Study on Adaptability of Polymer Flooding Technique in Reservoirs with Different Water-Wash Degree

The lab experiment with different water-wash natural cores for polymer flooding adaptability is established based on coring interpretation data of xing12-3-jian3222 well of Pu I3 layer in Daqing oil field. The water displacement efficiency of the cores are 70~80%, 40~50% and 10~20% respectively. Besides, feasibility of reducing residual oil after water flooding with the high concentrated and high molecular mass polymer is analyzed. Displacement effect of polymer is studied with 3 parallel cores by commingled injection and separate production. The results indicate that the adsorption of high molecular mass polymer and injection pressure gradient are affected more markedly by concentration than molecular mass in different water-wash degree reservoirs. Residual resistance factor and displacement pressure gradient increase with the concentration increase. The residual resistance in strong and moderate water-wash reservoirs can be met, and the injection capacity in weak water-wash reservoir is good with the polymer of 1.3g/L 25 times 10⁴ molecular mass. The parallel cores displacement results show that the profile controlling methods before high molecular mass polymer flooding can adjust the injection profile of moderate and weak water-wash reservoirs effectively and the producing degree are enhanced. The recovery efficiency is enhanced 21.12% when 1/3 profile modification radius with compound-ion profile control agent and 25times10⁴ molecular mass polymer with 1.3 g/L used, which improved 4.06% than 0.64 PV polymer slug alone.