength and elastic modulus were observed with increasing brine salinity. Scanning electron microscopy results showed NaCl crystals deposited in the pore spaces, which provides evidence of strength and modulus variation in sandstone after brine saturation. Microparameters in a PFC3D numerical model were calibrated for each brine salinity condition, and the numerically simulated results were compared with the experimental results. The numerical results agreed well with the triaxial compression test results, indicating the appropriateness and reasonability of the calibrated models.

Development and Application of New Multifunctional Foaming Agents to Enhance Production in Oil Wells

Summary Maintaining or increasing production from wells in mature oil reservoirs with high pressure, temperature, brine hardness, and salinity is a significant technological and economic challenge. These wells usually produce with a high gas-oil ratio and large water cuts and often operate with gas lift systems. This work focuses on the development and application of new multifunctional foaming agents (MFAs) to enhance production from oil wells under these conditions. The MFAs were developed based on molecular design and laboratory studies, which demonstrated that they can be used with water cuts exceeding 30% and in the presence of salinity and hardness levels up to 400,000 ppm and 180,000 ppm, respectively. Furthermore, these agents remain stable at temperatures up to 180°C. The production/lift efficiency of the MFAs was evaluated using two novel dynamic laboratory methods that are conducted close to the wellhead and at downhole conditions of temperature and pressure, respectively. The experimental results demonstrate a significant enhancement in the liquid production efficiency, with some cases showing an increase from no production to as much as 44% when the MFAs were used. The laboratory tests were also used to optimize the MFA type and concentration in the design of a field application. The field test was conducted in three oil wells with water cuts ranging from 40% to 90%, depths exceeding 5000 m, bottomhole temperature around 150°C, and brine hardness and salinity up to 180,000 ppm and 310,000 ppm, respectively. This is the first reported field test of MFAs for production enhancement under such challenging conditions. The MFA was coinjected with gas lift via the annulus. The MFA mixed with reservoir fluids in the tubing and generated foam downhole with concentrations ranging from 160 ppm to 750 ppm. The rheological properties of the foam were designed to prevent pressure losses and the formation of stable foam or emulsions at surface facilities. The field tests demonstrated that the MFA was able to increase oil production at a fixed gas lift injection flow rate. Alternatively, it was able to reduce lift gas consumption while maintaining or even increasing the original oil production.

Temperature, Salinity and Garlic Additive Shape the Microbial Community during Traditional Beetroot Fermentation Process.

Plant-based traditional fermented products are attracting a lot of interest in global markets. An example of them is beetroot leaven, which is valued for its high bioactive compound content. The variety of production recipes and the spontaneous nature of red beet fermentation favor its high diversity. This study aimed to analyze the impact of external factors-temperature, brine salinity, and garlic dose-on the beetroot fermentation and bacterial metapopulation responsible for this process. The research results confirmed the significant influence of the selected and analyzed factors in shaping the leaven physicochemical profile including organic acid profile and betalain content. Analysis of bacterial populations proved the crucial importance of the first 48 h of the fermentation process in establishing a stable metapopulation structure and confirmed that this is a targeted process driven by the effect of the analyzed factors. Lactobacillaceae, Enterobacteriaceae, and Leuconostocaceae were observed to be the core microbiome families of the fermented red beet. Regardless of the impact of the tested factors, the leaven maintained the status of a promising source of probiotic bacteria. The results of this research may be helpful in the development of the regional food sector and in improving the quality and safety of traditionally fermented products such as beetroot leaven.

Prediction of interfacial wetting behavior of H2/mineral/brine; implications for H2 geo-storage

