塔河油田奥陶系碳酸盐岩油藏溶洞发育规律

Development Regularity of Karstic Caverns of Ordovician Carbonate Reservoirs in Tahe Oilfield,Tarim Basin

塔河油田奥陶系碳酸盐岩缝洞型储层为该区最重要的油气生产层段。依据地质岩心(屑)、录井、钻井、测井、地震等多种资料,运用由点到线再到面的方法,探讨了塔河油田奥陶系碳酸盐岩油藏的溶洞发育规律。由区内溶洞充填砂泥岩的伊利石K-Ar同位素定年,得出其形成时间在369.33～451.90Ma,古溶洞的形成时间应该早于该时段或与该时段同时,即加里东中晚期—海西早期。溶洞的发育受控于古地貌,存在三个纵向溶洞带。岩溶水输入方式的不同,使得塔河地区溶洞的平面分布分区性较强。北部区奥陶系鹰山组和一间房组中的岩溶水为面状输入方式,南部有上奥陶统隔水层覆盖的区,鹰山组和一间房组中岩溶水为侧向输入方式,岩溶水的出口位置位于断裂带附近,尤其是断裂带与断裂带相交的部位。塔河油田北部和南部的岩溶水系统基本为一个统一的系统。建立了该区大气淡水岩溶模式。

Ordovician carbonate fissuring/cavernous reservoirs are the important oil pay beds in Tahe Oilfield.Based on the K-Ar isotopic dating for illite from sandstone and mudrock filling in the karstic caverns of the reservoirs,the formation time of cave-fillings is during 369.33-451.90Ma and thus that of the paleocaverns should be earlier than or equal to the 369.33-451.90Ma,which is corresponding to the late Caledonian-early Hercynian periods.There are three vertical cavern zones in Tahe area.Paleocavern development was controlled by paleo-landform.Karstic water input in different ways which resulted in the divisional distribution of caverns in plane in this area.In northern area,the karst water behaved as a planar way of input into the Ordovician Yingshan and Yijianfang strata while in the southern area,the water did as a lateral way of input into the same strata that are covered by impermeable upper Ordovician rocks.Exit of karstic water was located near the fault zone,The karstic water basically belongs to a unified system in the northern and the southern parts of the oilfield.A local model of meteoric karst reservoir is established.