鄂尔多斯盆地东缘BD区块煤层气富集沉积控制作用及有利区预测

Sedimentary controls of coalbed methane accumulation and prediction of favorable area in the BD area,eastern margin of Ordos Basin

利用钻测井和三维地震资料,运用沉积学和层序地层学理论和方法,分析了鄂尔多斯盆地东缘BD区块煤层气富集的地质背景和沉积控制作用,并结合地球物理技术,预测了煤层气有利区。结果表明:研究区内构造简单,煤层层数多,厚度大,埋深适中,煤储层物性好,煤体破坏弱,封盖能力强,含气量高,地下水矿化度较高,煤层气富集地质条件好;基于层序地层的划分,讨论了煤层气富集的沉积控制作用,提出煤层空间展布受控于层序地层格架,煤储层特征受控于成煤环境,煤层气藏围岩受控于沉积体系。在沉积控气作用分析的基础上,选取BD南三维工区4+5#煤层进行煤层气有利区多信息综合预测。经后续钻井验证,该位置的排采井已见良好效果,是BD区块目前采气量最高的部位。预测范围与实钻结果吻合度较高,为类似煤层气有利区预测提供了相应参考。

Based on the well and 3-D seismic data in BD area of eastern Ordos Basin,combined with the geology theory and method of sedimentology and sequence stratigraphy,the basic geological conditions and sedimentary controls of coalbed methane（CBM）accumulation were analyzed,and the prediction for favorable area of CBM was made based on the geophysical technique.The research results indicate that BD CBM block has good geological conditions with simple structure,moderate burial depth,good physical reservoir,weak destruction,strong save ability,high gas content and high groundwater salinity.The Sedimentary control function of CBM enrichment was discussed on the basis of the sequence stratigraphy division.It can be concluded from the research that the distribution of coal seam is controlled by sequence stratigraphic framework,the characteristic of coal reservoir is controlled by coal-depositional environment,the surrounding rock of CBM reservoir is controlled by sedimentary system.Based on the analysis of sedimentary controlling factor,we predict for CBM rich region in BD south 3dimensional area through multi-source information fusion methods.Verified by subsequent drilling,the wells in this place have good effects,which is currently the highest gas production part in BD block.The multi-source information fusion methods provide reference for foreasting in similar coalbed methane favorable areas,because the scope of prediction and actual drilling results are closely.