摘要
通过显微岩石矿物学分析、扫描电镜与能谱分析、阴极发光分析等确定了伴随川西坳陷中侏罗统沙溪庙组砂岩孔隙流体演化形成的自生矿物类型与产出关系，利用包裹体温度分析、同位素地质温度分析等确定了主要自生矿物的形成时期，主要利用电子探针微区成分分析技术测定了不同阶段形成的自生矿物的化学组成，并运用同位素分析、地层水分析、粘土矿物X-射线衍射分析等技术进一步获得了孔隙流体的演化特征。沙溪庙组砂岩孔隙流体早期富镁、富铁、偏碱性，随着埋深的增加和烃类的进入等逐渐向偏酸性演化，在转化过程中形成了绿泥石、石英、方解石、高岭石等矿物。自生绿泥石消耗了镁离子和铁离子，钠长石的溶蚀提供了钠离子，烃类注入提供了酸性流体，导致孔隙流体最终演化为现今富钠、富钙、偏酸性的CaCl型地层水特征。溶蚀作用改善了储层的储集性，自生绿泥石孔隙衬垫保护了原生孔隙，有利于形成有利储层。
Abstract
Water-rock-hydrocarbon interactions in the Middle Jurassic Shaximiao Formation sandstones, Western Sichuan, were studied to determine the relationship between authigenic mineral types and hydrocarbon generation through analyses of petrographic data, and scanning electron microscopy and cathode luminescence results.Formation timing of major authigenic minerals was also determined with analyses of inclusion temperature and isotope geo-temperature.Electron microprobe was employed to measure the chemical compositions of the minerals of different forming ages.Isotope analyses and formation water analyses were combined with X-ray diffraction to describe the evolving features of pore fluids of the formation.The result shows that the pore fluid in the Shaximiao Formation was originally characterized by high contents of Mg and Fe, and high pH value.As burial depth increased and hydrocarbon entered, the fluid gradually turned acid and formed minerals such as chlorite, quartz, calcite, kaolinite, and etc, during the process.With authigenic chlorite consuming Mg, and Fe, feldspar providing Na and the charging of hydrocarbon providing acidic fluids, the pore fluids finally turned into this CaCl type low-pH formation water with high content of Na and Ca.It should be noted that there are two factors that were favorable for the formation of good reservoirs:dissolution improved storage capacity of reservoirs and authgenic chlorite formed pore rim and helped preserving primary pores during the diagenetic process.
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