Abstract:In order to meet the practical demand of the field,with the means of the instrumental analysis,physics modeling and the reservoir engineering theory,the viscosity and molecular coil dimension of the compound polymer,obtained by mixing the polymers with different molecular weight of 1400×104,1900×104 and 2500×104,named as "middle molecular","high molecular" and "ultra-high molecular",and the oil displacement efficiency were investigated,in addition,the EOR mechanism of the compound polymer was also presented.The results showed that with the proportion of the "ultra-high molecular" polymer increasing,the molecular coil dimension and the viscosity of the compound polymer increased.Compared to the "high molecular" polymer,the molecular coil dimension of the compound polymer was broader and the abilities of salinity resistance and shearing resistance was stronger.The physics model experiment indicated that as far as the polymer solution with the same viscosity as was considered,the oil displacement efficiency of the compound polymer solution was better than that of "high molecular" polymer.The enhancement of oil recovery increased with the proportion of the "ultra-high molecular" polymer increasing.