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Cellulose graft copolymers having well-defined structures could incorporate the characteristics of both the cellulose skeleton and side chains, providing a new method for the preparation functionalised cellulose derivatives. Herein, a series of multifunctional cellulose grafted, alternating 3,4-dihydrocoumarin (DHC) and epoxide (EPO) copolymers (cell-g-P(DHC-alt-EPO)) were prepared in a metal-free DBU/DMSO/CO 2 solvent system without adding additional catalyst. Four examples of cell-g-P(DHC-alt-EPO) with tunable thermal and optical properties were synthesized by copolymerization of DHC with styrene oxide (SO), propylene oxide (PO), cyclohexene oxide (CHO) or furfuryl glycidyl ether (FGE) onto cellulose. The nonconjugated cell-g-P(DHC-alt-EPO) showed UV absorption properties with the maximum absorption peak at 282 nm and 295 nm and photoluminescence performance. A clustering-triggered emission mechanism was confirmed and consistent with DFT theoretical calculations. In DMSO solution, the copolymer (DHCSO5) with DP of 11.64 showed ACQ behaviour as the concentration increased. In addition, DHCSO5 had good antioxidant capacity with an instantaneous radical scavenging activity of 2,2-diphenyl-1-picrylhydrazine (DPPH) up to 65 % at a concentration of 40 mg/ ml and increased to 100 % after 30 min. Thus, the multifunctional cell-g-P(DHC-alt-EPO) materials had a variety of potential applications in the fields of fluorescent printing, bio-imaging, UV- shielding and antioxidants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (Copyright © 2023 Elsevier B.V. All rights reserved.)

Reductive activation of carbon dioxide (CO2) has drawn increasing attention as an effective and convenient method to unlock this stable molecule, especially via transition metal-catalyzed reactions. Taking the [TaC4O8]+ ion–molecule complex formed in the laser ablation source as a representative, the reactivity of the tantalum metal cation towards CO2 molecules is explored using infrared photodissociation spectroscopy combined with quantum chemical calculations. The strong absorption in the carbonyl stretching region provides solid evidence for the insertion reactions into C＝O bonds by the tantalum cation. Two inserted oxocarbonyl products are identified based on the great agreement between the experimental results and simulated infrared spectra of energetically low-lying structures in the singlet and triplet states. The pivotal role of two-state reactivity in driving CO2 activation among three different spin states is rationalized by potential energy surface analysis. Our conclusion provides valuable insight into the intrinsic mechanisms of CO2 activation by the tantalum metal cation, highlighting the affinity of tantalum for C＝O bond insertion in addition to typical "end-on" binding configurations. [ABSTRACT FROM AUTHOR]

Heavy oil reservoirs are often characterized by high viscosity and poor mobility, which is more complex with the presence of bottom water. The conventional vertical well development method has low oil recovery efficiency and limited controlled reserves of a single well. In addition, water cut can increase dramatically when the edge-bottom water breaks through. Horizontal well and CO2 huff-n-puff is an effective alternative development model for heavy oil reservoirs. This development method makes efficient use of CO2 and accords with the "Carbon Capture, Utilization, and Storage (CCUS)". The horizontal well can increase the drainage area. The dissolution of CO2 improves the mobility of crude oil and increases formation energy. In this paper, we established numerical simulation models based on the Liuguanzhuang oilfield in Dagang. The characteristics and producing rules of the horizontal well and CO2 huff-n-puff development in the heavy oil reservoir were studied. The results show that the production characteristics of horizontal well and CO2 huff-n-puff were similar to Steam-Assisted Gravity Drainage (SAGD). CO2 forms a viscosity reduction area above the horizontal well and the heavy oil flows into the wellbore due to gravity after viscosity reduction. The CO2 huff-n-puff can effectively enhance the production area of horizontal wells compared with the depletion development. However, the improvement in the production area gradually decreased as CO2 huff-n-puff cycles continued. There was a boundary of production area against the horizontal well, with the main production of heavy oil occurring at the upper and either end of the horizontal well. The CO2 huff-n-puff has a restraining effect on the edge-bottom water, which is confirmed via the proposed theoretical model. [ABSTRACT FROM AUTHOR]

