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Polymer flooding is an effective development technology to enhance oil recovery, and it has been widely used all over the world. However, after long-term polymer flooding, a large number of oilfields have experienced a sharp decline in reservoir development efficiency. High water cut wells, serious dispersion of residual oil distribution and complex reservoir conditions all bring great challenges to enhance oil recovery. In this study, the method of enhancing oil recovery after polymer flooding was studied by taking the S Oilfield as an example. A surfactant-polymer system suitable for high-permeability heterogeneous oilfields was developed, comprising biogenic surfactants and polymers. Microscopic displacement experiments were conducted using cast thin sections from the S Oilfield, and nuclear magnetic resonance was employed for core displacement experiments. Numerical simulation experiments were also conducted on the S Oilfield. The results show that the enhanced oil recovery mechanism of the surfactant-polymer system is to adjust the flow direction, expand the swept volume, emulsify crude oil and reduce interfacial tension. Surfactant-polymer flooding proves to be effective in improving recovery efficiency, significantly reducing the time of flooding and further enhancing the strong swept area. The nuclear magnetic resonance results indicate a high amplitude of passive utilization of residual oil during the surfactant-polymer flooding stage, highlighting the enormous potential for an increased recovery ratio. Surfactant-polymer flooding emerges as a more suitable technique to enhance oil recovery in the post polymer-flooding stage in high-permeability heterogeneous oilfields.

Globally, most oil fields use excessive water flooding to recover oil. By injection of water between wells, channels are created, which result in lower oil recovery. Water-plugging deep-profile control must be used to control the excessive water production from an oil reservoir. This laboratory study used sulfonated polyacrylamides with a molecular weight of 10.3-13.0 × 10 6 Da (FPAM) and polyethylenimine (PEI-600) to formulate a weak gel system to control excessive water production from deep formations. Using different FPAM and PEI-600 concentrations, the Sydansk bottle test approach was applied to evaluate the gelation time, strength, and stability of the weak gel. The weak gel concentration of 0.5 wt % FPAM and 0.4 wt % PEI-600 was confirmed for deep-profile control by this approach. The temperature and salt resistance of the selected weak gel system were evaluated using the same bottle test methodology. The gelation time depends on temperature: 5-7 days at <100 °C to 0.5 days >100 °C. Salinity >20,000 mg/L significantly affected the weak gel system's strength. By performing a viscometer test, the viscosity of the weak gel system at different times was evaluated, confirming the gelation time of the selected weak gel. Next, a microfluidic chip flooding test analyzed weak gel performance and plugging ability in porous media. This micromodel provided a visual analysis of the weak gel plug. Finally, a low- to medium-permeability sandstone core-flooding was conducted to determine the plugging rate of weak gel at the core scale, followed by an evaluation of the injection pressure, blocking effect, and oil recovery. According to the study, the selected weak gel has an extended gelation time with a significantly low viscosity, which affects its injectivity and can move from injection wells into deep formations. In the core-flooding test, the weak gel's blocking rate after 7 days of gelation time exceeded 90%., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The Henan Oilfield's medium-permeability blocks face challenges such as high temperatures and severe heterogeneity, making conventional flooding systems less effective. The starch gel system is an efficient approach for deep profile control in high-temperature reservoirs, while the nano-MoS 2 system is a promising enhanced oil recovery (EOR) technology for high-temperature low-permeability reservoirs. Combining these two may achieve the dual effects of profile control and oil displacement, significantly enhancing oil recovery in high-temperature heterogeneous reservoirs. The basic performance evaluation of the combination system was carried out under reservoir temperature. Displacement experiments were conducted in target blocks under different permeabilities and extreme disparity core flooding to evaluate the combination system's oil displacement effect. Additionally, the displacement effects and mechanisms of the starch gel and nano-MoS 2 combination system in heterogeneous reservoirs were evaluated by simulating interlayer and intralayer heterogeneity models. The results show that the single nano-MoS 2 system's efficiency decreases with increased core permeability, and its effectiveness is limited in triple and quintuple disparity parallel experiments. After injecting the starch gel-nano-MoS 2 combination system, the enhanced oil recovery effect was significant. The interlayer and intralayer heterogeneous models demonstrated that the primary water flooding mainly affected the high-permeability layers, while the starch gel effectively blocked the dominant channels, forcing the nano-MoS 2 oil displacement system towards unswept areas. This coordination significantly enhanced oil displacement, with the combination system improving recovery by 15.33 and 12.20 percentage points, respectively. This research indicates that the starch gel and nano-MoS 2 combination flooding technique holds promise for enhancing oil recovery in high-temperature heterogeneous reservoirs of Henan Oilfield, providing foundational support for field applications.

