Viscoelastic Surfactant Research Articles

Design of a salt-tolerant Gemini viscoelastic surfactant and the study of construction of wormlike micelle structure in high-salinity aqueous environment

Herein, a zwitterionic Gemini VES (named VES-C) with double ultra-long hydrophobic tails was designed and synthesized which aimed to construct WLM net-structures in high-salinity aqueous solution. Due to the carboxylic group on the spacer, it exhibits partial carboxyl betaine properties and performs well in high salinity environment. Molecular dynamic simulation was carried out and RDF curves were analyzed to predict and explain the mechanism of salinity tolerance of VES-C. Compared with cationic Gemini VESs, a series of experiments were conducted by varying salinity, including surface tension, DLS, 1H NMR and fluorescent probe, to explain the salt-tolerance mechanism of VES-C. The salinity cloudy point of VES-C surpasses 10 wt%, exhibiting superior salt-tolerance to those cationic Gemini VESs. Trough viscosity measurement, oscillatory measurement and microstructure observation, it proves that VES-C molecules can construct WLM netlike structures within the salinity range from 3 wt% to 10 wt% (optimal salinity: 4 wt%), thus VES-C can be applied as the clean thickener to prepared seawater or brine based fracturing fluid by constructing WLM netlike structure in high salinity aqueous environment, which leaves the preparation of clean fracturing fluid independent of freshwater resources.

Smart learning strategy for predicting viscoelastic surfactant (VES) viscosity in oil well matrix acidizing process using a rigorous mathematical approach

This piece of study attempts to accurately anticipate the apparent viscosity of the viscoelastic surfactant (VES) based self-diverting acids as a function of VES concentration, temperature, shear rate, and pH value. The focus not only is on generating computer-aided models but also on developing a straightforward and reliable explicit mathematical expression. Towards this end, Gene Expression Programming (GEP) is used to connect the aforementioned features to and the target. The GEP network is trained using a wide dataset adopted from open literature and leads to an empirical correlation for fulfilling the aim of this study. The performance of the proposed model is shown to be fair enough. The accuracy analysis indicates satisfactory Root Mean Square Error and R-squared values of 7.07 and 0.95, respectively. Additionally, the proposed GEP model is compared with literature published correlations and established itself as the superior approach for predicting the viscosity of VES-based acids. Accordingly, the GEP model can be potentially served as an efficient alternative to experimental measurements. Its obvious advantages are saving time, lowering the expenses, avoiding sophisticated experimental procedures, and accelerating the diverter design in stimulation operations.Article HighlightsThe Gene Expression Programming evolutionary algorithm is proposed for modeling the viscosity of Viscoelastic Surfactant-based self-diverting acids.The viscoelastic surfactant viscosity correlation presents high accuracy which is demonstrated through multiple analyses.The Gene Expression Programming algorithm is a reliable tool expediting the diverter design phase of each stimulation operation.

Research of a Surfactant Gel with Potential Application in Oilfield

Abstract In this study, a viscoelastic surfactant gel was composed using erucoylamine propyl betaine and other additives. The formulation of this viscoelastic surfactant gel solution was determined as: erucamide propyl betaine:oleic acid amide propyl betaine:octadecyl hydroxyl sulfonate betaine = 1.7%:1.36%:0.01%. Then the performance of viscoelastic surfactant gel fluid was evaluated. The results showed that the viscoelastic surfactant gel has good temperature resistance and salt resistance. At 50°C, the apparent viscosity reaches the maximum value, 37 mPa · s, and it displays high shear resistance under the shear rate of 170 s–1, with the viscosity retention of 83.3%. Kerosene (1%) can completely break the gel within 2 h, which can convert the gel into a surfactant solution soon. Also the gel shows high emulsion ability, which can benefit the oil displacement in oilfield. Finally this gel can enhance the oil displacement rate as high as 28%.

