The dimension of polymer molecular coil in polymer solution and "polymer/surfactant" displacement system and its influential factors were studied under the condition of high temperature and salinity, as well as the seepage property under the medium-low permeability reservoir environment, and the mechanism of their flowing rule was also analyzed, by making use of dynamic light scattering (DLS), scanning electron microscopy (SEM) and core flow experiment. The results show that, under the condition of high temperature and salinity, the dimensions of polymer molecular coils (D_h) both in the polymer solution and "polymer/surfactant" displacement system present a variation rule of "increases first and then decreases", with the polymer concentration increases. In addition, the surfactant is absorbed to polymer molecule in the form of micellar aggregate, resulting in a greater D_h in the "polymer/surfactant" displacement system when compared to the polymer solution. Under the condition of high salinity of solvent water and medium-low core permeability, the erosion and dilution of following injecting water can result in a concentration decreasing of retained polymer in the core, thereby the D_h increases, and eventually the residual resistance factors both of the polymer solution and "polymer/surfactant" system are greater than their resistance factors.

Key words: polymer solution, polymer/surfactant displacement system, salinity, configuration, molecular coil dimension, seepage property, mechanism analysis