This work focuses on the development of a novel high-temperature microemulsion for enhanced oil recovery in tight oil reservoirs. Microemulsions are a type of mixture that has properties of both liquids and solids; they have shown significant potential for improving oil recovery through spontaneous imbibition. Herein, a high-temperature-tolerant lower-phase microemulsion using a microemulsion dilution method was developed. The properties and morphological characteristics of the microemulsion were evaluated and proposed a mechanism for enhanced spontaneous imbibition oil recovery using imbibition tests and CT scanning technology. The results of the study showed that the optimum concentration of the microemulsion was 0.2 wt% and that it had good thermal stability, small droplet size, lower interfacial tension, good wettability alteration ability, and minimum adsorption loss. The imbibition and CT experiments demonstrated that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force. The study concludes that the solubilization coefficient and self-driving force were defined and calculated to quantitatively analyze the imbibition mechanisms and the results showed that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force.

Gas flooding and foam flooding are potential technologies for tertiary oil recovery in fractured-vuggy reservoirs. The development and mechanism research of fractured-vuggy reservoirs is difficult due to the complex structures and the strong heterogeneity of fractured-vuggy reservoirs. Visualization simulation is one of the effective methods to study the flow behavior of fluid in fractured-vuggy reservoirs. In this study, an upscaling method of visualization simulation from one dimension (1D) to three dimensions (3D) was established, and the physical models of fractured-vuggy reservoirs were designed and fabricated. Water flooding, gas flooding, and gel foam flooding were carried out in the models. The experimental results showed that gas flooding has a single flow channel and water flooding has multiple flow channels in fractures and vugs. Gel foam with an excellent capability of mobility control and a high microscopic displacement efficiency swept in all directions at a uniform velocity. The EOR mechanisms of gel foam in fractured-vuggy reservoirs were mainly as follows: reducing interfacial tension, increasing mobility ratio, selectively plugging high permeability channels, and discontinuous flow. In the displacement process of fractured-vuggy reservoirs, water should be injected from the well at the bottom of the reservoir, and gas should be injected from the well located in the vug at the high part of the reservoir. Gel foam with strong stability and high viscosity should be selected and injected in most kinds of injection wells in fractured-vuggy reservoirs. This study provides a complete method of visualization simulation for the study of flow behavior in fractured-vuggy reservoirs and provides theoretical support for the application of gas flooding and gel foam flooding in fractured-vuggy reservoirs.

In view of the relevance of organic thin layers in many fields, the fundamentals, growth mechanisms, and dynamics of thin organic layers, in particular thiol-based self-assembled monolayers (SAMs) on Au(111) are systematically elaborated. From both theoretical and practical perspectives, dynamical and structural features of the SAMs are of great intrigue. Scanning tunneling microscopy (STM) is a remarkably powerful technique employed in the characterization of SAMs. Numerous research examples of investigation about the structural and dynamical properties of SAMs using STM, sometimes combined with other techniques, are listed in the review. Advanced options to enhance the time resolution of STM are discussed. Additionally, we elaborate on the extremely diverse dynamics of various SAMs, such as phase transitions and structural changes at the molecular level. In brief, the current review is expected to supply a better understanding and novel insights regarding the dynamical events happening in organic SAMs and how to characterize these processes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The high-temperature reservoir (105 °C) in the Liubei block of Jidong Oilfield, with severe longitudinal heterogeneity, has entered a high water-cut stage. After a preliminary profile control, the water management of the oilfield still faces serious water channeling problems. To strengthen water management, N 2 foam flooding combined with gel plugging for enhanced oil recovery was studied. In this work, considering a high-temperature reservoir of 105 °C, a composite foam system and starch graft gel system with high temperature resistance were screened out, and displacement experiments in one-dimensional heterogeneous cores were carried out. Through the three-dimensional experimental model and numerical model of a 5-spot well pattern, physical experiments and numerical simulations were carried out respectively to study water control and oil increase. The experimental results showed that the foam composite