Oilfield Applications Research Articles

Shale core wettability alteration, foam and emulsion stabilization by surfactant: Impact of surfactant concentration, rock surface roughness and nanoparticles

Hexadecyltrimethyl ammonium bromide (HCTAB) and sodium dodecyl sulfate (SDS) are popular conventional surfactants with versatile industrial and oilfield applications. Knowledge of the optimum conditions for their applications for shale rock wettability modification, as well as foam and emulsion stabilization is relevant for hydrocarbon recovery process optimization. Influence of surfactant concentration, rock surface roughness and presence of nanoparticles in surfactant solutions on contact angles, oil-water interfacial tension (IFT), as well as foam and emulsion stabilization by HCTAB and SDS was investigated in this study. The interfacial properties measurements were conducted with Drop Shape Analyser (DSA 25), whereas the foam generation and stability properties were investigated via dynamic foam analyzer (DFA100). The emulsion stabilization and demulsification processes were investigated in Formulaction Turbiscan. Results showed an existence of optimum concentration of surfactant for obtaining the lowest contact angles, oil-water IFT reduction, as well as attaining maximum foam stability. The contact angle measured on rough core surfaces were smaller than the contact angle measured on smooth surfaces. Contact angles increased with increasing salnity concentration, but decreased with the increasing rock saturation time. Oil was more detrimental to foam stability when the generated foam was brought into contact with the resident oil, compared to when oil was added to the foaming solutions before foam generation. Lower contact angles, durable foam, and stable emulsion were produced in presence of oil and at high temperature via the synergy of nanoparticles and surfactants. Almost 66% decreased in contact angle was achieved with carbon nanotubes-SDS solutions, whereas Al 2 O 3 nanoparticles-HCTAB foam attained a viscosity of 99 mPa-s at 60 °C. The foam demonstrated shear thinning Newtonian fluids behaviors but attained a plateau after sometimes. The study suggests the conditions for optimization of conventional surfactants applications in conventional and unconventional reservoir. • Synergy of nanoparticles and surfactants on shale core wettability was studied. • Foams are less stable when they suddenly contacts the resident oil. • There is optimum surfactant concentration for maximizing interfacial activities. • Contact angle decreased by 66% in presence of carbon nanotubes-SDS solutions. • Al 2 O 3 -HCTAB foam attained a viscosity of 99 mPa-s at 60 °C.

Study on the impacting performance of a self-excited oscillation pulsed jet nozzle

The pulsive jet nozzle, which converts the continuous jet into a pulsive jet, is widely used in downhole well operations, such as drilling and perforation. In this paper, a self-excited oscillation pulsed jet nozzle is proposed basing on the Coanda effect. The effects of nozzle design, inlet flow rate, and target distance on the jet dynamics, such as the pulsive characteristics and impacting performance, were investigated. The transient flow pattern was studied with a high-speed camera, which showed a good agreement with the numerical results. Furthermore, with the increase of the inlet flow, the pulsation amplitude of impacting pressure of the Coanda nozzle increased. Based on the obtained data, the relationship between the pulsive frequency and Reynolds number and that between Strouhal number and Reynolds number was revealed. Under a confining pressure of 30 MPa, a target distance of 70 mm, and an inlet flow rate of 15 m/s, the error between the numerical impacting pressure and the experimental value was 9.7%, which confirmed the numerical approach could be used to predict the transient jet process. The obtained results can guide the design of a self-excited oscillation pulse jet nozzle and its oilfield application. • A self-excited oscillation pulsed jet nozzle with Coanda effect is proposed. • Computational fluid dynamics was applied to simulate the pulsive behavior. • Process parameters shown significant influence on the pulsive characteristics. • An error of 9.3% was achieved between numerical and experimental results.

