Star-like hydrophobically associative polyacrylamide for enhanced oil recovery: Comprehensive properties in harsh reservoir conditions

Nanotechnology Impact on Chemical-Enhanced Oil Recovery: A Review and Bibliometric Analysis of Recent Developments

Oil and gas are only two industries that could change because of nanotechnology, a rapidly growing field. The chemical-enhanced oil recovery (CEOR) method uses chemicals to accelerate oil flow from reservoirs. New and enhanced CEOR compounds that are more efficient and eco-friendly can be created using nanotechnology. One of the main research areas is creating novel nanomaterials that can transfer EOR chemicals to the reservoir more effectively. It was creating nanoparticles that can be used to change the viscosity and surface tension of reservoir fluids and constructing nanoparticles that can be utilized to improve the efficiency of the EOR compounds that are already in use. The assessment also identifies some difficulties that must be overcome before nanotechnology-based EOR can become widely used in industry. These difficulties include the requirement for creating mass-producible, cost-effective nanomaterials. There is a need to create strategies for supplying nanomaterials to the reservoir without endangering the formation of the reservoir. The requirement is to evaluate the environmental effects of CEOR compounds based on nanotechnology. The advantages of nanotechnology-based EOR are substantial despite the difficulties. Nanotechnology could make oil production more effective, profitable, and less environmentally harmful. An extensive overview of the most current advancements in nanotechnology-based EOR is provided in this paper. It is a useful resource for researchers and business people interested in this area. This review's analysis of current advancements in nanotechnology-based EOR shows that this area is attracting more and more attention. There have been a lot more publications on this subject in recent years, and a lot of research is being done on many facets of nanotechnology-based EOR. The scientometric investigation discovered serious inadequacies in earlier studies on adopting EOR and its potential benefits for a sustainable future. Research partnerships, joint ventures, and cutting-edge technology that consider assessing current changes and advances in oil output can all benefit from the results of our scientometric analysis.

Optimization of Fracturing Fluid and Retarded Acid for Stimulating Tight Naturally Fractured Bedrock Reservoirs

In tight naturally fractured bedrock reservoirs, hydrocarbons are typically stored in fractures, where hydraulic fracturing is needed to connect these fractures to the wellbore. The cross-linked gel is used as the fracturing fluid to reduce the fluid leak-off through natural fractures; however, it can cause formation damage due to its high content of residues after breaking. A synthetic polymer is introduced and evaluated that can maintain a high viscosity to minimize the leak-off , while having a low residue content after breaking. To further enhance the conductivity of the created fracture network, acid is applied to etch and roughen the created fracture faces. Because the target reservoir has a complex mineral composition, a three-step coreflood sequence using reservoir rock samples with controlled fracture widths is established to quantify the enhancement of different retarded acids and to reveal the mechanism behind it. The results indicate the synergy effect of reducing the acid concentration and surfactant adsorption on rock surfaces can lead to an obvious enhancement of the fracture permeability after acidizing, while the mud acid or hydrofluoric acid is not suitable for the target reservoir where concentrations of silicates and clays are relatively high.

Application of Polymers for Chemical Enhanced Oil Recovery: A Review

Polymers play a significant role in enhanced oil recovery (EOR) due to their viscoelastic properties and macromolecular structure. Herein, the mechanisms of the application of polymeric materials for enhanced oil recovery are elucidated. Subsequently, the polymer types used for EOR, namely synthetic polymers and natural polymers (biopolymers), and their properties are discussed. Moreover, the numerous applications for EOR such as polymer flooding, polymer foam flooding, alkali–polymer flooding, surfactant–polymer flooding, alkali–surfactant–polymer flooding, and polymeric nanofluid flooding are appraised and evaluated. Most of the polymers exhibit pseudoplastic behavior in the presence of shear forces. The biopolymers exhibit better salt tolerance and thermal stability but are susceptible to plugging and biodegradation. As for associative synthetic polyacrylamide, several complexities are involved in unlocking its full potential. Hence, hydrolyzed polyacrylamide remains the most coveted polymer for field application of polymer floods. Finally, alkali–surfactant–polymer flooding shows good efficiency at pilot and field scales, while a recently devised polymeric nanofluid shows good potential for field application of polymer flooding for EOR.

