Challenges and solutions in the application of the whole petroleum system theory

The concept of the whole petroleum system (WPS)proposed and the ordered distribution pattern of conventional and unconventional hydrocarbon reservoirs established serve to unify petroleum geology theories, providing an entirely new theory and methods for guiding hydrocarbon exploration and exploitation. However, when applied to complex geological conditions such as those of superimposed basins in China, the WPS theory, originally formulated under general geological conditions, encounters several challenges. First, due to the lack of objective indices for quantitative characterization and the disruptions caused by late-stage tectonic activities, the idenfitication or prediction of buoyancy-driven hydrocarbon accumulation depth (BHAD) is hard in practice. Second, the formation and distribution of hydrocarbon reservoirs are governed by the combined effects of multiple driving forces, multiple stages, and diverse elements, complicating the identification of the hydrocarbon accumulation dynamics and reservoir types. Third, reservoirs such as those of the carbonate and clastic types exhibit varying wettability and interfacial tension properties, which lead to difficulties in predicting the maximum burial depth of hydrocarbon reservoirs and favorable hydrocarbon enrichment areas under actual geological conditions. Last, during the evolution of the WPS, hydrocarbon migration and accumulation are controlled by multiple factors including dynamic force types, capillary pressure differences between source rocks and reservoirs, hydrocarbon fluid properties, and tectonic activities. Consequently, establishing the hydrocarbon enrichment model of the WPS remains a challenge. To address these challenges, we explore various methods and technologies based on data from globally discovered hydrocarbon reservoirs, including their physical properties, productivity variations, and wettability. Accordingly, we develop new methods for identifying the BHAD, assessing hydrocarbon accumulation dynamics, and predicting the maximum burial depth of oil and gas resources. Furthermore, we determine the hydrocarbon enrichment model of the WPS. The results of this study offer new approaches to improve, develop, and apply the WPS theory under complex geological conditions.