| The development of low permeability reservoirs in China is promising,and in these reservoirs,The main stage of the development is the waterflooding stage,and it has favourable universality and economy efficiency in practice.As the structure of low permeability reservoir is complex,the water flooding mechanism is different from general reservoir,the original mechanism is no longer universally applicable to low permeability reservoirs.Therefore,researching the fluid flooding mechanisms in low permeability reservoirs,and revealing the distribution of oil and water phase have vital significance in learning and developing reservoirs.The oil and water mechanism is studied in this paper,in addition to this,we carried out theoretical calculation and experimental verification of nonlinear flow and provided the pressure gradient in the research area.We also proposed the calculation formula of capillary with water film and compared the different characteristics of the capillary force according to the corresponding parameters of the research field.On the basis of this,the relative permeability of oil and water is proposed,combined with flow equation,the relative permeability of research area is calculated.Considering all these factors,numerical simulation is carried out to analysis the effect of water saturation and inject pressure.The results show that in the research area,when the capillary radius is less than500nm,the differences between the capillary with or without water film is distinct.While when the capillary radius is more than 500nm,it has little differences,the injected water can flow along the water film when considered the water film,and then the water relative permeability goes up and oil relative permeability goes down.The numerical simulation shows that in the fracturing process,the asymmetrical fractures have the highest production and the maximum economic benefit can be achieved by injecting 12m~3/d and with injecting pressure 6 MPa. |
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