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运用石油地质学与煤成气地质学等研究方法,分析了鲁西南地区煤成气盖层类型及其分布特征。研究表明,鲁西南地区除发育较好的煤成气烃源岩、储集层外,盖层保存也较完整,具备了该地区良好的煤成气成藏条件。在各凹陷区内,石炭—二叠系保存完整,其煤层上覆的泥质岩分布广泛,且多含有机质,厚度100～400m,其中包括一套对煤成气封闭能力最佳的杂色铝土质泥岩层(俗称“B层铝土”),厚10～30m;古近系也发育了多套以泥质岩为主的沉积,泥质岩总厚度达1000m以上,这些泥质岩大多为暗色,富集有机质。这些形成于不同时期的煤系地层上覆泥岩层共同构成了本区较好的区域性盖层。尤其在成武凹陷、鱼台凹陷和大汶口凹陷发育的古近系化学蒸发岩类——石膏、岩盐,是该地区煤成气最重要的区域盖层。
Using the methods of petroleum geology and geology of coal-formed gas, the types and distribution of coalbed gas cap rocks in the southwestern Shandong Province are analyzed. The study shows that the southwestern Shandong area is well preserved except for well-developed coal-derived gas source rocks and reservoirs, and possesses favorable coal-forming gas accumulation conditions in the area. Within each depression, the Permian-Permian system is well-preserved. The overlying mudstone in the coal seam is widely distributed and contains many organic matter with a thickness of 100-400 m, including a set of variegated gas with the best sealing capacity for coal-to-gas Bauxite mudstone (commonly known as “B-layer bauxite”), with a thickness of 10-30 m. Paleogene also developed sets of sediments dominated by argillaceous rocks with a total thickness of over 1,000 m. These argillaceous Rock mostly dark, rich in organic matter. These mudstone strata overlying the coal measures strata formed in different periods together constitute a better regional cap rock in this area. Paleogene chemical evaporites-gypsum and rock salt developed especially in Chengwu sag, Yutai sag and Dawenkou sag are the most important regional cap rocks of coal-forming gas in this area.