【摘要】 阐明碳酸盐胶结物的形成机制及对储层物性的影响具有重要意义,综合通过岩矿学、地球化学方法,分析了准噶尔盆地车拐斜坡区储层碳酸盐胶结物的赋存特征及形成机制,结果表明:δ¹³C_PDB值为-29.6‰～6.7‰,δ¹⁸O_PDB值为-19.2‰～-12.5‰,跨度较大,说明碳酸盐胶结物形成的物质来源及水岩相互作用的复杂性。δ¹³C_PDB和δ¹⁸O_PDB值分别较典型的海相或湖相的碳酸盐呈正偏移和负偏移,δ¹³C_PDB正偏移主要受到混合热液流体碳同位素分馏和少量沉积碳酸盐溶解的共同作用,δ¹⁸O_PDB值负偏移则可能是大气降水、深部热液等多种流体混合作用和成岩温度升高的影响造成的。车拐斜坡区碳酸盐胶结物的物质来源与有机酸脱羧产生的CO₂、黏土矿物压实排水作用、长石碎屑溶蚀及黏土矿物相互转换释放大量的Ca²⁺、Fe³⁺和Mg²⁺等离子有关,镜下观察发现研究区碳酸盐胶结物交代碎屑颗粒且伴随出现沥青质现象,以粉晶—粗晶形式赋存于排列紧密的碎屑颗粒之间,为成岩晚期产物,对储层物性起破坏作用。更多还原

【Abstract】 It is of great significance to clarify the formation mechanism of carbonate cementation and its influence on reservoir physical properties. By means of petrology and geochemistry, the occurrence characteristics and formation mechanism of carbonate cements in Cegai slope of Junggar Basin are analyzed. The results show that the distribution range of δ¹³ C_PDBvalue is-29.6 ‰～6.7 ‰, that of δ¹⁸ O_PDBvalue is-12.5 ‰～19.2 ‰, and it has a large span. All those indicate the material source of carbonate cementation and the complexity of water-rock interaction. δ¹³ C_PDBvalue has a positive offset with the typical marine or lacustrine phase of carbonate, while δ¹⁸ O_PDBvalue has the negative offset. The positive offset of δ¹³ C_PDBvalue is mainly affected by the carbon isotope fractionation of mixed hydrothermal fluid and the dissolution of a small amount of sedimentary carbonate. The negative deviation of δ¹⁸ O_PDBvalue may be caused by the mixing of various fluids—such as precipitation and deep hydrothermal—and the rise of diagenetic temperature. The material source of carbonate cements in Che-Guai slope is related to the CO₂ produced by the decarboxylation of organic acids, compaction and drainage of clay minerals, the dissolution of feldspar debris and the release of a large amount of plasma like Ca^{2 +}, Fe^{3 +}and Mg^{2 +}by conversion among clay minerals. Under the microscope, it is found that the carbonate cements are metasomatic to detrital particles and accompanied by asphaltene appearance, and appear in the form of crystal powder to macrocrystalline grain among the closely arranged clastic particles, as a product of late diagenetic stage, which destroy the physical properties of reservoirs.更多还原