A Review of Gemini Surfactants: Potential Application in Enhanced Oil Recovery

Gemini surfactants are a group of novel surfactants with more than one hydrophilic head group and hydrophobic tail group linked by a spacer at or near the head groups. Unique properties of gemini surfactants, such as low critical micelle concentration, good water solubility, unusual micelle structures and aggregation behavior, high efficiency in reducing oil/water interfacial tension, and interesting rheological properties have attracted the attention of academic researchers and field experts. Rheological characterization and determination of the interfacial tension are two of the most important screening techniques for the evaluation and selection of chemicals for enhanced oil recovery (EOR). This review deals with rheology, wettability alteration, adsorption and interfacial properties of gemini surfactants and various factors affecting their performance. The review highlights the current research activities on the application of gemini surfactants in EOR.     

Influence of different nanoparticles on the gas injection performance in EOR operation: Parametric and CFD simulation study

This study aims to simulate the process of enhanced oil recovery (EOR) during gas injection along with nanoparticles and investigate the affecting parameters in a conventional carbonate oil reservoir. Ansys Fluent software with a suitable multiphase model was used to simulate natural gas injection with a nanoparticle into a core sample. The simulation model was validated with a laboratory test of natural gas injection. Then, to obtain the optimal values of each of the parameters affecting the process of EOR during the natural gas injection along with nanoparticles, the design of the experiment was carried out with the help of Qualitek-4 software and the Taguchi method. Therefore, three factors, including nanoparticle type (clay, titanium oxide, and silica nanoparticles), nanoparticle diameter (2–50 nm), and the volume fraction of nanoparticles in the base fluid (0.5–5 vol.%), as influential factors on the EOR during natural gas injection along with nanoparticles were chosen. The results of the numerical study indicated that silica nanoparticles significantly affect EOR more than clay and titanium oxide nanoparticles. Moreover, the smaller the diameter of nanoparticles (close to 2 nm) and the more significant the volume fraction of nanoparticles in the base fluid (close to 5 vol.%), the higher the oil recovery factor will be. This phenomenon occurs due to changes in the density and viscosity of the base fluid and, consequently, improves the mobility ratio of the injected fluid. On the other hand, the tiny size of nanoparticles allows them to easily enter the pores of the reservoir rock without entrapping and producing oil from them. Eventually, the highest oil recovery factor (59%) was obtained using silica nanoparticles with a diameter of 2 nm and a volume fraction of 5 vol.% in natural gas injection.     

Role of nanoparticles on nanofluid boiling phenomenon: Nanoparticle deposition

Suspended nanoparticles inside the nanofluids can modify the characteristics of heated surfaces and the physical properties of the base liquids, offering a great opportunity to optimize boiling heat transfer. This paper reviews the mechanisms of nanoparticle deposition and the effects induced by deposited nanoparticles on surface roughness, force balance at the triple line, surface wettability, active nucleation site density, receding and advancing contact angles, boiling heat transfer coefficient and critical heat flux. Both enhancement and deterioration effects on boiling heat transfer coefficient and critical heat flux have been discussed. Most of the existing experimental data confirms the enhancement of critical heat flux using alumina nanofluid, however there is no consistency about its boiling heat transfer coefficient.     

A Study of the Technical Route of the Synthesis of Alkylbenzenes for Use as an Oil Displacement Agent

This paper describes the technology of synthesizing alkylbenzenes containing C_16–19 alkyl chains. The heavy alkylbenzenes were prepared by C_16–19 liquid paraffin dehydrogenation, followed by alkylation with benzene. A novel catalyst containing Pt and Sn as its main components for the dehydrogenation of C_16–19 paraffins to alkenes was prepared by vacuum impregnation and the catalyst exhibited high stability and selectivity. The alkylation of the C_16–19 alkenes and benzene had a conversion yield of 86.15% and a selectivity of 81.21%. The main alkylbenzenes was identified as monoalkylbenzene by IR and chromatography analysis. C_16–19 alkylbenzene sulfonates are found to give an ultra-low interfacial tension when mixing with crude oil/reservoir water.

