Experimental study on constant pressure of polymer flooding in second-class reservoirs

At present, the second-class oil layer has become the main polymer flooding replacement layer in the Lamadian Oilfield. The second-class oil layer has low permeability, low connectivity and serious heterogeneity. The results of the polymer flooding laboratory experiments are quite different from the field flooding effect. Polysystem design provides better guidance. Based on theoretical and field data analysis, this paper adopts constant pressure injection method. After the experimental injection fluid is seepage through a 1.5m long core, the core flooding experiment is carried out, that is, the problem of excessive pressure rise in polymer flooding is controlled, so that the injection fluid is closer to the oil layer. state of the injected system. The constant pressure polymer flooding experiment was used to establish the matching relationship between the polymer system and oil layers with different permeability, which effectively guided the design of the on-site polymer injection system. At present, indoor polymer flooding core experiments generally adopt the constant speed mode, without controlling the injection pressure. However, due to the influence of permeability, connectivity and other factors, the injection pressure increases greatly, and the reservoir water absorption is difficult, which leads to a great difference between the experimental results and the field effect. In order to make the indoor core experiment closer to the actual field injection state and better guide the design of polymer flooding scheme, it is urgent to optimize and improve the experimental method