Evaluation of Continuous Wavelet Transform (CWT) Attribute in Analysis of Gas Reservoir Distribution on Talang Akar Reservoir in “QDR” Field of Northwest Java Basin

Abstract

The presence of seismic data as a non-stationary signal is a challenge to be processed with good resolution. Frequency value that change with increasing time make processing in the time domain no longer able to be used optimally, so that a tool is needed to be able to change the domain into the frequency domain. Spectral decomposition with continuous wavelet transform (CWT) method is one of the tools that can be used. The window width used by the CWT method can be applied flexibly with wavelets contained in seismic data and become superior compared to the short time fourier transform (STFT) method. The “QDR” research location in the Talang Akar Formation has a reservoir with a target zone in the form of thin layers (below the thickness of tuning). The purpose of this study was to evaluate how well the CWT method was in mapping the distribution of gas reservoirs at the study areas. The wavelet used in the CWT analysis is a selected Mexican Hat wavelet from two other wavelets (Morlet and Gaussian). The interpretation stage is done by combining CWT maps with log data and TAF 3 and TAF3.2 structural maps. The presence of a gas reservoir can be seen in the CWT section for a frequency of 60 Hz after being validated with log data for the QDR-02 and QDR-04 wells. The frequency value will affect the thickness of the reservoir, the thicker the frequency value will be lower. The distribution of amplitude values for some frequency values at the study location tends to be randomly distributed. So that the CWT method is not good enough to map the distribution of the reservoir in the “QDR” field.