Formulation for chemical EOR: Development and evaluation of an ASP formulation In customer field conditions

Alkali surfactant polymer (ASP) flooding is an enhanced oil recovery (EOR) technology with an impressive potential for increasing incremental oil production from conventional hydrocarbon bearing reservoirs. A challenge to ASP application is the complexity of determining an effective formulation, typically requiring extensive laboratory screening of nearly countless combinations of surfactants and cosolvents. This paper focuses on demonstrating the utility of the hydrophilic–lipophilic deviation (HLD) concept for EOR application to simplify surfactant formulation workstreams seeking an economically viable ASP formulation for field application. In describing work performed for EOR application of ASP under customer conditions using crude oil, the discussion covers the initial evaluation of the promising surfactant formulation (interfacial tension and solubility), the improvement upon the formulation via HLD principles, and the evaluation of the improved surfactant formulation (coreflood studies). The final ASP formulation identified consisted of a 9 to 1 mixture of alkyl propoxy sulfate sodium salt (APS) to alkyl ethoxy sulfate sodium salt (AES) totaling 2000 ppm active surfactant content, 2.0 wt% Na₂CO₃, and 3000 ppm polyacrylamide polymer (all commercially available products). This formulation had ultra-low interfacial tension and favorable mixing behavior under reservoir conditions. In coreflood studies, the final formulation reproducibly achieved cumulative oil recovery of 96.4%–98.5% of original oil in place with only 0.3 PV of ASP injection with a chase alkali polymer injection.     

Enhanced heavy oil recovery through interfacial instability: A study of chemical flooding for Brintnell heavy oil

This study is aimed at developing an alkaline/surfactant-enhanced oil recovery process for heavy oil reservoirs with oil viscosities ranging from 1000 to 10,000 mPa s, through the mechanism of interfacial instability. Instead of the oil viscosity being reduced, as in thermal and solvent/gas injection processes, oil is dispersed into and transported through the water phase to production wells.Extensive emulsification tests and oil/water interfacial tension measurements were conducted to screen alkali and surfactant for the oil and the brine samples collected from Brintnell reservoir. The heavy oil/water interfacial tension could be reduced to about 7 × 10⁻² dyn/cm with the addition of a mixture of Na₂CO₃ and NaOH in the formation brine without evident dynamic effect. The oil/water interfacial tension could be further reduced to 1 × 10⁻² dyn/cm when a very low surfactant concentration (0.005-0.03 wt%) was applied to the above alkaline solution. Emulsification tests showed that in situ self-dispersion of the heavy oil into the water phase occurred when a carefully designed chemical solution was applied.A series of 21 flood tests were conducted in sandpacks to evaluate the chemical formulas obtained from screening tests for the oil. Tertiary oil recoveries of about 22-23% IOIP (32-35% ROIP) were obtained for the tests using 0.6 wt% alkaline (weight ratio of Na₂CO₃ to NaOH = 2:1) and 0.045 wt% surfactant solution in the formation brine. The sandpack flood results obtained in this project showed that a synergistic enhancement among the chemicals did occur in the tertiary recovery process through the interfacial instability mechanism.     

Effect of Nanoparticles on Viscosity and Interfacial Tension of Aqueous Surfactant Solutions at High Salinity and High Temperature

Surfactant flooding has widely been used as one of the chemically enhanced oil recovery (EOR) techniques. Surfactants majorly influence the interfacial tension, γ, between oil and brine phase and control capillary number and relative permeability behavior and, thus, influence ultimate recovery. Additives, such as nanoparticles, are known to affect surfactant properties and are regarded as promising EOR agents. However, their detailed interactions with surfactants are not well understood. Thus, in this work, we examined the influence of silica nanoparticles on the ability of surfactants to lower γ and to increase viscosity at various temperatures and salinities. Results show that the presence of nanoparticles decreased γ between n-decane and various surfactant formulations by up to 20%. It was found that γ of nanoparticles–surfactant solutions passed through a minimum at 35 °C when salt was added. Furthermore, the viscosity of cationic surfactant solutions increased at specific salt (1.5 wt.%) and nanoparticle (0.05 wt.%) concentrations. Results illustrate that selected nanoparticles–surfactant formulations appear very promising for EOR as they can lower brine/n-decane interfacial tension and act as viscosity modifiers of the injected fluids.     

Surfactant-Induced Wettability Alteration of Oil-Wet Sandstone Surface: Mechanisms and Its Effect on Oil Recovery

Different analytical methods were utilized to investigate the mechanisms for wettability alteration of oil-wet sandstone surfaces induced by different surfactants and the effect of reservoir wettability on oil recovery. The cationic surfactant cetyltrimethylammonium bromide (CTAB) is more effective than the nonionic surfactant octylphenol ethoxylate (TX-100) and the anionic surfactant sodium laureth sulfate (POE(1)) in altering the wettability of oil-wet sandstone surfaces. The cationic surfactant CTAB was able to desorb negatively charged carboxylates of crude oil from the solid surface in an irreversible way by the formation of ion pairs. For the nonionic surfactant TX-100 and the anionic surfactant POE(1), the wettability of oil-wet sandstone surfaces is changed by the adsorption of surfactants on the solid surface. The different surfactants were added into water to vary the core surface wettability, while maintaining a constant interfacial tension. The more water-wet core showed a higher oil recovery by spontaneous imbibition. The neutral wetting micromodel showed the highest oil recovery by waterflooding and the oil-wet model showed the maximum residual oil saturation among all the models.     

