三角洲朵体砂体富集区预测——以莺歌海盆地北部A构造黄流组为例

Sand rich areas prediction in delta lobe:Case study of the Miocene Huangliu Formation in A structure in the north of Yinggehai Basin

莺歌海盆地北部历经60余年的勘探至今尚未实现商业突破,而该区构造—岩性或岩性圈闭评价占比逐渐增多,该类圈闭评价的关键之一是砂体富集区预测。砂体富集区预测是储层分布预测的基础,砂体富集区往往是有利储层发育区,也是钻井的有利部位。但由于海上勘探新区钻井少或没有钻井,难以利用大量钻井岩心和测井资料确定沉积相和储层砂体分布;同时受地震分辨率限制,难以直接在地震资料中开展沉积微相研究,导致对有利砂体富集区预测受限。因此基于海平面变化与沉积体系域划分,在等时地层格架内开展复合朵体识别与沉积期次划分,寻找砂体富集的复合朵体;在富砂复合朵体内,通过朵体地震内幕结构特征、微古地貌分析,预测复合朵体内有利砂体富集区。研究表明,莺北斜坡带北段A构造黄流组发育高位域晚期沉积的三角洲砂体,可识别出5期三角洲复合朵体,其中最后一期朵体为海平面下降时发育的三角洲进积型复合朵体,砂体富集程度最高,预测朵体南北向中部条带为砂体集中发育区。研究成果为三角洲朵体有利储层分布预测、勘探井位部署提供指导。

After more than 60 years of exploration,commercial breakthroughs have not yet been achieved in the northern part of the Yinggehai Basin,and the proportion of structural lithologic or lithologic trap evaluations in this area is gradually increasing.One of the key to evaluating such traps is the prediction of sand rich areas.The prediction of sand rich areas is the foundation of reservoir distribution prediction,and sand rich areas are often favorable areas for reservoir development and also favorable locations for drilling.Sedimentary facies identification and favorable sand body distribution prediction are hard to be achieved with large number of cores and well log data,due to insufficient or no drilling in offshore exploration new areas.Due to the limitation of seismic resolution,it is difficult to directly conduct sedimentary microfacies research with seismic data,resulting in the limited prediction of favorable sand body enriched areas.Based on the analysis of sea level change and sedimentary system tracts division,identification of complex lobes and their sedimentary periods were conducted within the isochronous stratigraphic framework,and sand body enriched lobes were found.By analyzing the seismic internal structural characteristics and micro paleogeomorphology of the sand body enriched complex lobe,the favorable sandstone accumulation areas within the complex lobe were predicted.It has shown that the Huangliu Formation of the A structure in the northern section of the Yingdong Slope of Yinggehai Basin developed delta sand bodies deposited in the late stage of the high system tract,and five stages of delta lobes can be identified.The complex lobe developed in the last stage is a delta progradation complex lobe developed during sea level decline,which has the highest sandstone content among the lobes.It is predicted that the central north-south strip in the lobe is the sandstone concentrated area.The results can provide guidance for predicting the distribution of favorable reservoirs and deploying exploration wells.