我国页岩气富集类型及资源特点

根据页岩气聚集的机理条件和中、美页岩气地质条件的相似性对比结果认为：中国页岩气富集地质条件优越，具有与美国大致相同的页岩气资源前景及开发潜力。中国含气页岩具有高有机质丰度、高有机质热演化程度及高后期改造程度等“三高”特点，页岩气具有海陆相共存、沉积分区控制以及分布多样复杂等特点。以间接型和直接型页岩气划分方法为基础并结合中国区域地质特点，将中国的页岩气富集模式划分为南方型、北方型及西北型等3种，分别具有以下特点：①以扬子地台为核心的南方型页岩气聚集条件有利并以改造较为严重的海相古生界海相页岩聚气为主，具有单层厚度大、发育层位多、分布面积广、热演化程度高、后期改造强等特点；②以华北地台为主体的北方型页岩气具有古-中-新生界页岩发育齐全、沉积迁移特征明显、薄互层变化频率高、沉积相带分隔明显等特点；③以塔里木地台为基础的西北型页岩气储层以中-古生界为主，沉积类型多、有机碳丰度高、有机质热演化程度相对较低。结论认为：中国页岩气可采资源量约为26×10₁₂ m₃，大致与美国的28×10₁₂ m₃相当。

Accumulation types and resources characteristics of shale gas in China

Through comparison analysis of shale gas accumulation conditions and the similarity of geological conditions in the U.S.A and China, this study concluded that both countries have similar geological conditions favorable for shale gas accumulation and have approximate shale gas resource reserves and development potentials. In general, the gas-bearing shale layers in China possess high TOC, high thermal maturity and a high degree of later reformation. Shale gas accumulations are characterized by terrestrial facies deposit, controlled by sedimentation region division, and various and complicated distribution. Shale gas accumulations can be classified into direct and indirect types, and also can be divided into three types as southern type, northern type and north-western type according to the regional geologic conditions in China. The southern type of shale gas, distributed around the Yangtze plate, is mostly accumulated in the Paleozoic marine shale which experienced intensive structural reformation, and is featured by a large thickness of a single layer, multiple developed layers, a wide distribution area, high thermal maturity, and a high degree of later reformation, etc. The northern type of shale gas, distributed in the north China plate, is mostly accumulated in the groups from Paleozoic via Mesozoic to Neozoic, and is characterized by sedimentary migration, a high frequency of thin interbedded layers, and an obvious division between sedimental facies. The north-western type of shale gas, distributed around the Tarim Plate, is accumulated in the groups from Paleozoic to Mesozoic, and has the characteristics of various types of sedimentation, high TOC, and relatively low thermal maturity. It is concluded that the recoverable shale gas resources is predicated to be about 26 tcm in China, close to 28 tcm of that in the U.S.A.