An Improved Hilbert-Huang Transform And Its Application In Reservoir Prediction

Along with the improvement of the degree of exploration, The object of oil and gas exploration is becoming more and more complex. Conventional data interpretation and reservoir prediction techniques are difficult to meet the needs of exploration and development. Seismic instantaneous attributes (such as instantaneous frequency, instantaneous amplitude, instantaneous phase and so on) can reflect the geometric shape and physical characteristics of the reservoir. These instantaneous attributes have been widely used to identify the reservoir effectively. However, affected by the data base, algorithm accuracy and other factors, the reliability of seismic attribute parameters is not satisfactory. The main reason is that the seismic signal is a kind of non-linear and non-stationary signal. The traditional methods used in signal processing are mostly based on the method of stationary and linear signal processing, therefore, these traditional methods are not effective, and it is difficult to accurately reflect the formation information.Hilbert-Huang transform is a new method for dealing with non-linear and non-stationary data. The results obtained from this method can better reflect the characteristics of seismic signal itself, cause its time-frequency resolution greatly improved. But, there are several problems of the conventional HHT method in reservoir prediction in the field of application, such as mode mixing, endpoint effects and instantaneous frequency. These problems will have a serious impact on the seismic instantaneous attributes, causing the distortion and dislocation of the instantaneous attributes section, bringing a great interference to the explanations.Based on this, this thesis makes a comprehensive analysis of the reasons and results of mode mixing, endpoint effects and instantaneous frequency, and a deeply research of the previous research results. This thesis proposes a CEEMD method based on AR model prediction, combining with the NHT method, and developing a complete set of improved HHT method. The validity, accuracy and resolution of the proposed method are verified, it is proved that the method can effectively suppress the influence of the error of the mode mixing, the end effect and the instantaneous frequency in the instantaneous attributes of the non-stationary seismic signal.This thesis has got the following main points:(1)The CEEMD method based on the AR model can effectively restrain the mode mixing and the end effect problem in the conventional EMD method, the NHT method can significantly reduce the problem of instantaneous frequency error of conventional Hilbert transform in HHT.The resolution of the improved method is higher than nomal method.(2)By using improved method forward analysis of layered model and wedge model, It gets a conclusion of the relationship between seismic instantaneous attributes and reservoir geometry:The seismic signal instantaneous amplitude has a higher lateral resolution, it can accurately describe the formation and continuity of strata; The instantaneous frequency can reflect the longitudinal change of formation velocity; The instantaneous phase can accurately locate the upper and lower interface of the formation. According to the instantaneous parameters of seismic signal profile of the actual field data analysis, it gets a conclusion of the relationship between seismic instantaneous attributes and reservoir physical property:The seismic signal instantaneous amplitude attribute can accurately describe the development of sand body, it can reflect the difference of eservoir thickness and porosity. The instantaneous frequency attribute can reflect the thickness of the reservoir and the nature of the fluid. The instantaneous phase property can reflect the lateral continuity of the reservoir. Oil gas enrichment areas often have strong amplitude, low frequency and phase local anomalies.(3)Using instantaneous attribute analysis of synthetic seismic record with well logging data, this thesis studied the application of the seismic signal instantaneous attributes in the reservoir, and came to the conclusion:Through the combination of instantaneous amplitude and instantaneous frequency characteristics, can well reflect the formation of porosity, shale content and velocity variation in the longitudinal direction, distinguish between sandstone and mudstone. By using the characteristics of low frequency and strong amplitude, the reservoir can be effectively identified. Instantaneous phase properties can describe the change of the physical properties. The rapid and substantial reversal of instantaneous phase polarity on the reservoir interface, shows that this layer is Oil gas enrichment area. The instantaneous slope can accurately locate the geometric features of the boundary, thickness and depth of the reservoir. Combined with seismic, logging and geological data of multi-attribute comprehensive interpretation of the work area, can be more accurate and effective for the identification and prediction of the reservoir.This thesis makes the following innovations in the research process:(1)This thesis proposed a CEEMD method based on AR model prediction, combining with the NHT method, and developing a complete set of improved HHT method. It is proved that the method can effectively suppress the influence of the error of the mode mixing, the end effect and the instantaneous frequency in the instantaneous attributes of the non-stationary seismic signal.(2)This thesis developed the application of improved HHT method in reservoir prediction. Through the example analysis and the forward model, it gets a conclusion of the relation between instantaneous seismic attributes and reservoir geometry and properties. Combined with seismic, logging and geological data of multi-attribute comprehensive interpretation of the work area, can be more accurate and effective for the identification and prediction of the reservoir.In summary, this thesis developed a complete set of improved HHT method, using this method extract the instantaneous attributes of seismic signals. Then researched the relationship between these parameters and the geometrical and physical characteristics of the reservoir, In the end, the method is applied to reservoir prediction effectively by combining seismic, well logging and geological data with the instantaneous seismic attributes. In the end, by combining seismic, well logging and geological data with the instantaneous seismic attributes, effectively applied the method to reservoir prediction.