There are large, heavy oil reserves in Block X of the Xinjiang oilfields, China. Due to its large burial depth (1300 m) and low permeability (26.0 mD), the traditional steam-injection technology cannot be used to obtain effective development benefits. This paper conducts experimental and simulation research on the feasibility and mechanism of CO 2 -energized fracturing of horizontal wells and N 2 foam huff-n-puff in deep heavy oil reservoirs with low permeability in order to further explore the appropriate production technology. The foaming volume of the foaming agent at different concentrations and the oil displacement effect of N 2 foam at different gas/liquid ratios were compared by the experiments. The results show that a high concentration of foaming agent mixed with crude oil is more conducive to increasing the foaming volume and extending the half-life, and the best foaming agent concentration is 3.0∼4.0%. The 2D micro-scale visualization experiment results show that N 2 foam has a good selective blocking effect, which increases the sweep area. The number of bubbles per unit area increases as the gas/liquid ratio increases, with 3.0∼5.0 being the optimal gas/liquid ratio. Numerical simulation results show that, when CO 2 -energized fracturing technology takes into account the advantages of fracturing and crude oil viscosity reduction by CO 2 dissolution, the phased oil recovery factor in the primary production period can reach approximately 13.7%. A solvent pre-slug with N 2 foam huff-n-puff technology is applied to improve oil recovery factor following primary production for 5∼6 years, and the final oil recovery factor can reach approximately 35.0%. The methodology formulated in this study is particularly significant for the effective development of this oil reservoir with deeply buried depth and low permeability, and would also guide the recovery of similar oil deposits. [ABSTRACT FROM AUTHOR]

Thermal recovery technology is generally suitable for shallow lays due to the higher thermal loss for the deep heavy-oil reservoirs. Non-thermal recovery technologies, such as the non-condensate gas injection technology, are not limited by the reservoir depth and could be extensively applied for the heavy-oil reservoir. Many experimental studies and field applications of non-condensate gas injection have been conducted in heavy-oil reservoirs. The injected non-condensate gas could achieve dynamic miscibility with heavy oil through multiple contacts, which has a significant viscosity-reduction effect under the reservoir conditions. In addition, the equipment involved in the gas injection operation is simple. There are many kinds of non-condensate gases, and common types of gases include N2 and CO2 due to abundant gas sources and lower prices. Moreover, CO2 is a greenhouse gas and the injection of CO2 into the reservoir would have environmental benefits. The non-thermodynamic method is to inject N2 and CO2 separately to produce heavy oil based on the mechanism of the volume expansion of crude oil to form elastic flooding and reduce crude oil viscosity and foamy oil flow. Steam injection recovery of the thermodynamics method has the disadvantages of large wellbore heat loss and inter-well steam channeling. The addition of N2, CO2, and other non-condensate gases to the steam could greatly improve the thermophysical properties of the injected fluid, and lead to higher expansion performance. After being injected into the reservoir, the viscosity of heavy oil could be effectively reduced, the seepage characteristics of heavy oil would be improved, and the reservoir development effect could be improved. Non-condensate gas injection stimulation technology can not only effectively improve oil recovery, but also help to achieve carbon neutrality, which has a very broad application prospect in the future oil recovery, energy utilization, environmental improvement, and other aspects. [ABSTRACT FROM AUTHOR]

When developing heavy-oil reservoirs using steam-assisted gravity drainage (SAGD) technology, CO 2 is often used to reduce the viscosity of heavy oil and the heat loss of the steam chamber, thereby enhancing oil recovery. The limitation of experimental apparatuses, results in a maximum temperature of the reaction kettle of no more than 150 °C. Thus, the solubility of CO 2 in super-heavy oil and its impact on decreasing viscosity beyond 150 °C requires further discussion. Considering these issues, a high-temperature-resistant heavy-oil mixing apparatus was designed to measure the solubility of CO 2 in super-heavy oil and the relative density and viscosity of super-heavy oil under high temperatures and pressures. Core flooding experiments under 200 °C were conducted to explore the effects of CO 2 on oil displacement efficiency. The results indicated that solubility of CO 2 became significantly lower at 200 °C, when the viscosity and relative density of super-heavy oil decreased as pressure increased. The viscosity of super-heavy oil saturated with CO 2 decreased by 71.2%, and relative density decreased by 10.1% at 200 °C compared to those of degassed crude. At temperatures of 120 °C, 150 °C and 200 °C, the ultimate displacement efficiency of super-heavy oil increased by 6.6%, 19.2% and 21.4%, respectively, compared to a temperature of 60 °C. At pressures of 1.0 MPa, 2.0 MPa and 4.0 MPa, the ultimate displacement efficiency (46.7%) of super-heavy oil increased by 5.2%, 4.0% and 5.9%, respectively, compared to a pressure of 0.5 MPa. The experiments showed that CO 2 injection can effectively reduce the relative density and viscosity of super-heavy oil and improve oil recovery under high temperatures and pressures. CO 2 has good potential to improve SAGD efficiency in developing super-heavy-oil reservoirs. [ABSTRACT FROM AUTHOR]

