致密河道砂体精细刻画及富气区预测技术——以川中北部地区中侏罗统沙溪庙组为例

Fine characterization of tight channels and prediction of gas-rich areas:Case study of Middle Jurassic Shaximiao Formation in central and northern Sichuan Basin

川中北部地区中侏罗统沙溪庙组发育三角洲—河流沉积体系,纵向上发育多期河道砂组,叠置规律复杂,优质储层和富气区分布规律不清。采用“沉积相—物性—含气性”的研究思路,首先明确沙溪庙组砂岩优质储层具有“顶谷底峰”的反射特征;然后厘定23期河道发育期次和边界。结果表明:河道砂组主要由北东向南西条带状展布,河道宽度在100~4500 m之间;纵横波速度比小于1.68时沙二段河道砂组具有较高的含气概率,富气储层主要分布在河道砂体的边滩部位。研究成果形成了致密河道砂体精细刻画及富气区预测技术流程,为川中北部地区沙溪庙组致密气藏的规模增储和效益上产提供了重要的技术支撑。

The Shaximiao Formation in central and northern Sichuan is developing delta-river deposition system,with multiple river sand groups in the longitudinal development.This study adopts the idea of“sedimentation-physical-gas-bearing”.Firstly,the high-quality reservoir of the sandstone in the Shaximiao Formation has the reflection characteristics of the“peak bottom valley”;the river sand group is mainly displayed from the north to south and west.The width of the river is between 100-4500 m;it is believed that the vertical and horizontal wave speed ratio is less than 1.68.The layers are mainly distributed on the beach of the river sand body.The research results have formed a detailed portrayal of the dense river sand body and the predictive technical process of the rich area,which provides important technical support for the large-scale storage and benefits of densely hidden in the Shaximiao Formation in central and northern Sichuan.