Underground hydrogen storage (UHS) is a suitable option for large-scale and long-term storing of hydrogen (H2), which is considered a highly promising energy carrier, offering an efficient solution to replace fossil fuels and achieve net-zero carbon emission targets. The successful storage and withdrawal of H2 are highly dependent on the wettability of the H2/mineral/brine system. Despite the importance of the interfacial wetting behavior of H2/mineral/brine in sedimentary formations, no accurate and generalized model has been developed yet for a fast and valid prediction of the contact angle. In the context, three intelligent models, namely multi-layer perceptron (MLP), radial basis function (RBF), and least square support vector machine (LSSVM) have been proposed to accurately predict the contact angle of H2/mineral/brine systems. Another primary objective is to thoroughly scrutinize the extent to which various parameters influence the contact angle. Results of models approved their capability in validly predicting the contact angle for a wide range of mineral types, considering the effects of thermodynamic conditions, brine salinity, cushion gases, surface coating, and surface roughness. The results also demonstrated that the LSSVM model outperforms the MLP and RBF models with coefficients of determination (R2), root mean square error (RMSE) and average absolute relative deviation (AARD) of 0.9942, 1.6133 and 1.6924 %, respectively, indicating higher accuracy and reliability. Moreover, sensitivity analysis confirmed that the rock mineralogies, in particular the percentage of quartz and calcite, followed by the presence or absence of cushion gas, as well as surface roughness/contamination exerted a greater influence on predicting the contact angle within the H2/mineral/brine system.

A novel solar-powered thermal desalination unit coupled with a reverse osmosis plant to increase overall water recovery

The global water crisis could be alleviated by converting saline water to potable water through desalination technologies. Reverse osmosis is the dominant technology in the market. However, its brine disposal is challenging. This paper proposes and investigates a novel hybridization between a solar-driven reverse osmosis plant and a solar-driven thermal desalination unit to enhance the water recovery ratio (freshwater produced/feed saline water). The thermal desalination unit combines an adsorption cycle, ejectors, and a humidification-dehumidification cycle. The brine from the reverse osmosis unit is used as a feed for the thermal desalination unit to produce higher amounts of freshwater. The extra-high saline water discharged from the proposed system can be used for salt extraction in a solar pond as a byproduct. Theoretical and economic models are developed to evaluate the performance and cost of the proposed system. It is found that the recovery ratio of standalone reverse osmosis and the proposed hybrid desalination plant is 40.8% and 70.5%, respectively, having a feed salinity and brine salinity limit of 32,500 ppm and 110,000 ppm. The recovery ratio of the hybrid system could reach 84%, with brine disposal of 220 ppm (which is valid for salt crystallization processes). The reduction in freshwater cost by using the hybrid plant is 23% to 27% compared to the standalone reverse osmosis plant for 40,000 to 50,000 ppm feed salinity and 10 m3 plant capacity. The suggested system can produce freshwater of 83 and 47 m3 per ton of silica gel per day at the gained output ratio of 2.71 and 2.6 in June and December, respectively.

The effect of partial dissolution on sea-ice chemical transport: a combined model–observational study using poly- and perfluoroalkylated substances (PFASs)

Abstract. We investigate the effect of partial dissolution on the transport of chemicals in sea ice. Physically plausible mechanisms are added to a brine convection model that decouples chemicals from convecting brine. The model is evaluated against a recent observational dataset where a suite of qualitatively similar chemicals (poly- and perfluoroalkylated substances, PFASs) with quantitatively different physico-chemical properties were frozen into growing sea ice. With no decoupling the model performs poorly – underestimating the measured concentrations of high-chain-length PFASs. A decoupling scheme where PFASs are decoupled from salinity as a constant fraction of their brine concentration and a scheme where decoupling is proportional to the brine salinity give better performance and bring the model into reasonable agreement with observations. A scheme where the decoupling is proportional to the internal sea-ice surface area performs poorly. All decoupling schemes capture a general enrichment of longer-chained PFASs and can produce concentrations in the uppermost sea-ice layers above that of the underlying water concentration, as observed. Our results show that decoupling from convecting brine can enrich chemical concentrations in growing sea ice and can lead to bulk chemical concentrations greater than that of the liquid from which the sea ice is growing. Brine convection modelling is useful for predicting the dynamics of chemicals with more complex behaviour than sea salt, highlighting the potential of these modelling tools for a range of biogeochemical research areas.