Effect of different types of fracturing fluid on the microstructure of anthracite: an experimental study

ABSTRACT A systematic understanding of the effects of different fracturing fluids on the chemical and pore structure of coal is of great significance for the exploitation of coalbed methane (CBM). In this study, Fourier-transform infrared spectroscopy and mercury intrusion porosimetry were used to analyze the chemical and pore structure of coal samples treated by different fracturing fluids. The results show that fracturing fluid treatment has little effect on the coal aromatic structure. The oxygen-containing and hydroxyl structures of the coal samples treated by acidic and viscoelastic surfactant (VES) fracturing fluids increased by >17%, which is beneficial for gas desorption and thereby increases CBM yield, whereas those of the coal sample treated with deionized water decreased by 3.8%. The acidic and VES fracturing fluid treatments are also beneficial for coal pore connectivity, which promotes gas migration. The three types of fracturing fluids increased the macropore volume by >350%. The deionized water treatment reduced mesopores and micropores by 20% and 5%, respectively, while the transition pores increased by 2.3%, resulting in a 2.6% increase of the specific surface area, which is not conducive to gas desorption and migration. The acidic fracturing fluid treatment increased the mesopore volume by 53.3%, reduced the transition pore and micropore volumes by 5.3% and 32.5%, respectively, and reduced the surface area by 13.2%, which reduces the amount of adsorption sites and facilitates gas migration. However, the adsorption pores and mesopores after VES fracturing fluid treatment decreased by 17.6% and 26.7%, respectively, which indicates that this treatment does not transform most adsorption pores into migration pores.

Synthesis and Characterization of Surfactant for Retarding Acid-Rock Reaction Rate in Acid Fracturing.

Acid fracturing is an effective method to develop ultra-low permeability reservoirs. However, the fast reaction rate reduces the effect of the acid fracturing and increases the near-well collapse risk. Therefore, it is necessary to retard the acid–rock reaction rate. In this work, we synthesized an acid-resistant Gemini zwitterionic viscoelastic surfactant (named VES-c), which has good performances such as temperature resistance, salt resistance, and shear resistance. Besides, a low concentration of VES-c increases the viscosity of the acid solution. The CO2 drainage method was used to measure the reaction rate between the dibasic acid and dolomite/broken core. We find that the dibasic acid containing 0.3% VES-c retards the dolomite reaction rate of 3.22 times compared with only dibasic acid. Furthermore, the dibasic acid containing 0.3% VES-c exhibits uniform distribution and is not easy to adhere to the solid surface. The VES-c also is favorable to reduce the formation of amorphous calcium carbonate. Retarding the rate of acid–rock reaction and enhancing the acidification are mainly attributed to VES-c's salt-tolerance, anti-adsorption, and the property of increasing the viscosity of the solution. Hopefully, this kind of surfactant retarding reaction rate is applied to other acid–rock reactions.

Rheology of wormlike micellar gels formed by long-chained zwitterionic surfactants

Long-chained surfactant solutions have found widespread use in the oil and gas industry due to a host of attractive properties. In this paper, we characterize one such commercially used viscoelastic surfactant that forms a wormlike micellar gel at room temperature and a viscoelastic solution at higher temperatures. We probe both states by conducting linear and nonlinear rheological tests and analyze their behavior under the framework of micellar rheology. Our study outlines departure from behavior exhibited by more conventional micellar systems and uncovers interesting dynamics like shear-induced fracture and possible shear-banding in these materials. In doing so, we provide a detailed understanding of a novel class of wormlike micellar solutions.

Supercritical CO2 Foam Stabilized by a Viscoelastic Surfactant in Fractured Porous Media: The Effect of Fracture Surface Roughness

Supercritical CO₂ Foam Stabilized by a Viscoelastic Surfactant in Fractured Porous Media: The Effect of Fracture Surface Roughness

Deducing the Relation between Viscosity and Oil-Induced Structural Changes of Viscoelastic Surfactants Using a Kinetic Approach.

The present study relates viscosity reduction with time of a wormlike micellar solution to the micellar transitions that occur with time in the presence of three n-alkanes, namely, n-decane, n-dodecane, and n-hexadecane. Steady-shear rheology and small-angle X-ray scattering were used to deduce the relationship. The effect of n-alkane concentration was tested only with n-decane. There were at most three stages of viscosity reduction, which appeared in the following order: (i) the rising viscosity stage, (ii) the fast viscosity reduction stage, and (iii) the low-viscosity stage. The stages and rates of viscosity transition depended on the type of micelles present and the degree of micelle entanglement. Moreover, the rate of transition increased when the n-alkane concentration was increased and when the n-alkane molecular mass was reduced. n-Hexadecane induced only the first two stages of transition at a slower rate compared to the other oils.

