一种基于地震约束的井控匹配追踪煤层强反射消除技术

A seismic constraint-based technology for elimination of strong coal seam reflection via well-control and matching pursuit

鄂尔多斯盆地东缘临兴-神府区块太2段致密砂岩气层是该区主力气层,其上下均有煤层发育,煤层屏蔽了含气砂体的反射特征,利用常规地震储层预测方法不易识别。通过对鄂尔多斯盆地东缘临兴-神府区块太2段附近强反射振幅特征的分析,明确其产生机理,提出了一种基于地震约束的井控匹配追踪煤层强反射消除技术,即利用井旁地震道提取合理的煤层反射匹配波形,通过改进的匹配追踪算法动态调整匹配子波控制参数,获取煤层反射特征之后再从原始地震中将煤层强反射去除,突出砂岩反射特征。通过理论模型、合成记录及实际地震剖面进行了效果验证,消除煤层屏蔽的地震剖面目标砂体得以突出,反演预测结果与已钻井砂岩厚度吻合度较高。

The Linxing-Shenfu block is located in the eastern margin of Ordos basin.The Tai-2tight sandstone is the main gas productive reservoir in this block.Because the reflectance signature of gas sand is sheltered by the coal seam developed above and beneath the Tai-2formation,it is difficult to identify the gas layer using the conventional seismic reservoir prediction methods.We proposed a seismic constraint-based technology for elimination of strong coal seam reflection via well-control and matching pursuit on the basis of analyzing the strong reflection amplitude characteristics of the Linxing-Shenfu block in the eastern margin of Ordos basin and identifying its genetic mechanism.This technology extracts the reasonable matched waveform of coal seam using well-side seismic traces,then dynamically adjusts the matching wavelet control parameters with the improved matching pursuit algorithm,and eliminates strong coal seam reflection from original seismic after obtaining the reflectance signature to highlight the reflectance signature of tight sandstone.The feasibility of this method is verified through numerical modelling,synthetic seismogram and the actual seismic profile,the target sand body is highlighted through eliminating the sheltering of coal seam,and the prediction results are in good agreement with the thickness of drilled sandstone.