Time‐frequency attribute of seismic data using continuous wavelet transform

Abstract

A time-frequency decomposition that can provide higher frequency resolution at lower frequencies and higher time resolution at higher frequencies is desirable for analyzing seismic data. This is because the hydrocarbons in the reservoir are diagnostic at lower frequencies and thin beds can be resolved with enhanced time resolution at higher frequencies. In this paper we present a new method to compute the time-frequency spectrum using wavelet as a window that achieves this objective. Time-frequency spectrum is commonly used to compute various frequency attributes of seismic signal like single frequency, dominant frequency, center frequency and so forth. The conventional approach is to use short time Fourier transform (STFT) to obtain a time-frequency spectrum. Time-frequency resolution in the STFT is limited by the choice of a window length. The proposed time-frequency spectrum using CWT (TFCWT) in this work has the ability to adapt with the frequency content of the signal. The flexibility of not having to choose a window is an advantage of our method. We present two applications of TFCWT to real data sets in this paper. In the first example, we use TFCWT to enhance low frequency shadows caused by hydrocarbon reservoirs. In the second example, we apply the time frequency spectrum in interpreting time slices from a 3D seismic volume in frequency space to identify thin beds below tuning thickness.

Reservoir Fluid Substitution Effect in Heterogeneous Seismic Model

“…In this paper, Tesseral-2D software is used to study the characteristics of fluid substitution in heterogeneous reservoirs [19]. The study shows that after oil-gas Open Journal of Yangtze Gas and Oil substitution occurs in the weak heterogeneous reservoir, the amplitude difference from the reservoir to the bottom of the reservoir will experience a mutation process, which is from a positive maximum to a negative maximum; after oil-water substitution occurs in the weak heterogeneous reservoir, the amplitude difference from the reservoir to the bottom of the reservoir will undergo a mutation process, which is from zero to a positive maximum [20]. According to the sudden change of the amplitude difference between the two fluid substitution Open Journal of Yangtze Gas and Oil processes, the top and bottom of the full gas and water reservoirs can be determined, which is of great significance for identifying the nature of the fluid and we can monitoring the layer of the fluid in the process of gas or water flooding.…”

CF-AIDS: Comprehensive Frequency-Agnostic Intrusion Detection System on In-Vehicle Network

“…This trade-off can be limiting for non-stationary signals such as those in CAN data. To address this, the wavelet transform offers efficient solutions, providing high-frequency resolution at low frequencies and high-time resolution at high frequencies [45]. However, challenges arise regarding coefficient length variation based on wavelet labels and processing multidimensional data simultaneously, especially in deep learning approaches.…”

The estimation of spectra from time‐frequency transforms for use in attenuation studies

“…Although the spectral interference caused by closely spaced reflectors has been the subject of much study (Liner ) and been used to highlight thin bed tuning (Sinha et al . ), it is the aim of this paper to outline a method for accurately estimating the spectrum of a wavelet for use in seismic attenuation studies. In seismic data, it is often the case that strong reflectors may be closely spaced; thus, an analysis of how to estimate the spectrum of a reflection accurately in this scenario is of interest.…”