Search

Reservoir damage is a key factor affecting reservoir evaluation, ensuring stable reservoir production and improving the utilization rate of oil and gas resources. At present, the evaluation of damage caused by reservoir drilling fluid is too empirical, and there is a lack of methods for the high-precision evaluation of reservoir damage after drilling fluid invasion and pollution. In a block in the East China Sea, the production capacity is limited due to an excessive balance of drilling fluid and long exposure time. In order to ensure safe drilling, the dynamic damage mechanism of drilling fluid during drilling was analyzed. The core of the main reservoir of well XH-1 in a block in the East China Sea was selected for carrying out an experiment evaluating the dynamic damage caused by drilling fluid. According to the experimental results, the damage rate of reservoir permeability caused by drilling fluid invasion ranges between 58.25 and 87.25%, and the overall dynamic damage degree can be classified between medium and high. Combined with the experimental parameters, a mathematical model of drilling fluid invasion depth was established, and the calculation formulas of drilling fluid invasion depth and contaminated skin were derived. The results showed that the drilling fluid depth of the reservoir section corresponding to the core of well XH-1 was 0.47~0.83 m, and the contaminated skin factor was 1.22~13.41, which made up for the lack of evaluation methods of reservoir damage caused by drilling fluid and provided a theoretical basis for the optimization of drilling fluid parameters and exploration drilling technology in oilfield operations. [ABSTRACT FROM AUTHOR]

Purity metallic materials are increasingly demanded in modern manufacturing industries, but their applications are limited owing to their poor wear resistance and mechanical properties. Therefore, exploring an efficient hardening method to significantly enhance the hardness of pure metals is emergent in materials science. In this work, a series of high pressure and high temperature (HPHT) quenching experiments were carried out on several pure metals, with a maximum hardening factor exceeding 10. The results indicated that pressure has an unusual effect on refining grains and increasing the Hall–Petch coefficient ky. The ky value of pure Fe is 49.5 GPa*μm1/2 with a quenching pressure of 5 GPa, which is two orders higher than that of the untreated polycrystalline sample (0.2 GPa*μm1/2). In addition, we report an extreme hardness of 8.34 GPa in pure Ti induced by HPHT quenching, and the unprecedented hardening comes from the formation of the twin and lath martensitic substructures. The hardening mechanism of the HPHT quenching method is a combination of Hall–Petch hardening and work-hardening. Our results provide a practical route to achieve attractive mechanical properties in pure metals and shine a light on the hardening mechanism of metallic materials. [ABSTRACT FROM AUTHOR]

The hardness of materials is a complicated physical quantity, and the hardness models that are widely used do not function well for transition metal light element (TMLE) compounds. The overestimation of actual hardness is a common phenomenon in hardness models. In this work, high-quality Mn3N2 bulk samples were synthesized under high temperature and high pressure (HTHP) to investigate this issue. The hardness of Mn3N2 was found to be 9.9 GPa, which was higher than the hardness predicted using Guo's model of 7.01 GPa. Through the combination of the first-principle simulations and experimental analysis, it was found that the metal bonds, which are generally considered helpless to the hardness of crystals, are of importance when evaluating the hardness of TMLE compounds. Metal bonds were found to improve the hardness in TMLEs without strong covalent bonds. This work provides new considerations for the design and synthesis of high-hardness TMLE materials, which can be used to form wear-resistant coatings over the surfaces of typical alloy materials such as stainless steels. Moreover, our findings provide a basis for establishing a more comprehensive theoretical model of hardness in TMLEs, which will provide further insight to improve the hardness values of various alloys. [ABSTRACT FROM AUTHOR]

Magnetic materials attract great attention due to their fundamental importance and practical application. However, the relatively inferior mechanical properties of traditional magnetic materials limit their application in a harsh environment. In this work, we report an outstanding magnetic material that exhibits both fantastic mechanical and excellent magnetic properties, CuAl2-type Fe2B, synthesized by the high pressure and high temperature method. The magnetic saturation of Fe2B is 156.9 emu g−1 at room temperature and its Vickers hardness is 12.4 GPa which outclasses those of traditional magnetic materials. It exhibits good conductivity with a resistivity of 5.6 × 10−7 Ω m. Fe2B is a promising strong ferromagnetic material with high hardness, which makes it a good candidate for multifunction applications in a harsh environment. The high hardness of Fe2B originates from the Fe–B bond framework, and the strong ferromagnetism is mainly attributed to the large number of unpaired Fe 3d electrons. The competition of Fe 3d electrons to fall into Fe–B bonds or Fe–Fe bonds is the main factor for its magnetism and hardness. This work bridges the chasm between strong ferromagnetism and high hardness communities. [ABSTRACT FROM AUTHOR]

The D7b-type structure Mn3B4 was fabricated by high-temperature and high-pressure (HPHT) methods. Hardness examination yielded an asymptotic Vickers hardness of 16.3 GPa, which is much higher than that of Mn2B and MnB2. First principle calculations and XPS results demonstrated that double zigzag boron chains form a strong covalent skeletons, which enhances this structure's integrity with high hardness. Considering that the hardensses of MnB and Mn3B4 are higher than those of Mn2B and MnB2, zigzag and double zigzag boron backbones are superior to isolated boron and graphite-like boron layer backbones for achieving higher hardness. This situation also states that a higher boron content is not the sole factor for the higher hardness in the low boron content transition metal borides. Futhermore, the co-presence of metallic manganese bilayers contribute to the high d-electron mobility and generate electrical conductivity and antiferromagnetism in Mn3B4 which provide us with a new structure prototype to design general-purpose high hardness materials. [ABSTRACT FROM AUTHOR]

Correction for 'Synthesis and characterization of a strong ferromagnetic and high hardness intermetallic compound Fe2B' by Xingbin Zhao et al., Phys. Chem. Chem. Phys., 2020, 22, 27425–27432, DOI: 10.1039/D0CP03380D. [ABSTRACT FROM AUTHOR]