拉布达林盆地上库力组火山碎屑岩成岩作用特征

Diagenetic Characteristics of Pyroclastic Rocks in Shangkuli Formation,Labudalin Basin

通过薄片、铸体薄片及扫描电镜等技术手段,确定了拉布达林盆地上库力组岩石类型、成岩作用类型和孔隙类型。岩石类型主要包括火山角砾岩、熔结凝灰岩、晶屑-岩屑凝灰岩、玻屑凝灰岩、多屑凝灰岩和沉凝灰岩等。成岩作用类型有压实作用、蚀变作用、脱玻化作用、自生作用、溶解溶蚀作用和胶结作用等。拉布达林盆地上库力组火山碎屑岩所处的成岩阶段主要为早成岩阶段B期及中成岩阶段A期。孔隙类型主要为剩余粒间孔、填隙物内孔和溶蚀孔等,区内火山碎屑岩为中低孔特低渗型储层。机械压实作用和自生铁白云石及自生高岭石沉淀作用降低了储层物性,而绿泥石包壳和微晶石英包壳的胶结自生作用以及溶蚀溶解作用改善了储层物性。

Through thin-section, casting thin-section and scanning electron microscope, the authors ascertain rock types, diagenesis patterns and pore types of Shangkuli Formation. It was considered that rock types consist of vocanic breccia, ignimbrite, crystal-debris tuff,vitric tuff,multi-clastic tuff and sendimentary tuff etc. And diagenesis includes compaction, alteration, devitrification, authigenesis, erosion-dissolution and cementation etc. While diagenetic phases of Shangkuli Formation in Labudalin basin are divided into B stage of early diagenetic phase and A stage of middle diagnetic phase. And pore types are mainly comprised by intergranular pore, filling inner pore and solution pore, and so on. Pyroclastic rocks belong to reservoir beds with medium-low porosity and extra low permeability. It was thought that mechanical compaction, authigenic ankerite and precipitation of authigenic kaolinite reduced physical properties of the reservoir, while authigenesis of chlorite and microcrystalline quartz coatings and erosion-dissolution may improve them.