Layer Q Absorption Attenuation And Inverse Q Filtering Methods Research And Application

During the propagation of seismic waves in subsurface media,due to the influence of the viscoelasticity and heterogeneity of the subsurface media,the seismic wave energy is attenuated and the phase is distorted.This ultimately results in a significant reduction in resolution and signal-to-noise ratio of the seismic data.Adding difficulty to interpretation of seismic data and reservoir prediction.Layer absorption attenuation can be quantitatively described by the quality factor(Q).Since the quality factor is closely related to the internal structural characteristics of the medium and fluid properties such as saturation,porosity,and permeability of the medium,so it is very sensitive to oil and gas.On the one hand,the relatively accurate estimate of Q can provide useful and reliable reference information for well location selection,oil and gas detection,reservoir prediction,and so on.On the other hand,the quality factor is the basis of inverse Q filtering high-resolution processing.It can effectively compensate seismic wave amplitude attenuation,widen the data frequency band,and correct phase distortion by performing inverse Q filtering on seismic data.,thereby improving the seismic data resolution and signal-to-noise ratio.Finally,it provides more accurate information for high-precision tomography,thin layer identification,inversion of geophysical properties,and reservoir prediction.In this paper,based on the theory of absorption and attenuation,the quality factor and inverse Q filtering methods are studied and applied in detail.The improvement of the method to improve the stability of the quality factor and the adaptability of the inverse Q filtering method are improved.Provides detailed interpretation of seismic data and oil and gas reservoir prediction services.Its main research content includes the following four parts:1 ? Research on seismic attenuation and attenuation model.Based on the absorption attenuation theory of seismic waves,quantitative description of absorption attenuation parameters and comparison of absorption attenuation models provide the theoretical basis for subsequent Q value analysis and inverse Q filtering research.2?Analysis of quality factor extraction method.How to extract clean seismic wavelets from seismic records is a major problem faced in estimating Q values based on reflective seismic records.When using the frequency domain method to obtain the Q value from the reflection seismic records,the time-window analysis is needed to intercept the seismic wavelet,so that the intercepted wavelet is easily affected by noise and thin layer tuning,resulting in the Q value obtained in the frequency domain not accurate.In this paper,we combine improve the generalized S-transform with centroid frequency shift method and estimate the Q value from the time-frequency domain.This can accurately determine the time-domain position and frequency domain components of the wavelet and effectively overcome the effects of noise and thin-layer tuning.Through model tests,the layered Q values are obtained from the VSP synthetic seismic records and reflection seismic records respectively.The stability of Q value extraction methods in several frequency domains and time-frequency domains is compared and analyzed.The Q value extraction based on the improved generalized S-transform has strong anti-noise ability and the method is stable.3?Research on single-step inverse Q filter Based on equivalent weighted model.At present,the most common inverse Q filtering method is inverse Q filtering method based on wave field continuation.If this method is used to perform layer-by-layer wave field continuation inverse Q filtering based on the layered Q value model,it will amplify the high frequency noise background of seismic recording,reducing the seismic signal to noise ratio.The layered Q value estimated from VSP records and reflection seismic records can be used as an important basis for hydrocarbon prediction,but applying the layered Q value model to inverse Q filtering is not suitable.Therefore,equivalent Q values are extracted from reflection seismic records and applied to inverse Q filtering based on wave field continuation to perform single-step inverse Q filtering from the surface to the target horizon in order to effectively weaken the Q model factor.Enhancing the inverse Q filter compensation effect and stability.4?Research on variable gain-limited inverse Q filtering method.Stabilized inverse Q filter is currently the most commonly used and stable inverse Q filtering method.This method not only overcomes the numerical instability problem,but also compensates the seismic wave energy attenuation while correcting the phase distortion of the seismic wavelet.However,this method also has its limitations.When applying this method to inverse Q filtering,the stability factor needs to be set by the data processor's own experience.When the stability factor is not set properly,it will not be able to effectively compensate for deep amplitude attenuation or cannot effectively suppress high frequency environment noise.In this paper,based on stabilized inverse Q filter method,an inverse Q filter method with variable gain limit is proposed.This method sets the gain limit and the stability factor as parameters that change with time and the Q value,so that the gain control is more stable and effective.At the same time can also make up for the lack of stability factor method.Seismic data high-resolution processing is used to provide interpretation of seismic data and prediction of oil and gas reservoirs.High-resolution processing of seismic data before seismic data attributes extraction or inversion can often obtain better attribute profiles or inversion results.At the end of the paper,the variable gain-limited inverse Q filtering method was applied to the actual data to perform high-resolution processing on the seismic data.The results show that: based on the seismic data after variable gain-limited inverse Q filtering,the better attribute profile and wave impedance inversion profiles are obtained.From the reverse,the practicality and stability of the variable gain-limited inverse Q filtering method are proved.A good logging-seismic correspondence also verifies that the high-resolution seismic data obtained by this method is true and reliable.