白云岩是塔里木盆地深层主要的储层类型,对其成因认识是深层有利储层分布预测的基础,针对塔中1井下奥陶统白云岩开展了详细的岩石学与地球化学研究.结果表明,塔中1井下奥陶统发育泥-粉晶、细晶、粗晶3类白云岩,不同类型白云岩的地化特征具显著差异,其中泥-粉晶白云岩具较低的有序度,其δ18O、87Sr/86Sr比值与该时期的海水相近;粗晶白云岩具明显偏负的δ18O和最高的87Sr/Sr比值;细晶白云岩主要发育在溶蚀孔洞中,具较高的流体包裹体均一温度、较低的87Sr/86Sr比值特征.综合分析认为,泥-粉晶白云岩为准同生期白云石化的结果,粗晶白云岩是在热流体参与下早期白云岩重结晶的产物,细晶白云岩的形成与早二叠世末期的岩浆活动关系密切.%Dolostone is one of the most important reservoir types in Tarim Basin,and the genesis and the key control factors of dolostone are the basis of reservoir prediction.In this paper,we take the Lower Ordovician dolostones in Well Tazhongl as a case study and attempt to unreval their genesis and diagenetic fluids,and detailed petrology and geochemistry analysis were executed on samples of Well TZ1.The results shows that 3 types of dolostones which include mudpowder dolosotone,fine dolostone and coarse dolostone are distinguished.The results of petrology and isotopes of different kinds of dolostones indicate that Lower Ordovician dolostones in Well Tazhongl are characterized by multiple occurrence and multiple diagenetic fluids.Similar δ18O and 87Sr/86Sr ratio between mud-powder dolostone and sea water at that time suggest that this kind of dolostone occurred at penecontemporaneous period and sea water was the main diagenetic fluid.Coarse dolostone has the most minus δ18O and highest 87Sr/86Sr ratio,which indicate that this kind of dolostone probably recrystallized at the involvement of deep hot water with high 87Sr/86Sr ratio.The character of petrology and fluid inclusions of fine dolostone which mainly filled in caves show that fine dolostone occurred at hydrothermal conditions.Furthermore,lower 87Sr/86Sr ratio of cave filling dolostone probably implies that its diagenetic fluids correlated closely with the magmatic activity at the end of Early Permian in Tarim Basin.
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