Iron sulphide formation and interaction with corrosion inhibitor in H2S-containing environments

Corrosion of carbon steel in H2S-containing environments poses serious challenges to operations in oilfield and geothermal applications. Carbon steels exposed to H2S-containing environments are often susceptible to pitting and uniform corrosion, and linked to the properties of iron sulphide (FeS) layers that forms at the corroding interface. This paper investigates the corrosion characteristics of carbon steel in H2S-containing environments focussing on the early stage kinetics of FeS formation and its interaction with corrosion inhibitors (CI). Experiments were conducted in 3.5 and 5.8 wt% NaCl solution at 80 °C in 10% H2S-90% CO2-containing environments. In-situ electrochemical responses were measured using the linear polarisation resistance (LPR) technique. This was combined with post-experiment surface analysis; scanning electron microscopy (SEM) and X-ray diffraction (XRD) to investigate the nature and morphology of formed FeS. 3D surface profilometry was used to investigate the pitting corrosion characteristics of carbon steel caused by FeS interaction with CI. The results show a fast kinetics of FeS formation by direct reduction of H2S(aq) with a distinct and easily identifiable morphology, and evidence of minimum level of ferrite dissolution. The early stages of FeS formation and its interaction with CI have a strong influence on the overall corrosion characteristics of carbon steel. A dose of 30 ppm of a commercial corrosion inhibitor (CI); salts of nitrogenous molecules with a fatty acid group, at the corrosion interface induced a competition for surface absorption between CI and emerging FeS. Over the 48 h duration of this test, the FeS formation process was delayed and the mechanisms of its formation quickly became the main driver of pitting corrosion. The amount of CI dosed in this study was not able to prevent FeS-induced pitting corrosion attack on the surface.

Automated determination of interfacial tension and contact angle using computer vision for oil field applications

AbstractContact angle and surface tension are the two most widely used surface analysis approaches for reservoir fluid characterization in petroleum industries. The pendant drop method has among the most widely used techniques for the estimation of surface tension. The present work utilizes a python-based computer program to automatically determine interfacial tension (IFT) and contact angle from the pendant drop image acquired from a typical pendant drop apparatus. The proposed program uses python-based image processing libraries for the analysis of the pendant drop image. Also, the program is tested on images acquired from the standard solutions for the IFT and contact angle calculation showing promising results with a standard deviation of less than 1.7 mN/m.

Enhanced Nanofiltration Process of Thin Film Composite Membrane Using Dodecyl Phenol Ethoxylate and Oleic Acid Ethoxylate for Oilfield Calcite Scale Control.

This research studied the enhancing effect on the nanofiltration composite (TFCNF) membrane of two non-ionic surfactants on a thin-film composite nanofiltration membrane (TFCNF) for calcite scale (CaCO3) inhibition in oilfield application to develop a multifunctional filtration system: nanofiltration, antiscalant, and scale inhibitors. The effectiveness of dodecyl phenol ethoxylate (DPE) and oleic acid ethoxylate (OAE) as novel scale inhibitors were studied using the dynamic method. Scaling tests on the membrane were performed to measure the scaling of the inhibited membrane with and without scale inhibitors for salt rejection, permeability, and flux decline. The results revealed that the TFCNF membrane flux decline was improved in the presence of scale inhibitors from 22% to about 15%. The rejection of the membrane scales increases from 72% for blank membranes, reaching 97.2% and 88% for both DPE and OAE, respectively. These confirmed that scale inhibitor DPE had superior anti-scaling properties against calcite deposits on TFCNF membranes. Inhibited scaled TFCNF membrane was characterized using environmental scanning electron (ESEM), FTIR, and XRD techniques. The results of the prepared TFCNF membrane extensively scaled by the calcite deposits were correlated to its morphology.

Insights into Partial Slips and Temperature Jumps of a Nanofluid Flow over a Stretched or Shrinking Surface

This paper elucidates the significance of partial slips and temperature jumps on the heat and mass transfer of a boundary layer nanofluid flowing through a stretched or shrinking surface. Considerable consideration is given to the dynamic properties of the nanofluid process, including Brownian motion and thermophoresis. A similarity transform is introduced to obtain a physical model of nonlinear ordinary differential equations, and the Chebyshev method of collocation is used to numerically analyze the influences of parameters of physical flow such as slip, temperature jump, Brownian motion, thermophoresis, suction (or injection) parameters, and Lewis and Prandtl numbers. The numerical results for temperature and concentration profiles, and heat and mass transfer rates, are graphically represented, and insights into the effects of slips and temperature jumps are revealed. In the case of a stretched sheet, the slip parameter enhances the temperature field and increases the thermal boundary layer thickness as well as the concentration function’s boundary layer thickness. When the slip parameter is raised in the case of the shrinking sheet, the dual solutions for temperature and concentration functions are reduced. For the first solution, both the temperature and concentration functions drop as the slip parameter increases, but for the second solution, both the temperature and concentration functions rise as the slip parameter increases. The discoveries have applications in a number of disciplines, including heat transfer in a solar energy collector. Glass blowing, annealing, and copper wire thinning are just a few of the technical and oilfield applications for the current problem. In high-temperature industrial applications, radiation heat transfer research is critical.