A simulation study on hydrogel performance for enhanced oil recovery using phase-field method

Hydrogels are increasingly applied in oil recovery processes. This leads to more controlled flow of fluids in porous media. In this process, hydrogel is injected to the reservoir to block the high permeability areas. The trapped oil in low permeability regions, is then swept by water flooding. pH‐sensitive hydrogel microspheres were synthesized in another work of the authors, which effectively increased the oil recovery factor in experimental studies. In this communication, phase-field approach was used to simulate this process and to obtain the tuning parameters of the model including thickness of the contact surface (є), phase transform parameter (M₀), and excess free energy (∧). Diffusion of hydrogels was studied by Cahn–Hilliard conservative approach and the breakage, deformation, and plugging mechanisms were analyzed, based on pressure drop variations in micromodel. Moreover, Effective parameters on oil recovery factor were analyzed. Results indicated a good agreement between experimental and modeling studies of oil recovery factor in water and hydrogel flooding with absolute errors of 2.29% and 4.06%, respectively. The recovery factor was calculated using a statistical method which was in good agreement with the modeling results. The tuned parameters of the model were reported as, є = 111.7 µm, M₀ = 5 × 10⁻¹³ m³/s, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\wedge = - 0.0003$$\end{document}∧=-0.0003 J/m³.

A review of polymer nanohybrids for oil recovery

As oil fields go into their final stage of production, new technologies are necessary to sustain production and increase the recovery of the hydrocarbon. Chemical injection is an enhanced recovery technique, which focuses on increasing the effectiveness of waterfloods. However, the use of chemical flooding has been hampered by its relatively high cost and the adsorption of the injected chemicals onto the reservoir rocks. In recent years, nanofluids have been launched as an overall less expensive and more efficient alternative to other chemical agents. Nanoparticle inclusion is also proposed to mitigate polymer flooding performance limitations under harsh reservoir conditions. This review presents a comprehensive discussion of the most recent developments of polymer nanohybrids for oil recovery. First, the preparation methods of polymer nanohybrids are summarized and explained. Then, an explanation of the different mechanisms leading to improved oil recovery are highlighted. Finally, the current challenges and opportunities for future development and application of polymer nanohybrids for chemical flooding are identified.

Feasibility Study of Applying Modified Nano-SiO2 Hyperbranched Copolymers for Enhanced Oil Recovery in Low-Mid Permeability Reservoirs

To improve oil recovery significantly in low-mid permeability reservoirs, a novel modified nano-SiO₂ hyperbranched copolymer (HPBS), consisting of polyacrylamide as hydrophilic branched chains and modified nano-SiO₂ as the core, was synthesized via an in situ free radical polymerization reaction. The structure and properties of the hyperbranched copolymer were characterized through a range of experiments, which showed that HBPS copolymers have better stability and enhanced oil recovery (EOR) capacity and also smaller hydrodynamic radius in comparison with hydrolyzed polyacrylamide (HPAM). The flooding experiments indicated that when a 1000 mg/L HPBS solution was injected, the resistance factor (RF) and residual resistance factor (RRF) increased after the injection. Following a 98% water cut after preliminary water flooding, 0.3 pore volume (PV) and 1000 mg/L HPBS solution flooding and extended water flooding (EWF) can further increase the oil recovery by 18.74% in comparison with 8.12% oil recovery when using HPAM. In this study, one can recognize that polymer flooding would be applicable in low-mid permeability reservoirs.

Biodegradation of hydrolyzed polyacrylamide by a Bacillus megaterium strain SZK-5: Functional enzymes and antioxidant defense mechanism

Hydrolyzed polyacrylamide (HPAM) is the most widely used water-soluble linear polymer with high molecular weight in polymer flooding. Microbiological degradation is an environment-friendly and effective method of treating HPAM-containing oilfield produced water. In this study, a strain SZK-5 that could degrade HPAM was isolated from soil contaminated by oilfield produced water. Based on morphological, biochemical characteristics and 16S rDNA sequence homology analysis, the strain was identified as Bacillus megaterium. The biodegradation capability of strain SZK-5 was determined by incubation in a mineral salt medium (MSM) containing HPAM under different environmental conditions, showing 55.93% of the HPAM removed after 7 d of incubation under the optimum conditions ((NH₄)₂SO₄ = 1667.9 mg L^-1, temperature = 24.05 °C and pH = 8.19). Cytochrome P450 (CYP) and urease (URE) played significant roles in biological carbon and nitrogen removal, respectively. The strain SZK-5 could resist the damages caused by oxidative stress given by crude oil and HPAM. To our knowledge, this is the first report about the biodegradation of HPAM by B. megaterium. These results suggest that strain SZK-5 might be a new auxiliary microbiological resource for the biodegradation of HPAM residue in wastewater and soil.

