近岸水下扇沉积样式及地震响应特征新认识

New understandings of near-shore subaqueous fan sedimentary styles and its seismic responses

东营凹陷近岸水下扇内幕地震反射特征复杂,圈闭识别困难;并且对地层产状认识不足,导致油藏油水关系出现矛盾。为此,依据水槽沉积模拟实验分析近岸水下扇沉积样式,并通过三维正演模拟明确其地震响应特征。研究发现,多物源近岸水下扇可以划分为扇根、扇中、扇端、扇间4种亚相,内幕存在有规律的微相变化,导致4种亚相存在不同类型的构造及岩性圈闭。不同相带的圈闭具有不同的地震响应特征,因此,建立了沿相带变化的地震响应特征量板以指导不同类型圈闭的识别。此外,正演模拟结果表明,由于扇体高速陷阱导致时间域地震资料中扇根出现上拉现象,地层真实产状存在回倾。该观点能合理解释油藏油水关系,为同类型近岸水下扇油气藏勘探提供借鉴。

The trap identification in Dongying Depression is rather difficult because of complex seismic response characteristics of near-shore subaqueous fan.To solve this problem,we analyze sedimentary styles of glutenite in near-shore subaqueous fan based on a flume simulation experiment,and define seismic response characteristics with 3 Dforward modeling.It is found that multisource near-shore subaqueous fans can be divided into four sub-facies such as root-fan,middle-fan,edgefan,and inter-fan.Microfacies changes of the four sub-facies result in different types of structures and lithologic traps.Different traps correspond to different seismic response characteristics.Therefore,a seismic response-characteristics plate based on facies changes is established for the identification of different traps.In addition,it is found that the consequent deposition along a bedrock surface in the time-domain seismic data is caused by pitfall of high-velo-city of glutenite.The true occurrence of fan bodies is structurally inclined.This viewpoint can reasonably explain the oil-water relationship of reservoirs and provide a reference for the exploration of similar near-shore subaqueous fan reservoirs.