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%.

Rheology, characteristics, stability, and pH-responsiveness of biosurfactant-stabilized crude oil/water nanoemulsions

The successful utilization of nanoemulsions in several applications would require the formulation of emulsions with excellent characteristics. Ideally, the nanoemulsions should be stabilized using bioemulsifiers, which do not negatively impact the environment throughout their cradle-to-grave lifetime. Thus, crude oil-in-water (O/W) nanoemulsions with exceptional properties were prepared in this study using rhamnolipid biosurfactant as a bioemulsifier. The obtained results reveal that rhamnolipid can produce O/W nanoemulsions with an average droplet size as low as 35.0 ± 6.6 nm. The nanoemulsions also have highly negative zeta potential, low interfacial tension, and long-term kinetic stability. Interestingly, almost all the formulated O/W nanoemulsions using different rhamnolipid dosages and oil/water ratios showed three different flow behaviors (i.e., shear-thinning, Newtonian, and shear-thickening at low, medium, and high shear rates, respectively). Additionally, the nanoemulsion formulated using 50/50 crude oil/water volumetric ratio displayed higher apparent viscosity than the crude oil at elevated temperatures (greater than 63 ⁰C). Furthermore, despite that all the formulated nanoemulsions were extremely stable, they can be easily, completely, and quickly (within ≤ 1 h) switched-off if needed via pH-switching. The results presented herein demonstrate the potential of biosurfactants for enhanced oil recovery (EOR) and other oilfield applications.

Effects of Silica Nanoparticle after Modification with (3-Aminopropyl) Triethoxysilane and Its Combination with Surfactant for Enhanced Oil Recovery

Silica nanoparticle (SNP) shows exceptional characteristics and therefore attracts much attention in enhancing the oil recovery factor. However, it tends to agglomerate in the water phase due to the presence of tremendous surface free energy, which limits greatly application in oil fields. To this end, it is essential to perform the modification of the SNP surface to increase its dispersibility. In this work, (3-aminopropyl) triethoxysilane (KH550) was used to modify the SNP surface, and the structural characterization of the KH550-SNP was carried out using FT-IR and TGA. Then, a composite system (KH550-SNP/SDBS) was prepared by integrating negatively charged sodium dodecylbenzene sulfonate (SDBS) and positively charged KH550-SNP under the action of the electrostatic attraction force, and its interface properties and imbibition efficiency were further evaluated. The characterization results indicated that the modification process of the SNP surface by KH550 was successful. Besides, the interfacial tension (IFT) of the composite system (KH550-SNP: SDBS = 0.05%: 0.05%) was 0.6 mN/m and the water contact angle (CA) of the core slice treated with the composite system (KH550-SNP: SDBS = 0.05%: 0.01%) was 36.5° compared to the KH550-SNP of 15.1 mN/m and 42.6°, which stated that the composite system had better interface properties than the KH550-SNP. Finally, the imbibition recovery factors were 24.7% and 30.8% when the KH550-SNP and composite system (KH550-SNP: SDBS = 0.05%: 0.01%) was used.

Nanotechnology Helps Decrease Pressure, Increase Injection in Offshore China Oil Field

