聚合物驱后岩心孔隙结构变化特性研究

The Changes of Pore Structure of Polymer Flooded Sandstone Reservoir Cores

将直径 2 .5mm ,长 6 0mm ,水测渗透率分别为 0 .4 87、1.2 7和 2 .2 7μm2 的 3块大庆砂岩油藏岩心截成等长的2段 ,其中一段用质量浓度 10 0 0mg/L、矿化度 918mg/L的聚合物溶液驱替。所用聚合物 12 75 ,M =1.8× 7,HD=2 7.4 % ,驱替温度 4 5℃。用压汞法测定了聚驱后和未聚驱的 3组共 6块岩心的多项孔隙结构参数 ,用表列出了测定结果 ,给出了渗透率 0 .4 87μm2 的 1组岩心的孔隙分布曲线和渗透率贡献分布曲线。实验结果表明聚驱后①岩心水测渗透率有较大幅度下降 ,孔隙度略有下降 ;②岩心最大孔隙半径不变 ,孔隙半径均值和中值下降 ;③岩心孔隙分布的峰位和峰值均下降 ,渗透率贡献分布的峰位不变而峰值下降 ;④岩心各项孔隙结构参数中 ,分选系数、歪度、峰态、孔喉半径均值、结构特征系数、均质系数有不同程度下降 ,而结构系数和相对分选系数则升高。

Daqing sandstone reservoir cores (  25×60 mm) of permeability to aqueous phase 0.487,1.57 and 2.27 μm 2, respectively,are cut into two sections of equal length and one of them are flooded with polymer 1275 solution of concentration 1 000 mg/L and TSD 918 mg/L at 45℃. The polymer is of M =1.8×10 7 and HD =27.4%. A lot of parameters characterizing core pore structure is determined by using instrusive mercury measurements and is tabulated for the six core sections, polymer flooded and original, of 3 permeability classes with the pore size distribution and contribution to permeability distribution curves presented for low permeable class. The experimental results show that for polymer flooded core sections, ① the permeability to aqueous phase decreases significantly and the porosity?-?slightly; ② the maximal pore radius value is maintained unchanged but the mean and the median values are decreased; ③ the peak location and height of pore size distribution and the height of contribution to permeability distribution are decreased and the peak location of the latter distribution is kept unchanged; ④ of the characteristics of pore structure determined, sort index, skewness, kurtosis, radius mean, characteristic structure coefficiency, and homogeneity coefficieny are decreased in different extent while structure coefficiency and relative sort index?-?increased. The definition of these structural characteristics is given.