The ultra-fast laser heating process of nano-films is characterized by an ultra-short duration and ultra-small space size, in which the classical Fourier law based on the hypothesis of local equilibrium is no longer applicable. Based on the Cattaneo–Vernotte (CV) model and the dual-phase-lag (DPL) model, the two-dimensional analytical solutions of heat conduction in nano-films under ultra-fast laser are obtained using the integral transformation method. The results show that there is a thermal wave phenomenon inside the film, which becomes increasingly evident as the elapse of the lag time of the temperature gradient. Moreover, the wave amplitude in the vertical direction is much larger than that in the horizontal direction of the nano-film. By comparing the numerical result of the two models, it is found that the temperature distribution inside the nano-film based on the DPL model is gentler than that of the CV model. Additionally, the temperature distribution in the two-dimensional solution is lower than that in the one-dimensional solution under the same Knudsen number. In the comparison results of the CV model, the maximum peak difference in the thermal wave reaches 75.08 K when the Knudsen number is 1.0. This demonstrates that the horizontal energy carried by the laser source significantly impacts the temperature distribution within the film.

An improved dual-phase-lagging (DPL) model which reflects size effects caused by nanostructures is utilized to investigate the two-dimensional thermal conduction of nano silicon films irradiated by ultrafast laser. The integral transformation method is used to solve the conduction governing equation based on the improved DPL model. The variation of the internal temperature along the thickness direction and the radial direction of the thin film is analyzed. We find that the temperature increases rapidly in the heated region of the film, and as time goes by, the energy travels from the heated end to another end in a form of wave. Although both the improved DPL model and the DPL model can obtain similar thermal wave temperature fields, the temperature distribution in the film obtained by the improved DPL model is relatively flat, especially for high Knudsen number. Under the same Knudsen number, the temperature obtained by the two-dimensional improved DPL model is higher than that obtained by the one-dimensional model, and the temperature difference becomes larger and larger as time elapses.

No abstract

The main characteristics of Jimsar shale oil reservoir are of complex structure, strong heterogeneity and great difficulty in fracturing. It is mainly produced by volume fracturing technology, which is easy to form complex fracture networks. At present, the design and parameter optimization of fracturing scheme are not targeted, and the true 3D fracture simulation with geology-engineering integration is particularly important. On the basis of 3D geological modeling, the 3D geo-mechanical parameter distribution is determined by seismic data, logging data, experimental data, etc to simulate the stress environment in which the overburden pressure, surrounding rock pressure and lower strata pressure. And the 3D geo-mechanical parameter model is established by combining simulated analysis of the stress. On the basis of geological model, geomechanical model and natural fracture model, the natural fractures and faults determined by seismic, logging or discrete fracture modeling are integrated into the geomechanical model to complete the true 3D simulation of artificial fracture network based on true 3D geo-mechanical model. This simulation is the practice and improvement of the geology-engineering integration of shale oil reservoirs volume modification technology in Jimsar, which will deepen the geological understanding and strengthens the engineering technology supporting, provides reference basis for the optimization design of fracturing process and the maximization of the volume, and finally realizes the efficient development of shale oil in Jimsar.

No abstract