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30407, “Case Study of Nanopolysilicon Materials’ Depressurization and Injection-Increasing Technology in Offshore Bohai Bay Oil Field KL21-1,” by Qing Feng, Nan Xiao Li, and Jun Zi Huang, China Oilfield Services, et al., prepared for the 2020 Offshore Technology Conference Asia, originally scheduled to be held in Kuala Lumpur, 2–6 November. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. Nanotechnology offers creative approaches to solve problems of oil and gas production that also provide potential for pressure-decreasing application in oil fields. However, at the time of writing, successful pressure-decreasing nanotechnology has rarely been reported. The complete paper reports nanopolysilicon as a new depressurization and injection-increasing agent. The stability of nanopolysilicon was studied in the presence of various ions, including sodium (Na+), calcium (Ca2+), and magnesium (Mg2+). The study found that the addition of nanomaterials can improve porosity and permeability of porous media. Introduction More than 600 water-injection wells exist in Bohai Bay, China. Offshore Field KL21-1, developed by water-flooding, is confronted with the following challenges: - Rapid increase and reduction of water-injection pressure - Weak water-injection capacity of reservoir - Decline of oil production - Poor reservoir properties - Serious hydration and expansion effects of clay minerals To overcome injection difficulties in offshore fields, conventional acidizing measures usually are taken. But, after multiple cycles of acidification, the amount of soluble substances in the rock gradually decreases and injection performance is shortened. Through injection-performance experiments, it can be determined that the biological nanopolysilicon colloid has positive effects on pressure reduction and injection increase. Fluid-seepage-resistance decreases, the injection rate increases by 40%, and injection pressure decreases by 10%. Features of Biological Nanopolysilicon Systems The biological nanopolysilicon-injection system was composed of a bioemulsifier (CDL32), a biological dispersant (DS2), and a nanopolysilicon hydrophobic system (NP12). The bacterial strain of CDL32 was used to obtain the culture colloid of biological emulsifier at 37°C for 5 days. DS2 was made from biological emulsifier CDL32 and some industrial raw materials described in Table 1 of the complete paper. Nanopolysilicon hydrophobic system NP12 was composed of silicon dioxide particles. The hydrophobic nanopolysilicons selected in this project featured particle sizes of less than 100 nm. In the original samples, a floc of nanopolysilicon was fluffy and uniform. But, when wet, nanopolysilicon will self-aggregate and its particle size increases greatly. At the same time, nanopolysilicon features significant agglomeration in water. Because of its high interface energy, nanopolysilicon is easily agglomerated, as shown in Fig. 1.

Experimental Study on High-Performers Quaternary Copolymer Based on Host-Guest Effect.

A quaternary polymer (HGP) was prepared by the free-radical polymerization of acrylamide, acrylic acid, maleic anhydride functionalized β-cyclodextrin (MAH-β-CD), and N-(3-methacrylamidopropyl)-N, N-dimethylnaphthalen-1-aminium chloride (NAP). It was found that host–guest behavior occurred most effectively at a molar rate of NAP and CD with 1:1, which exhibited better solubility than hydrophobically associative polymer. Moreover, the as-prepared polymer has superior salt tolerance, shear resistance, and viscoelasticity due to host–guest strategy. More importantly, the HGP solution simulates the distribution of formation water in the Bohai SZ1-1 oilfield has good rheological properties at 120 °C. All results show that the proposed polymer could be a competitive candidate in oilfield applications such as fracturing fluids, displacement fluids, and drilling fluids.

Methane hydrate thermodynamic phase stability predictions in the presence of salt inhibitors and their mixture for offshore operations

A thermodynamic model is developed and used in this study to predict the phase equilibrium conditions of a methane -aqueous salt inhibitor -water hydrate system. The modified van der Waals-Platteeuw (vdWP) model is used to calculate the equilibrium condition of the hydrate phase. To compute the fugacities of gas and liquid phases, the Peng-Robinson equation of state (PR-EoS) and a previously developed Pitzer-Mayorga-Zavitsas-hydration model are used. The model predictions are compared to experimental results on methane hydrate phase equilibrium in the presence of an aqueous salt inhibitor. The absolute average relative deviation in predicted methane -aqueous salt inhibitor -water hydrate equilibrium pressure (AARD-P%) with the developed Pitzer-Mayorga-Zavitsas-Hydration model is 3.59% for CH4+NaCl, 1.52% for CH4+KCl, and 2.70% for CH4+ CaCl2. Finally, the hydrate suppression temperature caused by aqueous salt inhibitors and their mixtures on methane hydrate phase stability is calculated, and it is CaCl2>KCl>NaCl in that order. This work's phase equilibrium model demonstrates the potential application of determining methane hydrate equilibrium conditions in the presence of aqueous salt inhibitors and their mixtures used in offshore oil field applications.

