Slope of Seismic Spectral as a New Initiative of Hydrocarbon Indicator to Unlock Remaining Gas Potential in Very Shallow Interval of Tunu Field at Mahakam Delta

Abstract

Amplitude Versus Offset (AVO) methodology is massively used in the development of Tunu Shallow Zone (600-1500 m TVDSS), with high success ratio. However, when it comes to very shallow zone (<600 m TVDSS), the methodology is not working properly since the seismic gather data is limited and has poor quality. Therefore, application of new methodology is essential to unlock the remaining potential of gas accumulation in the particular interval.

Slope of Seismic Spectral approach is based on seismic signal behavior which tends to lose its high frequency component when passing through gas reservoir. Through decomposing the seismic signal into frequency spectrums, the Intercept and Gradient values of the spectrum on each seismic samples can be calculated. These parameters then transformed into Gas Probability data through the Probability Density Function, which indicates high probable gas occurrence. This result has been tested in the existing wells and will be applied for future wells planning.