| Two-phase relative permeability data are widely applied in modern reservoirengineering for simple reservoir engineering calculation or complicated numericalsimulation. There are some disadvantages in low-permeability reservoirs or inpolymer flooding by using traditional displacement methods in the laboratory toobtain the relative permeability, and the variation rules of two-phase relativepermeability could not be recognized actually. In this paper, calculating theory andapplication method of the relative permeability are studied during unsteady statetwo-phase flooding combining physical simulation with numerical simulation. Theunsteady state two-phase flooding process in the laboratory is deeply studied. Thestudy process and conclusions are as follows:1. Theory analysis shows that the relationship of the average water saturationand water injection multiple is monotone when using JBN method to calculaterelative permeability. A new polynomial regression method is developed to makesure the relationship monotone. Calculating accuracy is improved and data analysisis more reasonable.2. A more accurate method is developed to calculate the relative permeabilityin unsteady state flooding, based on the pressure distribution equation which isdeveloped by French scholar Marle. With this method, oil-water relativepermeability data can be obtained even if the water injection multiple is infinitelygreat. And the result is very valuable.3. We correct motion equation with threshold pressure gradient and develop amethod to calculate oil-water relative permeability in low-permeability reservoirs. Adimensionless parameter Re0is also obtained to describe the flowing characteristicsof low-permeability reservoirs. The value of Re0has direct ratio with injection rateand the viscosity of oil, but has inverse ratio with the permeability of the reservoir.4. Based on non-Newton seepage theory, we develop a two-phase flownonlinear mathematical model of non-Newton fluid flooding Newton fluid throughunsteady state flooding experiments. Derived the new polymer flooding relative permeability of calculation model, and given the corresponding solving methods andautomation software.5. The experiment process of unsteady state polymer flooding is improvedeffectively. And we develop a new rule to set the initial experimental pressure. Theassumed conditions of experimental process and mathematical model are consistentand the test result is satisfied.6. The experimental method to measure the inaccessible pore volume of thepolymer is developed. Many experimental results show that the inaccessible porevolume during polymer flooding increases with the increase of the molecularweight of the polymer, but decreases with the increase of the permeability of thecore.7. The study result of the relative permeability of polymer flooding in differentconditions shows that, when the molecular weight and concentration of the polymerincreases, the relative permeability of the water containing polymer decreasesgradually. Meanwhile, the oil-water phase region expands, and the residual oilsaturation decreases. Compared to water-wetting cores, the relative permeability ofthe oil of oil-wetting cores is a little smaller, but the relative permeability of thewater containing polymer is bigger. Moreover, the water cut increases more quickly.And the equal-permeability point and the right end point move to left. If polymerflooding is adopted after water flooding, the displacement efficiency of oil-wettingcores is better than that of water-wetting cores. The residual oil saturation decreaseswhen the permeability of the core increases, and the water cut increases much moreslowly. There is obviously mathematical relativity between the residual oilsaturation and the permeability.8. The relative permeability curve of polymer flooding from the new methodhas been applied into field experiments of numerical simulation. The productionindex calculated by this new method can fit the production performance better. Andthe predicted result is more creditable.
|
PDF Full Text Request