system had good temperature resistance up to 140 °C and oil resistance up to 50% oil saturation and was helpful to adjust the heterogeneous profile in a high temperature of 105 °C. The starch graft gel system had good injection performance, with a solution viscosity of 18.15 mPa·s, and its gel strength could effectively seal the high-permeability layer, with a gel viscosity of 34950.92 mPa·s. The displacement test results showed that after a preliminary implementation of N 2 foam flooding, N 2 foam flooding combined with gel plugging could still improve oil recovery by 5.26%. Compared with preliminary N 2 foam flooding, gel plugging could control the water channeling in the high-permeability zone near the production wells. The combination of foam and gel made N 2 foam flooding and subsequent waterflooding divert to flow mainly along the low-permeability layer, which was conducive to enhance water management and improve oil recovery. This method can be used as an effective technology to manage similar heterogeneous reservoirs., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Most of the oilfields are currently experiencing intermediate to late stages of oil recovery by waterflooding. Channels were created between the wells by water injection and its effect on the oil recovery is less. The use of water plugging profile control is required to control excessive water production from an oil reservoir. First, the well selection for profile control using the fuzzy evaluation method (FEM) and improvement by random forest (RF) classification model is investigated. To identify wells for profile control operation, a fuzzy model with four factors is established; then, a machine learning RF algorithm was applied to create the factor weight with high accuracy decision-making. The data source consists of 18 injection wells, with 70% of the well data being utilized for training and 30% for model testing. Following the fitting of the model, the new factor weight is determined and decisions are made. As a consequence, FEM selects 7 out of 18 wells for profile control, and by using the factor weight developed by RF, 4 out of 18 wells are chosen. Then, the profile control is conducted through a foam system proposed by laboratory experiments. A computer molding group numerical simulation model is created to profile the wells being selected by both methods, FEM and RF. The impact of foam system plugging on daily oil production, water cut, and cumulative oil production of both methods are contrasted. According to the study, the reservoir performed better when four wells were chosen by the weighting system developed by RF as opposed to seven wells that were chosen using the FEM model during the effective period. The weighting model developed by RF accurately increased the profile control wells' decision-making skills., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The CO 2 huff-n-puff process is an effective method to enhance oil recovery (EOR) and reduce CO 2 emissions. However, its utilization is limited in a channeling reservoir due to early water and gas breakthrough. A novel starch graft copolymer (SGC) gel is proposed for treating the channels and assisting with the CO 2 huff-n-puff process. Firstly, the bulk and dynamic performances of the SGC gel including rheology, injectivity and plugging ability are compared with the polymer gel in the laboratory. Then, 3D physical models with water channels are established to reveal the EOR mechanisms of gel assisted CO 2 huff-n-puff. Several pilot tests of gel assisted CO 2 huff-n-puff are also discussed in this paper. The bulk and dynamic experimental results show that although these two gelants have similar viscosities, the SGC gelant has a better injectivity compared with the polymer gelant. The SGC gel is predominantly a viscous solution, which make it easier to flow through the pore throats. The RF of the SGC gelant is only 0.58 times that of the polymer gelant. After the gelation, a 3D network-like gel with a viscosity of 174 267 mPa s can be formed using the SGC gelant. The RRF of the SGC gel is about three times that of the polymer gel, which shows that the SGC gel has a stronger plugging ability within the porous media. The 3D experimental results show that four cycles of gel assisted CO 2 huff-n-puff can achieve an EOR of 11.36%, which is 2.56 times that of the pure CO 2 huff-n-puff. After the channels are plugged by the SGC gel, the remaining oil of the near-wellbore area can be first extracted by CO 2 , and the oil of the deep formation can then be effectively displaced by the edge water. Pilot tests on five wells were conducted in the Jidong Oilfield, China, and a total oil production of 3790.86 m 3 was obtained between 2016 and 2021. The proposed novel SGC gel is suitable for assisting with the CO 2 huff-n-puff process, which is a beneficial method for further EOR in a water channeling reservoir., Competing Interests: The authors declare that there are no competing interests regarding the publication of this article., (This journal is © The Royal Society of Chemistry.)

