Tectonic and Hydrocarbon Accumulation Elements Characteristics of the Tethyan Realm in South China

Abstract:The evolution of the global Tethys Sea can be classified into three stages, Proto‐Tethys, Paleo‐Tethys and Neo‐Tethys. The Tethyan realm has distinctive features of zonations and segmentations along north‐south and east‐west, respectively, and has variable richness in oil and gas. The petroleum geological conditions of Tethys are complicated, partly represented by multi‐layer of source and seal rocks, and reservoirs. The hydrocarbon accumulation elements and periods of the Tethyan realm show gradually younger from west to east and north to south. South China is located in the north belt and Yangtze segment of the Tethyan realm, and its polycyclic tectonic movements were governed by the Tethyan and Pacific realms. The blocks in South China rotated clockwise and counter‐clockwise during their drift northward from Gondwana. The belts and segmentations of Tethys in South China are also clear, with six tectonic belts including: Chuxiong‐Sichuan; middle Guizhou‐Hunan‐Hubei; lower Yangtze; Xuefeng‐Jiangnan; Guangxi‐Hunan‐Jiangxi; and Cathaysia. Numerous faults, including compressional, compressional‐shear, extensional, extensional‐shear and shear are well developed in South China. The fault strikes are mainly NE, NW and NS, in which the NE is the dominant direction. Lower, middle and upper hydrocarbon assemblages, respectively corresponding to Proto‐, Paleo‐ and Neo‐Tethys, formed in the Tethyan realm of South China with the lower and middle having excellent hydrocarbon accumulation conditions. An integrated analysis of tectonic evolution, superimposed deformation and later hydrocarbon preservation shows that during the Neo‐Tethyan stage in South China, continental sediments were deposited and experienced intense tectonic deformation, which had resulted in different hydrocarbon pool‐forming features from those of the Neo‐Tethyan realm.