Chromium Acetate Research Articles

Removal of Moxifloxacin from Aqueous Solutions Using GO/Cr-MOFs.

The composite material, consisting of graphene oxide (GO) and chromium metal-organic frameworks (Cr-MOFs), was successfully synthesized by using a solvothermal method. The organic ligand employed was 2,5-dihydroxyterephthalic acid, while chromium acetate served as the source of the metal. The resulting material underwent characterization through Fourier transform infrared, scanning electron microscopy, and X-ray diffraction techniques. Subsequently, the adsorption capacity of the composite material toward moxifloxacin was evaluated. The results indicated a gradual increase in the moxifloxacin removal rate from GO/Cr-MOFs over time until reaching an equilibrium with a maximum removal rate of 90.4%. Additionally, it was observed that higher temperatures led to a decrease in the adsorption capacity. By incorporating 30 mg of GO/Cr-MOFs into a solution containing 40 ppm of moxifloxacin, the adsorption capacity could be maximized at 222.25 mg/g. Experimental data on MOF adsorption of moxifloxacin were analyzed using pseudo-first-order kinetics (PFO), pseudo-second-order kinetics (PSO), and Langmuir, Freundlich, and Temkin isotherm models for theoretical research purposes. Results showed that the PSO model exhibited a better correlation than the PFO model did. Furthermore, experimental data demonstrated good agreement with the Freundlich isothermal model, suggesting its effectiveness in accurately describing the adsorption process. Henceforth, it can be concluded that chemisorption plays a significant role in removing moxifloxacin by GO/Cr-MOFs. The van't Hoff equation analysis revealed an exothermic and spontaneous nature of moxifloxacin adsorption onto GO/Cr-MOFs. Compared to other materials, the GO/Cr-MOF composite exhibited high potential for applications such as drug removal or related fields.

RESEARCH OF CROSS-LINKED POLYMER SYSTEMS FOR APPLICATION IN FIELDS CONDITIONS LLC RN-PURNEFTEGAZ

At present time, many oil fields, especially in historically developed areas of oil production, such as Western Siberia, characterized by a mature stage of development, accompanied by a high level of watercut of the produced wells while maintaining significant residual oil reserves. In such conditions, it is necessary to provide for the use of various methods aimed at additional recovery of oil reserves. In particular, it is necessary to provide for the use of tertiary impact methods, a significant share of which is occupied by flow- diverting technologies. The meaning of their application lies in the injection of a small amount of chemical reagents aimed at reducing the permeability of water-washed zones by installing a water-insulating barrier in them and redirecting water filtration flows to previously non-flooded reservoir zones. It should be noted that, unlike most methods of increasing oil recovery, in the case of the use of flow-diverting technologies, the flooding agent does not change — both before and after pumping the rim of chemical reagents, water is used as a flooding agent.From an analysis of literary sources and experience in the use of various types of flow-diverting technologies, it follows that one of the most frequently used technologies, with high versatility of action, is the technology of cross-linked polymer systems based on polymers of the acrylamide series. In this connection, this work presents the results of cross-linked polymer systems studies for selected promising development objects of LLC RN-Purneftegaz. Formulations containing polymers in the concentration range from 0.18 to 1.0 % with the addition of 0,018–0,01 % chromium acetate cross-linker were investigated. Additionally, compositions with the addition of bentonite clay powder in an amount of 0.5 wt.% were studied. A study was carried out of solubility, compatibility with water, crosslinkability of compositions,viscosity properties of initial solutions and crosslinked systems based on them. The thermal stability of cross-linked polymer systems was studied at temperatures from 44 ℃ to 95 ℃ and different mineralization. Recommendations for the use of flow-diverting technologies have been developed.

Two chromium(II) acetate complexes with N-heterocyclic carbene (NHC) coligands.

