中国潜质页岩形成和分布

我国页岩盆地发育的大地构造背景复杂，板块规模偏小且地质活动性较强，彼此之间相互影响且在中、新生代以来受外缘板块环境影响较大，表现为南海北陆、南早北晚、南升北降等重大差异，在东西方向上，也由于塔里木与华北板块之间的演变差异而出现较大区别。中国页岩的分布主要受控于板块特点及构造、沉积之间的相互匹配，板块及其相互之间的相对运动造成了不同时代沉降沉积中心的迁移变化。塔里木、华北、华南三个板块均发生了四次沉降沉积中心的转移，但总体上表现为早古生代海相时期的由东向西转移、晚古生代海陆交互相时期的背离板块汇聚中心式转移、中生代陆相和海陆交互相时期的由东向西转移、新生代陆相时期的由西向东转移。潜质页岩及页岩气主要发育在中部地区，具有时代交替、南海北陆、东西分异、时空变迁等特点。南方下古生界海相页岩气原始地质条件优越，但有机质热演化程度高且后期改造强，页岩气的有利区分布既受控于构造与沉积条件，也更决定于构造与沉积两者的相互匹配；晚古生代为主的海陆交互相页岩分布范围广、累积厚度大，常与砂岩、煤系及灰岩频繁互层，有机质热演化程度较为适中，是我国页岩气进一步勘探开发的重要目标层系。北方以中新生代陆相为代表的页岩分布受控于盆地结构，是我国页岩油发育的主体区域。针对各套潜质页岩特点，页岩气勘探宜分别考虑。

Deposition and distribution of potential shales in China

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.