Study of Viscoelastic Properties of Fluids for Hydraulic Fracturing

The study focuses on the rheological behavior of a fluid based on a viscoelastic surfactant (Surfogel grade D, type 70-100, produced by JSC “Polyex”) in wide range of strain rates. This fluid is used for hydraulic fracturing technology as a proppant-carrying and proppant-retaining fluid in order to enhance oil recovery, including those with hard-to-recover oil and gas reserves. Quasi-static experiments to determine the values of the dynamic viscosity of the fluids under study were carried out using a falling ball viscometer (according to the Stokes method). The viscoelastic properties of fluids were studied using a Physica MCR501 rheometer with a cone-plane measuring system and an original rheometer with coaxial cylinders measuring system. The rheological properties of the fluid with the addition of proppant were studied using a Rheolab QS rheometer with a measuring system of the type of coaxial cylinders. The analysis of the rheological properties of fluids based on a viscoelastic surfactant has been carried out, and it has been established that fluids based on a viscoelastic surfactant has stable rheological properties over the entire range of strain rates, including fluid with proppant concentration up to 20%.

Research progress of viscoelastic surfactants for enhanced oil recovery

Although new energy has been widely used in our lives, oil is still one of the main energy sources in the world. After the application of traditional oil recovery methods, there are still a large number of oil layers that have not been exploited, and there is still a need to further increase oil recovery to meet the urgent need for oil in the world economic development. Chemically enhanced oil recovery (CEOR) is considered to be a kind of effective enhanced oil recovery technology, which has achieved good results in the field, but these technologies cannot simultaneously effectively improve oil sweep efficiency, oil washing efficiency, good injectability, and reservoir environment adaptability. Viscoelastic surfactants (VES) have unique micelle structure and aggregation behavior, high efficiency in reducing the interfacial tension of oil and water, and the most important and unique viscoelasticity, etc., which has attracted the attention of academics and field experts and introduced into the technical research of enhanced oil recovery. In this paper, the mechanism and research status of viscoelastic surfactant flooding are discussed in detail and focused, and the results of viscoelastic surfactant flooding experiments under different conditions are summarized. Finally, the problems to be solved by viscoelastic surfactant flooding are introduced, and the countermeasures to solve the problems are put forward. This overview presents extensive information about viscoelastic surfactant flooding used for EOR, and is intended to help researchers and professionals in this field understand the current situation.

Experimental Study on the Drag Reduction Performance of Clear Fracturing Fluid Using Wormlike Surfactant Micelles and Magnetic Nanoparticles under a Magnetic Field.

This paper examines a new study on the synergistic effect of magnetic nanoparticles and wormlike micelles (WLMs) on drag reduction. Fe3O4 magnetic nanoparticles (FE-NPs) are utilized to improve the performance of viscoelastic surfactant (VES) solutions used as fracturing fluids. The chemical composition and micromorphology of the FE-NPs were analyzed with FT-IR and an electron microscope. The stability and interaction of the WLM-particle system were studied by zeta potential and cryo-TEM measurements. More importantly, the influences of the temperature, FE-NP concentration, magnetic field intensity, and direction on the drag reduction rate of WLMs were systematically investigated in a circuit pipe flow system with an electromagnetic unit. The experimental results show that a suitable content of magnetic nanoparticles can enhance the settlement stability and temperature resistance of WLMs. A magnetic field along the flow direction of the fracturing fluid can improve the drag reduction performance of the magnetic WLM system. However, under a magnetic field perpendicular to the direction of fluid flow, an additional flow resistance is generated by the vertical chaining behavior of FE-NPs, which is unfavorable for the drag reduction performance of magnetic VES fracturing fluids. This study may shed light on the mechanism of the synergistic drag reduction effects of magnetic nanoparticles and wormlike micelles.

