双相介质理论检测页岩裂缝及其油气

Detection of shale fractures and oil/gas by biphasic medium theory

尝试用双相介质BISQ理论,在叠后地震数据上计算以频率为自变量的瞬时频散谱和瞬时吸收谱,用瞬时谱的频散和衰减信息检测页岩裂缝及油气。用迭代优化方法设计频宽为2Hz的25个分频算子,用分频算子对地震数据分频,用复数道分析技术对所有分频道进行"三瞬"计算,集合成瞬时振幅谱、瞬时频率谱、瞬时相位谱,用这3个瞬时谱计算瞬时频散谱和瞬时吸收谱。计算结果表明:在瞬时吸收谱的低频段可见到强吸收被弱吸收封闭的异常特征,在瞬时频散谱上伴有频散突变异常特征,两种异常共同构成检测页岩裂缝及油气的标志。用瞬时频散谱和瞬时吸收谱的衰减和频散的异常特征对8口已知井页岩储层的检测结果与钻井吻合。基于双相介质BISQ理论的瞬时频散谱和瞬时吸收谱可预测油气分布范围,提供钻探目标。

Using the biphasic medium BISQ theory,this paper tries to calculate the instantaneous frequency dispersion spectrum and the absorption spectrum taking frequency as the independent variable based on the post-stacked seismic data and to detect the shale fractures and the oil and gas via spectrum frequency dispersion and attenuation information on the instantaneous spectrum.By using the iterative optimization method,25 frequency division operators （whose bandwidth is 2 Hz） are designed,the frequency division is done to the seismic record using the frequency division operators,and tri-instant processing is conducted for all frequency division traces using the complex trace analytic method,which are then combined into instantaneous amplitude spectrum,instantaneous frequency spectrum and instantaneous phase spectrum.Then,calculation is done with these three instantaneous spectra to get the instantaneous spectral dispersion and absorption spectra.The calculatiori result has the following indications.First of all,in the low frequency of the transient absorption spectra,abnormal characteristics can be seen when the strong absorption is sealed by the weak absorption.Second,the instantaneous frequency dispersion spectrum is associated with the dispersion mutation.The above two anomalies jointly become the key signs in terms of detecting the shale fractures and the oil and gas.The test result of the shale reservoirs of 8 known wells by using the dispersion and attenuation anomalies of the instantaneous frequency dispersion spectrum and the absorption spectrum accords with the exploratory drilling result.So the instantaneous frequency dispersion spectrum and the absorption spectrum based on the biphasic medium BISQ theory can predict gas and oil distribution and locate drilling targets.