【摘要】 深部热液对碳酸盐岩储层的改造作用正逐渐受到人们的关注,并成为深部碳酸盐岩油气勘探的新方向。通过岩心观察、薄片鉴定、阴极发光实验、扫描电镜分析、地球化学分析及包裹体测温等方法,对塔里木盆地玉北地区奥陶系的热液活动进行了研究。结果表明,该区奥陶系白云岩具有明显硅化且发育溶蚀孔、洞的特征,溶蚀孔、洞中见石英晶簇与白云石等,岩石薄片和扫描电镜下可见具波状消光的白云石、鞍形白云石以及白云石晶间孔中充填的重晶石与黄铁矿等热液矿物。与普通白云岩相比,研究区硅质白云岩的Ce与Eu含量相对较富集,Ba与Zn含量相对较高,而Sr含量相对较低;从碳、氧同位素上看,硅质白云岩δ18OPDB明显偏负和具有较高的n(87Sr)/n(86Sr)值;流体包裹体具有较高的均一温度和盐度。结合研究区区域上发育基底深大断裂构造,认为该区奥陶系深部存在热液活动,并且碳酸盐岩经过热液改造后形成了良好的储集空间,这种改造对奥陶系深部白云岩勘探具有一定的指示意义。更多还原

【Abstract】 The alterations of deep hydrothermal fluids to carbonate reservoirs have gradually drawn much attention,and have become a new field for hydrocarbon exploration of deep carbonate reservoirs.Based on the analyses of cores,thin sections,cathodoluminescence,SEM,geochemistry and inclusion thermometry,the hydrothermal activities of Ordovician in Yubei area of Tarim basin were studied.The results show that silicification and dissolved pores can be observed in the dolomite of Ordovician,and some drusy quartz and dolomite can be found in pores of the dolomite.Dolomite with wavy extinction,saddle dolomite,as well as barite and pyrite filled in intercrystalline pores also can be seen via thin sections and SEM.Compared with ordinary dolomite,the siliceous dolomite contains relatively enriched Ce and Eu,with high content of Ba,Zn and low content of Sr.The carbon and oxygen isotopic composition of the siliceous dolomite is relatively lower and the ratio of n(87Sr) to n(86Sr) is higher than that of the ordinary dolomite,and the homogenization temperature and salinity of fluid inclusions also are relatively high.Combined with the regional basement faults,it is believed that hydrothermal activities exist in Ordovician in this area,and dissolved pores are produced in these events,which means a prospective significance for the exploration of Ordovician deep dolomite.更多还原