Abstract: After more than 50 years of exploration, the Dagang Oilfield faces many challenges such as difficulty in locating wells, difficulty in increasing reserves, difficulty in upgrading reserves, difficulty in producing reserves, and difficulty in enhancing efficient production. With high-quality resources, abundant data, sophisticated equipment and facilities, and great potentials for reserve increase in the Danggang oilfield, valid reserves have been discovered in the surrounding zones by actively dealing with challenges, enlarging potentials and establishing new development models based on new data; efficient reserve increase has been realized by breaking through old ideas and pre-exploring new layers; and new reserve targets have been found by re-recognizing old reservoirs and innovating processes, which make the oilfield active again and provide new ways to increase reserves. It has been proved that these practices are "gold keys" to increasing reserves, and good ways to break through difficulties and keep sustainable and healthy development of mature oilfields.

Key words: economical reserve increase, new block, new layer, new target