Permeability reduction and formation damage in porous media caused by fines (defined as unconfined solid particles present in the pore spaces) migration is one of the major reasons for productivity decline. It is well accepted that particle detachment occurs under imbalanced torques arising from hydrodynamic and adhesive forces exerted on attached particles. This paper reviewed current understanding on primary factors influencing fines migration as well as mathematical formulations for quantification. We also introduced salinity-related experimental observations that contradict theoretical predictions based on torque balance criteria, such as delayed particle release and attachment-detachment hysteresis. The delay of particle release during low-salinity water injection was successfully explained and formulated by the Nernst-Planck diffusion of ions in a narrow contact area. In addition to the widely recognized explanation by surface heterogeneity and the presence of low-velocity regions, we proposed a hypothesis that accounts for the shifting of equilibrium positions, providing new insight into the interpretation of elusive attachment-detachment hysteresis both physically and mathematically. The review was finalized by discussing the quantification of anomalous salinity effect on adhesion force at low- and high-salinity conditions., (Copyright © 2022. Published by Elsevier Ltd.)

The major oil fields are currently in the middle and late stages of waterflooding. The water channels between the wells are serious, and the injected water does little effect. The importance of profile control and water blocking has been identified. In this paper, the decision-making technique for water shutoff is investigated by the fuzzy evaluation method, FEM, which is improved using a random forest, RF, classification model. A machine learning random forest algorithm was developed to identify candidate wells and to predict the well performance for water shutoff operation. A data set consisting of 21 production wells with three-year production history is used, where out of the mentioned well data, 70% of them are implemented for training and the remaining are used for testing the model. After fitting the model, the new weights for the factors are established and decision-making is made. Accordingly, 16 wells out of 21 wells are selected by the FEM where 8 wells out of 21 wells are selected by the new factor weight created by RF for water shutoff. A numerical simulation model is established to plug the selected wells by both methods after which the influence of plugging on water cut, daily oil production, and cumulative oil production is compared. The paper shows that the reservoir had a better performance after eight wells were selected using a new weighting system created by RF instead of the 16 wells that were selected using the FEM model. The paper also states that the new weighting model's accuracy improved the decision-making abilities of the wells., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Polymer microspheres (PMs) are a kind of self-similar volume expansion particle, and their fractal dimension varies with hydration swelling. However, there is no unique fractal dimension calculation method for their characteristics. A new model is established in this paper, which is particular to calculate the fractal dimension of PMs. We carried out swelling hydration experiments and scanning electron microscope (SEM) experiments to verify the new model. The new model and the box-counting model were used to calculate the fractal dimensions of PMs based on the hydration experiment results. Then, a comparison of the calculation results of the two methods was used to verify the validity of the model. Finally, according to the new model calculation results, the fractal dimension characteristics of PMs were analyzed. The research results indicate that the new model successfully correlates the cumulative probability of the PMs dispersed system with the fractal dimension and makes fractal dimension calculation of PMs more accurate and convenient. Based on the experiment results, the new model was used to calculate the fractal dimension of PMs and the box-counting model, and its findings were all 2.638 at initial state hydration and 2.739 and 2.741 at hydration time as of day 1. This result verifies the correctness of the new model. According to the hydration swelling experiments and the new model calculation results, the fractal dimension is linear correlated to the average particle size of PMs and the standard deviation average particle size. This means the fractal dimension of PMs represents the space occupancy ability and space occupancy effectiveness., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Zhao, Yan, Hou, Diwu, Liu, Hou and Li.)