An investigation on the applicability of Parachor model for the prediction of MMP using five equations of state

Miscible gas injection is generally used as one of the most efficient methods in the enhanced oil recovery. Minimum miscibility pressure (MMP) is an important parameter in the miscible gas injection projects, since local displacement efficiency in the reservoir media is highly dependent on the MMP. Therefore, an appropriate estimation of MMP would bring significant economic benefits. This paper presents a comparative study on five representative equations of state (EoSs) for predicting MMP using Parachor model together with the criterion of zero interfacial tension (IFT) at the miscibility conditions. The predicted MMP values are compared with the experimental data obtained from the most reliable measurement technique, so called slim tube method. Such a prediction would enables us to judge the accuracy of the results obtained from different equations of state as well as the capability of Parachor model to calculate the MMP. The results of predictions obtained for five oil-gas systems in this study reveal reliable MMP values within 5% of accuracy.     

A stabilized foam formulation using FTP-SDS surfactants for wettability alteration and flow diversion in carbonate fractured oil reservoirs

Foam injection contributes to improved oil recovery through flow diversion, reduction of interfacial tension (IFT), and wettability alteration of the rock while its stability is an issue. In this article, nitrogen-foam was optimally formulated using fluorocarbon tubiguard protect (FTP) surfactant stabilized with sodium dodecyl sulfate (SDS) co-surfactant that was later experimentally considered for oil recovery in a fractured carbonate rock taken from an oil field in the Middle East. The results showed that the 5:1 volume ratio of fluorocarbon surfactant and SDS (FS51) generates a stable foaming agent with ability of changing the wettability of the carbonate rock surfaces to an intermediate gas-wet state. A series of core-flood experiments at HPHT conditions were also carried out and designed to properly represent matrix-fracture media using both a horizontally and vertically oriented setup. The oil saturated cores were flooded with nitrogen gas first followed by foam injection. It was concluded that foam can divert the gas to flow from fractures to the matrix blocks and result in a significant oil recovery. The contact angle tests that performed after core-flood experiments revealed the wettability changes of fracture surfaces from an oil-wet to a gas-wet state. This allows gas to be imbibed into the matrix blocks by capillary force and results in enhancement of ultimate oil recovery. This study revealed that trapped oil in matrixes blocks that had not been drained during the gas injection process could be produced by designing a stable foam that sustainably diverts injected fluid from fractures to matrix zone.     

How to Attain Ultralow Interfacial Tension and Three-Phase Behavior with Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 4: Robustness of the Optimum Formulation Zone Through the Insensibility to Some Variables and the Occurrence of Complex Artifacts

In enhanced oil recovery, not only the low-tension performance, but also the robustness at optimum formulation is an important issue. The fourth part of our review series is dedicated to robustness, defined as the width of the zone exhibiting three-phase behavior around the optimum formulation, whatever the scanned variable. It is first corroborated from a screening of the available data in the literature that the tension minimum is inversely proportional to the square of the three-phase range in the HLD scale. However, since there is still an inaccuracy of about a factor 10 in the tension minimum, some significant improvement can be attained in some cases by increasing the three-phase behavior width in two ways. The first approach consists of finding systems that are insensitive to some formulation variable such as temperature, surfactant mixture composition or concentration, and water-to-oil ratio. The second way is to produce an artifact through which the optimum formulation is produced twice in a scan. If the distance between the two events in the scan is reduced down to be zero, their corresponding three-phase behavior zones merge and result in a wider WIII region with a low tension. Several cases of such events are reported: alkaline scans, anionic-nonionic and anionic-cationic mixture changes, linear change in composition in three-surfactant mixture, partial precipitation from a surfactant mixture in a salinity scan, and excessive partitioning of polyethoxylated nonionics. More complex transitions with three effects in a single scan or three concomitantly scanned variables show even more possibilities in practice.     

