Abstract: Two-dimensional etching models were constructed with varying levels of preferential petroleum migration pathway (PPMP) development based on the pore-throat distribution characteristics of PPMPs in mid-to-high permeability reservoirs, for studies on the microscopic distribution of residual oil in PPMPs and their evolutionary characteristics. By analyzing the adaptability of different methods for altering streamline mobilization, we have taken the first steps towards revealing the mechanism of streamline mobilization alterations in the residual oils of PPMPs. We also quantified strategies for altering streamline mobilization via numerical simulations of oil reservoirs. The results indicate that increases in displacement speed can greatly reduce the quantity of residual oil in weakly preferred migration pathways, whereas the changes that occurred in strongly preferred migration pathways were relatively minute. The residual oils in PPMPs were divided into four types according to the morphology of their storage and formative mechanisms, namely, dead angle types, parallel types, enveloping types, and circumfluent types. The first two types were almost completely unaffected by the scale of PPMPs and displacement speed, whereas the two latter types showed significant decreases with increases in displacement speed if the PPMPs are relatively small in scale. Methods for altering streamline mobilization should be designed to overcome preferential pathways. When the appropriate alterations are made in streamline mobilization methods, the injection-production ratio of strongly preferred pathways should be suitably decreased, and the reverse should occur for weakly preferred pathways.

Key words: waterflooding, preferential petroleum migration pathways, residual oil, streamline mobilization, simulations