A Study On The Fluid Entry Profile Reverse Of Polymer Injection Well And Its Enfluence On Flooding Effect

In recent years, many petroleum engineers have done lots of work on the threshold pressure gradient, and have got many achievements about it, but most of the research was on the theory, the application about it was very little. Polymer flooding has been used widely in China, and has contributed a lot to the EOR, but when the polymer flooding comes into middle and later stage, some blocks with relatively higher aeolotropies come with some special phenomena called the fluid entry profile reverse phenomena in which the high permeability zone absorbs more water than the middle and low permeability zones, even more than the high permeability zone in the water flooding, while the middle and low permeability zones absorb less water than the middle and low permeability zone in the water flooding, and affects the oil increase effect of polymer flooding badly. Aiming at the practical need in the oilfield, the author induces the threshold pressure gradient into the traditional Darcy's law to found the non-linear Darcy's law with the threshold pressure gradient, establish the math model, solve the equation and programmed the software to analyze the fluid entry profile reverse phenomena, the results show that that the permeability contrast, the molecular weight, the injection velocity and the injection time influence the phenomena, when other condition is the same, the bigger the permeability contrast, the earlier the phenomenon appears, the more the fluid entry profile reverses, the worse the polymer flooding is influenced; the bigger the molecular weight, the earlier the phenomenon appears, the more the fluid entry profile reverses, the worse the polymer flooding is influenced; the faster the injection velocity, the earlier the phenomenon appears, the more the fluid entry profile reverses, the worse the polymer flooding is influenced; the later the injection time is, the later the phenomenon appears, the less the fluid entry profile reverses, the less the polymer flooding is influenced, which give some guidance to settle this bad phenomena of the reverse of the fluid entry profile.