Longitudinal small-scale residual oil accurate potential tapping method for ultra-low permeability reservoir

The invention provides a longitudinal small-scale residual oil accurate potential tapping method for an ultra-low permeability reservoir, which comprises the following steps of: S1, determining a strong water washing layer section and a residual oil enrichment section of a production layer according to an oil well residual oil test result; s2, active oil displacement liquid is injected into strong water washing layer sections above and below the remaining oil enrichment section; s3, closing the well and diffusing; s4, windowing and sidetracking an ultra-short radius horizontal well in the remaining oil enrichment section along the minimum horizontal principal stress; s5, multi-cluster perforation is conducted in the horizontal section of the horizontal well; s6, multi-seam fracturing is conducted in the horizontal section of the horizontal well; and S7, oil well pumping production. According to the method, the ultra-short radius sidetrack drilling horizontal well is drilled on the remaining oil enrichment sec