An experimental assessment of seawater alternating near-miscible CO2 for EOR in pre-salt carbonate reservoirs

Enhanced oil recovery (EOR) methods considering the injection of seawater and CO2 have been widely investigated and applied in the Brazilian pre-salt fields. The high availability of these fluids in offshore facilities makes seawater alternating CO2 (CO2WAG) a viable and environmentally friendly EOR method. It combines the advantages of seawater injection and CO2 injection to improve fluid mobility control and viscous fingering attenuation. In this study, in addition to the core flooding test of secondary seawater flooding and the tertiary CO2WAG, different experimental determinations provided a better understanding of the mechanisms related to the EOR methods applied to a carbonate core composed mainly of dolomite, and their interactions with pre-salt oil, brines and CO2. A 13.30% incremental oil recovery was achieved by alternating seawater with CO2. Considering formation brine, non-carbonated seawater, or seawater saturated with CO2, contact angle measurements revealed that the wettability alteration is not significant when dolomite is slightly water-wet, even in the presence of CO2. On the other hand, measures of brine/oil, brine/CO2/oil and CO2/oil interfacial tension emphasize the beneficial effects of this gas for EOR, in near-miscible conditions. This is achieved by the reduction of capillary and interfacial forces that act by trapping the oil in the pores of the medium. The brine salinity, the presence of magnesium in dolomite and the oil's low TAN/TBN ratio proved to be essential factors in determining the slightly water-wet wettability of the dolomitic rock and the interfacial tension between the phases. Furthermore, for the experiments carried out in the presence of brine with solubilized CO2, a considerable variation in the oil drop volume was observed due to the mass transfer of CO2 between the phases. Finally, experimental results showed that the additional oil recovery was mainly associated with oil swelling, viscosity reduction, and mobility increase, which occur even in near-miscible conditions during CO2WAG.

Monte Carlo simulation of the maximum migration distance of CO[formula omitted] in a sloping aquifer

Carbon capture and storage in saline aquifers is broadly considered a viable technology for reducing anthropogenic impact on the environment. However, a secure CO2 storage can be compromised by the depositional environments of target reservoirs, which can influence the CO2 migration in subsurface. The disposal of CO2 in a sloping aquifer can result in a substantial gas migration in the updip direction from the injection well until all gas becomes trapped. It thus can reach far more than desired regions from the well where the potential leakage paths to the surface can exist. This study aims at understanding the principal parameters that the maximum migration distance in the updip direction depends on, which can be important for estimating the risks of CO2 leakage through old abandoned wells in the regions of intensive subsurface exploration. Using the Monte Carlo method, an extended parametric study is performed by running 3-D reservoir simulations of CO2 storage in random aquifers characterized by various petrophysical and thermobaric parameters, saturation functions and brine salinity, and for the wells operated under different target rates. Herewith, the modeling accounts for such relevant physical phenomena as the phase transitions, the gravity and capillary forces, the hysteresis behavior of the relative permeability, etc. It is shown that the maximum migration distance at the post-injection stage is characterized by just two similarity criteria and the critical gas saturation for the drainage and imbibition processes. It is found that the CO2 plume shape at the moment of the well shut-in influences the subsequent gas transport. A new simple relation parameterizing the revealed dependence is proposed and validated against the sampled maximum migration distances. The relation is useful for an instant estimating the size of the contaminated zone around a projected CO2 well and for ranking the potential storage sites.

Evaluating the role of salts on wettability alteration in dolomite rocks: Possibility of water based oil mobilization application

While many low salinity studies have been conducted on chalks, calcite minerals and sandstone rocks, few research articles have explored the same for applications in dolomite rocks. To explore the effect of mineralogy, a comparative study on the wettability alteration in the presence of low salinity brines for 2 carbonate rocks of varying composition was studied. The contact-angle experiments were performed for two carbonate samples. One carbonate sample was composed of ∼100 % dolomite mineral whereas the other carbonate rock sample was composed of both dolomite and calcite mineral (5 % calcite and 95 % dolomite). The ionic solutions were composed of NaCl, MgCl2, CaCl2 and CaSO4 single salt solutions of concentration (500 ppm to 5000 ppm). The contact angle reduction was observed in the following order CaSO4 > MgCl2 > CaCl2 > NaCl for the carbonate sample containing calcite and dolomite minerals and the maximum reduction in contact angle for the carbonate sample containing dolomite and calcite minerals was observed for CaSO4 brines was 26.13 % for 1000 ppm concentration. The contact angle reduction observed for the carbonate sample containing dolomite mineral was found to be in the following order MgCl2 > CaCl2 > CaSO4 > NaCl and the maximum reduction in contact angle was observed for MgCl2 brines was 24.58 % for 3000 ppm concentration. The wettability alteration observed in the carbonate sample containing dolomite mineral was less as compared to the carbonate sample containing calcite and dolomite mineral. In the presence of MgCl2 brines, the pH of the brines dominates the mineral dissolution, thereby improving or reducing the extent of wettability alteration. However, the complete wettability reversal has not been observed in this study. An increase in temperature (from 70 to 90 °C) was found to be favourable for wettability alteration while the presence of calcites, along with dolomites has the potential to further improve oil recovery.

