Following the application of polymer flooding in Daqing Oilfield, the heterogeneity between different layers has intensified, resulting in the formation of more favorable seepage channels and cross-flow of displacement fluids. Consequently, the circulation efficiency has decreased, necessitating the exploration of methods to enhance oil recovery. This paper focuses on experimental research utilizing a newly developed precrosslinked particle gel (PPG) combined with alkali surfactant polymer (ASP) to create a heterogeneous composite system. This study aims to improve the efficiency of heterogeneous system flooding after polymer flooding. The addition of PPG particles enhances the viscoelasticity of the ASP system, reduces the interfacial tension between the heterogeneous system and crude oil, and provides excellent stability. The heterogeneous system has high resistance and residual resistance coefficients during the migration process in a long core model, achieving an improvement rate of up to 90.1% under the permeability ratio of 9 between high and low permeability layers. Employing heterogeneous system flooding after polymer flooding can increase oil recovery by 14.6%. Furthermore, the oil recovery rate of low permeability layers can reach 28.6%. The experimental results confirm that the application of PPG/ASP heterogeneous flooding after polymer flooding can effectively plug high-flow seepage channels and improve oil washing efficiency. These findings hold significant implications for further reservoir development after polymer flooding.
Abstract Two‐dimensional conjugated metal–organic frameworks (2D c ‐MOFs) are emerging as a unique subclass of layer‐stacked crystalline coordination polymers that simultaneously possess porous and conductive properties, and have broad application potential in energy and electronic devices. However, to make the best use of the intrinsic electronic properties and structural features of 2D c ‐MOFs, the controlled synthesis of hierarchically nanostructured 2D c ‐MOFs with high crystallinity and customized morphologies is essential, which remains a great challenge. Herein, we present a template strategy to synthesize a library of 2D c ‐MOFs with controlled morphologies and dimensions via insulating MOFs‐to‐ c ‐MOFs transformations. The resultant hierarchically nanostructured 2D c ‐MOFs feature intrinsic electrical conductivity and higher surface areas than the reported bulk‐type 2D c ‐MOFs, which are beneficial for improved access to active sites and enhanced mass transport. As proof‐of‐concept applications, the hierarchically nanostructured 2D c ‐MOFs exhibit a superior performance for electrical properties related applications (hollow Cu‐BHT nanocubes‐based supercapacitor and Cu‐HHB nanoflowers‐based chemiresistive gas sensor), achieving over 225 % and 250 % improvement in specific capacity and response intensity over the corresponding bulk type c ‐MOFs, respectively.
Electret fiber-based air filtration materials find extensive applications in various fields, including particulate matter filtration, indoor purification, and epidemic prevention. However, achieving high-efficiency filtration with low resistance and long-term stability remains a challenge. In this study, we present a novel approach to fabricate sheath-core bicomponent spunbond filters (BCSFs) doped with polytetrafluoroethylene nanoparticles (PNPs) using bicomponent spunbond, through-air bonding, and corona charging techniques. This strategy enables the filtration material to possess low air resistance, long-term stable filtration efficiency, and a high dust holding capacity. The resulting BCSFs-PNPs exhibit remarkable filtration performance, with a filtration efficiency of 99.25% and a dust holding capacity of up to 11.48 g m-2, while maintaining a pressure drop as low as 37.87 Pa. Notably, the filtration efficiency of BCSFs-PNPs only experienced a slight decrease of 3.58% over a period of 180 days, demonstrating excellent long-term stability. The successful preparation of BCSFs-PNPs using corona charging technology holds great promise and offers valuable insight for the design and application of advanced air filtration materials.
Abstract Heterogeneity is a significant feature of the reservoirs after polymer flooding, resulting in challenges for further enhanced oil recovery (EOR) in heterogeneous reservoirs. In order to further improve oil recovery in the reservoirs after polymer flooding, a novel EOR system (ASP-PPG composite system) was developed using preformed particle gel (PPG) and alkali-surfactant-polymer system (ASP system). We designed an oil saturation monitoring device and a large-scale 3D heterogeneous physical model to evaluate the performance of the system. The performance of the system and the ASP system were tested. Based on the testing results, the fluid migration patterns and enhanced oil recovery mechanisms of the ASP-PPG system in an actual heterogeneous reservoir were investigated using the oil saturation monitoring device and the 3D physical model. Experimental results indicate that the ASP-PPG system has a higher viscosity and better profile control ability than the ASP system. Additionally, the interfacial tension can be maintained at a low level, around 10−3 mN/m. Flooding experiments using the three-dimensional heterogeneous physical model demonstrated the excellent elastic deformation ability of PPG, which can dynamically block the large pores that formed after the polymer flooding and effectively improve the heterogeneity of reservoirs. After injecting the ASP-PPG system, the recovery factor of the model increased by 15.8%. Specifically, the sweep coefficient of high, medium, and low permeability layers increased by 4.36%, 19.6%, and 37.55%, respectively. Moreover, the oil displacement efficiency increased by 7.4%, 14.4%, and 17.9%, respectively. These results highlight the synergistic effect of combining PPG and ASP systems, significantly enhancing heterogeneous reservoir recovery after polymer flooding.
Particulate matter (PM) and airborne viruses bring adverse influence on human health. As the most feasible way to prevent inhalation of these pollutants, face masks with excellent filtration efficiency and low press drop are in urgent demand. In this study, we report a novel methodology for producing high performance air filter by combining melt blown technique with corona charging treatment. Changing the crystal structure of polypropylene by adding magnesium stearate can avoid charge escape and ensure the stability of filtration performances. Particularly, the influence of fiber diameter, pore size, porosity, and charge storage on the filtration performances of the filter are thoroughly investigated. The filtration performances of the materials, including the loading test performance are also studied. The melt blown materials formed by four layers presented a significant filtration efficiency of 97.96%, a low pressure drop of 84.28 Pa, and a high quality factor (QF) of 0.046 Pa
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