Percolation Theory Research Of Weakly Compressible Fluid Flow Considering Wall-liquid Interaction

The flow of fluid in low permeability porous media has nonlinear seepage characteristics, the descriptions of the flow pattern is usually on the basis of the experiment of the seepage law, and then the mathematical model of non-Darcy seepage is established, however, the results failed to reveal the mechanism and physical nature of the nonlinear seepage, the analysis results that starting from the basic theory is always absent. This paper analyzes the root cause from the perspective of fluid mechanics, by adopting the experimental analysis, theoretical model and numerical simulation methods, the theory model of fluid seepage that considering liquid-solid interface function of slightly compressible fluid is established. Providing a new method and laid a theoretical foundation for the research of the nonlinear seepage law of porous media.First of all, the paper start with the experiment of the micro circular pipe flow, the nonlinear flow of fluid in micro scale is studied. Through analyzing the influence factors of nonlinear of micro flow, the nonlinear flow characteristics were found and the phenomenon of start-up pressure gradient is appeared. From the perspective of liquid-solid interface function, the wettability of the tube wall surface, the velocity of the fluid in the micro circular pipe that with the same diameter is increased and the flow resistance is reduced. This result reflects the liquid-solid interface forces have the important influence to the fluid flow in micro circular tube.Integrating application of theoretical analysis methods, such as fluid mechanics, seepage flow mechanics, modern mathematical theory, modern nonlinear dynamics, considering the influence of long-term solid liquid electrostatic force, van der Waals force and the micro compressibility of the fluid, the nonlinear equations are established. Introducing the vortex function and stream function, using the regular perturbation method, the approximate analytic solution of velocity and pressure distribution is obtained. The calculation results show that the nonlinear characteristic of the fluid and micro-scale effect is obvious considering the interface force and nonlinear characteristic under the condition of slightly compressible of the fluid. The root cause of the nonlinear flow is revealed from the perspective of the micro fluid compressibility and liquid solid interface reaction.On the basis of single-phase flow mathematical model in microtubules, the transient fluid mathematical model of two-phase that considering liquid-solid interface effect and the slightly compressible of fluid is established. Using the mathematical model of two-phase flow in microtubules, the capillary bundle model that reflects the characteristics of the porous medium flow is established. The influence of the micro compressibility of the fluid and the fluid solid interface force to the law of the water flooding in two cases is comparative analyzed:one case is that the entry end and export end have constant pressure, the other case is that the entry end has constant flow rate, export end have constant pressure.The flow of the slightly compressible fluid considering liquid-solid interface function in the network model is simulated with water drive oil dynamic network model. The. affection of the micro fluid compressibility, liquid solid interface reaction, average throat scale and driving pressure to the type and proportion of the remaining oil distribution is analyzed. His results show that the compressibility and liquid-solid interface function have great influence on residual oil ratio which gives first place to tufted remaining oil. The smaller the average throat radius, the higher the proportion of residual oil which gives first place to tufted remaining oil. When the throat radius increases, pressure gradient increases and the residual oil is less, the membranous residual oil is difficult to displace. The liquid-solid interface force has a largest impact to the formation of tufted remaining oil and membranous remaining oil, this providing a basis theoretical to produce remaining oil.