Nitrogen gas flooding and foam flooding have been widely used for oil and gas development in fracture-vuggy carbonate reservoirs. However, flow behaviors of nitrogen and foams are not very clear owing to the complex connectivity of fractures and vuggys. In this work, four types of micro-visual fracture-vuggy models were designed and fabricated to systematically investigate the dynamic flow behaviors of nitrogen and foam in fracture-vuggy structures. Results indicate that the swept volume and oil displacement efficiency can be improved more by foam flooding than by nitrogen flooding owing to the abilities of foams on mobility adjustment, IFT reduction, and oil emulsification. The presence of vuggy can strengthen the effect of gravity differentiation during nitrogen flooding, while foam flooding can diminish the gravity differentiation effect. Besides, pressure difference at the curved oil-gas interface plays a great role in the flow characteristics of nitrogen and foam. Moreover, the EOR rate is used to evaluate the EOR potential of nitrogen foam flooding technology over nitrogen flooding technology. This work systematically reveals the dynamic flow behaviors of nitrogen and foam in various micro visual fracture-vuggy structures, which can provide theoretical support for the development of the fracture-cavity reservoir., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)

Diffusion coefficients are necessary to describe the mass transfer and adsorption rate of CO 2 in formation fluids. However, data is scarcely reported for actual reservoir conditions of high pressure and temperature, which are normal in most scenarios of the CO 2 -enhanced oil recovery process in China's fractured-vuggy reservoirs and carbon storage process. Accordingly, this work employed the pressure decay method (PD) and relevant mathematical models to determine the CO 2 diffusion coefficient in both liquids and cavern filling porous media at 50 MPa and 393 K. The effects of the type of reservoir fluids, the properties of carven filling porous media, and water saturation on CO 2 diffusion coefficients were investigated. Results in bulk reservoir liquids showed that the CO 2 diffusion coefficient in the oil sample was 4.1243 × 10 -8 m 2 s -1 , much higher than those in the pure alkane phase, pure water and brine sample from reservoirs. Results of CO 2 diffusion in carven filling porous media saturated with oil demonstrated a significant dependence on properties such as porosity and permeability, and a correlation in the CO 2 diffusion coefficients between the bulk oil phase and cavern filling porous media in the form of touristy was documented. CO 2 diffusion in the fractured cavern porous media was much higher than that without fracture. An increase in water saturation reduced CO 2 diffusion coefficients in the carven filling porous medium studied, herein. Thus, the CO 2 diffusion coefficient is essentially related to the type of liquid and properties of the filling media., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Polymer microsphere (PM) profile control has been attributed to improving sweep efficiency during the oil development process. The critical factors for PM conformance control are the plugging properties controlled by matching the relationship between the throat diameter and particle size and the injection parameters. A new matching relationship between the reservoir and PM based on the function of blocking rate and the ratio of throat diameter to microsphere diameter ( C R ) is established to choose the most appropriate PM size. The blocking rate indicates that it will get the most excellent plugging effect when C R is 0.5. The displacement experiments under different injection concentrations and other injection volumes show that the blocking rate is increased by injection concentration and finally stabilized. A similar trend is presented between the injection volume and plugging rate. The optimal injection concentration is 0.5%, and the optimal injection volume is 0.3 PV. According to the new size selection method and injection parameter optimal method, PM100 chooses to conduct field application. PM100 presents a good performance with a success rate of 37.5% and a validity period of more than 120 days, and its daily oil production rate increased 1.7 times, on average, and finally, the total oil increase is 556 t. The optimal size microsphere shows a good EOR effect, which indicates that this size selection method is reasonable., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The CO 2 huff-n-puff process is an effective method to enhance oil recovery; however, its utilization is limited in heterogenous edge-water reservoirs due to the severe water channeling. Accordingly, herein, a stable N 2 foam is proposed to assist CO 2 huff-n-puff process for enhanced oil recovery. Sodium dodecyl sulfate (SDS) and polyacrylamide (HPAM) were used as the surfactant and stabilizer, respectively, and 0.3 wt% of SDS + 0.3 wt% of HPAM were screened in the laboratory to generate a foam with good foamability and long foam stability. Subsequently, dynamic foam tests using 1D sand packs were conducted at 65 °C and 15 MPa, and a gas/liquid ratio (GLR) of 1 : 1 was optimized to form a strong barrier in high permeable porous media to treat water and gas channeling. 