松辽盆地南部小城子地区下白垩统泉一段辫状河沉积判识标志与分布特征

松辽盆地南部泉头组一段下部的Ⅲ-Ⅴ砂组为坳陷沉降初始阶段的沉积,是重要的农安油层储集体。但其特征复杂,成因不明,严重阻碍了对储层展布特征的认识。以松辽盆地南部小城子地区为例,通过岩心、测井、地震及粒度分析等多角度成因特征的综合分析,得出泉头组一段下部Ⅲ-Ⅴ砂组主要为特殊背景下的近源、坡陡的小型辫状河沉积,并进一步区分出了河道、冲积平原2种沉积亚相及4种沉积微相;建立了松辽盆地南部泉一段辫状河判识的岩石类型组合、岩石结构构造、剖面砂体分布等6点标志;进而根据地震相与沉积相的对应关系,明确了该区泉一段下部Ⅲ-Ⅴ砂组辫状河沉积的时空展布和变化规律。

Determinative marks and distribution characteristics of braided river deposits in 1st section of Quantou Formation of Lower Cretaceous in Xiaochengzi area,southern Songliao Basin

The Ⅲ-Ⅴ sedimentary sand bodies in the lower part of the 1st section of the Quantou Formation in the southern Songliao Basin were deposited at the beginning of depression sedimentation, and they were important for the Nongan oil reservoirs. Complicated characteristics and unclear origin had delayed the study of reservoir distribution. A case study was carried out in the Xiaochengzi area of the southern Songliao Basin. Through analyzing the multiple perspectives of characteristics about cores, well logging data, seismic interpretation, grain size analysis and so on, the results showed that the Ⅲ-Ⅴ sand bodies in the lower part of the 1st section of the Quantou Formation were proximal and small braided river deposits under special background. 2 sedimentary subfacies (river and flood plain) and 4 sedimentary microfacies were further divided. 6 determinative markers such as rock type combination, rock texture and sand body distribution on profile were concluded for the determination of braided river. According to the relationship between seismic and sedimentary facies, the distribution and variation of braided river deposits in the Ⅲ-Ⅴ sand bodies in the lower part of the 1st section of the Quantou Formation were made clear.