层序与古地貌约束下的地震相分析

Seismic Facies Analysis on the Condition of Sequence and Palaeogeomorphology

针对渤海PL构造区深层古近系钻井少、地震成像差引起的储层预测难点,充分挖掘各种地质和地震信息,摸索出一套快速、有效的储层预测方法。首先通过层序分析恢复湖盆的演化阶段,明确储层发育的主要层位;其次通过制作各层序的时间厚度图来分析古地貌,明确储层可能发育的平面位置;最后在层序和古地貌的约束下进行地震相分析,刻画储层的平面展布。分析显示,PL构造区深层古近系有利储集相带为扇三角洲、碳酸盐岩浅滩和辫状河三角洲。扇三角洲和碳酸盐岩浅滩形成于湖泊初始发育期,前者呈楔形填充型前积反射位于凸起边缘断坡带,后者呈退积型叠瓦状反射位于水下隆起带;辫状河三角洲形成于湖泊萎缩期,呈低角度前积反射分布于凸起边缘斜坡区。

Aiming at reservoir prediction difficulty in the deep Paleogene of Bohai PL structure area due to lack of well data and poor seismic imaging,, the paper probed out a set of fast and effective methods for res- ervoir prediction by fully excavating various geology and seismic information. Firstly, it restored the evo- lution stages of lake filling and specified the potential horizon of the reservoir by sequence analyzing. Sec- ondly, it analyzed the palaeogeomorphology from the time-thickness graph of every sequence and specified plane position of reservoir developing. Lastly, it analyzed seismic facies on the condition of sequence and palaeogeomorphology, and described the plane distribution of reservoir. The results showed that favorable reservoir facies in the study area were fan delta, carbonate bank and braided delta. Fan delta and carbonate bank developed at lake initialing stage, showed wedge-shaped filled progradation reflection located on the slope break near the uplift margin and retrogradational imbricate reflection located on uplift underwater re- spectively. Braided delta developed in the lake dwindling period, showed low-angle progradation reflection located slope along uplift. Study results provide significant reference to the well plan of deep exploration in the PL structure area, and will guide reservoir prediction of similar study area.