3D heterogeneous models were established in the laboratory, and N 2 -foam-assisted CO 2 huff-n-puff experiments were conducted after edge-water driving. The results showed that an oil recovery of 13.69% was obtained with four cycles of N 2 -foam-assisted CO 2 injection, which is twice that obtained by the CO 2 huff-n-puff process. The stable N 2 foam could temporarily delay the water and gas channeling, and subsequently, CO 2 fully extracted the remaining oil in the low permeable zones around the production well. Pilot tests were conducted in 8 horizontal wells, and a total oil production of 1784 tons with a net price value (NPV) of $240 416.26 was obtained using the N 2 -foam-assisted CO 2 huff-n-puff process, which is a profitable method for enhanced oil recovery in heterogenous reservoirs with edge water., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Much research has been carried out on nanoscale polymer microspheres (PMs) in laboratories in recent years. However, there are limited reports on the practical application of nanoscale PMs in ultralow permeability reservoirs. This paper reports a field application case of nanoscale PMs for in-depth profile control in the ultralow permeability oil reservoir. In the paper, the characteristics of the reservoir and the problems faced during development are analyzed in detail. Then, the PMs with calibration diameters of 300 nm and 800 nm are researched by evaluation experiments, and are selected for in-depth profile control in the ultralow permeability oil reservoir. Finally, according to the effect of the pilot application, the performance of PMs is evaluated, and a more suitable size for the pilot test reservoir is determined. The experiment's results show that the PMs have a good capacity for swelling and plugging. For the PMs with a calibration diameter of 300 nm, the final equilibrium swelling ratio is 56.2 nm·nm -1 , and the maximum resistance coefficient and the blocking rate after swelling are 3.7 and 70.31%, respectively. For the PMs with a calibration diameter of 800 nm, the final equilibrium swelling ratio is 49.4 nm·nm -1 , and the maximum resistance coefficient the blocking rate after swelling are 3.5 and 71.42%, respectively. The performance evaluation results show that nanoscale PMs can be used for in-depth profile control in the ultralow permeability oil reservoir. After the application of PMs in the pilot test area, the average water cut decreased by 10.4%, the average liquid production of single well-increased by 0.9 t/d, and the average thickness of the water-absorbing layer increased by 1.77 m. Comparing the dynamic data variation of well-groups using the PMs with the calibration diameter as 800 nm and the calibration diameter as 300 nm, it indicates that, for the pilot test area, PMs with a calibration diameter of 300 nm are more suitable than PMs with a calibration diameter of 800 nm., (Copyright © 2020 Hou, Zhao, Jia, Yuan, Zhou, Liu and Hou.)

Emulsions, including oil-in-water (O/W) and water-in-oil (W/O) emulsions, can play important roles in both controlling reservoir conformance and displacing residual oil for enhanced oil recovery (EOR) projects. However, current methods, like high-shear mixing, high-pressure homogenizing, sonicators and others, often use lots of extra energy to prepare the emulsions with high costs but very low energy efficiency. In recent decades, spontaneous emulsification methods, which allow one to create micro- and nano-droplets with very low or even no mechanical energy input, have been launched as an overall less expensive and more efficient alternatives to current high extra energy methods. Herein, we primarily review the basic concepts on spontaneous emulsification, including mechanisms, methods and influenced parameters, which are relevant for fundamental applications for industrials. The spontaneity of the emulsification process is influenced by the following variables: surfactant structure, concentration and initial location, oil phase composition, addition of co-surfactant and non-aqueous solvent, as well as salinity and temperature. Then, we focus on the description of importance for emulsions in EOR processes from advances and categories to improving oil recovery mechanisms, including both sweep efficiency and displacement efficiency aspects. Finally, we systematically address the applications and outlooks based on the use of spontaneous emulsification in the practical oil reservoirs for EOR processes, in which conventional, heavy, high-temperature, high-salinity and low-permeability oil reservoirs, as well as wastewater treatments after EOR processes are involved., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The formation of dominant water channels is a serious problem for most oilfields, which results in low sweep efficiency. Recently, gels regarded as materials for the conformance improvement of water have attracted significant attention for increasing the sweep efficiency in many reservoirs suffering from water invasion but no effect on oil displacement efficiency. Nanogel particles possessing synergic properties that increase sweep efficiency and oil displacement efficiency have not been previously reported. Herein, economical high-viscosity α-starch nanogel particles were synthesized through a free radical reaction to play the synergistic role of gel and nanoparticles. The average diameter of the nanogel particles was 30 nm with a dispersion viscosity of 250 mPa s at 90 °C. A linear formula describing the relationship among the nanogel particle dispersion viscosity, temperature and concentration was also perfectly fitted. Core flooding experiments have demonstrated that both light and heavy oil recovery rates reached around 30%. The EOR mechanisms and flow behaviors of the nanogel particles were revealed through 2-D visualized model experiments under different conditions. On the one hand, nanogel particles could displace oil droplets from the rock surface due to the creation of the structural disjoining pressure. On the other hand, nanogel particle dispersion with high viscosity could increase the sweep efficiency and drag oil clusters out of the oil phase. Therefore, nanogel particles could be regarded as a potential candidate for enhancing oil recovery., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

