Experimental Study On Percolation Characteristics And Flow Field Changing Characteristics Of Water Flooding In Sandstone Reservoir At The Late Stage Of Extra High Water Cut Stage

The oil-water percolation law and flow field development in the reservoirs with very high water cuts are complicated.The coexistence of inefficient water circulation and highly dispersed residual oil makes it difficult to further improve oil recovery.In order to deeply tap the remaining potential of ultra-high-water-cut oilfield,approaches including theoretical calculations and physical simulation experiments are involved to study the characteristics of relative permeability and remaining oil distribution,flow field monitoring and simulation methods,flow field evolution and feasibility of adjustment measures during the water flooding in late ultra-high water cut stage following the idea of "starting from the seepage characteristics and gradually expanding to the application to indoor flow field simulation”.Firstly,facing the defects of relative permeability measurements in late ultra-high water cut stage,the improvement of the measuring approach is made in this study and its feasibility is proved.The improved method is implemented to measure the relative permeability curve of loose sandstone during high-pore-volume water flooding.The main controlling factor of the morphological characteristics of the relative permeability curve is analyzed to be the distribution of microscopic remaining oil.Utilizing the ultraviolet fluorescent technology,the morphological characteristics of residual oil in different water cut stages are studied.It is shown the dispersion of microscopic remaining oil is intensified as the water cut increase and the portions of remaining oil in different existing status tend to reach a unity.According to the seepage characteristics of water and oil in late ultra-high water cut stage,combined with the analysis of the under the existence of flow in the porous medium,the singlepoint self-heating temperature sensing device and corresponding saturation measuring methods,The theory,method and method are established for effective monitoring of the percolation velocity of a single-phase fluid in a multiphase percolation process.The correlation between the of the reservoir model and resistivity as well as that between saturation and the heat conductivity of the model is then established,which sets basis of the flow speed monitoring and calculation.Utilization of this method can provide fundamental and necessary parameters to support the evaluation of the physical simulation of the flow field in late ultrahigh water cut stage.To make more effective flow field simulation and evaluation by indoor physical experiment,there's a necessity to make full use of the monitored parameters besides seeking more parameter measuring methods.Only in this way a true and objective experimental and evaluation results can be obtained.Based on the obtained boundary of inefficient circulation combined with test results such as saturation,pressure,flow rate,a method for integrated evaluation and adjustment of the flow field is put forward,using which a comprehensive analysis is performed on the characteristics of the flow field in the late high water cut period based on the results of large-scale water-flooding physical simulation experiment.The periodical flooding is selected out to be a relatively reasonable IOR method because of the more homogeneous saturation field distribution,fewer low-efficiency circulation areas,smaller non-Darcy flow and high-pore-volume water flooding areas formed.In this paper,the micro-physical properties were directly related to the microscopic remaining oil characteristics and macro percolation phenomena.The theory and method for monitoring the percolation velocity in the reservoir model during indoor physical simulation are proposed innovatively and the integrated evaluation method of the flow field during the physical simulation of water flooding is given.Those researches can provide the necessary theoretical and technical support for the precise exploration of reservoir potential,tapping of remaining oil,and enhancement of reservoir oil recovery in ultra-high water-cut late stage oilfields.