The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high ...heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-scale horizontal well cluster, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×104 t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.
Based on the previous studies and development practice in recent 10 years, a quantitative evaluation method for the adaptability of well patterns to ultra-low permeability reservoirs was established ...using cluster analysis and gray correlation method, and it includes 10 evaluation parameters in the four aspects of optimal evaluation parameters, determination of weights for evaluation parameters, development stage division, and determination of classification coefficients. This evaluation method was used to evaluate the well pattern adaptability of 13 main ultra-low permeability reservoirs in Triassic Chang 6 and Chang 8 of Ordos Basin. Three basic understandings were obtained: Firstly, the well pattern for ultra-low permeability type-I reservoirs has generally good adaptability, with proper well pattern forms and well pattern parameters. Secondly, square inverted nine-spot well pattern is suitable for reservoirs with no fractures; rhombic inverted nine-spot injection pattern is suitable for reservoirs with some fractures; and rectangular well pattern is suitable for reservoirs with rich fractures. Thirdly, for the ultra-low permeability type-II and type-III reservoirs, with the principles of well pattern form determination, the row spacing needs to be optimized further to improve the level of development of such reservoirs.
An immunized mouse phage display scFv library with a capacity of 3.34 × 109 CFU/mL was constructed and used for screening of recombinant anti-ciprofloxacin single-chain antibody for the detection of ...ciprofloxacin (CIP) in animal-derived food. After four rounds of bio-panning, 25 positives were isolated and identified successfully. The highest positive scFv-22 was expressed in E. coli BL21. Then, its recognition mechanisms were studied using the molecular docking method. The result showed the amino acid residue Val160 was the key residue for the binding of scFv to CIP. Based on the results of virtual mutation, the scFv antibody was evolved by directional mutagenesis of contact amino acid residue Val160 to Ser. After the expression and purification, an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) based on the parental and mutant scFv was established for CIP, respectively. The IC50 value of the assay established with the ScFv mutant was 1.58 ng/mL, while the parental scFv was 26.23 ng/mL; this result showed highly increased affinity, with up to 16.6-fold improved sensitivity. The mean recovery for CIP ranged from 73.80% to 123.35%, with 10.46% relative standard deviation between the intra-assay and the inter-assay. The RSD values ranged between 1.49% and 9.81%. The results indicate that we obtained a highly sensitive anti-CIP scFv by the phage library construction and directional evolution, and the scFv-based IC-ELISA is suitable for the detection of CIP residue in animal-derived edible tissues.
There are two kinds of displacement mechanisms and three different seepage stages during horizontal well development process with water injection energy. A reasonable injection-production working ...system of the basic principles and parameters are determined according to the evaluation results of horizontal well development test on the basis of understanding fundamental rules. (1) Advanced water injection energy supplement mode is proposed with the combination of injection wells and large volume water fracturing of horizontal wells. (2) Theoretical calculation chart of directional well advanced water injection and water injection intensity is established for various reservoirs. (3) The timing of advanced water injection should follow the completion of the horizontal wells. (4) Reasonable initial production of horizontal well is determined by the relationship of remaining fluid volume with row spacing, advanced injection water volume and flood front advancing velocity. (5) Reasonable production flowing pressure is slightly greater than saturation pressure before water injection does not work, when it works, the reasonable production flow pressure maintains no less than two-thirds of saturation pressure, and adjust it timely combining with dynamic production. Based on the research results, the HQ oilfield put 80 horizontal wells into production during 2013, the proportion of water-breakthrough wells reduces from 8.8% to 3.0%, the annual decrease of the average production of single horizontal well is controlled within 15%.
MnO/C core-shell nanowires with varying carbon shell thickness were synthesized
via
calcining resorcinol-formaldehyde resin(RF) with different amounts of hydrothermally synthesized MnO
2
nanowires. ...The relationship between the carbon shell thickness and the anode performance of the MnO/C materials was discussed. With a suitable carbon shell thickness(6.8 nm), the MnO/C core-shell nanowires exhibit better cycling and rate performance than those with a smaller or larger thickness. The TEM results show that after 50 cycles, the core-shell structure with this thickness can be retained, which leads to superior performance. This contribution provides a significant guiding model for optimizing the electrochemical performance of MnO/C core-shell materials by controlling the thickness of carbon shells.
