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The thermal properties of a porous medium have been emphasized for its essential value in rock thermal engineering. Traditional theoretical and experimental methods on thermal conductivity studies of porous media usually contain homogeneous and isotropic assumptions with subjective idealization. Starting from the Digital Rock Physics (DRP), this paper establishes a digital internal structure model of a homogeneous rock through the processes of noise reduction, threshold segmentation, algorithmic process and three-dimensional (3D) reconstruction based on a series of micro-CT (computer tomography) images of the rock. With high quality meshes compatible with the Computational Fluid Dynamics (CFD) software, the Effective Thermal Conductivity (ETC) values are numerically obtained in three Representative Element Volume (REV) blocks with consistent porosity property. The results show that there is a 5% variation between the highest and lowest ETC data along different heat conduction directions. In addition, the simulation results satisfactorily fit with the empirical self-consistent model for ETC prediction of porous media. It is expected the innovative method reported in the present work can provide a feasible and reliable alternative for analyzing the rock thermal and other physical properties based on the accurate description of the internal microscale structures of the porous media.

A numerical analysis employing the stochastic population balance (SPB) model is presented on foam displacement behavior in a water saturated heterogeneous porous media consisted of two parallel layers of medium with different permeabilities. Detailed parameter studies of the two key parameters of the SPB model, bubble generate rate Kg and maximum bubble density n∞, are carried out to understand foam flow behavior and mechanisms in the heterogeneous porous media. Numerical results indicate variation of Kg and n∞ values could significantly affect the ongoing foam flooding process and lead to obviously different pressure drops and sweep efficiencies. The parameter of Kg stands for the formation rate of foam, therefore determines the distance and time for foam fluid reaching equilibrium in the displacement process. Higher Kg values result in higher pressure drop and lower water saturation after foam sweeping through the heterogeneous porous media. The parameter of n∞, on the other hand, determines directly the magnitude of foam apparent viscosity through defining the maximum bubble density of the flooding foam fluid. Larger n∞ values lead to higher pressure drops and higher foam sweep efficiencies of the heterogeneous porous media. Reasonable numerical results indicate the SPB model could adequately describe foam displacement process in the heterogeneous media, therefore supplies an important alternative for foam mechanistic studies to promote essentially the foam field applications.

Taking typical meandering river deposits of Ng52+3 in the west 7th block of Gudong Oilfield as an example, the influence of point-bar-sandstone superposition structure on flooding law and remaining oil distribution is studied by means of seismic architecture interpretation under the guidance of point-bar geometry. Meanwhile, the influence of morphological parameters and lithology of lateral accretionary surfaces on remaining oil and development characteristics is discussed. The seismic waveform and amplitude of point-bar boundary sandstones are obvious when they overlap with each other. The connectivity of superimposed zones between boundary sandbodies of point-bars is poor. The remaining oil near the superimposed zones is enriched when base-of-channel sandstone that infills abandonment (PI) and the earliest sandstone at the beginning of migration of the point bars (PI) superimposed with each other. Remaining oil is relatively not enriched when PI sandstones of point-bars are superimposed in superimposed zone. Remaining oil is relatively enriched in the upper point-bar sandstone at the superimposed zone. The effective shielding area effective distance to obstruct fluid flow of mudstone section of lateral accretionary surfaces is 50–80 m along the lateral direction of lateral-accretion surfaces, and the remaining oil is not enriched in the same point bar within the range of 50–80 m around oil and water wells. The physical property section of lateral-accretion surfaces in the middle and lower part of the surfaces has a certain blocking effect on flow and can obviously reduce the recovery degree. Seismic architectural interpretation plays an important role in predicting remaining oil enriched areas and prolonging oil field life in order to improve oil recovery.

Ultrasonic power supply is one of the key factors to determine the quality of ultrasonic cutting, which affects the machining performance and efficiency of ultrasonic cutting system. In this paper, a power supply for ultrasonic vibration cutting is presented. The proposed ultrasonic power supply consists of rectifier and filter module, inverter module, impedance matching module, feedback module and control system module. Also, software based on FPGA is designed to realize the digital control of the output frequency. Experimental studies are carried out on the prototype to validate stability and reliability of the ultrasonic power supply.