Remaining Oil Distribution Characteristics and Potential Tapping Strategies for Integral Reservoirs at Different Waterflooding Stages.

Insufficient or ambiguous understanding of remaining oil distributions at different waterflooding stages probably leads to low efficiency or ineffective injection water circulation at the late stage of waterflooding in integral reservoirs. In our work, numerical simulation of waterflooding of typical formation in integral reservoirs was performed, and the remaining oil distributions at varied waterflooding stages were characterized by the "Four-points and Five-types" classification method, and then corresponding potential tapping strategies were proposed to finally enhance recovery at the waterflooding late stage. Results show that the remaining oil type is enriched oil at the stage of low-medium-high water cut (60%-80%), and potential tapping strategies are a subdivision of the stratum series, adjustment of the injection-production well network, and infilling and improving the well network; at the stage of a super-high water cut (90%), high water-consuming oil (HWC oil) and super-high water-consuming oil (SHWC oil) are the main remaining oil types, and potential tapping strategies are changing the direction of the flow field, adjusting the injection-production well pattern, and optimizing the well network; at the late stage of a super-high water cut (≥95%) with high water consumption, the remaining oil is mainly the super-high water-consuming one, and potential tapping strategies are flow line adjustments + chemical flooding, gas flooding, etc.; and at the late super-high water-cut stage (≥97%) with HWC oil, most remaining oil is SHWC oil, followed by HWC oil, with the total of enriched oil and relatively enriched oil accounting for 5%, and potential tapping strategies are in-depth profile control + displacement. At the late super-high water-cut stage (≥98%) with SHWC oil, most remaining oil is SHWC oil and the total of other types accounts for less than 1/5, and potential tapping strategies are nonhomogeneous composite flooding + well network adjustments after an oil wall. Implementation results reveal that the potential tapping strategy is effective for exploiting the remaining oil in integral reservoirs, which would provide guidance for potential tapping of the remaining oil.