Synthesis and evaluation of magnetic surfactants for high temperature oilfield application

Magnetic surfactants are a unique class of amphiphiles that can manage self-assembly in a controlled manner in the presence of the applied magnetic field. However, any surfactant for oilfield application must be soluble in water and exhibit high heat stability as it needs to stay in harsh reservoir conditions. Herein, we report a synthesis of two new magnetic surfactants that contain different hydrophobic moieties (ethoxylated alky tail and oleic tail). The chemical structures of the magnetic surfactants and their nonmagnetic parent surfactants were elucidated by ESI-MS, NMR (1H, 13C), and FTIR analysis. Both surfactants display good aqueous solubility due to the insertion of ethoxy units and unsaturation in the hydrophobic tail. The effect of hydrophobic tails on heat and surface/interface properties was investigated. Rendering to thermal gravimetric curves, the degradation temperature of magnetic surfactants was near 270 °C. This clearly showed that the magnetic surfactants contain high thermal stability for elevated temperature reservoirs. However, the effect of change of hydrophobic tail appears to be insignificant in thermal stability tests. An analysis of the surface tension showed that magnetic surfactants were more effective than corresponding nonmagnetic surfactants exhibiting higher surface tension (γ) reduction of water even with no magnetic field. Moreover, the magnetic surfactant containing an ethoxylated alkyl tail showed more surface tension (γ) reduction of water than a magnetic surfactant with an oleic tail. The research outcome on the synthesized magnetic surfactants makes them an attractive choice in a harsh oilfield environment. To the best of our knowledge, this is the first report on the magnetic surfactants that can toleratate high temperature reservoir conditions.

Effect of single-step silica nanoparticle on rheological characterization of surfactant based CO2 foam for effective carbon utilization in subsurface applications

Foams represent the most viable method of gas mobility control in subsurface reservoirs. However, their wider oilfield application is constrained due to their low stability. In this study, the role of single-step silica nanofluids (size ~30–150 nm) on the rheological behavior of surfactant-based carbon dioxide (CO2) foams was investigated for effective carbon utilization in porous media. Nanofluids, of varying nanoparticle size (36–148 nm) and concentration (0.1–1 wt%), displayed excellent dispersion stability. Pickering CO2 foams of varying sizes (20–40 µm) were developed. CO2 foams were analyzed for foam volume, stability, and rate of liquid drainage. Increasing silica size was found to show a detrimental effect on foam stability while increasing concentration improved foam stability. The foam stability was found to be greatly dependent on test temperature and above 90 °C, Pickering foam exhibited higher foam degradation. For foam, the rheological measurements were conducted at 1 bar as a function of temperature (30–90 °C). Pickering CO2 foams showed non-Newtonian shear thinning behavior where increasing nanoparticle concentration (0.5–1 wt%) yielded a 6–13% increase in foam viscosity. The foams also showed strong viscoelastic nature with the presence of both G′ and G″ over the entire range of investigated strain and amplitude sweep. From the viscoelastic characterization of CO2 foams, it was established that foam behavior was dominated by elastic nature (G′ > G″) at low stress values (10–20 strain %) while increasing stress (>20 strain %) produced liquid-like (G″ > G′) dominance in the behavior of foam. Finally, hysteresis analysis was reported to understand the role of a heterogeneous pore environment (where varying shear conditions usually prevail) on the flow properties of CO2 foams. The addition of silica nanofluid stabilizes CO2 foams and their application is proposed in carbon storage and utilization applications like enhanced oil recovery.