Tetra-kis(μ-acetato-κ2 O:O')bis-{[1,3-bis-(2,6-diiso-propyl-phen-yl)imidazol-2-yl-idene-κC 2]chromium(II)} tetra-hydro-furan disolvate, [Cr2(C2H3O2)4(C27H36N4)2]·2C4H8O or [Cr2(OAc)4(IDipp)2]·2C4H8O (1), and tetra-kis-(μ-acetato-κ2 O:O')bis-{[1,3-bis-(2,4,6-tri-methyl-phen-yl)imidazol-2-yl-idene-κC 2]chromium(II)},{Cr2(C2H3O2)4(C21H24N2)2] or [Cr2(OAc)4(IMes)2] (2), were synthesized from anhydrous chromium(II) acetate [Cr2(OAc)4] and the corresponding NHC (NHC = N-heterocyclic carbene) in toluene as solvent. Both complexes crystallize in the triclinic system, space group P. The mol-ecular structures consist of Cr2(OAc)4 paddle-wheels that carry two terminal NHC ligands. This leads to a square-pyramidal coordination of the chromium atoms.

Chromium and Methionine Effects on Amino Acid Uptake, Gene Expression, and Protein Abundance in Bovine Satellite Cells

The objective of the study was to evaluate the effects of chromium (Cr) and methionine on myogenic gene expression, GLUT4 and insulin receptor (IR) synthesis, and amino acid uptake in differentiated bovine satellite cells. Cells were treated with 0, 1, or 10 μM of chromium acetate (CrAc) and 0, 1, or 10 mg/mL of methionine, with cells utilized for the amino acid assay receiving 0.1 μM instead of 1 μM of CrAc. The addition of 10 μM of Cr tended to downregulate AMPKα mRNA gene expression (P < 0.1). Myogenin was impacted by methionine and CrAc with high doses and low doses upregulating expression (P < 0.01). The ratio and protein levels of AMPKα to pAMPKα, GLUT4, and IR abundance were not affected (P > 0.1). Increase in time decreased concentrations of leucine, isoleucine, threonine, methionine, phenylalanine, glutamine, ornithine, lysine, and cysteine (P < 0.01) in conditioned media. Over time, alanine increased (P < 0.01). Methionine inclusion increased alanine, proline, glutamic acid, ornithine, and tryptophan concentrations, as well as decreased leucine, isoleucine, and cysteine (P < 0.01). CrAc only affected glutamine and tryptophan, which both increased with CrAc dose, whereas alanine decreased (P < 0.01). Methionine decreased over time within the 10 mg/mL group (P < 0.01). Tryptophan was generally unaffected but decreased in the 0 mg/mL group at 48 h. Cysteine decreased with a decreased dosage of CrAc at 24 h (P < 0.01). Lysine was generally unaffected by this interaction (P > 0.1), with the exception of the 0.1 μM treatment group at 24 h being higher (P < 0.01). CrAc affected the uptake of alanine, glutamine, and tryptophan (P < 0.01). Methionine inclusion increased alanine, proline, glutamic acid, ornithine, and tryptophan, as well as decreased leucine, isoleucine, and cystine (P < 0.01). Increased time saw a significant decrease in leucine, isoleucine, threonine, methionine, phenylalanine, glutamine, ornithine, lysine, and cystine (P < 0.01) and an increase in alanine (P < 0.01).

Simultaneous Cr(VI) Reduction and Dexamethasone Phosphate Oxidation with Organo-metallic Sludge Formation Under UV Irradiation: Kinetics, Degradation Pathways, and Mechanism

