RESEARCH ON CO2 FLOODING FOR IMPROVED OIL RECOVERY IN WATER FLOODING ABANDONED RESERVOIRS

CO2 injection is an effective technique for improved oil recovery in light oil reservoirs, especially for water flooding abandoned reservoirs. In this study, the lower part of Es1 reservoirs in Pucheng oilfield was introduced as the target reservoir. By studying the minimum miscible pressure in CO2 flooding, the reservoir could achieve miscible flooding. Long core displacement experiments proved that water alternating CO2 flooding could significantly improve the recovery. For the reservoir characteristics, anti-corrosion technology in the process of injection was researched, and the H-20 inhibitor was screened. A channeling blocking agent in combination with the delayed expansion of gel particles and cross-linked copolymer was used to control the gas fluidity. The Pu 1-1 well groups were optimized to conduct a field trial. The cumulative injected liquid CO2 was 19219.95 ton, 0.248 PV and the cumulative increasing oil was 4520.9 t. The predicted recovery will increase by 8.3%. The successful implementation of the project can provide technical attempt for completion of energy to succeed and energy-saving emission reduction targets.</span

A Study on the Mechanism of Urea-assisted Steam Flooding in Heavy Oil Reservoirs

The Biqian-10 block, located in Henan Oilfield of Sinopic, contains many thin and interbedded reservoirs, which have been operated by cyclic steam stimulation for 20 years or more. Therefore, it is a challenge to implement the conventional steam flooding. In order to improve the recovery of steam flooding, urea was used to assist steam flooding. Urea can decompose into CO2 and NH3, which are beneficial to enhance oil recovery (EOR). For the sake of exactly quantifying the mechanism of urea assisted steam flooding (UASF), the UASF model was built according to the experimental results. The simulation results show that CO2 is the key point for EOR, and its pressurization function is more effective than the decrease in oil viscosity by dissolving CO2. The emulsification of crude oil for NH3 is weak in interfacial tension tests; thus the effect of emulsification can be ignored in the simulation. The UASF can improve the recovery by about 17.4%, which is 6.8% higher than steam flooding.</span

Converting Corncob to Activated Porous Carbon for Supercapacitor Application

Carbon materials derived from biomass are promising electrode materials for supercapacitor application due to their specific porosity, low cost and electrochemical stability. Herein, a hierarchical porous carbon derived from corncob was developed for use as electrodes. Benefitting from its hierarchical porosity, inherited from the natural structure of corncob, high BET surface area (1471.4 m2·g−1) and excellent electrical conductivity, the novel carbon material exhibited a specific capacitance of 293 F·g−1 at 1 A·g−1 in 6 M KOH electrolyte and maintained at 195 F·g−1 at 5 A·g−1. In addition, a two-electrode device was assembled and delivered an energy density of 20.15 Wh·kg−1 at a power density of 500 W·kg−1 and an outstanding stability of 99.9% capacitance retention after 4000 cycles

Experimental study on scaling and adhesion characteristics in water-producing gas wellbore

A water-producing gas well in deep water encounters problems of high cost and substantial operational difficulties in scale prevention and descaling. To determine the characteristics of wellbore scaling and its influencing factors, it is important to accurately predict the scaling risk in deepwater gas wells so that anti-scale measures can be optimized. In this study, a high-temperature and high-pressure reactor and aslim metal tube at atmospheric pressure were used to simulate the scaling process of formation water in a gas wellbore under static and flowing conditions. The amount of scaling, distribution of scaling particles, and wellbore blockage risk were investigated. The results show that: (1) Carbonate scaling in formation water occurs at high temperature and low pressure. The scaling ion concentration, CO2 partial pressure, gas phase proportion, and MEG content are the main factors affecting the scaling amount. Only a part of the scaling particles attaches to the tube wall. The remainder will disperse in water, and can be produced out or stranded in the wellbore, depending on the hydrodynamic conditions in the wellbore. The scaling particles easily precipitate and block in horizontal and inclined well sections. (2) The adhesion of scaling particles on the tube wall is severely affected by the scaling tendency of the formation water. As the scaling tendency of water increases, the scaling ions tend to transfer to the tube wall and scale on the tube wall. However, when the scaling tendency is sufficiently high, more scaling particles will be produced in water because of the limited mass transfer speed. (3) The production of gas and water has an important influence on wellbore scaling, output, and distribution. A large water rate results in a large amount of scaling, but the scaling particles in the wellbore are distributed widely and are easy to produce, which causes a small blockage risk in the wellbore. In comparison, gas production has little influence on the amount of scaling, but it can make the scaling particles deposit more intensively in the wellbore and increase the risk of blockage. The knowledge gained in this study can provide baseline information for the accurate prediction of scaling and plugging risk in gas wellbores

