基于井-震联合的辫状河沉积微相分析

Microfacies analysis of braided river deposits based on seismic-to-well ties： A case study of the Jin-77 well block in the Dongsheng gas field， Ordos Basin

李宏涛

Hongtao LI

为了弄清鄂尔多斯盆地东胜气田杭锦旗锦77井区下石盒子组1段（简称盒1段）层序沉积特征，通过岩心、测井和地震等资料研究岩石相测井曲线响应和地震反射特征，结合不同结构砂体地球物理正演结果，总结了盒1段沉积微相、测井相和地震相三相综合响应模式，划分了下石盒子组及其上、下地层各级层序界面，研究了内部沉积微相特征；利用地球物理属性地层切片技术，井-震结合、互为约束，确定了H1-2沉积微相平面展布。研究结果表明：①根据下石盒子组高频层序格架及砂体分布，将盒1段划分为4个小层。砂体主要分布在H1-1—H1-3小层，每个小层厚15 ~ 20 m。②综合盒1段岩性、沉积构造、沉积相标志、垂向组合和砂体分布特征，认为主要为低可容纳空间、物源供给充分、河道不固定的游荡性辫状河沉积，心滩、河道充填和泛滥平原是最主要的三种沉积微相。主要目的层H1-2小层发育近南北向条带状展布的辫状河道3 ~ 4条，宽度介于1 ~ 8 km，北部河道是心滩微相发育的有利部位。

This study aims to identify the sedimentary characteristics of sequences in the 1st member of the Lower Shihezi Formation （hereafter referred to as the He 1 Member） in the Jin-77 well block within the Hangjinqi area， Dongsheng gas field， Ordos Basin. To this end， we investigate the log responses and seismic reflection signatures of lithofacies in the He 1 Member using data from core observations， well logs， and seismic data. In combination with the geophysical forward modeling results of sand bodies with various architectures， we summarize the comprehensive response patterns of sedimentary microfacies， log facies， and seismic facies of the He 1 Member. Accordingly， the sequence boundaries of the Lower Shihezi Formation and its overlying and underlying strata are delineated and the characteristics of their internal sedimentary microfacies are explored. What’s more， an integration and mutual constraining of well logs and seismic data is applied to determine the planar distribution of the sedimentary microfacies of the H1-2 sublayer using geophysical attribute-based stratal slicing technology. The results indicate the He 1 Member can be divided into four sublayers based on the high-frequency sequence framework and sand body distribution of the Lower Shihezi Formation. Sand bodies in the member are concentrated in the H1-1， H1-2， and H1-3 sublayers， with each sublayer measuring 15 ~ 20 m in thickness. A comprehensive analysis of lithologies， sedimentary structures， sedimentary facies markers， vertical lithologic assemblages， and sand body distribution characteristics reveals that the He 1 Member consists primarily of wandering braided-river deposit with limited storage space， sufficient supply， and unstable channels， and its main sedimentary microfacies include mid-channel bars， channels， and floodplains. The H1-2 sublayer， as the primary target interval， contains three or four nearly SN-trending braided river channels with widths ranging from 1 to 8 km. Among these channels， those in the north are identified as favorable sites for the development of mid-channel bar microfacies.

10.11743/ogg20250107