四川盆地侏罗系沙溪庙组浊沸石特征及油气勘探意义

Laumonite and its significance for petroleum exploration in Jurassic Shaximiao reservoir, Sichuan Basin

岩心观察及野外剖面考察表明,四川盆地的川中、川东北地区沙溪庙组砂岩普遍含浊沸石胶结物,其含量一般为5%～8%,最高可达18%。通过对含浊沸石砂岩进行铸体薄片、电镜扫描、电子探针及有机包裹体等分析,认为浊沸石主要形成于早成岩阶段B期,酸性火山岩岩屑在碱性地层水条件下蚀变并提供Si、Ai、Ca等成分,在砂岩孔隙中形成浊沸石胶结,然后在中成岩阶段A期,凉高山组、大安寨组烃源岩中的有机质脱羧形成大量有机酸,沿着断裂或裂缝向上运移到沙溪庙组河道砂岩中,溶蚀其中的浊沸石胶结物,形成浊沸石次生溶孔。勘探实践表明,现已找到的侏罗系油藏中的油气大部分聚集在浊沸石溶孔中。

Shaximiao Formation sandstone reservoir contains 5%-8% （Max. 18%） laumonite cement. Studies of casting thin sections, SEM, electronic probe and organic inclusion in the reservoir suggest that the laumonite cement was formed mainly in B period of early diagenesis. The acidic igneous grains altered in alkaline formation water, supply Si, Ai, Ca, and caused the laumonite cement in sandstone pores. In A period of late diagenesis, organic matter from Lianggaoshan and Daanzhai Formation source rocks were discarboxylated to organic acid, migrated up along faults or fractures to the channel sand of Shaximiao Formation and eroded the laumonite cement. The laumonite dissolving porosity is generated. Exploration results demonstrate that the hydrocarbon of Jurassic reservoir mainly accumulated in the laumonite dissolved pores.