Characteristics of tectonic evolution in China since Neogene and the distribution pattern of natural gas
WANG Ting-bin (Exploration and Production Research Institute, Sinopec, Beijing 100083, China)
China is located in a triangular zone surrounded by three major plates. It is one of the tectonic active areas since the Neogene in the world. The major characteristics related to reservoir and preservation of hydrocarbons are as follows. (1) In western China, the reactivation of paleo-orogenic belts resulted in the formation of Chinese style foreland basins and overthrust structures in their leading edges. The drastic subsidence and rapid sedimentation since the Neogene would not only accelerate the evolution process of organic matters in the deeply buried source rocks, but also create favorable geologic conditions for the formation of biogenic gas reservoirs. (2) Multiple tectono-thermal events and high heat-flow values have promoted the rapid evolution of organic matters and reservoir forming process, as well as the formation of abnormally high pressures and mud diapers and other specific structures. (3) Multistaged tectonic movements would be favorable to the rapid migration and episodic charging and storing of hydrocarbons; they would also provide the sites favorable for super-late and rapid reservoir formation. (4) Major faults, magmatism and activity of hot fluid at depths would not only promote the formation of organic-origin oil and gas reservoirs, but also accelerate the major expulsion and accumulation of inorganic-origin gas. The characteristics of tectonic evolution since the Neogene have the most extensive and profound effects in western China where the foreland basins have become one of our important gas accumulation province. It is also the final period of formation or finalized period of gas reservoirs in those basins. About one hundred small faulted basins within the orogenic belts become our new domain of oil and gas exploration. In central China, all the gas fields in Sichuan basin have been finally formed and finalized during this period; and in Ordos basin, natural gas has been further enriched in Jingbian-Wushenqi area during this period. In eastern China, a series of large- and medium-sized oil and gas fields have been formed in Bohai sea area, and gas reservoirs of various origins have also been formed in other basins or depressions. In the offshore area, the Neogene tectonic movements have not only promoted the rapid formation of organic-origin gas reservoirs, but also accelerated the formation of inorganic-origin gas reservoirs, which constitute the reservoir model with unique characteristics. From our studies, we conclude that owing to the specific geological conditions in China since the Neogene and the characteristics of natural gas being very easy to migrate, accumulate and dissipate, the formation and finalization of most gas fields have been controlled by the history of tectonic evolution since the Neogene. The history of tectonic evolution would be of momentous significance to the distribution pattern of natural gas in China.
【Fund】： 国家“十五”科技攻关课题“我国油气工业上游发展战略研究”( 2 0 0 1BA60 5A 1)
【CateGory Index】： P618.13
【CateGory Index】： P618.13