Hooked gemini viscoelastic surfactant based on linolenic oil for oil recovery and its various gel-breaking mechanisms

Hooked gemini viscoelastic surfactant (HGVES) was designed and synthesized by reactions of linolenic acid with 3-(Dimethylamino)-1-propylamine, 3-Chloro-2-hydroxypropanesulfonic acid sodium salt and isophorone diisocyanate. The structure was characterized by FT-IR and 1HNMR. The properties of HGVES were compared with gemini viscoelastic surfactant (GVES) by surface tension, transmittance, rheological behavior, dynamic light scattering and SEM. The result showed that the fracturing performance of HGVES was superior to that of GVES. The critical micelle concentrations (CMC) of HGVES and GVES were 7.69 × 10−5 and 9.68 × 10−5 mol/mL, respectively. Rheological experiments showed that HGVES and GVES were pseudoplastic fluids and HGVES had better viscoelastic behavior. Proppant suspension experiments showed that support suspension performance decreased with the temperature increasing, and the static setting rate was 0.1013 mm/s when the temperature was at 80 °C. Meanwhile, the mechanisms of different gel-breaking agents were also studied, comparing with HGVES and gel-breaking products by FT-IR, 1HNMR, rheological behavior and SEM. The results showed that hydrocarbon oil gel-breaking agents would not destroy the molecular structure of HGVES, while strong oxidant gel-breaking would destroy the double bond of carbon. NaHSO3 would have addition reaction with double bond. The core damage permeability of 2 wt% HGVES was 5.35%, and there was no residue in all gel-breaking solutions. Therefore, this kind of hooked gemini viscoelastic surfactant can be used in oil fracturing to improve oil recovery.

Effect of aromatic acid on the rheological behaviors and microstructural mechanism of wormlike micelles in betaine surfactant

The rheology and microstructural behaviors of viscoelastic surfactant solutions induced by different organic acids are fascinating. However, the viscosity and viscoelasticity behavior of some surfactants such as oleyl amidopropyl betaine (OAPB) surfactant is very poor even at high concentrations. To improve these properties at low concentrations, a system of OAPB and phthalic acid (OPA) at a mass ratio of 3:2 has been developed. The rheological behaviors and microstructural aggregations of the OAPB/OPA system were measured by rheometer, transmission electron microscopy (Cryo-TEM), and dynamic light scattering (DLS). The experimental results showed that the addition of OPA significantly increases the viscoelasticity and viscosity properties of the OAPB viscoelastic micelle solutions at 25°C. The improvements of these properties are attributed to the formation of a micellar network due to the addition of OPA. The rheology and micellar properties were found to transform a transparent viscous water like a fluid at pH 7 to a viscoelastic fluid at pH 2.9. The zero-shear viscosity and relaxation times declined exponentially with an increase of temperature indicating a reduction in the average micellar lengths. The properties changes were attributed to the strength of electrostatic attractions, hydrophobic effects, and hydrogen bonding between OAPB and OPA molecules. Since the current system can be easily tuned by pH for at least 3 circles without deterioration of its properties, the system unlocks the significant prospect for designing stimuli-responsive smart materials for various industrial applications.

Wormlike micelles properties and oil displacement efficiency of a salt-tolerant C22-tailed amidosulfobetaine surfactant

