Presenter: Paula Ascaryani
Date: 2016/12/01
Abstract
A high-amplitude anomaly in seismic signal, i.e. direct hydrocarbon indicator (DHI), may also occur as the result of interference between the top and the bottom of thin bed. This phenomenon is widely defined as tuning effect. The main problem is how to interpret which events correspond to tuning effect or purely hydrocarbon anomaly. Based on reflective properties, a thin bed may be conveniently defined as one whose thickness is less than about λ/8 or λ/4, where λ is predominant wavelength. Interference as the result of tuning effect could be confirmed by the shape of seismic wavelet, the relation of the bed thickness to the seismic wavelet, and the relation of reflection coefficient with its polarization. To analyze the presence of tuning thickness, some previous studies emphasized different methods such as amplitude tuning curve and frequency tuning curve analysis. Interference usually leads misinterpretation whether it is a product of DHI or geometry changes. To minimize misconception in interpreting seismic responses, therefore, phase rotation by 270 0 and transfer function method are used to resolve the interference and distinguish where the top and bottom is. From modeling study of North Poland’s high amplitude anomaly, we could rotate the zero phase wavelet to 270 0 and estimate the zero crossing between two interfaces. The results are used to develop criteria for interpretation. Furthermore, it is used to define the transfer function and remove the high-amplitude anomalies caused by the constructive interference between the reflected signal from the top and bottom of the thinning stratum.
Reference
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