松辽盆地南部含片钠铝石砂岩储层岩石学特征及成因

 针对松辽盆地南部白垩系含片钠铝石砂岩储层,应用岩石学及同位素地球化学的原理和方法,对含片钠铝石砂岩储层的岩石类型、成岩共生序列和片钠铝石的产状及成因进行系统研究。研究结果显示,含片钠铝石砂岩储层的岩石类型以长石砂岩和长石岩屑砂岩为主,成岩共生序列依次为黏土矿物包壳-次生加大长石-次生加大石英、自生微晶石英、自生高岭石-方解石-油气充注-CO₂ 充注-片钠铝石-铁白云石。松辽盆地南部片钠铝石的δ¹³C_PDB 为-0.342%~0.329%,δ¹⁸O_PDB 变化范围为-1.922%~-0.954%,与已证实形成于无机CO₂背景、且同岩浆活动有成因联系的片钠铝石极为相近;而与片钠铝石平衡的CO₂气的碳同位素值为-0.992%~-0.423%,与松辽盆地南部CO₂气藏中CO₂的碳同位素一致,说明松辽盆地南部片钠铝石与气藏中的CO₂具有相同的碳来源,均为幔源-岩浆成因。

Petrology characteristics and the origin of dawsonite-bearing sandstone reservoir in southern Songliao Basin

This paper studies the petrologic characteristics of the dawsonite- bearing sandstone reservoirs of the Cretaceous in southern Songliao Basin,the diagenetic sequence of the dawsonite-bearing sandstone, and the occurrence and the origin of the dawsonite based on the principles and the methods of the petrology and the isotope geochemistry. The petrologic study shows that the dawsonite-bearing sandstones are mainly composed of the arkoses and the feldspathic litharenite. The diagenetic sequence is shown to be the clay coating cementation-secondary feldspar overgrowth-secondary quartz overgrowth, authigenic quartz, kaolinite-calcitehydrocarbon charging-CO₂ charging-dawsonite-ankerite. The analysis of the carbon and oxygen isotope composition indicates that the dawsonite δ¹³C_PDB values range from -0.342% to 0.329%, and δ¹⁸O_PDB values range from -1.922% to -0.954%, as is similar to the proved dawsonite formed in the organic background and related to the magmatic activity. The calculated δ¹³C_PDB values of CO₂ gas in the isotope equilibrium with the dawsonite ranging from -0.992% to -0.423%, are consistent with the δ¹³C_PDB values of the inorganic CO₂ in the southern Songliao Basin. These values indicate that the CO₂ that forms the dawsonite and that from the gas reservoir have the same source, which is the mantle-sourced origin.