Abstract P-38: Tunable Soft Networks of Wormlike Micelles and Clay Particles

Background: Over the past few decades, there has been a great deal of interest in the aqueous self-assembly of surfactant molecules into giant wormlike micelles (WLMs). These cylindrical aggregates undergo reversible breakdown processes and in favorable cases can grow up to few tens of micrometers that is comparable with the length of high molecular weight polymer. The viscoelastic properties of WLMs can be easily modified by different additives like salts or polymers. A new emerging research area consists of tuning the WLM solution properties by inorganic nanoparticles. It suggests, in particular, the use of networks of entangled WLMs as a matrix for producing soft nanocomposites with different kinds of embedded nanoparticles that are promising for controlled release, template synthesis, and oilfield applications. These materials can combine adaptive rheological properties of the WLM matrix and the functionality of nanofiller. Methods: Rheometry and cryo-transmission electron microscopy were combined to investigate the structure and properties of mixed WLMs of zwitterionic oleylamidopropyl dimethyl betaine and anionic sodium dodecyl sulfate surfactants and platelike particles of bentonite clay. Results: This system demonstrates the formation of giant linear long-lived WLMs, which even at extremely low surfactant concentrations reach a sufficient length to entangle with each other and form a temporally persistent network. The stability of these micelles can be due to electrostatic attraction between the headgroups of the anionic and zwitterionic surfactants and favorable volume/length hydrophobic ratio in the surfactant mixture. At increasing surfactant concentration, the long-lived linear micelles transform into fast-breaking branched micelles. Stable viscoelastic suspensions of clay particles in semi-dilute solutions of WLM were elaborated. They represent a novel type of soft nanocomposite with the tunable matrix. Structural studies revealed that the clay is dispersed in a dense network of entangled WLM in the form of 100-nm tactoids. Rheological investigations demonstrated that clay particles can induce an increase of viscosity and relaxation time by up to one order of magnitude. The effect of the clay becomes more pronounced with increasing content of anionic surfactant, when the micelles become branched. This behavior was explained by the stabilization of micelle-nanoclay junction points due to the screening of the repulsion between positively charged fragments of zwitterionic head groups by added anionic surfactant. Conclusion: The pronounced effect of nanoparticles on the viscoelasticity of the network formed by branched WLMs was observed for the first time. The nanoparticles-WLM junctions were confirmed by cryo-TEM data. The elaborated systems are of interest for many industrial applications.

WITHDRAWN: A comprehensive review on critical affecting parameters on foam stability and recent advancements for foam-based EOR scenario

Foam injection process is a promising new technique of enhanced oil recovery (EOR), which tackles the issues induced by gas-based EOR scenarios such as viscous fingering and gravity segregation phenomena. The potential of foam-based EOR technique has attracted the great attention of the upstream oil industry over the past decades. Besides the successful oilfield applications of the foam injection for improving oil recovery efficiency, there are many challenges regarding to the stability, quality and foamability of the foam solution at elevated pressures and temperatures. In addition, the responsible mechanisms of foam injection at micro-scale has not been well attended in the available literature. This paper reviews the most relevant published researches on the foam-based EOR for a better understanding and delineation. In this work, the critical affecting parameters on foam stability and quality are discussed in details. In addition, the predominant mechanisms of foam generation are comprehensively clarified. In the following, the practical methods for investigation of the foam stability are explained and compared. Finally, the recent advancements for development of foam solution and enhancement of the foam stability are presented and the flaws of studies in this subject are illustrated.

Effect of nanoparticle on rheological properties of surfactant-based nanofluid for effective carbon utilization: capturing and storage prospects.

Previous studies have shown insufficient dispersion and thermal stability of nanofluids for high-temperature carbon capture and storage applications. Compared to the other NPs, TiO2 nanofluids exhibit superior stability due to their high zeta potential. In previous studies, TiO2 nanofluids have shown superior performance in heat transfer and cooling applications along with importing the stability of other nanofluids like SiO2 in form of nanocomposites. Therefore, in this study, a nanofluid formulation consisting of titania nanofluid in a base solution of ethylene glycol (EG) with different co-stabilizers such as surfactants was synthesized for better dispersion stability, enhanced electrical, and rheological properties especially for the use in high-temperature industrial applications which include carbon capture and storage along with enhanced oil recovery. The formulated nanofluid was investigated for stability using dynamic light scattering (DLS) study and electrical conductivity. Additionally, the formulated nanofluid was also examined for thermal stability at high temperatures using an electrical conductivity study followed by rheological measurements at 30 and 90 °C. At a high temperature, the shear-thinning behavior of EG was found highly affected by shear rate; however, this deformation was controlled using TiO2 nanoparticles (NPs). Furthermore, the role of surfactant was also investigated on dispersion stability, electrical conductivity followed by viscosity results, and it was found that the nanofluid is superior in presence of anionic surfactant sodium dodecyl sulfate (SDS) as compared to nonionic surfactant Triton X-100 (TX-100). The inclusion of ionic surfactant provides a charged layer of micelles surrounding the core of a NP and it produced additional surface potential. Consequently, it increases the repulsive force between two adjacent NPs and renders a greater stability to nanofluid while nonionic surfactant allowed monomers to adsorb on the surface of NP via hydrophobic interaction and enhances the short-range interparticle repulsion, to stabilize nanofluid. This makes titania nanofluid suitable for widespread high-temperature applications where conventional nanofluids face limitations. Finally, the application of the synthesized titania nanofluids was explored for the capture and transport of CO2 where the inclusion of the anionic surfactant was found to increase the CO2 capturing ability of titania nanofluids by 140-220% (over the conventional nanofluid) while also showing superior retention at both investigated temperatures. Thus, the study promotes the role of novel surfactant-treated titania nanofluids for carbon removal and storage and recommends their applications involving carbonated fluid injection (CFI) to carbon utilization in oilfield applications.

