东濮凹陷文79块沙二下亚段高分辨率层序地层结构模型研究

High-resolution sequence stratigraphy model of Es22 in W79 block,Dongpu depression

通过对东濮凹陷文79块沙二下亚段测井资料分析,综合岩心、地震资料,并引入最大熵谱分析技术,将东濮凹陷文79块沙二下亚段划分为2个长期基准面旋回LSC1-LSC2、6个中期基准面旋回MSC1-MSC6,以及58个短期基准面旋回。应用旋回等时对比技术,选取中期旋回作为对比骨架,建立东濮凹陷文79地区沙二下亚段层序地层格架。同时,对层序格架内沉积相进行分析,确定研究区为分支河体系的曲流河扇沉积,归纳层序格架内砂体发育与展布的特点。结果显示:LSC1为基准面下降半旋回,自下往上A/S(Accommodation/Sediments)比值减小,可容纳空间逐渐减小,河道/漫岸比值增加,砂体连通性变好;LSC2为基准面上升半旋回,自下往上A/S比值增加,可容纳空间逐渐增大,河道/漫岸比值减小,砂体连通性变差。

According to the theory of high-resolution sequence stratigraphy and correlation analysis of cores,logs and seismic data as well as the application of INPEFA technique,long-,middle-and short-term base level cycles in the lower second member of Shahejie formation in Dongpu depression were described in detail.2 long-term,6 middle-term,and 58 short-term base level cycles were identified.Based on the chronostratigraphic correlation of middle-term cycles,sequence stratigraphy framework was estab-lished and used to predict the sedimentary types and its distribution law.This area mainly developed as meandering river fan.The change in vertical facies indicated that the entire LSC1 was formed during a base level falling or A/S（Accommodation/Sediments） decreasing period,which was in fact a semi-cycle of long-term scale,showing that the ratio of channel to overbank was increased from bottom to top;LSC2 was formed during a base level rising or A/S increased period,and the ratio of channel to overbank was decreased from bottom to top.