Bohai Q oil field is a large-scale river facies sandstone reservoir. After entering the ultra-high water-cut stage, the remaining oil is highly dispersed, the low-efficiency wells are increased. It is difficult to achieve stable production and low-cost development. Based on the analysis of existing development issues and constraints in Bohai Q oil field, low efficiency wells are divided into classes. According to drilling, logging, sealing coring and production data, the plane and longitudinal flooding types and characteristics in the ultra-high water-cut stage have been analyzed and the remaining oil enrichment mode has been summarized as well. At the same time, focusing on the management of low-efficiency wells and high-efficiency residual oil recovery, we have explored a multi-method approach, including the adjustment of injection and mining, the reconstruction and the side drilling. Relevant measures have been successfully applied in Bohai Q oil field. The comprehensive water cut is stable at 93% in the oil field and decline in oil field production has slowed significantly. The achievements and methods provide an effective way for the treatment of low-efficiency wells and high-efficiency recovery in oil field of the same nature during ultra-high water-cut period.