| Summary: | Low-frequency passive seismic (LFPS), discussed in recent years, has emphasized a strong correlation between the spectral properties and the presence of hydrocarbon reservoirs. While the theoretical background supporting this phenomenon is still debated, its application has been popular in Indonesia and exposes broad possibilities for exploration. In this study, we conducted a survey at an oil field in Central Java, Indonesia, investigating the case of using this technique as a direct hydrocarbon indicator (DHI). In spatial and temporal measurements, we examined the hydrocarbon-related energy above the reservoir boundary based on several attributes of passive seismic recordings: polarization, power spectral density (PSD), and vertical-to-horizontal spectral ratio (VHSR). We address some issues: (1) the anomalies are not always vertically polarized, so the use of VHSR is unlikely to be reliable; and (2) the anomalies are getting amplified during days, so in anomalies mapping, normalizing the amplification requires calibration. Regardless, LFPS is still applicable in quantifying hydrocarbon-related energy. We recommend using PSD as a primary spectral attribute for DHI. In addition, it is also critical to synchronize the measurements at different sites to obtain an unbiased quantification of hydrocarbon-related energy.
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