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哈萨克斯坦滨里海盆地东缘上石炭统KT-Ⅰ油层组主要发育局限海台地—开阔海台地碳酸盐沉积,间夹蒸发岩层。由于区域性白云石化作用,KT-Ⅰ油层组中白云岩广泛分布,为主要油气储集层。研究表明,白云岩中白云石为泥晶、粉晶或细晶,半自形—他形;略富钙,有序度较低(0.336～0.504);δ18OPDB值在-1.06‰～+2.45‰之间,比石炭纪海水(δ18OPDB值介于-1‰～-2‰之间)偏正;δ13CPDB值在+3.36‰～+5.94‰之间,与石炭纪海水(δ13CPDB值介于+3.1‰～+4.7‰之间)接近;锶同位素值接近石炭纪海水(87Sr/86Sr值在0.7082～0.7088之间);微量元素Mn含量平均为92.57μg/g,Fe含量平均为447.52μg/g,接近被交代的灰岩含量;Na和K含量的平均值分别为198.80μg/g和5.89μg/g,显示交代流体为蒸发海水。上述岩石学和地球化学资料表明,研究区石炭系KT-Ⅰ油层组白云岩具有渗透—回流机理白云岩的特征。
The main developmental limitation of the upper Carboniferous KT-Ⅰ reservoir in the eastern margin of the Caspian Basin in Kazakhstan is the carbonate carbonate deposition and interbedded evaporites in the offshore platform and the open platform. Due to the regional dolomitization, the dolostones in the KT-Ⅰ oil layer are widely distributed and are the major oil and gas reservoirs. The results show that the dolomite in dolomite is of the crystal type, the pink crystal or the fine crystal, the semicircle-shape of him, the slightly rich of calcium, the orderliness is low (0.336-0.504), the δ18OPDB value is -1.06 ‰ ~ + 2.45 ‰ (Δ18CPD value between -1 ‰ ~ -2 ‰); δ13CPDB value is between +3.36 ‰ and +5.94 ‰, and the δ13CPDB value is +3.1 ‰ ~ + 4.7 ‰); the strontium isotope value is close to the Carboniferous seawater (87Sr / 86Sr value between 0.7082 and 0.7088); the average content of trace elements Mn is 92.57μg / g and the average Fe content is 447.52μg / g, The contents of limestone were interpreted; the average values of Na and K were 198.80μg / g and 5.89μg / g, respectively, indicating that the fluid was evaporating seawater. The above petrological and geochemical data show that the Dolomites of the Carboniferous KT-Ⅰ Formation in the study area are characterized by the infiltration-return mechanism dolomite.