Wormlike micelles formed by amidosulfobetaine surfactants present advantage in increasing viscosity, salt-tolerance, thermal-stability and shear-resistance. In the past few years, much attention has been paid on rheology behaviours of amidosulfobetaine surfactants that normally bear C18 or shorter tails. Properties and oil displacement performances of the wormlike micelles formed by counterparts bearing the long carbon chain have not been well documented. In this paper, the various properties of C22-tailed amidosulfobetaine surfactant EHSB under high salinity (TDS = 40g/L) are investigated systematically, including solubility, rheology and interfacial activity. Moreover, its oil displacement performance is studied for the first time. These properties are first compared with those of C16-tailed counterpart HDPS. Results show that the Krafft temperature( TK) of EHSB decreases from above 100°C to 53°C with the increase of TDS to 40 g/L. Increasing concentration of EHSB in the semidilute region induces micelle growth from rod-like micelles to wormlike micelles, and then the worms become entangled or branched to form viscoelastic micelle solution, which will increase the viscosity by several orders of magnitude. The interfacial tension with oil can be reduced to ultra-low level by EHSB solution with concentration below 4.5 mM. Possessing dual functions of mobility control and reducing interfacial tension, wormlike micelles formed by EHSB present a good displacement effect as a flooding system, which is more than 10% higher than HPAM with the same viscosity. Compared with the shorter tailed surfactant, the ultra-long tailed surfactant is more efficient in enhancing viscosity and reducing interfacial tension, so as to enhance more oil recovery. Our work provides a helpful insight for comprehending surfactant-based viscoelastic fluid and provides a new viscoelastic surfactant flooding agent which is quite efficient in chemical flooding of offshore oilfield.

Salinity‐ and Heat‐Tolerant VES (Viscoelastic Surfactant) Clean Fracturing Fluids Strengthened by a Hydrophobic Copolymer with Extremely Low Damage

AbstractAs good thickeners for clean fracturing fluids, high salt‐tolerant surfactants have received increasing attention. Based on previous studies, we have further studied the performances of four surfactants, EDAS (JS‐SO), EHSB (JS‐OH‐SO), ETAC (JN) and EDHB (JS‐OH), in monovalent (NaCl) and divalent (CaCl2) salts. This is of great significance for the application of high‐salinity formation water to directly prepare fracturing fluids. The results showed that in high‐salinity aqueous solutions, both zwitterionic surfactants and cationic surfactants can exhibit extremely strong salt tolerance. The addition of the counter ion salt can destroy the internal salt, thus increasing water solubility of zwitterionic surfactants. Cationic surfactants have strong water solubility, and the counter ion Cl− will weaken the electrostatic shielding effect between the head groups. Surfactants can still maintain excellent network structures under high‐salinity conditions. This is mainly owing to the extreme insensitivity of zwitterionic surfactants to salts and the large initial head group area of cationic surfactants. In actual applications, the formation water from the Tahe Oilfield was used directly to prepare the fracturing fluids. Testing the rheological properties of fracturing fluid systems found that adding a small amount of hydrophobic associating polymers can increase the temperature resistance from 100 °C to 140 °C, and the final viscosity can be maintained above 30 mPa S. At the same time, they all showed excellent proppant suspension properties and extremely low core damage rates. The results indicated that even in high‐salinity formation water and high‐temperature formation, these fracturing fluid systems still have good performances, extremely low damage and meet fracturing fluid industry standards.

A Novel CO2 Responsive Viscoelastic Surfactant based Clear Fracturing Fluid for High-Temperature Unconventional Reservoir

An unconventional reservoir is a term to describe a hydrocarbon resource that could not be technically or economically recoverable without stimulation. Unconventional oil and gas resources are 4-5 times over conventional oil and gas resources. Currently, there is a limitation for using slick-water volume fracturing and gas (water) injection adding energy for drainage and displacement individually. Also, the efficient hydrocarbons production from the high-temperature unconventional reservoir is the main challenge. In the current study, a CO2 based viscoelastic surfactant fracturing fluid with a specific molar ratio of erucic acid, 2,6,10-trimethyl-2,6,10-triazaundecane, potassium hydroxide, and carbon dioxide (EA-TMTAD-KOH-CO2) was developed as a good candidate for high-temperature and water alternating treatment for high-temperature unconventional reservoirs. The fracturing fluid will play the role of “one with multi-purpose” by proppant-carrying, CO2 energy supplementary displacement, and surfactant imbibition drainage displacement. The fracturing fluid (EA-TMTAD-KOH-CO2) performance evaluation method for determination of shear and heat resistance, viscoelasticity, proppant carrying capacity, gel breaking ability, and salt tolerance is employed as evaluation indices by using HTHP rheometer. The rheological results of steady shear viscosity of the fracturing fluid system confirm that the EA-TMTAD-KOH-CO2 was observed in the properties of a wormlike micelles (WLMs) structure, micelles assembly, and the intermolecular interactions. The steady shear viscosity above 41 mPa.s at a shear rate of 170 s‒1 and temperature 95 °C validates the excellent proppant carrying capacity as per national industry standards of the fracturing process. Further, the gel structure breaking at temperature 135 °C and 170 s‒1 bear the shear viscosity less than 5 mPa.s, which results in a rapid flow back from the well after the fracturing process. Moreover, the fluid system has high salt tolerance against different inorganic salts such as NaCl, KCl, CaCl2, and MgCl2 using different concentrations. By retaining the desirable qualities such as; easy to prepare, environment friendly, commercially available, high in viscoelasticity, and thermally stable; the fracturing fluid system (EA-TMTAD-KOH-CO2) will be an outstanding candidate in industrial applications like water-alternating and high-temperature unconventional reservoirs.