Microbial mineralization (corrosion, decomposition, and weathering) has been investigated for its role in the extraction and recovery of metals from ores. Here we report our application of biomineralization for the microbial enhanced oil recovery in low-permeability oil reservoirs. It aimed to reveal the etching mechanism of the four Fe(III)-reducing microbial strains under anaerobic growth conditions on Ca-montmorillonite. The mineralogical characterization of Ca-montmorillonite was performed by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and energy-dispersive spectrometry. Results showed that the microbial strains could efficiently reduce Fe(III) at an optimal rate of 71%, alter the crystal lattice structure of the lamella to promote interlayer cation exchange, and efficiently inhibit Ca-montmorillonite swelling at a rate of 48.9%. IMPORTANCE Microbial mineralization is ubiquitous in the natural environment. Microbes in low-permeability reservoirs are able to facilitate alteration of the structure and phase of the Fe-poor minerals by reducing Fe(III) and inhibiting clay swelling, which is still poorly studied. This study aimed to reveal the interaction mechanism between Fe(III)-reducing bacterial strains and Ca-montmorillonite under anaerobic conditions and to investigate the extent and rates of Fe(III) reduction and phase changes with their activities. Application of Fe(III)-reducing bacteria will provide a new way to inhibit clay swelling, to elevate reservoir permeability, and to reduce pore throat resistance after water flooding for enhanced oil recovery in low-permeability reservoirs., (Copyright © 2018 American Society for Microbiology.)

Alkaline-surfactant-polymer (ASP) flooding is considered to be one of the most promising tertiary oil recovery techniques. Nevertheless, its low sweep efficiency in a multilayer heterogeneous reservoir limits field applications. In this work, linearly descending viscosity, a novel injection pattern of ASP flooding, was used for mobility control. Three-dimensional multilayer heterogeneous core models were designed and fabricated. ASP flooding experiments were conducted in the laboratory, and the remaining oil distribution was measured during flooding. Fluid samples obtained from production wells were used for the viscosity measurement. Contrast experiments were made using another two injection patterns including constant viscosity fluid injection and linearly ascending viscosity fluid injection. The results indicated that ASP flooding with linearly descending viscosity improved oil recovery by over 25%, which was a better performance than that obtained using the other two injection patterns. As the different injection patterns presented a similar recovery in the high permeability layer, the sweep efficiency of ASP fluid in the middle and low permeability layers contributed to the difference in the ultimate oil recoveries. In addition, the initial viscosity of the ASP slug had the greatest effect on the mobility modification. Linearly descending viscosity had the highest initial viscosity, leading to the highest fluid distribution rate in the middle and low permeability layers. In addition, higher effluent viscosity was obtained and an earlier viscosity peak occurred in ASP flooding with linearly descending viscosity. Therefore, the sweep efficiency in middle and low permeability layers was remarkably enlarged by using linearly descending viscosity. Thus, increasing the viscosity of the displacement agent as early as possible was found to be significantly in a multilayer heterogeneous reservoir. This study provides an insight into ASP flooding in multilayer heterogeneous reservoirs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Introduction. Converging evidence suggests that PDE-4 (phosphodiesterase subtype 4) plays a crucial role in regulating cognition via the PDE-4-cAMP cascade signaling involving phosphorylated cAMP response element binding protein (CREB). Objective. The primary endpoint was to examine the neurocognitive effects of extract Sceletium tortuosum (Zembrin) and to assess the safety and tolerability of Zembrin in cognitively healthy control subjects. Method. We chose the randomized double-blind placebo-controlled cross-over design in our study. We randomized normal healthy subjects (total n = 21) to receive either 25 mg capsule Zembrin or placebo capsule once daily for 3 weeks, in a randomized placebo-controlled 3-week cross-over design. We administered battery of neuropsychological tests: CNS Vital Signs and Hamilton depression rating scale (HAM-D) at baseline and regular intervals and monitored side effects with treatment emergent adverse events scale. Results. 21 subjects (mean age: 54.6 years ± 6.0 yrs; male/female ratio: 9/12) entered the study. Zembrin at 25 mg daily dosage significantly improved cognitive set flexibility (P < 0.032) and executive function (P < 0.022), compared with the placebo group. Positive changes in mood and sleep were found. Zembrin was well tolerated. Conclusion. The promising cognitive enhancing effects of Zembrin likely implicate the PDE-4-cAMP-CREB cascade, a novel drug target in the potential treatment of early Alzheimer's dementia. This trial is registered with ClinicalTrials.gov NCT01805518.

