基于S变换的吸收衰减技术在含气储层预测中的应用研究

The application of an S transform based absorption and attenuation technique for prediction of gas-bearing reservoir

(中国石油大学(华东)地球科学与技术学院,山东青岛266555)

Wang Xiaojie,School of Geosiciences,China University of Petroleum(East China),Qingdao 266555,China

地层品质因子Q值反映了介质的吸收衰减特性,是检测气藏的重要参数。当研究区地质情况较复杂,存在如火成岩等高阻抗体时,难以区分强振幅是由含气还是高阻抗体引起。首先利用相似背景分离技术对地震资料进行预处理,去除与地层特征无关的信息;然后对叠前地震资料进行S变换,得到S域时频谱,再利用S域谱比法逐道求取频谱比斜率值;最后通过线性回归得到零偏移距地层Q值。该方法充分利用了叠前地震资料含有丰富的地层信息和S变换具有较高的时频分辨率等优点。将该方法应用于实际地震资料提取地层Q值,计算结果表明,在含气区Q值比较低,异常现象明显,在非含气区例如高阻抗体处Q值比较高,无异常现象,从而更真实地反应出地层的吸收特征,提高了含气储层的预测精度。

The formation quality value Q reflects the absorption and attenuation characteristics of medium,which is an important parameter for gas detection.When the geologic conditions are complex,for example,existing high-impedance geologic bodies such as igneous rock,it is difficult to distinguish the strong amplitude caused by gas or high-impedance geologic bodies.In order to solve the problem,firstly,pre-processing is carried out on seismic data by using the similar background separation technique to remove the information irrelevant to stratigraphic characteristics. Then,time-frequency spectrum in S domain is obtained by applying the S transform on pre-stack seismic data,combined with spectral ratio method in S domain,the slope of spectral ratio.Finally,by linear regression we can obtain the Q value of zero-offset seismic data.This method makes full use of the advantages of the pre-stack seismic data containing more information than the post-stack seismic data and high time-frequency resolution of the S transform.Moreover,the method was applied to extract the Q value of actual seismic data.The results show that Q values in the gas-bearing zone are relatively low and anomalies are obvious;on the contrary,in the non-gas-bearing zone such as high-impedance geologic bodies,Q values are relatively high,and there is no anomaly.Thus,the technique can better reflect the absorption characteristics of formation and improves the prediction accuracy of gas-bearing reservoir.

10.3969/j.issn.1000-1441.2012.01.005