To enhance the extraction efficiency of oil fields and identify new potential for oil field succession, a comprehensive study on the potential exploitation of the Heidimiao oil reservoir in the Gu121 well area was conducted. Based on a re-evaluation of the geological characteristics of the developed blocks, the Heidimiao oil reservoir in the Gu121 well area was selected for reservoir prediction, showing a trend of extension along the source direction. This study integrated research on the oil field structure, reservoir, well-seismic combination, attribute inversion prediction, and economic benefit evaluation. From the production dynamics, the oil-water interface on the west side of the well area reaches −1130 m. According to the hydrocarbon accumulation rules, the eastern fault block of the fault is structurally elevated from west to east, with the accumulation formed by near east-west channels and north-south faults. From the extracted inversion plane attributes of the Heidimiao sub-layer, the HII5 sub-layer shows a large-scale development of sand bodies, generally distributed in a banded pattern, with sand body thickness mainly concentrated between 4–8 m. Comprehensive studies indicate that the Heidimiao layer in the northwest and southeast directions of the Gu121 well area, extending along the east-west channels, has potential for expansion. The application of well-seismic combination to delineate reservoir distribution, combined with dynamic and static analysis to locate remaining oil-rich areas, and the use of straight-line combined well network types to exploit remaining oil, can effectively slow down the decline rate of the oil field and increase its profitability.