五宝场区块侏罗系沙溪庙组二段沉积相特征分析及砂体预测

Sedimentary-facies characteristics and sandbody extension of the Jurassic Shaximiao 2 Member,Wubaochang block,Sichuan Basin

为了掌握五宝场构造侏罗系沙溪庙组二段沉积相及砂体展布情况,在古生物方面不具备对沉积相进行描述的条件下,通过颜色、岩石学结构、沉积构造、测井相标志等岩石学信息来归纳五宝场侏罗系沙溪庙组沉积相标志;对比相标志与实钻井,从筛选有利微相砂体敏感参数着手,通过优选地震属性,利用三维空间雕刻快速识别岩性变化特征,确定主要砂体边界;在伽马不能完全区分砂泥岩条件下开展泥质含量反演,选V_(sh)=25%作为砂泥岩分界线开展岩石敏感参数分析。结果表明:(1)沙溪庙组沉积为曲流河、曲流河—三角洲,有利微相是边滩、水下分流河道及河口坝,五宝场沙二段的主要储层位于沙二1亚段底部,属于特低孔低渗储层,非均质性强;(2)水下分流河道及河口坝是该区最有利的砂体发育微相;(3)人工干预下的砂体自动雕刻结果显示沙二段1号、2号、8号砂体厚度及空间展布与实钻井较为符合,并展示出1号砂体最具开发潜力。

To be fully aware of both sedimentary-facies characteristics and sandbody extension of the Jurassic Shaximiao 2 Member in Wubaochang block,the facies biomarkers in Shaximiao Formation were summed up according to petrological data such as color,texture,depositional architecture,and logging sign.And then,with selecting sensitive parameters in favorable microfacies sandbody as the beginning,a few variations in lithology were identified through 3D space depicting and by means of optimizing seismic attributes after comparing the biomarkers with those from actual drilling.Moreover,the principal boundary was ascertained for the sandbody.Finally,taking V_(sh)=25%as the boundary line between sandstone and mudstone,an inversion of shale content was conducted in certain circumstance that both sandstone and mudstone could not be distinguished via gamma rays,and the sensitive parameters were further analyzed.Results show that(1)for Shaximiao Formation with meandering river,meandering river and delta as the fundamental depositional facies,the favorable microfacies cover point bar,underwater distributary channel and mouth bar.And the principle reservoirs of Shaximiao 2 Member in Wubaochang block are mostly found at the bottom of the first Shaximiao 2 submember,which are featured by extra-low porosity and low permeability,and strong heterogeneity;(2)both underwater distributary channel and mouth bar should be the most favorable microfacies for sandbody extension;and(3)with manual help,the automatic depicting illustrates that both thickness and spatial distribution of No.1,No.2,and No.8 sandbodies in Shaximiao 2 Member are roughly consistent with those from drilling practice,just representing No.1 sandbody as the most development prospective.