Research and Application of Segmentation Unblocking Technology for Horizontal Well Screen

Horizontal well screen completion process has its own advantages, but there are also some problems, in which the screen blockage seriously affects its efficacy. However, due to various factors (such as heavy components in crude oil plugging the sand filter), the implementation of conventional pickling and sand washing operations is not ideal. In response to this problem, this paper proposes a new unblocking technology - segmentation unblocking technology for horizontal well screen. Firstly, on the basis of studying principle of the technology, optimization of water jet method and hydraulic sanding nozzle, nitrogen foam water jet experiment and water jet construction displacement experiment are carried out for horizontal well screen, which laying the foundation for application of segmentation unblocking technology. Further, horizontal well screen segmentation unblocking experiment and oilfield application are carried out. Optimization results of water jet method show that, For large displacement construction with still wellhead, whole section construction selects type of inlet liquid through annulus between oil pipe and casing pipe and outlet liquid through oil pipe. For small displacement construction with frequent dynamic wellhead, segmentation construction selects type of inlet liquid through oil pipe and outlet liquid through annulus between oil pipe and casing pipe. Optimization results of hydraulic sanding nozzle show that Streamlined nozzle is better than nozzle with iso variable. Experiment results of horizontal well screen segmentation unblocking show that, segmentation unblocking technology can effectively improve productivity of horizontal well and oilfield application achieved good results. Five wells were shut-in, periodic shut-in or low production before segmentation unblocking. After segmentation unblocking, daily oil increment can reach 23.57 t, and interval cumulative oil increment can reach 4756 t.

Preparation and evaluation of soft preformed particle gels for conformance control in carbonate reservoir

In this paper, we studied on the nanocomposite preformed particle gels (PPGs) for conformance control in fractured-vuggy carbonated reservoirs. The nanocomposite PPGs were synthesized via free radical polymerization, consist of acrylamide (AM), N-vinylpyrrolidone (NVP). PPGs were evaluated at 130 °C and salinity of 2.2 × 105 mg/L. Swelling ratio (Sw) and storage modulus (G′) were measured as a function of aging time. A three-stage swollen history is discovered by means of fitting the power-law relation of modulus and volume fraction. It is inferred that the deviation is caused by stress relaxation and secondary cross-link, respectively. Experimental results show that increasing the concentration of monomer, cross-linker and clay leads to a higher swelling ratio and lower modulus during the aging term. PPGs with 30 wt% monomers, NVP: AM ratio of 6:4, 0.25 wt% cross-linker and 3.0 wt% clay exhibit optimum properties for conformance control at high temperature reservoirs. The propagation and blocking efficiency of PPGs were evaluated in an ideal fracture model. The match relation of particle size and fracture width was discussed. Industrial PPGs products with various sizes were prepared. Toughness measurements and infrared spectrum (IR) show that the properties of PPGs are stable during the scale up production. Finally, the field application in Tahe oil field is briefly introduced.

Mechanism of Protective Action of Inhibitors Based on Quaternary Ammonium Compounds

Currently, inhibitory protection is one of the most effective and common methods of protecting the inner surface of oil field equipment from corrosion. The work explores the mechanism of protective action of new inhibitors based on quaternary ammonium compounds and assesses feasibility of their practical application in oil fields of OJSC Surgutneftegas. Studies were conducted on samples made of pipe steels A 568M, A 516-55 and 13CrV (rus 13ХФА) in a model produced water solution. Three corrosion inhibitors were tested. Parameters of the mechanism of protective action of reagents were determined by potentiodynamic analysis.