In this study, we investigated the concurrent elimination of two distinct contaminants: organic matter in the form of dexamethasone phosphate (DexP) and an inorganic substance, chromium (Cr), employing UV irradiation. UV irradiation serves as a potent tool for breaking down organic materials, leading to the production of benign by-products, namely CO2 and H2O. Under optimal conditions characterized by a 30:1 DexP/Cr molar ratio and a pH level of 9, remarkable removal efficiencies were attained. In a mere 20 min, approximately 100% of DexP and 82.73% of Cr were effectively removed. Intriguingly, the removal of Cr exhibited an initially sluggish rate, with deposition commencing only after the breakdown of the DexP structure. This transformation was accompanied by the emergence of various sludge forms, each possessing unique characteristics. Utilizing Fourier-transform infrared (FTIR) analysis, we identified these sludge forms as chromium(III) hydroxide (green sludge), chromium(III) hydroxide (brown sludge), chromium(III) oxide (tiny green crystals), chromium(II) acetate chromium trioxide (red brick), and chromium oxide (black sludge). Further experimentation with varying concentrations of Cr and DexP, ranging from 50 to 150 mg L−1, yielded a range of rate constants (kobs) from 0.33 to 0.15 and removal efficiencies (robs) from 16.8 to 23.4% in the UV/DexP/Cr process. Energy efficiency output (EEO) calculations revealed that Cr precipitation ranged from 24.65 to 5.74 kW h m−3, whereas DexP EEO ranged from 12.54 to 4.73 kW h m−3. Of significant importance is the observation that when these two contaminants are removed simultaneously, the overall energy consumption is substantially lower compared to the scenario where pollutants are addressed individually. This finding underscores the efficiency and potential energy cost savings achievable through the concurrent removal of DexP and Cr using UV irradiation, making it a promising approach for environmental remediation.

Tetra-kis(μ-acetato-κ2O:O')bis-[(tetra-hydro-furan-κO)chromium(II)

The title compound, [Cr2(C2H3O2)4(C4H8O)2] or [Cr2(OAc)4(THF)2] (OAc is acetate, THF is tetra-hydro-furan), was obtained by recrystallization of anhydrous chromium(II) acetate [Cr2(OAc)4] from hot tetra-hydro-furan. The centrosymmetric complex forms monoclinic crystals, space group C2/c, and consists of two CrII atoms bridged by four acetate ligands. Additionally, each CrII atom is coordinated by a terminal THF ligand, which leads to a square-pyramidal coordination.

Nanosized amorphous and nanocrystalline titania doped by Cr as novel, efficient, and cost-effective cool-colored nanopigments

Ceramic cool-colored nanopigments (NPGs) are becoming more promising in painting applications for their cooling and aesthetic performance. The phase structure and the doping by color elements play a crucial role in the performance of nanopigments. Throughout this study, pure titania (TiO2) and chromium (Cr)-doped TiO2 NPGs in nanosized amorphous and nanocrystals structures were synthesized using a simple hydrolysis route. The molar ratios of chromium (III) acetate hydroxide: titanium tetra isopropoxide are 0%, 5%, 15%, and 25%. The synthesized NPGs were studied as-synthesized and after annealing at 500oC and 700oC. X-ray diffraction analyses, FTIR and high-resolution transmission electron microscope (HRTEM) were utilized to explore the microstructure and property of the synthesized NPGs. Also, surface area of the synthesized NPG samples was estimated by BET measurement. Optical property of synthesized NPGs was specified by UV/Vis/NIR spectroscopy. The combined influences of the annealing temperature and Cr addition on the phase structure, grain growth and near infrared (NIR) reflectivity of NPGs have been investigated. Pure white TiO2 NPG annealed at 700oC was displayed the higher NIR solar reflectance (R* = 94.72%) than the other investigated NPGs. The presence of Cr ion in annealed TiO2 NPGs caused a massive reduction in R* which is reaching out to 21.5% for the highest Cr concentration with annealing at 700oC. While the NIR reflectivity of as-synthesized pure TiO2 was slightly reduced from 87.49% to 77.05% as Cr ion content was increasing. The reflectance parameter in the visible region (RVIS*) was determined for the studied NPGs to define their aesthetic performance. Moreover, the color coordinates CIE (L*, a* &b*) and (ho, C*) were presented for the investigated NPGs according to the perpendicular form and the polar form, respectively.

