Marginal oilfields refer to the development of oilfields with insufficient economic benefits by conventional methods under current economic conditions due to objective reasons (geological reserves, geographical location, development technology, engineering investment and taxation, etc.). In China, after nearly 30 years of large-scale offshore oil exploration and development, a large number of high-quality large and medium oilfields have been proven in offshore areas such as the Bohai Bay, South China Sea, and East China Sea. With the deepening of exploration and development, newly discovered oil fields belong to small marginal oil fields. Generally, the oil or gas reserves are limited, the structure is broken and complicated or they are located in remote areas. It has poor economic benefits with conventional development technology due to low output, large one-time investment in the construction of production platforms and the laying of subsea pipelines, and a long period of capital return. It is not attractive for cooperative development with foreign investors. Offshore marginal oil fields often lose commercial exploitation value due to mismatches in reserves and production with development costs.