彬长地区延安组沉积作用对煤层气赋存的影响

Analysis on the influence of deposition of Yan'an Formation in Binchang district on coalbed methane concentration

从基准面变化,沉积相变,煤层厚度变化,煤层顶底板特征方面分析了沉积作用对彬长地区煤层气赋存的影响。研究表明:厚煤层形成于基准面上升旋回的末端,是煤层气形成和富集的首要条件;沉积相对煤层气赋存的影响较为复杂,不同沉积相带和沉积微相对煤层发育控制不同;煤层厚度大,含气量高,易于形成煤层气富集区。煤层顶、底板岩性以泥岩、粉砂岩为主,其中以泥岩为顶、底板的厚煤层为煤层气富集提供有利条件。

The influence of deposition on coalbed methane in Binchang district is discussed by analyzing the characteristics of seam roof and floor,the variation of base level,sedimentary facies and the thickness of coalbed.The results show that thickness coalbed is formed on the top of rising cyclothems,which is the first condition for the coalbed methane formation and enrichment.The influence of coalbed methane enrichment by sedimentary facies is complicated,thus,it is so different in forming coal seam when controlled by varies facies of microfacies.If the coal seam is thicker,the gas content is higher,which can be easily to form rich contained coalbed methane field.The lithology of roof and floor of coal seam are major mudstone and siltstone,in particular,it is a favorable condition for coalbed methane concentration in thick coal seams when mudstone to be the roof and floor rock.