Development of a novel temperature-resistant and salt-resistant double-cationic surfactant with “super thick hydration layer” for clean fracturing fluid

In recent years, cationic surfactants have received extensive attention in cleaning fracturing fluid thickeners due to various unique properties. At the same time, the development of temperature-resistant and salt-resistant clean fracturing fluid is the key to deep well oil and gas resource development. In this study, the rigid-soft combined strategy is adopted for molecular structure designs. N,N-dimethylcyclohexylamine and epichlorohydrin are used as the initial reactants; after the ring-opening reaction occurs, they are quaternized with erucamide propyl dimethyl ammonium to synthesize a novel double-cation viscoelastic surfactant, SY–JS. With double-cationic charges on the head group, water molecules are selectively adsorbed around the cation lattice to increase the hydration layer, and thus, salt tolerance is improved. Cyclohexane with a rigid structure improves temperature resistance. The ultra-long unsaturated hydrophobic tail imparts excellent heat tolerance and dissolubility to the designed viscoelastic surfactant. The clean fracturing fluid prepared by 3 wt% SY–JS with 130,000 ppm NaCl or KCl performs well under a shear rate of 170 s−1 at 140 °C, and the apparent viscosity remains above 30 mPa s−1 after 120 min.. Additionally, the results show that single-tail surfactants exhibit excellent performance at approximately 140 °C. Afterward, the brine produced from Rumaila and Jiyuan oil fields is used to prepare brine-based clean fracturing fluids, and evaluations, including proppant suspension, gel breaking, and permeability damage, were conducted. The results show that the brine-based clean fracturing fluid completely meets the requirements of hydraulic fracturing industrial application.

Organic Acid-Enhanced Viscoelastic Surfactant and Its Application in Fracturing Fluids

Viscoelastic surfactant (VES) fracturing fluids, with the advantages of low residues, complete gel breaking, and low formation damage, have received considerable attention in hydraulic fracturing techniques. However, the complicated synthesis process and high costs limit the widespread application of VESs. Herein, a VES fracturing fluid composed of wormlike micelles was developed by coupling an ultralong hydrophobic chain surfactant N-erucamidopropyl-N,N-dimethylamine (EA), with p-phthalic acid (p-PA), which behaved as a “Gemini-like” surfactant via noncovalent interactions. The macroscopic appearance and viscosity of this fluid were responsive to the regulation of pH values. Then, the related fracturing performance of this fluid was systematically investigated, from which it could be concluded that the VES fluid exhibited good temperature and shear resistance, excellent proppant-carrying and gel-breaking abilities and also caused less damage to core permeability and low corrosion of steel under acidic conditions. Finally, the rheological properties of the VES fluid could be switched multiple times without any decay by changing the pH values, indicating its excellent reusability for fracturing procedures. Consequently, this study demonstrates potential applications of reusable VES fracturing fluids based on supramolecular pH-responsive surfactants.