Investigation of silica nanoparticles grafted with sulphonated polymer for enhanced oil recovery at high temperature and high salt

Nano-fluids' application for enhanced oil recovery (EOR) has attracted noticeable attention and formed a new research area in recent years. Currently, the greatest challenge in this area is to formulate stable nano-fluids for oil reservoirs with high temperatures and salinity. To overcome the limitations of its application in high-temperature drilling, polymer-coated nanoparticles (SiO₂-PAMPS NPs) were prepared via solution polymerization of 2-acrylamide-2-methyl-1-propane sulphonic acid (AMPS) from the surface of aminopropyl-functionalized silica nanoparticles. The SiO₂-PAMPS NPs were characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and dynamic light scattering (DLS). The results indicated that the AMPS was successfully grafted onto the surface of silica nanoparticles, and the average diameter of SiO₂-PAMPS NPs was about 16 nm. The nano-fluids showed noticeable stability in American Petroleum Institute (API) brine (2 wt.% CaCl₂ and 8 wt.% NaCl) at 90°C beyond 46 days. When amphipathic nanoparticles were introduced to brine at 90°C, the potential of the nano-fluids in recovering oil was evaluated by investigating the interfacial tension with kerosene oil and the oil contact angle in the nano-fluids. The contact angle of the glass sheet surface before treatment was about 144°, while after SiO₂-PAMPS NPs treatment for 72 h, it became about 92°. Meanwhile, the nano-fluids showed an excellent enhancing emulsibility property, which plays a vital role in promoting the development of EOR in high-temperature and high-salt environments.     

三次采油用表面活性剂结构对油/水界面性能的影响

测定了几种不同分子结构的磺酸盐类阴离子表面活性剂、两性表面活性剂和非离子表面活性剂水溶液与国内某油田原油间的界面张力。结果表明:磺酸盐类表面活性剂降低油水界面张力的能力相对较高,且磺酸盐的烷链长度、芳环种类对界面张力的影响较大,调整磺酸盐的分子结构可以使油水界面张力降低到10~(-2)mN/m数量级;醇/酚醚类非离子表面活性剂以及两性表面活性剂仅能使油水界面张力降低至0.1 mN/m~10 mN/m数量级。     

A critical analysis of challenges and opportunities for soil fertility restoration in Sudano-Sahelian West Africa

Since the 1970s, research throughout West Africa showed that low soil organic matter and limited availability of plant nutrients, in particular phosphorus and nitrogen, are major bottlenecks to agricultural productivity, which is further hampered by substantial topsoil losses through wind and water erosion. A few widely recognized publications pointing to massive nutrient mining of the existing crop–livestock production systems triggered numerous studies on a wide array of management strategies and policies suited to improve soil fertility. Throughout Sudano-Sahelian West Africa, the application of crop residue mulch, animal manure, rockphosphates and soluble mineral fertilizers have been shown to enhance crop yields, whereby yield increases varied with the agro-ecological setting and the rates of amendments applied. In more humid areas of Western Africa, the intercropping of cereals with herbaceous or ligneous leguminous species, the installation of fodder banks for increased livestock and manure production, and composting of organic material also proved beneficial to crop production. However, there is evidence that the low adoption of improved management strategies and the lack of long-term investments in soil fertility can be ascribed to low product prices for agricultural commodities, immediate cash needs, risk aversion and labour shortage of small-scale farmers across the region. The wealth of knowledge gathered during several decades of on-station and on-farm experimentation calls for an integration of these data into a database to serve as input variables for models geared towards ex-ante assessment of the suitability of technologies and policies at the scale of farms, communities and regions. Several modelling approaches exist that can be exploited in this sense. Yet, they have to be improved in their ability to account for agro-ecological and socio-economic differences at various geographical scales and for residual effects of management options, thereby allowing scenario analysis and guiding further fundamental and participatory research, extension and political counselling.     

新型表面活性剂疏水缔合聚合物提高原油采收率的性能研究

介绍了渤海海上油田二元复合驱驱油的设计与开发方案,以新型表面活性剂(非离子型表面活性剂:DMES-14、TX-100)和疏水缔合聚丙烯酰胺(HAPAM)为主。二元复合驱驱油体系主要需要双子表面活性剂双十四酸乙二酯双磺酸盐型表面活性剂(DMES-14),疏水缔合聚丙烯酰胺以及取自海上油田平台的回注水。该体系同时对粘度和表面张力进行了研究。结果表明,该体系在不要求浓度的情况下可以达到超低界面张力2.48×10~(-3) m N/m,在油藏中粘度可达到55 m Pa;随后的岩心驱替试验表明,在水驱含水75%的状况下进行二元复合驱驱油效果可提高至38.6%以上。总之,该实验研究提供了非离子表面活性剂与疏水缔合水溶性聚合物驱油体系的实用信息以及可以在渤海海上油田进行大规模应用HAPAM。     

