塔东寒武系白云岩成因及储集层演化特征

通过岩心观察、薄片鉴定、地球化学分析.研究塔里木盆地东部地区寒武系白云岩岩石学特征和地球化学特征,综合分析白云岩成因及白云石化模式,揭示白云岩储集层演化特征及有利储集层发育机制.寒武系白云岩主要发育于上寒武统突尔沙克塔格组,主要分布在塔东西部的台地边缘带和东部的中缓坡.碳、氧、锶同位素分析和微量元素测试、流体包裹体测温等研究结果显示,研究区泥晶-粉晶白云岩与细晶-粗晶白云岩具有不同的地球化学特征,形成干超盐度、埋藏和高温热液3种白云石化环境,经历了渗透回流白云石化、埋藏白云石化和高温热液白云石化3种白云石化模式的叠加作用.研究区有利于优质储集层形成的白云石化作用叠加方式主要有准同生期渗透回流白云石化+埋藏自云石化、渗透回流白云石化+高温热液白云石化、埋藏白云石化+高温热液白云石化;不利的自云石化作用有单-白云石化和渗透回流白云石化+埋藏白云石化+高温热液白云石化.图14表3参39

Cambrian dolomite origin and reservoir evolution in east Tarim Basin

The petrologic and geochemical characteristics of the Cambrian dolomite are studied through core observation, thin section analysis and geochemical analysis. The evolution and development mechanism of the reservoir are revealed by comprehensive analysis of the origin and dolomitization models. The Cambrian dolomitization is developed in the Upper Cambrian Torsuqtagh Formation and distributed in the marginal zone of platform in the west and middle gentle slope in the east of eastern Tarim. The study on the carbon, oxygen and strontium isotopes, the testing of trace elements and the temperature measuring of fluid inclusions reveal that the micrite-crystal and cryptomere-macrocrystalline dolomites of the region of interest have different geochemical characteristics, were developed in three dolomitization environments including extra salinity, bury and hydrothermal fluid, and experienced the stacking of three dolomitization models including penetration reflux dolomitization, burial dolomitization and hydrothermal fluid dolomitization. The beneficial dolomitization models are penecontemporaneous penetration reflux dolomitization + burial dolomization, penetration reflux dolomitization + hydrothermal fluid dolomitization, and burial dolomitization + hydrothermal dolomitization. The adverse dolomitization models in the dolomite reservoir are simple dolomitization and penetration reflux dolomitization + burial dolomitization + hydrothermal fluid dolomitization.