Abstract:

The polymer flooding blocks in Daqing oilfield had entered the subsequent stage of water flooding development. Due to the long-term water polymer flooding, the preferential seepage channels in the oil layers were highly developed, and the inefficient and ineffective circulation were serious. In order to achieve the goal of further EOR after polymer flooding, the dominant seepage channels must be accurately identified and effectively blocked. The conventional description methods, such as the coring, logging, profile testing and production performance, were with few and discontinuous data, low accuracy and high cost. As it was difficult to identify, by the streamline numerical simulation technique, and based on the study of typical blocks, we screened the key parameters and established the permeability time-varying model and mathematical model of comprehensive identification index. Then according to the initial value iterative method and combined with expert experience, we proposed the weight of the key parameters. At the same time, the dominant seepage channels were quantitatively graded according to the comprehensive identification index. The results showed that the calculated distribution of dominant seepage channels in typical blocks were highly consistent with the actual water absorption profile test results, which meant that the established method could accurately describe the distribution law of dominant seepage channels after polymer flooding. The research had important guiding significance for identifying and effectively sealing the dominant seepage channels, and provides strong support for the further efficient development after polymer flooding

Key words: dominant seepage channel, streamline numerical simulation, permeability, composite identification index