Abstract: Many oil fields in the Bohai Oilfield are currently in the stage of high water cut and low recovery. Thus, it is urgent to conduct in-depth research on the potential of these oil fields to maintain stable production. After 20 years of directional well development, Bohai B Oilfield has developed a set of layers with combined production and strong injection, resulting in severe interlayer interference and difficulties in tapping the potential of the remaining oil. Owing to the limited resolution of existing seismic data, it is not possible to identify the reservoir structure inside the braided river composite sand body, including the vertical and horizontal distribution of the interlayer and thin sand body. Therefore, directional well development is currently mainly used. Here, the seismic signal harmonic frequency enhancement technology is proposed, which directly uses the fundamental component of seismic data to predict harmonic and subharmonic information, and then adds it to the original seismic data to expand the high- and low-frequency seismic information, achieving the purpose of frequency enhancement. This method overcomes the limitations of traditional convolutional models, eliminating the need of well information and to estimate seismic wavelets and assume sparse stratigraphic reflection coefficients, thereby reducing the human subjective factors. The research results, verified through dynamic and static information, showed that the seismic signal harmonic frequency enhancement technology can effectively and finely identify the internal structure of braided river sand bodies, help to transform directional wells into horizontal wells for development, avoid interlayer interference, and promote efficient extraction of the remaining oil.