FEATURES OF RHEOLOGICAL CHARACTERISTICS OF WATER INSULATION MATERIALS BASED ON POLYMER-DISPERSED ORGANOMINERAL REAGENTS

In most of the fields developed by the flooding method, there is an advanced flooding of borehole products associated with water breakthrough through the reservoir, backwater circulation, and also leakiness of the production column. In order to limit the extraction of "excess" water, water insulation technologies are widely used, in which hydrogels of various nature occupy a prominent place. For the rational use of water insulation technologies, it is necessary to know the rheology features and filtration characteristics of grouting materials. This article presents the results of experimental determination of a number of rheological characteristics of a composite insulating material based on sodium silicate, polyacrylamide (PAA), chromium acetate and rice husk dispersion. Rheological measurements were carried out in the oscillatory mode, which provide information about the elastic and viscous characteristics of the sample under study. The elastic modulus (accumulation modulus) characterizes the accumulated deformation energy in the system and reflects the property of the sample as a solid (elastic component). The viscous modulus (loss modulus) determines the energy dissipation and is responsible for the behavior of the sample as a liquid (viscous component). In each case, the range of linear viscoelastic behavior was determined as an interval of strain values in which the structure of the sample under study is not destroyed by deformation. Hydrodynamic modeling is increasingly used in the design of the RIW, which allows not only to reduce the time to justify the processing parameters, but also to increase its efficiency. For the convenience of subsequent hydrodynamic modeling, the results were processed using a two-component Burgers model to obtain the parameters of the elements of this model, which are a kind of «digital passport» of waterproofing materials.

Green synthesis of Cr2O3 nanoparticles by Cassia fistula, their electrochemical and antibacterial potential

Chromium oxide (Cr2O3) nanoparticles (NPs) find applications in modern science and technology due to their chemical stabilities, high-density corners and magnetic/electrical/catalytic properties. Current studies were performed to produce the (Cr2O3)aq and (Cr2O3)et NPs by treating chromium acetate with the aqueous and ethanolic extracts, respectively of Cassia fistula leaves; the same reaction was also performed in the presence of NaOH to yield the (Cr2O3)aqNa and (Cr2O3)etNa NPs, respectively. The synthesized NPs were characterized by XRD, FTIR, Raman spectroscopy,UV–Vis spectroscopy, SEM, TGA and DSC analysis and examined for their electrochemical properties. Their antibacterial potential was tested by biofilm inhibition and agar well diffusion methods. XRD studies revealed that Cr2O3 NPs possessed hexagonal crystal structures with the crystallite sizes of 14.85 to 23.90 nm; the lowest size (14.85 nm) was possessed by (Cr2O3)et. FTIR and Raman spectroscopies verified the +3-oxidation state of chromium and corresponding Cr-O and Cr=O vibrations. Raman spectroscopy determined A1g vibration modes (540.50–557.07 cm−1) with rhombohedral Cr2O3 structure, high degree of crystallinity and existence of Cr3+ ions in octahedral coordination whereas Eg vibration modes were displayed at 306.04–350.87 cm−1 and 602.47–613.81 cm−1. UV–Visible spectroscopy has shown band gaps in the range of 4.06–4.40 eV. The SEM images demonstrated the spherical morphology with a high degree of agglomeration between fine particles. The synthesized NPs exhibited good thermal stabilities up to 600 °C. The CV curves displayed the oxidation–reduction peaks and reversible behavior whereas GCD curve indicated the possible energy storage applications of NPs. (Cr2O3)aqNa NPs showed the highest specific capacitance (234.35 mAhg−1) at 1 mA current density. The biofilm inhibitions of the investigated NPs were comparable to those of the standard antibacterial drug (ciprofloxacin); the activity of (Cr2O3)etNa was found even better than that of ciprofloxacin. The NPs were more active against Escherichia coli (Gram-negative) as compared to those against Staphylococcus aureus (Gram-positive).

