Abstract:

The tectonic setting that develops shale in China is complex. Located respectively in the northwestern, northern and southern China, Tarim, North China and South China plates are relatively limited while their geological activities are relatively strong. They impact each other and independently controls the tectonic movements and sedimentary environment. Furthermore, the three plates have been influenced greatly by the peripheral plates since Mesozoic. Tectonicsedimentary setting of the plates are very different. For example, South China plate is dominated by marine facies while North China plate is by continental facies. Shales in South China plate developed earlier than that in North China plate. South China plate was principally uplifted to make mountains while North China plate principally subsided to create new basins in Mesozoic and Cenozoic vertically. Also, evolution difference exists latitudinally between Tarim plate and North China plate. The distribution of shales in China is mainly controlled by plate characteristics and the mutual matching between the tectonic and sedimentation since plates and their movements caused migration of subsidence deposition centers in different periods. This kind of migrations have happened for four times respectively in all of the three plates since Paleozoic, i.e., migrating westwards in early Paleozoic in marine settings, migrating away the plate convergence center in Late Paleozoic in transitional environments, migrating eastwards in Mesozoic in continental and transitional settings, and migrating westward in Cenozoic in continental environments. As a result, potential shale and shale gas concentrate in middle China with great alternation of deposition and distinguish migration of distribution. Original geological conditions for shale gas of early Paleozoic in South China are excellent, but gas shales are highly or over matured and strongly reformed. The distribution of favorable areas for potential shales are restricted by tectonic and sedimentary conditions, even the mutual matching of each other. The transition shales are the most potential target, which are always interbedded frequently by sandstones, coal series and limestones with extensive distribution, large total thickness and moderate maturation of organic matter. Continental shales from Mesozoic and Cenozoic in North China plate are controlled by the basin structure, which are the main areas for shale oil exploration. Shale gas exploration and exploitation should be carried out according to their own geological properties and conditions.

Key words: Subsidence and deposition, Sedimentary migration, Potential shales, Distribution regularity, China