Study On The Flow Behavior Of Elastic Particles And The Mechanism Of Utilizing Residual Oil In Porous Media

The long-term waterflooding development has led to the entry of high water cut stages in mature oilfields,with problems such as rapid decline in production,continuous rise in comprehensive water cut,and ineffective circulation of injected water.Traditional chemical flooding techniques,represented by polymers,have limited effectiveness in enhance oil recovery,while heterogeneous composite flooding based on elastic particles B-PPG is an effective alternative development technique.In view of the problems that the characteristics of elastic particle B-PPG percolation are not clear,the matching mechanism with reservoir pore throat needs to be studied,and the injection effect of some blocks is not ideal,relevant research has been carried out in this paper.For the five kinds of B-PPG used in this paper,the elastic modulus,swelling ratio,particle size distribution characteristics and viscosity increasing ability of B-PPG were measured by physical and chemical properties characterization.The results show that the elastic moduli of five kinds of B-PPG are distributed between 0.7 and 44.1 Pa,with water absorption and swelling capacity,and the swelling ratio is distributed between 24.8 and27.8.#1,#3,#4 B-PPG particle size is small,and the D₅₀ is distributed between 525 and550μm.#2 and#5 B-PPG have larger particle sizes,with D₅₀ of 1456μm and 1466μm,respectively.In addition,B-PPG has certain tackifying properties.The effect of elastic modulus,matching coefficient,and injection rate on the flow behavior of B-PPG was studied by sand pack flow experiment.The results show that when the median diameter(D₅₀)of B-PPG is in the range of 525 to 550μm,considering the injection capacity and plugging performance,the reasonable elastic modulus of B-PPG dispersion system is in the range of 10.3 to 42.2 Pa.When the median diameter(D₅₀)of B-PPG is 1465μm,the reasonable elastic modulus of B-PPG dispersion system cannot exceed 44.1 Pa.When the matching coefficient is between 15.2 and 32.0,and the F_rr is between 40.0 and 66.1,B-PPG can form effective plugging.The injection rate has an important impact on the flow behavior of B-PPG,when the injection rate is within the range of 0.5～1.5m L·min^-1,F_r and F_rr in the range of 32.1～93.5 and 24.8～66.1,respectively.Currently,B-PPG has good injection and plugging performance.Through homogeneous and heterogeneous sand pack displacement experiments,the oil displacement effect of B-PPG with different elastic modulus and particle size are studied from the macro layer.The results show that the increment of oil recovery increases with the increase of B-PPG elastic modulus and decreases with the increase of B-PPG particle size.When the elastic modulus of B-PPG is 0.7 Pa and 42.2 Pa respectively,the slug combination displacement effect of high elastic modulus B-PPG followed by low elastic modulus B-PPG is better than that of low elastic modulus B-PPG followed by high elastic modulus B-PPG.When the elastic modulus of B-PPG is 10.3 Pa and 42.2 Pa respectively,the slug combination displacement effect of low elastic modulus B-PPG followed by high elastic modulus B-PPG is better than that of high elastic modulus B-PPG followed by low elastic modulus B-PPG.B-PPG can significantly increase the liquid absorption ratio of the low permeability layer and effectively alleviate the heterogeneity.Through micro visual displacement experiment,the ability of B-PPG to expand swept volume was explored from the micro layer.The results show that the sweep volume capacity of B-PPG with elastic modulus between 0.7 and 42.2 Pa increases with the increase of elastic modulus.B-PPG can effectively displace the remaining oil perpendicular to the direction of the main streamline,and can displace the columnar,clustered,continuous,and membranous remaining oil.