Dual crosslinked poly(acrylamide-co-N-vinylpyrrolidone) microspheres with re-crosslinking ability for fossil energy recovery

Microspheres have been proposed to be applied in controlling wastewater production for mature oilfields and migrating leakage for gas and nuclear waste storage. However, it remains challenging for stacked microspheres to maintain strong blocking ability in micron-sized small pores or fractures. In this study, a novel microsphere was developed with comprehensive properties including high deformability and long re-crosslinking time upon tunable swelling ratio for the applications. A dual covalent and physical crosslinking strategy was used to develop novel microspheres reinforced by a hydrogen bond (H-bond, between pyrrole ring and amide group) and coordination bond (between chromium acetate (CrAc) and carboxyl group via hydrolysis process). The microspheres were fabricated via radical suspension copolymerization of acrylamide (AM) and N-vinylpyrrolidone (NVP) in the presence of N, Nʹ-methylene-diacrylamide (MBA) with subsequent introduction of CrAc. MBA induced the strong crosslinking through a chemical covalent bond and H-bond triggered the weak crosslinking which was anticipated to prohibit the hydrolysis of the amide group. The H-bond delayed the formation of CrAc coordination bond by delaying the formation of carboxyl groups, resulting in achieving the re-crosslinking of the microspheres. As a result, the microspheres exhibit the tunable initial size (8–165 μm) and swelling ratio (30–630 μm), with controllable network parameters. The microspheres showed high migration ability (can transport through pores with 1/16 size of microsphere itself), and long re-crosslinking time (up to 16.5 days). The re-crosslinked gel demonstrated dual network structure with districted mesh size ζ distribution.

Infrequent Cubane-Like Chromium Sulfide Cluster with σ-Donor Ligands with Efficient Electrocatalytic Property Toward Hydrogen Evolution Reaction.

The exploitation of efficient and economical electrocatalysts for hydrogen evolution reaction (HER) is of exceeding interest in renewable clean-energy technologies. Herein, the facile solvothermal reaction of S and chromic acetate in ethylenediamine (en) achieved a novel organic hybrid chromium sulfide [Cr4(μ3-S)4(en)4(SH)4]·0.25H2O (1), which offers a new type of antiferromagnetic cubane-like chromium sulfide cluster with σ-donor en ligands. 1 was utilized in combination with Ni nanoparticles and porous Ni foam (NF) to fabricate a Ni/1/NF electrode as an efficient cathodic catalyst, indicating excellent electrocatalytic property toward HER.

Feasibility Study of Recrosslinkable Preformed Particle Gels for Natural Gas Injection Profile Control

SummaryRecrosslinkable preformed particle gel (RPPG), a preformed particle gel (PPG) of which particles can bond together to form a strong bulk gel system after being placed inside the target formation, has been successfully applied to control conformance problems for waterflooding projects. However, no research has been conducted about whether RPPG is feasible in improving gasflooding performance in mature reservoirs. The study presents a systematic evaluation of acrylamide (AM) and 2-acrylamide-2-methylpropane sulfonate acid (AMPS)-based RPPG including phase stability under different gel-gas kinetics and plugging performance to natural gas and water. Different experimental apparatuses were designed to quantify and visualize the RPPG phase stability under static and dynamic gel-gas interactions. The RPPG phase stability was evaluated under a different range of injection pressure, gas exposure time, and swelling ratio (SR). Also, the RPPG stability was compared to the in-situ gel system hydrolyzed polyacrylamide crosslinked with chromium acetate [HPAM/Cr(III)], which has been applied in oil fields to control gas injection conformance. The RPPG plugging efficiency was evaluated using open fractured cores with different apertures. The results showed that the RPPG was stable under both static and dynamic gel-natural gas interactions and was stable when being exposed to an acidic environment with an insignificant total percentage weight loss (<3%). Additionally, the strength of the RPPG was further improved with the longevity of the gas exposure. Furthermore, different from the in-situ gel system HPAM/Cr(III), which exhibited a high degree of dehydration under natural gas and exhibited substantial syneresis under acidic conditions, the microstructure of the RPPG remained stable after the dynamic gas exposure. The results of the coreflooding experiments demonstrated that the RPPG had excellent plugging efficiency, which was closely related to the SR and the fracture aperture. This is the first study where a polymer gel system has been systematically assessed through varied testing methodologies using natural gas as opposed to other studies where nitrogen (N2) was used to simulate natural gas behavior. The robustness of the RPPG system makes it a viable candidate for improving the gasflooding processes in mature reservoirs dominated by conformance problems such as void space conduits (VSCs), fractures, and high-permeability channels.

