中国煤层气盆地地质特征与资源前景

Geological features and resource potentials of coalbed methane basins in China

中国大陆含煤盆地集中分布在塔里木-华北板块、华南板块及准噶尔-兴安活动带的构造活动相对稳定的陆块或地块上,形成时代主要为石炭—二叠纪、晚三叠世—早白垩世和第三纪。依据所处大地构造域的位置及沉积构造特征,大体分为板内克拉通型与陆内断陷、坳陷型。含煤盆地中形成煤层气藏受下列条件控制:(1 )古气候、古植物、古地理、古构造以及沉积环境控制了煤的形成、分布及品质;(2 )构造变形直接控制了盆地的整体封存条件,影响了盆地中煤的埋深及煤储层的渗滤性;(3)煤岩变质程度一是影响生气量,二是影响煤岩的渗滤性;(4)封盖层和水动力条件决定煤层气藏的保存状态。经测算,中国大陆煤层气资源丰富,有2 0×1 0 1 2 m3

Coal basins in Chinese mainland are mainly distributed in Tarim-North China plate, South China plate and the relatively stable landmasses and land blocks in Junggar-Xing'an active belt, and have mainly been formed in Permo-Carboniferous, Late Triassic-Early Cretaceous and Tertiary. They can be divided into intraplate cratonic basins and intracontinental rift-depression basins according to their locations in tectonic domain and sedimentary structural features. Reservoiring of coalbed methane in coal basins have been controlled by the following factors: (1) formation, distribution and quality of coals have been controlled by palaeoclimate, fossil plant, palaeogeography, palaeostructure and depositional environment; (2) tectonic deformation has controlled directly the entire sealing conditions of the basins and influenced the burial depth of coal beds and filtration properties of coal reservoirs; (3) degree of metamorphism has influenced both the amount of coalbed methane generated from coal and the filtration properties of coal beds; (4) sealing and hydrodynamic conditions would have determined the preservation of coalbed methane reservoirs. The prospective coalbed methane resources in China have been estimated to be 20 TCM (trillion cubic meters).