An Efficient Interpretation Method for Matrix Acidizing Evaluation and Optimization in Long Heterogeneous Carbonate Reservoirs

Summary Since its discovery in 1971, numerous matrix stimulations have been performed in South Pars field. However, there are still various challenges surrounding stimulation job design and evaluation methods. To tackle these issues, 16 matrix operations were selected to be analyzed from different phases of the development project of the reservoir. The objective of this study is to introduce an efficient interpretation method to determine optimum treatment volume (gal/ft), compare the effectiveness of diverters, calculate stimulation ratio (SR), and forecast post-acid production behavior from surface treating data. The modified inverse injectivity (Iinv) method, which is fully discussed by Safari et al. (2021), is used in this study. The obtained data were analyzed in terms of Iinv decreasing trend, Iinv humps, and pre-/post-acid Iinv during the stimulation process. In addition, pre-/post-stimulation surface testing data are gathered and analyzed. These data are coupled with post-acid Iinv to find a correlation to predict production behavior of treated wells. SR is defined as the ratio of pre-acid Iinv to post-acid Iinv of a treated well. Finally, SR values are validated with available production logging tool (PLT) data from two stimulation operations. First, the obtained results indicated that optimum treatment volume (gal/ft) of acid depends on well conditions. It means that wells with high initial formation damage require more volumes of stimulation fluids. In this regard, wells treated with 27/27 gal/ft treatment volume design [27 gal/ft 28% hydrochloric acid (HCl) and 27 gal/ft 15% viscoelastic surfactant (VES)] were understimulated. Although treatment volume design of 53/53 gal/ft seems to be adequate for low-skin wells, higher treatment volume (gal/ft) would further enhance productivity of highly damaged wells. This result was confirmed by stimulation of a damaged well with treatment volume of 60/60 gal/ft. Finally, the most reliable design applied in the field so far is the 70/70 gal/ft treatment volume. Second, Iinv analyses depicted that better diversion is observed in wells with lower injectivity and higher damage. At the next step, the calculated SR values showed an average deviation of less than 10% from downhole PLT data. Ultimately, the produced results demonstrated that there is a direct relation between the post-acid Iinv and surface drawdown in this field. Therefore, production behavior of treated wells can be correlated by having access to post-acid Iinv. The novelty of this work pertains to use of surface treating data recorded during a stimulation operation to generate Iinv and its associated analysis curves to evaluate performance of matrix stimulation operations. By applying this method, optimum volume of acid and diverter, diversion effectiveness, SR, and an estimation of post-acid surface drawdown can be obtained from the simple surface treating data. The secondary-produced data could lead to a better understanding of carbonate reservoir behavior during matrix stimulations such as in the South Pars field.

In Silico Modelling of Viscoelastic Surfactants: Towards NLO Response and Novel Physical Insights through Bridging Acceptor

Development of materials with promising nonlinear optical (NLO) properties is getting attention of both theoretical and experimental communities in fundamental and applied research. In present quantum chemical calculations, potential use of viscoelastic surfactants for NLO properties and associated applications has been discussed. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations at B3LYP level of theory and 6–311 + G(d, p) basis set have been performed to evaluate the electronic properties, photophysical characteristics, ionization potential (I), electron affinity (A), electronegativity (X), chemical potential (μ), global hardness (η), global softness (S), global electrophilicity (ω), frontier molecular orbital (FMO), natural bond orbital (NBO) analysis, linear and NLO properties or first hyperpolarizability (β) of N-(3-((3-hydrosulfonylpropyl)dimethyl-l4-azaneyl)propyl)-hydroxy- decanamidehydrate based four representative compounds/surfactants as system 1, system 2, system 3 and system 4. The FMO analysis confirmed the successful migration of charge transfer among the molecules. The NBO analysis has confirmed that the presence of non-covalent interactions (NCIs) and hyper-conjugative interactions (HCIs) are pivotal cause for the stability of the studied systems (1–4). The NLO analysis has also shown that the investigated viscoelastic surfactants hold significant NLO properties (752.28–758.53 a.u) which are better than standard molecule recommended for the NLO activity of said viscoelastic surfactants. We hope that this computational insight may provide new ways for the utilization of viscoelastic surfactants as NLO material for optoelectronic applications. Exploring the NLO behavior of N-(3-((3-hydrosulfonylpropyl)dimethyl-l4-azaneyl)propyl)-hydroxy-decanamidehydrate based four novel viscoelastic surfactants. The insight may provide new ways for the utilization of viscoelastic surfactants as NLO material for optoelectronic applications.