层序地层格架中岩溶储层发育的预测模型

Predictive model for karst reservoirs in sequence stratigraphic framework

对露头剖面中不同类型高频层序中岩溶的发育特征进行了研究。在典型钻井中,通过精细的成像测井和常规测井对岩溶发育段进行了识别,对层序内部和界面上、下系统的碳同位素进行了分析,探讨了不同类型层序中和不同级别层序界面下岩溶发育的规律。研究结果表明,在受基准面变化旋回所控制的碳酸盐岩层序内,岩溶储层的有利发育部位应是在不同级别基准面升降过程中能周期性暴露遭受溶蚀的地区。这种地区在一个层序的发育过程中是可以预测的。以塔里木盆地寒武—奥陶系为例,在不同级别的层序中,基准面上升期的地层超覆带、高位期的前积带—顶超削截带及其向陆方向是岩溶发育的有利地区。

The development characteristics of karst in the different kinds of high-frequency sequences from the outcrop sections were studied. The karst horizons were recognized with the FMI and conventional well logs in the typical wells. The stable carbon isotopes in the sequences, above and below sequence boundaries were systematically analyzed. The characteristics of karst developed in the different types of sequences and below the different orders of sequence boundaries were discussed. The multi-stage karst horizons developed below the sequence boundaries were resulted from the periodic exposure of the formation during high frequent fall of sea level. The base level became lower as the scale of the karst horizon got larger in a progradational sequence. The favorable areas for the karst development in a sequence are those places where the periodic exposure occurred with the periodic fall of sea level. Such favorable areas for karst development are predictable. The on-lap zones in the period of base level rising, the top-lap and the progradational zones in the stage of high stand and gradual fall of base level are the favorable areas for the development of karst reservoirs in the Cambrian-Ordovician of Tarim Basin.