基于Wigne-Ville分布和短时傅立叶变换时频分布计算地震波衰减梯度

Estimation of Seismic Wave Energy Attenuation Gradient Based on WVD and STFT

地震波在储集层中传播时,伴有能量的剧烈衰减,且频率越高能量衰减越快,因此,通过地震波高频端能量衰减梯度能够灵敏地检测地层中是否有烃类流体存在。短时傅里叶变换的时频分辨率不及Wigne-Ville分布,而Wigne-Ville分布虽有高的时频分辨率但存在交叉项的干扰。应用Wigne-Ville分布和短时傅里叶变换相结合的方法来计算地震信号的时频分布,然后利用高频成分能量分布与对应频率的拟线性关系估算出地震波能量衰减梯度。实际资料表明,基于短时傅立叶变换联合Wigner-Ville分布的能量衰减梯度在储集层预测中有较高的应用价值。

Seismic wave propagation in oil-gas reserw）irs accompanies intense energy attenuation, and the higher the fi＇equency, the faster the energy attenuation. So the energy attenuation gradient can be applied to detecting if hydrocarbons exist in reservoirs. The time-frequen- cy resolution of short-time Fourier transform （STFT） is affected by window size, while Wigner-Ville distribution （WVD） is affected by cross part. This paper computes the time-frequency distribution of seismic signals based on WVD and STFT, and then estimates the seismic wave energy, attenuation gradient using the quasi-linear relationship between the high frequency component energy distribution and the corre- sponding frequency. The case study indicates that this method has a higher value of application in reservoir predielion.