Spherical polyelectrolyte brushes as nanoreactors for the generation of metallic and oxidic nanoparticles: Synthesis and application in catalysis

If long chains of a polyelectrolyte are densely affixed to colloidal spheres, a spherical polyelectrolyte brush (SPB) results. It has been demonstrated that most of the counterions that balance the charges of the polyelectrolyte chains in aqueous solution are confined within the brush layer. Some years ago it has been shown that metal ions confined within a SPB can be reduced to yield well-defined metal nanoparticles with high catalytic activity. In a similar way, metal oxides as TiO₂ and MnO_x can be generated within the brush layer. Here we review this work with special emphasis on catalysis. We first discuss recent papers that study the confinement of the counterions within SPB and the consequences thereof for the solution properties of the SPB. Then a survey of synthetic studies on these composite particles is presented. Finally, a comprehensive review of the investigations on the catalytic activity of metallic and oxidic nanoparticles generated on SPB will be given. All results obtained on these systems demonstrate SPB act as true “nanoreactors” that can be used for an efficient and safe handling of metallic and oxidic nanoparticles in catalysis without impeding their catalytic activity.     

Preparation and Performance Evaluation of Fatty Amine Polyoxyethylene Ether Diethyl Disulfonate for Enhanced Oil Recovery in High‐Temperature and High‐Salinity Reservoirs

To enhance oil recovery in high‐temperature and high‐salinity reservoirs, a novel fatty amine polyoxyethylene ether diethyl disulfonate (FPDD) surfactant with excellent interfacial properties was synthesized. The interfacial tension (IFT) and contact angle at high temperature and high salinity were systematically investigated using an interface tension meter and a contact angle meter. According to the experimental results, the IFT between crude oil and high‐salinity brine water could reach an ultra‐low value of 10^?3 mN m^?1 without the aid of extra alkali at 90°C after aging. The FPDD surfactant has strong wettability alternation ability that shifts wettability from oil‐wet to water‐wet. The FPDD surfactant with a high concentration also has good emulsion ability under high‐temperature and high‐salinity conditions. Through this research work, we expect to fill the lack of surfactants for high‐temperature and high‐salinity reservoirs and broaden its great potential application area in enhanced oil recovery.     

A study of shape optimization on the metallic nanoparticles for thin-film solar cells

The shape of metallic nanoparticles used to enhance the performance of thin-film solar cells is described by Gielis'' superformula and optimized by an evolutionary algorithm. As a result, we have found a lens-like nanoparticle capable of improving the short circuit current density to 19.93 mA/cm². Compared with a two-scale nanospherical configuration recently reported to synthesize the merits of large and small spheres into a single structure, the optimized nanoparticle enables the solar cell to achieve a further 7.75% improvement in the current density and is much more fabrication friendly due to its simple shape and tolerance to geometrical distortions.     

Effect of additives concentration on the surface properties and performance of PVDF ultrafiltration membranes for refinery produced wastewater treatment

The aim of this study was to investigate the effect of pore-forming hydrophilic additives on the porous asymmetric polyvinylideneflouride (PVDF) ultrafiltration (UF) membrane morphology and transport properties for refinery produced wastewater treatment. PVDF ultrafiltration membranes were prepared via a phase inversion method by dispersing lithium chloride monohydrate (LiCl·H₂O) and titanium dioxide (TiO₂) nanoparticles in the spinning dope. The morphological and performance tests were conducted on PVDF ultrafiltration membranes prepared from a different additive content. The top surface and cross-sectional area of the membranes were observed using a field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX) analysis. The surface wettability of porous membranes was determined by the measurement of a contact angle. The mean pore size and surface porosity were calculated based on the permeate flux. The results indicated that the PVDF/LiCl/TiO₂ membranes with lower TiO₂ nanoparticles loading possessed smaller mean pore size, more apertures inside the membrane with enhanced membrane hydrophilicity. LiCl·H₂O has been employed particularly to reduce the thermodynamic miscibility of dope which resulted in increasing the rate of liquid–liquid demixing process. The maximum flux and rejection of refinery wastewater using PVDF ultrafiltration membrane achieved were 82.50 L/m² h and 98.83% respectively at 1.95 wt.% TiO₂ concentration.