Amplitude Versus Frequency (AVF) as an Alternative Method for Detecting Gas Presence in Carbonate Reservoirs: A Case Study of the Baturaja Formation, South Sumatra Basin

Abstract

Accurate characterization of heterogeneous carbonate reservoirs remains challenging because conventional amplitude-based seismic methods may be affected by complex lithology, pore systems, and fractures. This study evaluates the application of Amplitude Versus Frequency (AVF) integrated with Continuous Wavelet Transform (CWT) to identify hydrocarbon-bearing zones in the Baturaja Formation, South Sumatra Basin. The analysis uses 3D Post Stack Time Migration (PSTM) seismic data integrated with well-log, checkshot, and marker data from three wells (B1, N1, and N2). Well-to-seismic tie analysis yielded correlation coefficients of 0.702, 0.638, and 0.805, respectively, confirming reliable seismic–well integration. CWT spectral decomposition was performed over a frequency range of 10–70 Hz, followed by AVF analysis to evaluate frequency-dependent amplitude attenuation. The results show dominant low-frequency anomalies and predominantly negative AVF gradients within the target interval, indicating attenuation of high-frequency seismic energy. These responses are consistent with low water saturation and low gamma-ray values observed in the wells, supporting their interpretation as gas-bearing carbonate reservoir zones. AVF horizon slicing further reveals laterally continuous anomalies concentrated in the eastern to northeastern part of the study area. The results demonstrate that CWT-based AVF provides complementary frequency-dependent information for hydrocarbon identification and reservoir delineation, offering a useful approach for reducing interpretation uncertainty in heterogeneous carbonate reservoirs. To the best of the authors’ knowledge, its application to the Baturaja Formation remains limited, highlighting the contribution of this study to frequency-based carbonate reservoir characterization.