Laboratory experiments and pilot applications have proved that urea is an efficient agent to enhance heavy oil recovery. Numerous studies have been conducted to investigate the mechanisms of urea co-injection process in steam flooding or cyclic steam stimulation. However, investigations of applying urea in steam assisted gravity drainage (SAGD) process are rarely published. The mechanism of enhanced oil recovery in the urea assisted SAGD process has not been fully understood. Laboratory experiments and numerical simulations were conducted to study the decomposition rate of urea, the effect of urea decomposition products on reservoirs and pipelines, and the distribution of effective decomposition products of urea in the steam chamber at conditions of different concentrations, temperatures, and injection rates. The results show that the solubility of the effective urea decomposition products affects their distribution in the formation because of the huge difference between the solubility in oil and water. In SAGD process, urea cannot be completely decomposed and will produce solid decomposition products, which could block the reservoir pores and production pipelines in certain conditions. Moreover, numerical simulation indicates that the use of low-concentration urea injection in SAGD can effectively enhance oil recovery and oil production rate, while high-concentration urea can reduce the oil recovery and oil production rate. In addition, it was proved that CO 2 mainly exists at the edge of the steam chamber and NH 3 is distributed in the irreducible water near the well-bore. CO 2 is more effective than NH 3 for enhancing oil recovery in urea assisted SAGD. Studies indicate that urea co-injection is a feasible method for enhancing oil recovery in the SAGD process. [ABSTRACT FROM AUTHOR]

A series of cellulose grafted alternating cyclic anhydride (CA) and epoxide (EPO) copolyesters (cell- g -P(CA-alt-EPO)) have been prepared in the novel DBU/DMSO/CO 2 cellulose solvent system. The DBU acted both as a reagent for cellulose dissolution and as a catalyst for ring-opening copolymerization (ROCOP) of cellulose with EPO and CA. The structural features and thermal performances of cell- g -P(CA-alt-EPO) were characterized via MALDI-TOF, FT-IR NMR, TGA, DSC and XPS. Perfectly alternating sequence distributions and controlled molecular weights of a series of cell- g -P(CA-alt-EPO) were easily achieved by a variation of the CA or EPO. The cell- g -P(CA-alt-EPO) also had satisfactory UV-absorbing properties and cellulose grafted phthalic anhydride and glycidyltrimethylammonium chloride exhibited outstanding antibacterial behavior. Antibacterial activity against Escherichia coli and Staphylococcus aureus were 96.7% and 99.4% respectively. Thus, cell- g -P(CA-alt-EPO) with good solubility, melt processability, UV absorption and antibacterial properties have potential applications in UV-shielding and antibacterial agent fields. [Display omitted] • Cellulose grafted alternating Cell-g-P(CA-alt-EPO) were prepared in the CO 2 solvents system without adding external catalyst. • The DBU acted both as a reagent for cellulose dissolution and as a catalyst for the ROCOP of anhydride and epoxide. • The structure and properties of the Cell-g-P(CA-alt-EPO) were tailored by altering anhydride and epoxide. • The Cell-g-P(CA-alt-GTMAC) showed excellent antibacterial activity. [ABSTRACT FROM AUTHOR]

Abstract The primary recovery of conventional heavy oil (with viscosity <150 mPa s) in deep reservoirs often has a low recovery factor (RF) and high-pressure drawdown. It is important to propose effective and economic recovery methods to enhance oil recovery of these reservoirs. A top-driving, carbon dioxide (CO 2)-assisted hot-water flooding method is developed and presented in this paper. Laboratory experiments, including CO 2 solubility and one-dimensional (1D) core flooding tests, were conducted based on oil samples from a deep and pressure-depleted conventional heavy oil reservoir. Numerical simulations were conducted to study and discuss the mechanisms. The results from laboratory experiments show that the dissolved CO 2 in the oil reduced the oil viscosity by 30% at 57 °C and 2.0 MPa, and the displacement efficiency of carbonated 120 °C hot-water flooding was comparable to that of 200 °C steam flooding. The CO 2 -assisted hot-water flooding method requires substantially less energy input than the steam flooding method. Numerical simulation indicates that the CO 2 and hot-water co-injecting process results in viscosity reduction, increased pressure, increased sweeping volume, and, consequently, improved oil recovery. The top-driving and CO 2 -assisted hot-water flooding method provides a technical and cost-effective method for enhancing oil recovery in the post-primary recovered heavy oil reservoirs. Highlights • CO 2 solubility both in oil and water were tested under various temperatures and pressures. • Experiments of water, steam, carbonated water, and CO 2 flooding were conducted at various temperatures. • CO 2 -assisted hot-water flooding was designed with a flexible and adaptable well pattern. • Mechanisms and performances of the proposed method were illustrated by numerical simulations. • CO 2 -assisted hot-water flooding process is an economically effective method to recover deep heavy reservoirs. [ABSTRACT FROM AUTHOR]