Enhanced Oil Recovery Mechanism Of Polymer Flooding In High Permeability Ordinary Heavy Oil Reservoir

Although ordinary heavy oil accounts for a large portion of the world’s petroleum resources,and are particularly abundant in China’s offshore,its high viscosity and high seepage resistance make water flooding development prone to finger-in phenomenon,resulting in rapid rises in water content,rapid production decline,and low recovery rates.Based on the aforementioned issues,the polymer flooding ordinary heavy oil cold recovery technology has been developed,which can considerably to increase the development effect of thick oil reservoirs,however the mechanism of recovery enhancement is unknown.We explain the mechanism of residual oil utilization in polymer flooding ordinary heavy oil,describe the microscopic seepage behavior of viscoelastic polymer flooding ordinary heavy oil,analyze the factors affecting the development effect of polymer flooding ordinary heavy oil,and reveal the mechanism of recovery enhancement in this study,which is based on nuclear magnetic resonance,laser confocal,and microscopic visualization displacement experiments.The changes in crude oil mobilization,remaining oil distribution,and flow of each component of ordinary heavy oil during polymer flooding ordinary heavy oil were examined using microscopic detection techniques such as nuclear magnetic resonance,laser confocal,and indoor displacement tests.The oil signal in medium and large pores reduced significantly after polymer injection,and the degree of recovery improved by 12.54%in the polymer flooding stage,with the degree of recovery in small pores at 1.49%.Polymer flooding boosts the wave degree of small pore space and repulsion significantly.The microscopic percolation behavior of polymer in porous media and the utilization of residual oil after water flooding was examined during polymer flooding in ordinary heavy using microscopic imaging experiments and numerical simulation of flooding in porous media.All types of residual oil are used to varying degrees in the polymer flooding process,with the result being better for the cluster,pore surface film,and blind end varieties.The development of tensile flow is mainly flooding by the pore structure of shrinkage and expansion,which is dispersed in the core area of the fluid and surrounded by shear flow at the periphery,according to the flow structure of viscoelastic polymer at different De numbers.The repulsive action of viscoelastic polymer on ordinary heavy oil is mostly dependent on shear flow,and the presence of tensile flow can effectively enlarge the wave region of shear flows and mobilize the residual oil in the blind end structure.The polymer repellency of ordinary heavy oil in porous media is obvious for tiny pores,and the repellency efficiency is also higher in large pores,according to seepage features of polymer repellency of ordinary heavy oil in porous media.With the best repelling effectiveness and the least oil left in the pore throat,the polymer viscosity was 88 mPa·s,and the repelling efficiency was 67.7%.The repelling effect is diminished by the increased concentration of polymer solution,which causes elastic instability and "blocked" flow and rapids in the pore space,causing the repelling pressure to not create a good connection and form vortex,energy dissipation,and energy dissipation.A mathematical model of the seepage flow of polymer flooding ordinary heavy oil with viscoelastic properties is developed and solved in an implicit differential explicit manner to analyze the effects of different factors on the development effect of polymer flooding ordinary heavy oil based on differences in the content of light,medium,and heavy components in the recovered fluid under different flow ratios of polymer flooding ordinary heavy oil.The best polymer injection conditions for the ordinary heavy oil reservoir with a viscosity of 188 mPa·s are polymer molecular weight of 19 million,injection concentration of 1500 mg/L,injection rate of 0.14 PV/a,and injection section plug size of 0.4 PV.The paper’s findings can provide a theoretical foundation for efficient polymer flooding development technology in ordinary heavy oil reservoirs,improve the scientific accuracy of the optimized polymer flooding development scheme in ordinary heavy oil reservoirs,and clarify the microscopic mechanism of polymer viscoelastic effect on ordinary heavy oil reservoir recovery enhancement.