Evaluation of the coupled impact of silicon oxide nanoparticles and low-salinity water on the wettability alteration of Berea sandstones

This study investigated experimentally the coupled effects of hydrophilic SiO2 nanoparticles (NPs) and low-salinity water (LSW) on the wettability of synthetic clay-free Berea sandstone. Capillary pressure, interfacial tension (IFT), contact angle, Zeta potential, and dynamic displacement measurements were performed at various NP mass fractions and brine salinities. The U.S. Bureau of Mines (USBM) index was used to quantify the wettability alteration. Furthermore, the NP stability and retention and the effect of enhanced oil recovery by nanofluid were examined. The results showed that LSW immiscible displacement with NPs altered the wettability toward more water wet. With the decreasing brine salinity and increasing NP mass fraction, the IFT and contact angle decreased. The wettability alteration intensified most as the brine salinity decreased to 4000 mg/L and the NP mass fraction increased to 0.075%. Under these conditions, the resulting incremental oil recovery factor was approximately 13 percentage points. When the brine salinity was 4000 mg/L and the NP mass fraction was 0.025%, the retention of NPs caused the minimum damage to permeability.

Synergetic Interfacial Tension Reduction Potential of Silica Nanoparticles and Enzyme

The co-existence of multiphase fluids in the hydrocarbon reservoir rock pores plays a fundamental role in oil recovery processes because of the strong effect of interfacial forces that exist at the interface of these immiscible fluids. In this study, the effects of enzyme and silica nanoparticles on crude oil-brine interfacial tension were investigated under varied brine salinities and brine compositions. The results showed that the application of silica nanoparticles alone in brines of varied compositions and salinities does not significantly modify the crude oil-brine IFT. The use of enzyme and combined enzyme-nanoparticles however significantly reduced crude oil-brines IFT but the contribution of silica nanoparticles to the IFT reduction was not significant. The result of this study is relevant to the design and applications of enzyme and nanoparticles enhanced oil recovery processes.

Prediction of shale wettability using different machine learning techniques for the application of CO2 sequestration

Understanding the behavior of carbon dioxide (CO2) wetting in shale formations is crucial for various applications such as CO2-enhanced oil recovery, CO2 foam hydraulic fracturing, and CO2 storage in saline aquifers and shale formations. However, traditional laboratory methods to determine shale wettability, including contact angle measurements and nuclear magnetic resonance spectroscopy, can be time-consuming and expensive. This study aims to overcome these limitations by utilizing machine learning (ML) techniques to estimate shale wettability based on shale characteristics and experimental conditions.A dataset was collected, encompassing different shale samples under various conditions, including pressure, temperature, and brine salinity, to predict shale wettability. Pearson's correlation coefficient and linear regression analysis were employed to assess the relationship between the contact angle value and other input parameters. ML models, including decision tree, random forests, function networks, and gradient boosting regressor, were utilized for shale wettability prediction.Operating pressure, temperature, rock mineralogy, and total organic content were identified as influential factors on shale wettability. While the linear regression model showed limited accuracy, the ML models, especially random forests, decision tree, gradient boosting regressor, and function networks, effectively predicted the contact angle value with high R2 values. Gradient boosting regressor demonstrated the best performance, achieving R2 values of 0.99 and 0.98 for the training and testing datasets, respectively, with a root mean square error below 5 degrees. Sensitivity analysis revealed the significant impact of pressure on shale wettability, with low pressures resulting in water-wet shale regardless of other shale properties.The study highlights the efficacy of the developed ML models in predicting shale wettability in the context of CO2-water-shale systems, providing a faster and more affordable alternative to complex experimental analyses.