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The modal analysis of steering system was made because of the excessive vibration of a certain forklift truck when the engine at medium and low speed conditions at first in this paper. The vibration optimum design was put forward to reduce the vibration of steering wheel by the method of Uniform Design. the test results show that the stiffness of improved steering system is increased and the vibration is decreased obviously on the basis of the invariability of costs,especially when the engine at low speed,the acceleration of vibration on direction x,y,z are reduced 83. 8%,90. 3%,83. 7% respectively. The optimum method provides references for the optimum design of body and frame type structures.

Many factors need to be considered in the evaluation of tight conglomerate reservoirs, including the microscopic pore-throat structure, pore connectivity, lithology, porosity, permeability, and clay mineral content. The contents and types of clay minerals reflect the mineral evolution process during the deposition of the reservoir and can reflect the reservoir's physical properties to a certain extent. In this study, cores from the Baikouquan Formation in Mahu were used to comprehensively analyze the effects of the clay mineral content on the physical properties of a tight conglomerate reservoir, including field emission scanning electron microscopy (FE-SEM), casting thin section observations, X-ray diffraction (XRD), interface property testing, high-pressure mercury injection, low temperature N2 adsorption, and nuclear magnetic resonance (NMR)-movable fluid saturation testing. The results revealed that differences in different lithologies lead to differences in clay mineral content and pore structure, which in turn lead to differences in porosity and permeability. The interface electrification, adsorption, and specific surface area of the reservoir are positively correlated with the clay mineral content, which is mainly affected by the smectite content. As the clay mineral content increases, the proportion of nanoscale pore throats increases, and the core becomes denser. The saturation of the movable fluid controlled by the >50 nm pore throats in the tight conglomerate ranges from 8.7% to 33.72%, with an average of 20.24%. The clay mineral content, especially the I/S (mixed layer of Illite and montmorillonite) content, is negatively correlated with the movable fluid. In general, the research results clarified the relationship between the lithology and physical properties of clay minerals and the microscopic pore structure of the tight conglomerate reservoirs in the Baikouquan Formation in the Mahu area. [ABSTRACT FROM AUTHOR]

After primary and secondary recovery of tight reservoirs, it becomes increasingly challenging to recover the remaining oil. Therefore, improving the recovery of the remaining oil is of great importance. Herein, molecular dynamics simulation (MD) of residual oil droplet movement behavior under CO2 displacement was conducted in a silica nanopores model. In this research, the movement behavior of CO2 in contact with residual oil droplets under different temperatures was analyzed, and the distribution of molecules number of CO2 and residual oil droplets was investigated. Then, the changes in pressure, kinetic energy, potential energy, van der Waals' force, Coulomb energy, long-range Coulomb potential, bond energy, and angular energy with time in the system after the contact between CO2 and residual oil droplets were studied. At last, the g(r) distribution of CO2–CO2, CO2-oil molecules, and oil molecules-oil molecules at different temperatures was deliberated. According to the results, the diffusion of CO2 can destroy residual oil droplets formed by the n-nonane and simultaneously peel off the n-nonane molecules that attach to SiO2 and graphene nanosheets (GN). The cutoff radius r of the CO2–CO2 is approximately 0.255 nm and that of the C–CO2 is 0.285 nm. The atomic force between CO2 and CO2 is relatively stronger. There is little effect caused by changing temperature on the radius where the maximum peak occurs in the radial distribution function (RDF)-g(r) of CO2–CO2 and C–CO2. The maximum peak of g(r) distribution of the CO2–CO2 in the system declines first and then rises with increasing temperature, while that of g(r) distribution of C–CO2 changes in the opposite way. At different temperatures, after the peak of g(r), its curve decreases with the increase in radius. The coordination number around C9H20 decreases, and the distribution of C9H20 becomes loose. [ABSTRACT FROM AUTHOR]

The shale gas productivity model based on shale gas nonlinear seepage mechanism is an effective way to reasonably predict productivity. The incomplete gas nonlinear effects considered in the current production prediction models can lead to inaccurate production prediction. Based on the conventional five-zone compound flow model, comprehensive gas nonlinearities were considered in the improved compound linear flow model proposed in the paper and a semianalytical solution for productivity was obtained. The reliability of the productivity model was verified by the field data, and then, the 20-year production performance analysis of the gas well was studied. Ultimately, the key influencing factors of the fracture control stage and matrix control stage have been analyzed. Research indicated the following: (1) the EUR predicted by the productivity model is higher than the EUR that the comprehensive nonlinear effects are not considered, which demonstrated that the various nonlinear effects cannot be neglected during the production prediction to ensure the greater calculation accuracy; (2) during the early production stage of shale reservoir, the adsorbed gas is basically not recovered, and the cumulative adsorption contribution rate does not exceed 10%. The final adsorption gas contribution rate is 23.28%, and the annual adsorption rate can exceed 50% in the 20th year, showing that free gas and adsorbed gas are, respectively, important sources of the early stage of production and long-term stable production; (3) the widely ranged three-dimensional fracturing reformation of shale reservoirs and reasonable bottom hole pressure in the later matrix development process should be implemented to increase the effective early production of the reservoir and ensure the earlier gas production process of the matrix development. The findings of this study can help for better ensuring the prediction accuracy of the estimated ultimate recovery and understanding the main influencing factors of the dynamic performance of gas wells so as to provide a theoretical reference for production optimization and development plan formulation of the shale gas reservoirs. [ABSTRACT FROM AUTHOR]

Geochemical data have been used as the most effective proxies for determining palaeoclimate and palaeoenvironmental conditions. In this article, we conduct a systematic review on a variety of geochemical data of sediments that are considered proxies for tracing palaeoclimate and palaeoenvironmental information. Comprehensive studies have been carried out on the palaeoproductivity, redox conditions, palaeoclimate, and the acquired data on the enrichment mechanism of organic matter have been summarized. The general mechanisms of the geochemical data regarded as the palaeoclimate and palaeoenvironmental archives include the characteristics of mineral composition, major and trace elements, and rare earth elements. The palaeoproductivity index, including the Ba and P, indicate that the organic‐rich shale was deposited in a high‐productivity water column. The trace elements revealed that the Longmaxi units recorded variable redox conditions from anoxic to aerobic. The elements V, U, Th, Ni, and Co together with the U/Th, V/Cr, Ni/Co, and V/(V + Ni) are essential indicators for defining the redox conditions. The NASC‐normalized REE + Y distribution indicates that the Longmaxi Formation was slightly altered by detrital materials in reduced and acidic environments. The Sr/Cu and MgO/CaO all reveal that the palaeoclimate was gradually transformed from humid to dry heat. The Sr/Ba ratio implies that the water depth fluctuates frequently at the early stage of sedimentation. All geochemical data integrated with the sedimentary characteristics show that anoxic conditions, high palaeoproductivity, and relatively humid palaeoclimates contributed to the accumulation of organic‐rich shale. We propose that jointly utilizing various geochemical and sedimentary indices can expand the outlook of the palaeoenvironment and provide a better understanding of the organic matter accumulation mechanisms. [ABSTRACT FROM AUTHOR]