Study On Characteristics Of Fluid Flow In LPY Ultra-Low Permeability Fractured Reservoir Water Flooding

At present,the development of low permeability/ultra-low permeability reservoirs is more and more prominent in China's oilfields development.The reservoir characteristics,fluid properties reservoirs are quite different from the medium-high permeability reservoirs,leading to percolation theory,oil-water distribution,water injection development methods are also very different.LPY ultra-low permeability reservoir has occurred the problems of the decline of production and the increase of water-cut,so it is necessary to clarify the mechanism and laws of oil-water percolation.Based on the detailed analysis of the geological and reservoir data of LPY reservoirs,the characteristics of LPY ultra-low permeability fractured reservoirs are clarified.Based on the tree-like model model,the complex coupling model of LPY double-fracture ultra-low permeability reservoir is established,and the matching relationship among pore-throat-microcrack is expounded.The tensor theory and equivalent continuous medium theory are used to study the effect of micro-cracks on reservoir permeability.The nonlinear percolation experiment and the two-phase percolation experiment were carried out,and the role of capillary force in the ultra-low permeability fractured reservoir was emphasized.The sorptiondisplacement movement in the development of LPY water flooding was also expounded.Finally,the development effect and influencing factors of unstable water injection were studied by numerical simulation,and the unstable water injection scheme was optimized,and the field application suggestions were put forward.Reservoir research shows that the micro-cracks of LPY ultra-low permeability fractured reservoirs develop,the pore size of the matrix is in the same order of magnitude as the microcracks,and the large cracks have poor connectivity and cannot form a fracture network.Therefore,they belong to the fractured reservoir with homogeneous characteristics.Permeability tensor model calculations show that micro-cracks can significantly improve reservoir permeability,but at the same time increase reservoir heterogeneity.Laboratory experiments show that there is a starting pressure gradient in the LPY reservoir,and the capillary force has a large change in the phase infiltration curve.The characteristics of the sorption-displacement movement in the ultra-low permeability fractured reservoir with homogeneous characteristics are described.The mathematical model of the sorptiondisplacement movement shows that the sorption and displacement are both in the development of reservoir water flooding.Important role.Numerical simulation studies show that unstable water injection can play the role of “precipitation and oil increase”,and the capillary force,the injection cycle and the fluctuation of injection volume all have an effect on the unstable water injection effect.