Application of Renewable Natural Materials for Gas and Water Shutoff Processes in Oil Wells

We propose a complex sealing compound for increasing the efficiency of shutoff operations based on natural materials processing for materials such as sand, peat, rice, and husks. We studied the influence of mechanical activation processes on the mechanical and rheological properties of the developed sealants. Through mechanochemical activation, sand dissolution in a low-concentrated alkali solution was possible, and gelling the resulting sodium silicate while reinforcing it with undissolved sand particles to obtain a sealant composition. We used this approach to produce a hybrid sealing compound based on activated rice husks with up to 20% biogenic silicon dioxide combined with mechanically activated peat: the maximum shear strain of the hybrid sealant was 27.7 ± 1.7 Pa. We produced hydrogels based on sodium silicate, polyacrylamide, and chromium acetate, reinforced with mechanically activated rice husks. We studied the sealants’ rheological and filtration properties and observed the respective viscoplastic and viscoelastic properties. An increase in the dispersion concentration from 0 to 0.5% increased the maximum strain value of undestroyed hydrogel’s structure in the range 50–91 Pa and the maximum shear strain from 104 to 128 Pa. The high residual resistance factor values of the ideal fracture model make the natural and plant-renewable raw materials very promising for repair and sealing work.

Simultaneous Cr (VI) reduction and diazinon oxidation with organometallic sludge formation under photolysis: kinetics, degradation pathways, and mechanism.

In this study, simultaneous removal of an organic matter (diazinon, DIZ) and an inorganic substance (chromium, Cr) was used. Breaking down of organic matter by UV irradiation produces various radicals, including sulfides, carboxyl, hydroxyl, hydrated electrons, and various organic radicals that are highly reactive and help us to precipitation inorganic substance (Cr). The optimal condition was 30:1 DIZ:Cr molar ratio, pH 9, and about 100% and 82.3% of DIZ and Cr were obtained in 30min. Cr deposition was very slow at first. After the destruction of the DIZ structure, Cr deposition began, and various types of sludge with disturbed properties were formed. These sledges were analyzed by FTIR analysis and showed that green sludge could be chromium (III) hydroxide; brown sludge due to chromium (III) hydroxide, tiny green crystals from chromium (III) oxide, red brick from chromium (II) acetate chromium trioxide, as well as black sludge caused by chromium oxide were identified. In UV/DIZ/Cr process, kobs and robs range obtained 0.33-0.15 and 16.8-23.4 $ with both Cr and DIZ concentration increased from 50 to 150mg L-1. Also, EEO for Cr precipitation was 24.65 to 5.74 and for DIZ 12.54 to 4.73 (kwh m-3). Depending on the amount of energy consumption, TCS was 37.19 to 10.47 for Cr precipitation and 4.46 to 1.25 $. It is important to note that when both pollutants are exposed to ultraviolet light, more energy and cost are generally required from UV/DIZ process and less than of UV/Cr process. But it should be noted that in fact 50mg L-1 of chromium and 50mg L-1 of DIZ are being removed at the same time. In UV/DIZ and UV/Cr processes that are exposed to ultraviolet radiation alone, only one of them is removed. Also, when these two pollutants are being removed at the same time, the total amount of energy is much less than the total energy consumption of the pollutants one by one.

