国内外低阶煤煤层气储层特征对比研究

Study on characteristics comparison of low rank coal coalbed methane reservoirs at home and abroad

中国低阶煤煤层气资源丰富,但勘探和认识程度较低,煤层气成藏条件、煤储层特征和资源潜力等方面研究不足。首先分析了中国低阶煤分布特点和煤层气成因,基于二连盆地、海拉尔盆地、准东地区、吐哈盆地与美国粉河盆地和澳大利亚苏拉特盆地的煤层气地质资料,探讨了国内外盆地地质构造演化,对比分析了国内外盆地煤阶和煤岩组成、含气量、孔隙度、渗透率和水文地质条件等特征,指出了国内外低阶煤盆地在煤层气含量构成、储层物性条件及水文地质条件等方面的差异,并全方面地阐明了国内外低阶煤盆地含气量差异性的原因。研究结果表明:国内外低阶煤盆地地质构造特征和煤岩特征相似,且煤层气主要是次生生物成因气,国内外低阶煤盆地煤层含气量随埋深总体呈现为先增加后降低的趋势;国内低阶煤盆地与粉河盆地含气量介于0~4m^3/t,但是含气量梯度差异大,埋深相同的条件下,国内低阶煤盆地煤岩含气量低于粉河盆地和苏拉特盆地的含气量。水文地质条件是影响低阶煤煤层气含气量差异的最为重要的因素之一,国内低阶煤盆地水文地质条件差,导致煤层含气量低,粉河盆地和苏拉特盆地水文地质条件好,则含气量高。国内外低阶煤盆地渗透率差异大;国内低阶煤盆地渗透性差,一般小于1.0×10^-3μm^2,粉河盆地和苏拉特盆地渗透性好,要比国内低阶煤盆地高1~2个数量级,导致了国内低阶煤盆地与美国粉河盆地和澳大利亚苏拉特盆地在低阶煤煤储层特征方面的巨大差异。

China’s low rank coalbed methane resources are abundant,but the degree of exploration and understanding is low,and the research on coalbed methane accumulation conditions,coal reservoir characteristics and resource potential is insufficient.Based on CBM geological data from the Erlian Basin,Hailar Basin,Zhundong Area,Tuha Basin,Powder River Basin in the United States and the Surat Basin in Australia,this paper first analyzed the distribution characteristics of low rank coal and the origin of CBM in China.It then discussed the characteristics of the geological structure of evolution and analyzed the characteristics of coal rank,composition of coal,gas content,porosity,permeability and hydro-geological conditions.The differences of CBM content,reservoir property and hydro-geological conditions in the low coal rank basins were pointed out,and the reasons for the differences in the gas content between domestic and foreign basins were expounded.The results show that the geological and structural characteristics of the low coal rank basins in China are similar to those in foreign countries,and CBM is mainly secondary biogenic gas.The gas content both at home and abroad increases first and then decreases as the burial depth increases.The gas content of the low coal rank basins in China and the Powder River Basin is between 0~4 m 3/t,but the gas content of in the low coal rank basins is lower than that in the Powder River Basin and the Surat basin in Australia under the same buried depth.The hydro-geological condition of low coal rank CBM gas content difference is one of the most important factors,and the poor hydro-geological conditions in China causes the low coal bed gas content.But the hydro-geological conditions of the Powder River Basin and the Surat Basinare good,so the gas content is high.The permeability of basins varies greatly from country to country.The permeability of domestic basins is poor,generally less than 1.0×10^-3μm^2.The permeability of the Powder River Basin and the Surat Basin is good,and the permeability is 1~2 orders of magnitude higher than that of domestic low coal rank basins.Therefore,there is a great difference in low rank coalbed methane resources between the domestic basin and the Powder River Basin in the United States and the Surat basin in Australia.