基于正演模拟和地震分频分析的三角洲薄砂体储层预测——以北部湾盆地海中凹陷涠洲组为例

Delta thin sand reservoir prediction based on forward modeling and seismic frequency division analysis:Case study of Weizhou Formation in the Haizhong Sag of Beibuwan Basin

涠洲组是北部湾盆地海中凹陷的主要储集层,砂体的精细刻画研究对于该区域储层预测有着重要意义。涠洲组储层具有厚度薄、连续性差的特点,原始地震资料主频偏低,常规的薄砂体识别技术在该区应用效果较差。在正演模拟基础上,结合研究区实际钻井数据,利用分频分析方法对海中凹陷涠洲组三角洲前缘砂体开展精细刻画。研究表明:研究区目的层砂体顶界面为波谷,底界面为波峰;地震波振幅和能量与砂体厚度呈正相关;随着频率的提高,砂体的纵向分辨率逐渐增强。对比实际钻遇砂体在原始数据体和分频数据体同一剖面响应情况表明,分频数据体与原始数据体相比,对不同厚度的砂体识别优势明显。利用不同分频数据体对涠洲组三段三角洲前缘砂体进行精细刻画,结果符合三角洲前缘扇体展布规律,识别效果较好。

Weizhou Formation is the main reservoir in Haizhong Sag of Beibuwan Basin.The study of fine characterization of sand body is of great significance to the reservoir prediction in this region.Weizhou Formation reservoir is characterized by small thickness and poor continuity as well as low main frequency seismic data,which incapacitates the use of conventional thin sand recognition technology.This paper presents the fine characterization of sand body in delta front at Weizhou Formation in Haizhong Sag with frequency division analysis method been adopted which is based on forward modeling technique and actual drilling data in the studied area.The results show that the top and bottom interface of the sand body target layer is trough and peak,respectively.The amplitude and energy of seismic waves are positively correlated with the thickness of the sand body.The longitudinal resolution of the sand body gradually increases with the increase of frequency.The comparison between original data body and the frequency division data body of the response of the actual drill sand body in the same profile indicates that the latter has significant advantages in identifying sand bodies of different thicknesses.Based on various frequency division data bodies,the sand bodies of delta front of the third member of Weizhou Formation are delicately depicted,and the results are in line with the distribution law of the delta front fan.