一种古沉积期曲流河道演化过程重建方法

A method of reconstructing evolutionary process of meandering channel in Paleo-sedimentary period

为了实现曲流河的过程沉积学研究,在大量曲流河内部结构定量描述研究成果以及现有密集井网资料的基础上,系统总结了一套曲流河道沉积演化过程的恢复方法实现对曲流河道沉积过程恢复.首先利用"初末流线包络线法",完成对点坝的宏观界定和识别,并借鉴以前成熟的曲流定量表征方法,对识别出的点坝逐一进行结构解剖,并使之达到侧积体层次,然后对相邻点坝的同期侧积体进行组合,并对组合好的同期侧积体,按曲流河蛇曲演化的顺序,依次累加叠覆,直至最后一期河道.叠覆的过程,就是再现曲流河沉积演化过程.利用上述方法对吉林油田杨大城子油层组q4-17小层曲流河沉积恢复.结果表明:q4-17小层平面发育有7个点坝,由南至北呈串珠交错展布,其中,Z20井区点坝估算的长度约为668m,宽度约69m,侧积倾角平均为10°,侧积夹层间距约32.8m.沉积期平面上主要发育8期次曲流演化过程,并使砂体侧向有规律地分异.通过对点坝侧积体形成过程的恢复,可以有效指导河流相砂体平面预测,并且为油田布井、调剖等开发方案的调整提供参考.

Based on previous quantitative descriptions of the meanders internal structure and existing dense network data,a set of method was systematically summarized to recover the evolutionary process of meandering river deposition.The specific implementation began with the definition and identification of point bars at a macro level by the method of envelop track of meandering channel.Referring to previous mature methods of meanders quantitative characterization,the identified point bars were dissected separately into lateral accretion bodies.Afterwards,simultaneous lateral accretion bodies of adjacent point bars were combined,and then their assemblages were accumulated and superimposed in turn from early to late according to the evolution rule of meandering river.The superposition process is a representation of the depositional process of meandering river.The meandering rivers from q4-17 thin layer of Yang-dachengzi ore-bearing formation of Jilin Oilfield were studied by the above reconstruction method,and the recovery results show that the thin bed mainly develops 7point bars,moniliform and interlaced from north to south,among which the point bar from Z20 well is about 668 min length,69 min width,10°of lateral accretion inclination on average level,and 32.8mof lateral accretion interlayer spacing.The q4-17 thin layer mainly develops 8periods of meandering evolutionary process in the depositional stage which makes sandbodies in meandering river differentiate regularly along lateral directions.The recovery of point bar lateral accretion body formation process can effectively direct the plane prediction of fluvial sandbodies,and provide references for development programs such as distribution of wells and the adjustment of oil reservoir profile.