Research on the Formulation System of Weak Gel and the Influencing Factors of Gel Formation after Polymer Flooding in Y1 Block

After long-term polymer flooding, water channeling, and ineffective water circulation occur in oil wells, which seriously affect polymer flooding efficiency and oilfield recovery. The weak gel system has the property of delaying cross-linking. After the weak gel system enters the deep formation, the cross-linking reaction is carried out, which can achieve the purpose of deep regulation and flooding. In this paper, according to the formation characteristics of high temperature, high permeability, and large pores in Y1 block (a block in the Daqing Yushulin Oilfield), the formulation of weak gel system was developed. The optimal formulation was determined by parameters such as gel-forming properties, stability, viscoelasticity, and rheology. Finally, the best formulation for the Y1 block is that containing 0.22% of polyacrylamide (HPAM) and 0.15% of chromium (III) acetate system. The gel-forming time of the formulation is 8 h, and the viscosity can be maintained at 15,000–24,000 mPa·s. Next, this paper studied the factors that affect the gelation of formulations, mainly including dissolved oxygen content, bacterial content, insoluble suspended solids content, and metal ions in the formulation water. The results show that the critical point of the worst effect is the oxygen content close to 1.5 mg/L, and the optimal critical point of oxygen content of the gel system is 7 mg/L. The bacteria in the prepared water degrade the weak gel solution. The more bacteria, the more serious the degradation of the weak gel. A small amount of insoluble suspended solids will greatly increase the viscosity of the weak gel solution, but will accelerate the gel-breaking time. When the content of insoluble suspended solids is high, more than 1000 mg/L, a precipitate will be formed at the bottom of the solution, and the difference in the content of insoluble suspended solids in this interval has little effect on weak gels. The metal ion that mainly affects the gelation effect is Fe2+. With the increase of Fe2+ mass concentration, the viscosity of weak gel decreases sharply.

Soft Movable Polymer Gel for Controlling Water Coning of Horizontal Well in Offshore Heavy Oil Cold Production.

Horizontal well water coning in offshore fields is one of the most common causes of rapid declines in crude oil production and, even more critical, can lead to oil well shut down. The offshore Y oil field with a water cut of 94.7% urgently needs horizontal well water control. However, it is a challenge for polymer gels to meet the requirements of low-temperature (55 °C) gelation and mobility to control water in a wider range. This paper introduced a novel polymer gel cross-linked by hydrolyzed polyacrylamide and chromium acetate and phenolic resin for water coning control of a horizontal well. The detailed gelant formula and treatment method of water coning control for a horizontal well in an offshore field was established. The optimized gelant formula was 0.30~0.45% HPAM + 0.30~0.5% phenolic resin + 0.10~0.15% chromium acetate, with corresponding gelation time of 26~34 h at 55 °C. The results showed that this gel has a compact network structure and excellent creep property, and it can play an efficient water control role in the microscopic model. The thus-optimized gelants were successively injected with injection volumes of 500.0 m3. The displacement fluid was used to displace gelants into the lost zone away from the oil zone. Then, the formed gel can be worked as the chemical packer in the oil–water interface to control water coning after shutting in for 4 days of gelation. The oil-field monitoring data indicated that the oil rate increased from 9.2 m3/d to 20.0 m3/d, the average water cut decreased to 60~70% after treatment, and the cumulative oil production could obtain 1.035 × 104 t instead of 3.9 × 103 t.

Influence study of flue gas on chromium acetate/HPAM gel in flue gas flooding reservoir

Polymer gels are potential plugging agents for gas mobility control in flue gas flooding reservoirs. However, the influence of flue gas on performances of polymer gels have not been clearly clarified so far. In this study, the effect mechanism of flue gas on chromium acetate/partially hydrolyzed polyacrylamide (HPAM) gel system has been elucidated in detail. Dynamic light scattering (DLS) and polymer rheological tests demonstrated that CO2 composed in flue gas altered the HPAM configuration by the decrease of hydrodynamic radius (Rh) and polymer viscosity. Moreover, CO2 delayed the chromium acetate cyclic trimer dissociating into linear trimer and retarded the cross-linking process, which weakened the gelation performance and gel strength. The O2 composed in flue gas led to polymer degradation and seriously impaired the gel long-term stability. Fourier transform infrared spectroscopy (FTIR) analysis revealed that the breakage of Cr-O bond and the disruption of gel network structure were induced by the comprehensive effect of O2 and CO2.