Li-rich layered oxides have attracted much attention for their potential application as cathode materials in lithium ion batteries, but still suffer from inferior cycling stability and fast voltage ...decay during cycling. How to eliminate the detrimental spinel growth is highly challenging in this regard. Herein, in situ K+-doped Li1.20Mn0.54Co0.13Ni0.13O2 was successfully prepared using a potassium containing α-MnO2 as the starting material. A systematic investigation demonstrates for the first time, that the in situ potassium doping stabilizes the host layered structure by prohibiting the formation of spinel structure during cycling. This is likely due to the fact that potassium ions in the lithium layer could weaken the formation of trivacancies in lithium layer and Mn migration to form spinel structure, and that the large ionic radius of potassium could possibly aggravate steric hindrance for spinel growth. Consequently, the obtained oxides exhibited a superior cycling stability with 85% of initial capacity (315 mA h g–1) even after 110 cycles. The results reported in this work are fundamentally important, which could provide a vital hint for inhibiting the undesired layered-spinel intergrowth with alkali ion doping and might be extended to other classes of layered oxides for excellent cycling performance.
Low initial Coulombic efficiency (ICE) is an obstacle for practical application of Li‐rich Mn‐based layered oxides (LLOs), which is closely related with the irreversible oxygen evolution owing to the ...overoxidized reaction of surface labile oxygen. Here we report a NH4F‐assisted surface multicomponent integration technology to accurately control the ICE, by which oxygen vacancies, spinel‐layered coherent structure, and F‐doping are skillfully integrated on the surface of treated LLOs microspheres. Though the regulation on the removed amount of labile oxygen by surface integrated structure, the ICE of LLOs cathodes can adjust from starting value to 100 %. X‐ray absorption spectroscopy, refined X‐ray diffraction, and scanning transmission electron microscopy show that the removed labile oxygen mainly comes from Li2MnO3‐like structure. Even operating at a high cut‐off voltage of 5 V, the capacity retention of integrated sample at 200 mA g−1 is still larger than 98 % after 100 cycles.
Oxygen vacancies, a spinel‐layered coherent structure, and F‐doping are integrated synchronously on the surface of Li1.2Mn0.6Ni0.2O2 microspheres by the modification of NH4F. This process improves the initial Coulombic efficiency and capacity stability.
This paper studies a moving horizon estimation approach to solve the constrained state estimation problem for uncertain networked systems with random packet loss. The system model error range is ...known, and the packet loss phenomena are modeled by a binary switching random sequence. Taking the model error, the packet loss, the system constraints, and the network transmission noise into account, a time-varying weight matrix is obtained by solving a least-square problem. Then, a robust moving horizon estimator is designed to estimate the system state by minimizing an optimization problem with an arrival cost function. The proposed estimator ensures that the optimal estimated state can be obtained in the worst case. Furthermore, the asymptotic convergence of the estimator is analyzed and some sufficient conditions for convergence are given. Finally, the validity of the proposed approach can be demonstrated by numerical simulations.
The practical applications of Mn3O4 in lithium‐ion batteries are greatly hindered by fast capacity decay and poor rate performance as a result of significant volume changes and low electrical ...conductivity. It is believed that the synthesis of nanoscale Mn3O4 combined with carbonaceous matrix will lead to a better electrochemical performance. Herein, a convenient route for the synthesis of Mn3O4 nanoparticles grown in situ on hollow carbon nanofiber (denoted as HCF/Mn3O4) is reported. The small size of Mn3O4 particles combined with HCF can significantly alleviate volume changes and electrical conductivity; the strong chemical interactions between HCF and Mn3O4 would improve the reversibility of the conversion reaction for MnO into Mn3O4 and accelerate charge transfer. These features endow the HCF/Mn3O4 composite with superior cycling stability and rate performance if used as the anode for lithium‐ion batteries. The composite delivers a high discharge capacity of 835 mA h g−1 after 100 cycles at 200 mA g−1, and 652 mA h g−1 after 240 cycles at 1000 mA g−1. Even at 2000 mA g−1, it still shows a high capacity of 528 mA h g−1. The facile synthetic method and outstanding electrochemical performance of the as‐prepared HCF/Mn3O4 composite make it a promising candidate for a potential anode material for lithium‐ion batteries.
Restricted expansion: The practical applications of Mn3O4 in lithium‐ion batteries are greatly hindered by fast capacity decay and poor rate performance as a result of significant volume changes and low electrical conductivity. A composite composed of Mn3O4 nanoparticles on hollow carbon nanofibers (HCF/Mn3O4) was synthesized by a facile in situ method. The unique nanostructure leads to excellent electrochemical performance (see figure).
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