Research On Pore Level Oil-water Two Phase Distribution And Microscopic Flow Mechanism

Numerical simulation of porous media percolation is one of the important measures to study the dynamic development of reservoir.With the rapid development of computer technology,the numerical simulation of porous media percolation has become an increasingly important basic tool in different engineering fields.Due to the complexity of pore flow,the essential characteristics of the pore-level flow have not been really embodied in the current numerical models.Therefore,it is of great theoretical and practical significance to study the microscopic distribution and flow mechanism of oil-water two-phase in porosity.It was analyzed that the residuals of the wetting phase caused by the non-wetting fluid into the capillary and the two-phase distribution on the capillary section.A single-angle capillary model was presented.The variation law of the saturation in the capillary of the regular polygon was deduced,and the influence of the size and position on the saturation of the capillary was discussed.The oil-water distribution of the different contact angles of the triangular cross-section capillary of six different shape factors was calculated.The volume flow rate of oil-water and the velocity distribution in capillary were studied by computational fluid dynamics software,and the influence of water film on the relative permeability of oil phase was discussed.Based on the experiment results of oil droplets migration in circular capillary,the equivalent viscosity model was proposed.The pressure drop of single oil droplet slug and multi-oil droplets was studied.By comparing the results of equivalent viscosity model with numerical simulation results,the influence of oil viscosity and capillary number on the equivalent viscosity was discussed.By simulating the process and pressure drop of oil droplet slug in non-circular cross-section capillary,the influence of the water channel on the migration and pressure drop of oil droplets was discussed.The results show that the sharper the corner of the polygonal cross sections with different sides,the greater the wetting phase saturation in the section,and the larger the flow direction of the wetting phase in the axial direction.When the corner position was different,the wetting phase saturation was different,and reached the maximum when the meniscus of different corners just contact;The volume ratio and the relative permeability of the different triangular cross-section capillary were consistent with the same water saturation,which was independent of the size and cross-sectional shape of the capillary.The relative permeability curve was suitable for the triangular capillary oil-water flow with the same physical properties.For the discontinuous flow in the circular cross-section capillary,two equivalent viscosities were proposed:hold-up viscosity?_fand separate viscosity?_of.The reason that the pressure drop rapidly decreased at the time of separate period was obtained:the disappearance of the capillary pressure difference and the decrease of equivalent viscosity.When the oil saturation was constant,with the number of slugs increased,the pressure drop of the capillary force increased.During the hold-up period,the trend of capillary pressure drop with the velocity deviated from linearity,and the total pressure drop?35?P of the capillary was not linear with the displacement speed v,with non-Darcy flow;When the oil droplets slugs reached steady flow stage,the flow was Darcy flow.For discontinuous flow in non-circular cross-section capillaries,when the displacement speed was less than the critical velocity,the proportion of the portion covered by the water film and the portion directly contacting the inner wall changed,and the flow was non-Darcy flow.When the displacement speed was higher than the critical velocity,slug out of the inner wall,the flow became Darcy flow.