Experimental Study Of Viscosity On Heavy Oil-water Relative Permeability Curves

As an essential knowledge for describing the percolation characteristic of fluid flows in the porous media and calculating various reservoir engineering parameters,the correct oil-water relative permeability data is the fundamental guarantee of the project design of heavy oil reservoir development.However,there is still lack of systematic experimental and theoretical study on the influence mechanism of heavy oil-water relative permeability curves,let alone functions for reservoir simulation and the prediction of heavy oil-water relative permeability data as the varying production conditions.Therefore,for better develop heavy oil reservoirs,it is urgent need to methodical survey on influence factors of heavy oil-water relative permeability and establish its corresponding empirical formulas.A large number of experiments with three different heavy oils from Shengli Oilfield Caoqiao block are conducted to investigate the affecting factors of heavy oil-water relative permeability.Firstly,the properties of heavy oil and oil-water surface are evaluated,mainly including oil viscosity at different dilution extents or temperatures,the rheological behaviors of heavy oil,oil-water interfacial tension and rock wettability.Then,numerous core flooding displacements under different experimental conditions by adjusting those parameters mentioned above are performed to reveal the relationship between the parameters mentioned above and the oil-water relative permeability,the residual oil saturation and the irreducible water saturation.Finally,the empirical equations for predicting the heavy oil-water relative permeability data are established by regression analyzing the experimental data.The experimental results indicate that temperature and oil dilution extent have obvious significance on the properties of heavy oil and oil-water surface,especially in lower temperature range and lower oil dilution extent.With the increase of temperature and oil dilution extent,the oil viscosity sharply decreases and the non-Newton rheological behavior tends to be weaker.The temperature making the fluid from non-Newton to Newton is proportional to oil viscosity.And the oil-water interfacial tension shows a minor decline trend,of which value ranges from20 to 40mN/m.The value of water-wet index increases with the temperature,suggesting that the rock alters to be more wet.Whereas,the rock wettability of the porous media in this paper does not change any more when the temperature reaches 80?.There is an outstanding feature of heavy oil-water relative permeability curve that oil-phase relative permeability is high,while water-phase relative permeability is very low.For heavy oil-water system,the steady state technique can provide more reliable relative permeability data than the unsteady state method.All the factor covering temperature,oil composition,oil-water viscosity ratio and oil-water interfacial tension except reservoir oil and crude oil have a great influence on the heavy oil-water relative permeability.With the increase of temperature,oil dilution extent and the viscosity ratio decreases,the value of oil and water relative permeability shifts to bigger and the two-phase flow area tends to be larger,while the irreducible water saturation and the residual oil saturation represents a down trend.It is not difficult to trace that the nature of the change of the influence factor mentioned above is the variation of the viscosity ratio.When the viscosity ratio is a constant,the relative permeability curve is also definite.Only when its value reaches 10^-1 order of magnitude,the interfacial tension plays an important role on oil-water relative permeability.And it has a great impact on the residual oil saturation,while it affects the irreducible water saturation less.As the interfacial tension decreases,both oil and water flow ability are increased.Considering the influence mechanism of oil-water relative permeability,a correlation as a function of oil-water viscosity ratio is established to predict the relative permeability and its endpoint data.