Homogeneous synthesis of hydroxyethyl acrylate catalyzed by organochromium(III) complexes: Kinetics and ligand effect

The ring-opening reaction of ethylene oxide with acrylic acid catalyzed by organochromium(III) complexes is the most promising route for the industrial synthesis of 2-hydroxyethyl acrylate. However, the heterogeneous batch process with highly explosive gaseous ethylene oxide possesses difficulties on the process optimization and safety. To resolve these problems, homogeneous synthesis process is developed by pressurization and in-line mixing of ethylene oxide and acrylic acid. Stop-flow microreactor is applied to investigate the homogeneous reaction characteristics with high efficiency. A reduced kinetic model on the basis of the simplified reaction network is proposed with good calibration results. The catalytic process of ring-opening reaction is distinguished from the non-catalytic one according to the kinetic model parameters. After recognizing the activation process of catalyst during reaction and fulfilling it before reaction, the ligand effect is quantitatively studied by carefully comparing the catalytic features of four types of organochromium catalysts, chromium(III) acetate, chromium(III) 2-ethylhexanoate, chromium(III) picolinate and chromium(III) acetylacetonate, indicating a high efficiency catalyst might contain such ligand (or support) that possesses weak interaction with Cr metal center as well as considerable steric hindrance.

The Potential of Ultrahigh Strength Gel through Novel Multistage Reinforcement Method for Sealing Operations in Medium to Ultralow Temperature Reservoirs

Summary Polymer gels are widely used in sealing operations in the oil and gas industry. Gel with high strength is strongly needed to perform such operations as fluid loss control, temporary plugging, casing integrity treatment, and water shutoff, etc. In this paper, a simple method is proposed to obtain ultrahigh strength gel (USGel), which is called multistage reinforcement method (MRM) and implies the philosophy of noncompetitive crosslinking, multistage reinforcement of molecular chains, and increased entanglement. By this method, acrylamide (AM), xanthan (XC), and two crosslinkers [N,N'-Methylenebisacrylamide (MBA), chromium acetate (Cr3+)] are selected to develop an USGel with potential for medium to ultralow temperature reservoir applications. The thermal stability and sealing performance of USGel are evaluated. The effect of component concentration, gelant pH, and temperature on the strength and gelation time of USGel are investigated. Counterintuitively, adding solid materials even reduces USGel strength. The strength of USGel exceeds other gels by comparison with reported stress-strain data from similar literature. After data fitting analysis, without considering the XC concentration, 1% Cr3+ can increase the strength of the gel by 78.32 times, while other gels with 1% reinforcement material (e.g., solid materials) can only increase by 1.09 to 1.35 times. At low concentrations (0.4% XC and 0.2% Cr3+), USGel strength can also reach 84.59–383.21 kPa at 15°C to 105°C when strain = 60%. Environmental scanning electron microscope(ESEM) and gelation data are used to further reveal the multistage reinforcement mechanism of USGel and the reason for strength reduction owing to adding solid materials. USGel is promising to be applied in sealing operations in medium to ultralow temperature reservoirs.

A Novel Branched Polymer Gel System with Delayed Gelation Property for Conformance Control

SummaryExcessive water production from oil reservoirs not only affects the economical production of oil, but it also results in serious environmental concerns. Polymer gels have been widely applied to decrease water production and thus improve oil production. However, traditional polymer gels such as partially hydrolyzed polyacrylamide (HPAM)/chromium (III) gel systems usually have a short gelation time and cannot meet the requirement of some conformance control projects. This paper introduces a novel polymer gel system of which crosslinking time can be significantly delayed. A branched polymer grafted from arginine by the surface initiation method is synthesized as the backbone, chromium acetate is used as the crosslinker, and no additional additives are used for the gel system. The results show that the gelation time of this system can be delayed to 61 days at 45°C and 20 days at 65°C because of the rigid structure of the branched polymer and the excellent chromium (III) chelating ability of arginine. The polymer gels have been stable for more than 150 days at 45 and 65°C. Coreflooding and rheology tests have demonstrated that this branched polymer has good injectivity and shear resistance in high-permeability rocks.