Abstract: The Jiyang depression, being explored for over 50 years, has entered a stage of subtle reservoir exploration. During the 12th Five-Year Plan, exploration targets became even more complicated. To enhance efficiencies of explorations, new geologic models were built to tap potentials of mature zones, by assessing available resources, improving quality of seismic data and highlighting bottlenecks in geologic studies on shallow and mid-deep formations. In this way, new breakthroughs were achieved in existing oilfields through reinterpretation of available data. To explore areas with bottleneck challenges, marginal reservoirs, Neogene fluvial channel sandstone reservoirs, deep formations and other potential targets, new models for early oil and gas migration and accumulation, multilevel sequential uncomfortable traps, description of fluvial channel sandstone reservoirs, structure of complex faulting zones, and assessment of sandy conglomerates on steep slopes were established for fine exploration. In addition to the discovery of the Qingnan oilfield and the Sanhecun oilfield, 14 key breakthroughs were made in preliminary exploration. In total, 12 potential reservoirs with reserves of tens of millions of tons each were identified. Explorations during the 12th Five-Year Plan show that there are great potentials in highly explored areas, which can be efficiently through innovation.

Key words: reservoir description, subtle reservoir, early oil and gas migration and accumulation, multilevel sequential, geologic model, reverse-time migration, Jiyang depression