Artificial fractures can easily occur and propagate in shale reservoir bedding. Their height restricts the volume of fracturing modification. A physical simulation of true triaxial hydraulic fracturing was used to analyze the characteristics of fracture morphology and the fracturing curve, as well as explore the influence of horizontal multi-bedding on the hydraulic fracture propagation of shale reservoirs. The results showed that a weaker bedding strength increased bedding fracture activation and reduced the fracture height. A higher bedding density increased the fracture complexity and reduced the main fracture height. A high injection flow can easily cause morphologically complex multi-bedding fractures. A higher injected fracturing-fluid viscosity increased the layer-penetration ability of the main hydraulic fracture when it expanded and reduced the opening degree of the bedding plane. This study provides technical support for the hydraulic fracturing design of shale reservoirs.

Metal powder pressing is an important key process in the field of powder metallurgy, and the densification process and the degree of densification are affected by factors such as powder properties, die parameters, and the pressing process. Since it is difficult to accurately calculate the number of powder particles by traditional methods, a multi-particle model combining the discrete element method (DEM) and the finite element method (FEM) is used in this study to analyze the effects of the powder stacking structure, the metal composition ratio, the pressing force, the holding time, and the friction coefficient of the inner wall of the die on the densification process. In the modeling process, each powder particle is treated as an individual and represented using the von Mises yield function and Cauchy stress. In this paper, the bi-directional compression molding process and micromechanical behavior of monometallic copper powders and copper–aluminum composite powders with the same particle size are simulated using a coupled DEM–FEM method, which remedies the lack of research in this field. First, the micromechanical behaviors of the particles during compression molding are elucidated, including shape evolution, stress distribution, and force-chain dynamics; second, the effects of aluminum content, initial packing density, and die-wall friction on densification are quantified; and then the models are validated based on empirical formulas (e.g., Hecke’s and Huang Peiyun’s equations). By sharing multi-scale simulations with parametric analysis and combining theoretical modeling with practical industrial applications, the densification mechanism of composite metal powders is dissected, which provides a sizable example for process optimization.

In this paper, the analysis method which coupled discrete element method (DEM) and finite element method (FEM) is used to simulate the double compaction of random packing of Cu and Al composite powders with multiple particle sizes. Cu and Al composite powders with varying particle size ratios from 1:2 to 1:5 were generated by DEM and then imported to MSC. Marc software (MSC.MARC2015 version) to construct FEM analysis. The effects of metal ratios, compaction pressure and size ratios on the relative density and von Mises stress of the compact were studied. The results show that the average relative density of the compact increases with the Al content, and the stress decreases. The stress in the Cu particle is particularly higher than that in the Al particle, mainly because the contact normal force of the Cu particle is nearly parallel at each contact surface. Therefore, the phenomenon of stress concentration is easier to occur within copper particles. When Al content is 30wt.%, the particle size difference enhances densification efficiency by up to 12.3%, as evidenced by an initial relative density increase from 0.7915 to 0.8047, primarily due to smaller Cu particles effectively filling interparticle voids. When the compaction pressure is fixed, the average relative density of the compact with the particle size ratio 1:5 is higher than the others, and the contact forces inside the particles significantly decrease.

Compared with the rod-pumping oil production system of the conventional pumping unit, the structure of the down-hole oil-water separation system from the rod pump is more complicated, and the down-hole working conditions are worse. Existing technology no longer meets the needs of its downhole condition diagnosis. It seriously affected the production output and economic benefits of the oil field. Because of this, a fault pre-diagnosis method for the downhole oil-water separation system from the rod pump was proposed. Through the theoretical calculation of oil well production and pump efficiency. After field investigation and collection of many suspension point indicators diagrammed for comparison and analysis, the injection pump’s failure probability was 90% above. At this time, the extraction pumps work normally. Therefore, a reverse calculation method is proposed: establish and solve the static/dynamic load model of the production pump, and obtain the load-displacement function of the production pump. The load-displacement function of the suspension point derived from the suspension point indicator diagram is subtracted from the calculated load-displacement function of the production pump to obtain the load-displacement function of the injection pump so that the working condition diagnosis can be performed according to the injection pump work diagram. In the application of 18 wells within the field, the judgment result of injection pump failure and the result of pump inspection coincided with 91.3%, which verified the correctness of the calculation model. This method provides necessary theoretical guidance for the field application and working condition diagnosis of rod pump downhole oil-water separation system and is of great significance for improving the comprehensive benefit of oilfield production.

The flow mechanism of CO₂ flooding serves as the theoretical foundation for examining the synergic integration of oil recovery and CO₂ storage. Immiscible CO₂ flooding has attracted considerable research attention due to its simplicity and cost-efficiency. However, minimal studies are available regarding the flow characteristics and EOR mechanism of immiscible CO₂ flooding in in-situ temperature-pressure coupling conditions at the pore scale. Therefore, this study employed a modified high-temperature, high-pressure microfluidic system to simulate the in-situ CO₂ and water injection processes in a combined temperature-pressure environment and analyze the multiphase flow characteristics in the pores. The injection rate, displacement pressure difference, displacement efficiency, and residual oil distribution were quantitatively analyzed at different pressures. The results indicated higher residual oil clustering after water flooding at the same injection rate. CO₂ flooding significantly reduced residual oil clustering and enhanced the oil flooding effect. The multiphase flow dynamics, type of remaining oil in different injection conditions, and flow characteristics of immiscible CO₂ flooding were determined. A higher confining pressure interrupted the CO₂ flow, which destabilized the displacement front increased the recovery efficiency by 12.9%. Furthermore, a higher injection rate and displacement pressure increased the recovery efficiency by 24.9% and 6.1%, respectively.

Wang, S.; Dong, K.; Song, W.; Li, J., and Xing, C., 2018. Influence of stress shadow on multi-fractures initiation mechanism under volume fracturing in offshore oil drilling. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 172–178. Coconut Creek (Florida), ISSN 0749–0208. In order to reveal the multi-fractures initiation mechanism, according seepage theory, the full three-dimensional multi-fractures initiation local stress model was built by considering the existed of first fracture, the mechanism of stress shadow and initiation pressure change law of follow up fractures were given by simulation methods and combined the maximum tensile stress theory, the reliability was verified by application example. The analysis shows that: The stress shadow caused the existed of compaction zone near the fracture, the stress type was changed in the compaction zone, the minimum principal stress was increased, these lead ...