Preparation of a selective flocculant for treatment of oily wastewater produced from polymer flooding and its flocculant mechanism

There are residual polymers in the oily wastewater produced from polymer flooding (OWPF); keeping the residual polymer in the water during the flocculation is meaningful and challenging. In this paper, a selective flocculant (denoted as PDC10) which can remove the oil while keeping partially hydrolyzed polyacrylamide (HPAM) in water was prepared by copolymerization of decyl two methyl vinylbenzyl ammonium chloride (C10MVBA) and dimethyl aminopropyl methacryamide (DMAPMA). By using oil removal and HPAM retention as evaluation indexes, the synthesis condition of PDC10 was optimized. The optimum PDC10 exhibited oil removal of 98.0% and HPAM retention of 80.5%. Its HPAM retention is much higher than that of a regular cationic flocculant. Measurements of zeta potential, interfacial tension, interfacial dilational modulus and a dual polarization interferometry (DPI) test were carried out for investigating the flocculation mechanism of PDC10. The mechanism of PDC10 was that it can bridge and flocculate oil droplets by electrostatic interaction and hydrophobic interaction. It also preferred to distribute at the interface, and its interaction with HPAM in bulk water was weak, which confirms its selective flocculation properties.

Enhanced Oil Recovery by a Suspension of Core-Shell Polymeric Nanoparticles in Heterogeneous Low-Permeability Oil Reservoirs

Polymeric nanoparticle suspension is a newly developed oil-displacing agent for enhanced oil recovery (EOR) in low-permeability reservoirs. In this work, SiO₂/P(MBAAm-co-AM) polymeric nanoparticles were successfully synthesized by a simple distillation–precipitation polymerization method. Due to the introduction of polymer, the SiO₂/P(MBAAm-co-AM) nanoparticles show a favorable swelling performance in aqueous solution, and their particle sizes increase from 631 to 1258 nm as the swelling times increase from 24 to 120 h. The apparent viscosity of SiO₂/P(MBAAm-co-AM) suspension increases with an increase of mass concentration and swelling time, whereas it decreases as the salinity and temperature increase. The SiO₂/P(MBAAm-co-AM) suspension behaves like a non-Newtonian fluid at lower shear rates, yet like a Newtonian fluid at shear rates greater than 300 s⁻¹. The EOR tests of the SiO₂/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability cores show that SiO₂/P(MBAAm-co-AM) nanoparticles can effectively improve the sweep efficiency and recover more residual oils. A high permeability ratio can result in a high incremental oil recovery in parallel cores. With an increase of the permeability ratio of parallel cores from 1.40 to 15.49, the ratios of incremental oil recoveries (low permeability/high permeability) change from 7.69/4.61 to 23.61/8.46. This work demonstrates that this SiO₂/P(MBAAm-co-AM) suspension is an excellent conformance control agent for EOR in heterogeneous, low-permeability reservoirs. The findings of this study can help to further the understanding of the mechanisms of EOR using SiO₂/P(MBAAm-co-AM) suspension in heterogeneous, low-permeability reservoirs.

Hyper-branched structure—an active carrier for copolymer with surface activity, anti-polyelectrolyte effect and hydrophobic association in enhanced oil recovery

Herein, a hyper-branched polymer h-PMAD with, simultaneously, surface activity, an anti-polyelectrolyte effect and a hydrophobic association was prepared via aqueous solution free radical polymerization, and characterized by IR, NMR, TG–DTG and SEM. The polymer h-PMAD provided excellent comprehensive properties in terms of surface activity, thickening, water solubility, rheology and aging, which were compared with studies of HPAM and the homologous linear polymer PMAD. Specifically, the IFT value was 55.40 mN m⁻¹, 789.24 mPa s apparent viscosity with a dissolution time of 72 min, 97.72, 90.77 and 105.81 mPa s with Na⁺, Ca²⁺ and Mg²⁺ of 20 000, 2000 and 2000 mg L⁻¹, respectively. Meanwhile, the non-Newtonian shear thinning behavior had a 96.33% viscosity retention while the shear rate went from 170 s⁻¹ to 510 s⁻¹ and then returned to 170 s⁻¹ again and 0.12 Hz curve, with an intersection frequency of G′ and G′′. Also, it had 33.51% and 50.96% viscosity retention in formation and deionized water at 100 °C and a low viscosity loss in formation water at 80 °C over 4 weeks. Moreover, the h-PMAD had an EOR of 11.61%, was obviously higher than PMAD with 8.19% and HPAM with 5.88%. Most importantly, the better EOR of h-PMAD over that of PMAD testified that the hyper-branched structure provided an active carrier for copolymers with functionalized monomers to exert greater effects in displacement systems, which is of an extraordinary meaning.

Herein, a hyper-branched polymer h-PMAD with, simultaneously, surface activity, an anti-polyelectrolyte effect and a hydrophobic association was prepared via aqueous solution free radical polymerization, and characterized by IR, NMR, TG–DTG and SEM.