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The fluid front motion is an important phenomenon during anisotropic fluid flow in rock engineering. The pore pressure and mechanical responses may be significantly influenced and show an obvious difference near the moving fluid front. However, few studies have been conducted to investigate the front motion of different types of fluids during anisotropic fluid flow. In this work, a numerical model was proposed to detect the front motion of water, nitrogen, and CO2 in anisotropic shale reservoirs. The full coupling effects among mechanical deformation, fluid flow, and moving boundary in anisotropic porous media were considered in the model construction. The impacts of different fluid properties among water, nitrogen, and CO2 on the anisotropic fluid flow have been discussed. Then, the proposed model was applied to study the differences in front motion among different types of fluids in anisotropic shales. The impacts of permeability and mobility on fluid front motion were investigated. The theoretical equations for predicting the fluid front motion of different types of fluids were established by introducing corresponding correction coefficients to the previous formulas. The results showed that the model can well describe the anisotropic fluid permeation process. The fluid front motion increased with the increase of permeability and mobility. At the same permeability or mobility, the nitrogen front motion was the largest and the water front motion was the smallest. The difference in fluid front motion among water, nitrogen, and CO2 was caused by the difference of their viscosity and compressibility. The proposed formulas can fast and accurately predict the evolution of fluid front motion for different types of fluids. [ABSTRACT FROM AUTHOR]

The tests were performed on low carbon steel plate. In the tension fatigue tests, two angle values (φ = 0° and φ = 45°) have been chosen, which were the angles between the loading and the rolling direction. The influence of strain path change on the subsequent initial work softening rate and the saturation stress has been investigated. Dislocation microstructure was observed by transmission electron microscopy. It was found that the strain amount of preloading in tension has obviously affected the cyclic softening phenomenon and the initial cyclic softening rate. It was observed that the reloading axial stress for φ = 45° case increased more than that of φ = 0°? case, due to the anisotropism of Q235. In the fatigue crack propagation tests, the experimental results show that with increasing the pretension deformation degree, the fatigue crack growth rate increases, especially at the near threshold section. [ABSTRACT FROM AUTHOR]