Multidimensional stressors and depressive and anxiety symptoms in adolescents: A network analysis through simulations

Background: Existing research has established associations between various stressors and adolescent mental health, primarily from a variable-level perspective. However, a symptom-level understanding about which stressors and symptoms might play a important role is scarce.Methods: The sample consisted of 15,570 adolescents aged 10 to 19. Participants completed questionnaires which assessed multidimensional stressors, depressive symptoms, anxiety symptoms, and demographic information. Network analysis was conducted to explore the relationships between stressors and depressive and anxiety symptoms. Additionally, to identify effective targets for the treatment and prevention of adolescent mental health issues, symptom-specific intervention simulations were performed on the network to investigate changes in symptom values in response to the alleviation and aggravation of specific stressors and symptoms.Results: Findings revealed that academic stressors exhibited stronger associations with anxiety symptoms than other stressors, particularly nervousness. Family relationships were more closely linked to depressive symptoms than other stressors, particularly suicidal ideation. Academic stressors emerged as an effective intervention target, and uncontrollable worry as an important prevention target. With the exception of academic stressors, simulating aggravation interventions on symptoms resulted in more changes in overall symptom activation than alleviation interventions.Limitations: A cross-sectional design did not uncover network changes over time and the sample was non-clinical.Conclusions: This study highlights the importance of addressing academic stressors to alleviate adolescents&#39; depressive and anxiety symptoms and reveals that uncontrollable worry is a key prevention target. The findings are helpful for clinicians and educators to develop effective strategies to protect adolescents&#39; mental health.</p

Integration of CuO nanosheets to Zn-Ni-Co oxide nanowire arrays for energy storage applications

The structure of materials in supercapacitors plays great importance in facilitating fast ion transport. Herein, we incorporated two-dimensional Cu-oxide nanosheets (2D NSs) in one-dimensional Zn-Ni-Co-oxide nanowire arrays (1D NWAs) on three-dimensional (3D) substrate. The integrated CuO/Zn-Ni-Co oxide electrode material exhibited a high specific capacity of 1261C g-1 at a current density of 1 A g-1 and retained 92.2% of its capacity after 20,000 cycles. Density functional theory-based calculations were employed to validate the structural and electronic properties of the prepared materials. Moreover, the hybrid supercapacitor (HSC) device was engineered by using the as-prepared CuO/Zn-Ni-Co oxide electrode material as a positive and integrated functionalized multi wall carbon nanotubes (MWCNTs-COOH), activated carbon (AC), and reduced graphene oxide (rGO) as negative electrode. We highlighted the variance in using two different equations for energy density calculations. The HSC device delivered a high energy density of 74 Wh kg-1 at a power density of 1.02 kW kg-1. We also demonstrated illumination of multiple color LEDs for &gt;600 s. The eye-catching results demonstrated that the integrated and structured 2D NSs/1D NWAs based CuO/Zn-Ni-Co oxide from materials can be used for practical applications.600 s. The eye-catching results demonstrated that the integrated and structured 2D NSs/1D NWAs based CuO/Zn-Ni-Co oxide from materials can be used for practical applications

