松辽盆地北部浅层气的地震“亮点低频”识别

Seismic "bright spot low frequency" recognition method of shallow gas in North Songliao Basin

松辽盆地北部浅层天然气资源潜力较大。针对这些浅层天然气资源,探索了有效识别和预测方法。首先针对松辽盆地三角洲前缘相带泥包砂地质特征及埋藏浅、层速度低、分辨率高的地震特征,利用高保真三维地震资料沿层振幅属性切片,有效地识别出了河口坝和水下分流河道砂体的强振幅地震反射特征,即砂岩储层的地震"亮点"特征。在有效地预测出河口坝和水下分流河道砂体的基础上,针对浅层砂岩含气以后,气层层速度明显变低、地震反射波频率也明显变低的实际,应用沿层频率属性切片,有效地识别出气层的地震"低频"特征。从而,形成了松辽盆地浅层天然气的地震"亮点低频"识别方法。根据实际钻探验证,预测的符合率高达80%。

The resource potentials of shallow gas in North Songliao Basin are large. Methods to effectively recognize and forecast the above resources have been deeply explored. First of all, for the geological features of mud enwrapping sand, seismic features of shallow buried depth, low formation velocity and high resolution of delta front belt, the strong amplitudes of mouth bar sand and underwater distributary channel sand have been clearly recognized with the help of amplitude attribute slice of high-fidelity 3D seismic data along the formation, i. e. the bright seismic characteristics of sandstone reservoirs. Based on effectively forecast results above, ＂low-frequency＂ seismic characteristic of gas reservoir has been effectively recognized by the above slice, for both the formation velocity of gas reservoir and the frequency of seismic reflection waves become low obviously for shallow gas sandstone. Therefore the recognizing method of seismic ＂Bright spot low frequency＂ of shallow gas in Songliao Basin has been developed. According to the actual drilling facts, the predicted coincident ratio has been proven up to 80% ; this result possesses important significance for speeding up the shallow gas exploration steps and accurate predicting favorite exploration targets in the future.