Risk analysis and play evaluation of marine residual basins in South China

Multiple cycles of hydrocarbon generation, reserve and cap assemblages with sea at the bottom and continent at the top developed in South China. There were mainly 2 sets of marine accumulation assemblages including Sinian-the Lower Paleozoic and the Middle-Upper Paleozoic. On plane map, the study area was divided into 2 accumulation zones (the southern one and the northern one) by the Jiangshao-Shiwandashan Fault. In the northern accumulation zone, 2 sets of accumulation assemblages developed, while in the southern accumulation zone, only the Middle-Upper Paleozoic assemblage existed. The distribution of ancient reservoirs and oil-and-gas shows was controlled by ancient uplifts. Petroleum accumulation experienced over 3 stages of tectonic events, for example, oil generating in Caledonian-Hercynian stages, oil cracking to gas in Indosinian stage, and adjusting and deforming in Yanshanian-Himalayan stages. The present marine reservoirs in South China have distinctive residual features. Their exploration degrees are low, techniques are not mature, and the knowledge about accumulation rules is restricted. The risks are higher for normal petroleum explorations, lower for marine superimposed basin explorations, and the lowest for unconventional shale gas explorations. The marine strata in South China were evaluated and the favorable zones for exploration were pointed out.