Background: Converging evidence suggests dysregulation of epigenetics in terms of histone-mediated acetylation/deacetylation imbalance in Parkinson's disease (PD). Targeting histone deacetylase (HDAC) in neuronal survival and neuroprotection may be beneficial in the treatment and prevention of neurodegenerative disorders. Few pharmacological studies use the transgenic model of PD to characterize the neuroprotection actions of a lead compound known to target HDAC in the brain., Methods: In our study, we investigated neuroprotective effects of liposomal-formulated curcumin: Lipocurc™ targeting HDAC inhibitor in the DJ-1(Park 7)-gene knockout rat model of PD. Group I (DJ-1-KO-Lipocurc™) received Lipocurc™ 20 mg/kg iv 3× weekly for 8 weeks; Group II: DJ-1 KO controls (DJ-1 KO-PBS) received i.v. phosphate-buffered saline (PBS). Group III: DJ-1-Wild Type (DJ-1 WT-PBS) received PBS. We monitored various components of motor behavior, rotarod, dyskinesia, and open-field behaviors, both at baseline and at regular intervals. Toward the end of the 8 weeks, we measured neuronal apoptosis and dopamine (DA) neuron-specific tyrosine hydroxylase levels by immunohistochemistry methods at post-mortem., Results: We found that DJ-KO Group I and Group II, as compared with DJ-1 WT group, exhibited moderate degree of motor impairment on the rotarod test. Lipocurc™ treatment improved the motor behavior motor impairment to a greater extent than the PBS treatment. There was marked apoptosis in the DJ-1 WT group. Lipocurc™ significantly blocked neuronal apoptosis: the apoptotic index of DJ-1-KO-Lipocurc™ group was markedly reduced compared with the DJ-KO-PBS group (3.3 vs 25.0, p<0.001). We found preliminary evidence Lipocurc™ stimulated DA neurons in the substantia nigra. The ratio of immature to mature DA neurons in substantia nigra was statistically higher in the DJ-1-KO-Lipocurc™ group (p<0.025)., Conclusions: We demonstrated for the first time Lipocurc™'s anti-apoptotic and neurotrophic effects in theDJ-1-KO rat model of PD. Our promising findings warrant randomized controlled trial of Lipocurc™ in translating the novel nanotechnology-based epigenetics-driven drug discovery platform toward efficacious therapeutics in PD.

Background: Immuno-modulatory effects of ginseng, including both immuno-stimulatory and immuno-suppressive effects, have been widely reported. This study aims to determine whether the paradoxical immuno-modulatory effect is related to unique phytochemical profiles of different North American (NA) ginseng, namely aqueous (AQ) and alcoholic (ALC) extracts., Methods: AQ and ALC extracts were prepared and their immuno-bioactivity were studied in vitro in murine macrophages (Raw 264.7) through measuring the direct stimulatory production of pro-inflammatory mediator and cytokines as well as the suppression of lipopolysaccharide (LPS)-stimulatory response by the two extracts. Gel permeation chromatography was used to fractionate and isolate phytochemicals for characterization of ginseng extracts., Results: AQ extract up-regulated the production of nitric oxide (NO), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) while ALC extract did not. ALC extract but not AQ extract suppressed LPS-induced macrophage NO and TNF-α production. These immuno-stimulatory and suppressive effects were exhibited at similar extract concentrations. Moreover, the macrophage-stimulating activity of the AQ extract was inhibited in the presence of ALC extract. Fractionation of AQ extract revealed the presence of two major peaks at 230 nm with average molecular weights of 73,000 and 37,000 Da. The first fraction had similar elution volume as the crude polysaccharide (PS) fraction isolated from the AQ extract, and it was the only bioactive species. Parallel fractionation study of ALC extract yielded similar elution profiles; however, both sub-fractions were devoid of PS. Fraction I of the ALC extract suppressed LPS-induced NO production dose-dependently., Conclusion: ALC extract of NA ginseng, which was devoid of PS, was immuno-inhibitory whereas the AQ extract, which contained PS, was immuno-stimulatory. These extract-related anti-inflammatory and pro-inflammatory effects may be considered as the Yin and Yang actions of ginseng.