Applicable scope of oxygen-reduced air flooding and the limit of oxygen content

The mechanisms of oxygen-reduced air flooding (ORAF) and the explosion limit and the corrosion control approaches were studied based on the pilots of oxygen-reduced air flooding (ORAF) in the Dagang, Changqing and Daqing oil fields in China. On the foundation of indoor investigations and pilots, the explosion limits, oxygen reduction limits and corrosion control approaches were clarified. When the temperature of reservoir is equal to and higher than 120 °C, there is a violent reaction between oxygen and crude oil, that means the effect of low temperature oxidation would be fully taken use of to enhance oil recovery by air flooding directly; nitrogen dominated immiscible flooding with oxygen-reduced air should be applied in cases where reservoir temperature is below 120 °C with little oxygen consumption and little heat generated. The oxygen-reduced air flooding is suitable for 3 types of reservoirs: low permeability reservoir, water flooding development reservoir of high water-cut and high temperature and high salinity reservoir. In the process of development, in order to ensure safety, the oxygen reduction limits should be controlled fewer than 10%, while oxygen-reduced air can obviously reduce the corrosion rate of pipes; The surface pipelines and injection wells don't need to consider about oxygen corrosion with no water, special materials and structure of pipe or corrosion inhibitor can be applied to the surface pipelines and injection wellbores with water. Air/oxygen-reduced air is a low-cost displacement medium and it could be applied in many special conditions of low permeability reservoir for energy supplement, huff and puff and displacement, that means oxygen-reduced air flooding has become the most potential strategic technology in 20 years. Key words: oxygen-reduced air flooding, explosion limit, oxygen-reduction limit, low temperature oxidation, oxygen corrosion contro

Activated Microporous Carbon Derived from Almond Shells for High Energy Density Asymmetric Supercapacitors

Via the activation treatment of carbonized almond shells with HNO₃ and KOH, activated microporous carbon (AMC-3 and AMC-2) was successfully synthesized. These two AMC electrodes demonstrate remarkable electrochemical behaviors such as high rate capability, high specific capacitance, and excellent cycle stability when serving as electrodes for supercapacitors. More importantly, through the use of a Zn–Ni–Co ternary oxide (ZNCO) positive electrode and the AMC negative electrode, asymmetric supercapacitors (ASC) were assembled that deliver superior energy density (53.3 Wh kg^–1 at a power density of 1126.1 W kg^–1 for ASC-2 and 53.6 Wh kg^–1 at a power density of 1124.5 W kg^–1 for ASC-3) and excellent stability (82.7% and 83.4% specific capacitance retention for ZNCO//AMC ASC-2 and ZNCO//AMC ASC-3, respectively, after 5000 cycles). Through these two methods, low-cost, renewable, and environmentally friendly electrode materials can be provided for high energy density supercapacitors

Templated and Catalytic Fabrication of N‑Doped Hierarchical Porous Carbon–Carbon Nanotube Hybrids as Host for Lithium–Sulfur Batteries

Nitrogen-doped hierarchical porous carbon and carbon nanotube hybrids (N-HPC–CNTs) are fabricated by simple pyrolysis of the N-rich raw material melamine-formaldehyde (MF) resin in the presence of nano-CaCO₃ and a bimetallic combination of Fe–Co catalyst. During carbonization, nano-CaCO₃ acts as a template for creating a hierarchical porous carbon, and the N atoms originated from MF resin are in situ doped into the carbon matrix simultaneously. Meanwhile, volatile gases generated by the thermal decomposition of MF resin could serve as carbon and nitrogen sources to grow nitrogen-doped CNTs on HPC. The growth mechanism is the same as that for conventional chemical vapor deposition (CVD) growth of CNTs on the metal catalysts, but the technological requirements are obviously not as harsh as those for the CVD method. Low-cost raw materials and simple equipment are sufficient for the growth. Moreover, the density and length of the CNTs are tunable, which can be simply adjusted via applying different amounts of Fe–Co catalysts. Such an N-doped hybrid structured carbon with mesopores can not only effectively prompt the physical and chemical adsorption of polysulfides but also ensures a fast electron transfer because of the incorporation of CNTs, which provides sufficient conducting pathways and effective connections between the CNTs and HPC. Furthermore, CNTs grown on HPC can act as physical barriers to block the large pores on HPC, thereby reducing the polysulfide loss. Benefiting from the advantages, the N-HPC–CNT hybrids are a desirable host prospect for Li–S batteries