Research Progress in the Petroleum and Natural Gas Geological Theory of China

AbstractThe Chinese landmass, as a composite region, consists of multiple small continental blocks, such as Sino‐Korea, Yangtze, Tarim, etc., and orogenic belts. Because of its distinctive tectono‐sedimentary evolution, China's oil/gas‐bearing regions differ remarkably from that elsewhere in the world. For instance, in comparison to the Middle East oil/gas‐bearing regions which are characterized by Mesozoic‐Cenozoic marine oil/gas‐bearing beds, early oil and gas discoveries in China are distributed mainly in Mesozoic‐Cenozoic continental sedimentary basins. Generation of oil from terrestrial organic matter, or terrestrial oil generation, and the formation of large oil/gas fields in continental sedimentary basins were previously the major characteristics of petroleum geology of China. However, in the past 20 years, a series of major oil and gas discoveries from marine strata have been made. Marine oil/gas fields in China are mainly distributed in the Tarim, Sichuan, and Ordos basins, which are tectonically stable and covered with Mesozoic‐Cenozoic deposits. In these basins, hydrocarbon‐bearing strata are of old age and the oil/gas fields are commonly deeply‐buried. Cumulatively, 995 oil/gas fields have been found so far, making China the fourth largest oil‐producing country and the sixth largest gas‐producing country in the world. In terms of petroleum and natural gas geology, theories of hydrocarbon generation from continental strata, such as terrestrial oil generation and coal‐generated hydrocarbons, etc., have been established. Significant progress has been made in research on the sequence stratigraphy of continental strata, formation mechanisms of ultra‐deep clastic reservoirs, and hydrocarbon accumulation in the continental subtle reservoir. Regarding research on the marine petroleum geology of China, with respect to the major characteristics, such as deeply‐buried reservoirs, old strata, and multiple phases of transformation, important advances have been made, in areas such as the multiple‐elements of hydrocarbon supply, formation of reservoirs jointly controlled by deposition, tectonic activities, and diagenetic fluid‐rock reactions, and oil/gas reservoirs formed through superimposed multi‐stage hydrocarbon accumulation. As more and more unconventional hydrocarbon resources are discovered, unconventional oil and gas reservoirs are under study by Chinese petroleum geologists, who endeavor to come up with new discoveries on their formation mechanisms.