Human beings have been exploring, developing, and utilizing oil and gas resources for more than 150 years. The progress of oil and gas exploration can be roughly divided into four stages: oil and gas exploration from seepage situations, trap exploration, exploration by petroleum system theory, and unconventional oil and gas reservoir exploration. Unconventional oil and gas exploration is a breakthrough to conventional oil and gas accumulation, by which a lot of continuously distributed unconventional oil and gas reservoirs have been discovered in the forbidden area where it is impossible to form oil and gas reservoirs according to the classical petroleum geological theory. The unconventional oil and gas reservoir is characterized with extensive and continuous distribution and great potential for resources, but from which the effective capacity should be obtained by special measures. The biggest difference between unconventional and conventional oil and gas reservoirs is that unconventional migration and accumulation are neither dominated by buoyancy nor controlled by traps. At present, unconventional oil and gas exploration has encountered a series of major challenges in practice, including the difficulty in characterizing the differences between unconventional and conventional oil and gas reservoirs, unclear distribution boundary, unclear correlation, and the lack of a unified classification scheme, quantitative criteria, and a joint genetic model. The concept of the whole petroleum system provides new ideas and new theoretical guidance for the exploration and development of conventional and unconventional oil and gas resources under complex geological conditions. The research of the whole petroleum system includes the total factors of hydrocarbon accumulation, the whole process of formation and evolution, the full range of resource distribution, as well as the all-around prediction and evaluation. Based on the academic thought of the whole petroleum system, with the support of the National Basic Research Program of China (973 Program) and other projects, and taking the research of oil and gas thresholds-controlling accumulation as the breakthrough point, the drilling results of 80 762 conventional and unconventional oil and gas reservoirs in 12 237 exploratory wells in 6 representative basins in China (Tarim Basin, Junggar Basin, Sichuan Basin, Ordos Basin, Bohai Bay Basin, and Songliao Basin) are analyzed and compared with those of the conventional and unconventional oil and gas reservoirs found in North America. Further, in combination with the statistical analysis of the differences of 52 926 proven oil and gas reservoirs in 1 186 basins around the world, four achievements have been made in the quantitative evaluation of the whole petroleum system. (1) It has been found that there are three categories and 10 types of oil and gas thresholds in the whole petroleum system, the genetic mechanism and oil and gas control characteristics are revealed, and the research method and discrimination criteria are also put forward. (2) The formation and distribution model of hydrocarbon resources jointly controlled by oil and gas migration and accumulation thresholds is established, and a new method for predicting and evaluating effective resources is proposed. (3) A model of oil and gas reservoir distribution controlled by dynamic field is established, and a new technology for predicting and evaluating favorable accumulation fields and zones is also put forward. (4) A reservoir-controlling model based on the combination of distribution thresholds is established, and a new optimized technology of favorable accumulation zones and drilling targets is developed. The application results of the quantitative evaluation method of the whole petroleum system in the genetic classification of conventional and unconventional oil and gas reservoirs, the prediction of residual resources, and the evaluation of the potential of natural gas hydrate resources around the world show a development direction of the research of the whole petroleum system in the future. © 2022, Editorial Office of ACTA PETROLEI SINICA. All right reserved.
