Publications

Hydrocarbon-bearing sand in the shallow Mahakam delta is classified as gas sand type-III where the amplitude is brightening with offset. In most cases, at shallow intervals where the seismic sensitivity is in the range of fluid identification, the AVO is working well. Anticipating future field development, simultaneous seismic inversion is routinely studied in the Mahakam area with the primary objectives being effective well planning and for refining the geological model. Evaluation of petroelastics crossplots in Impedance and Poisson Ratio domains have shown positive separation of hydrocarbon sand to the shale background. These key parameters are then used as a basis for further output from seismic inversion and are useful for seismic litho-facies classification. After substacks alignment to improve quality and consistency between partial stacks due to un-optimal NMO correction, the initial seismic QC computation over the interval recommended dividing the inversion study to more than one interval in order to stabilize wavelet estimation. Sufficient numbers of shear sonic were also needed to be recomposed for better common wavelet and better low frequency model building. This paper will elaborate the challenges and results of elastic inversion for the shallow Mahakam area, especially at the Sisi-Nubi field. Several iterations have to be performed in order to obtain the best results and laterally variant wavelet has to be deployed in inversion engine to overcome fast lateral changing of seismic characteristics in the surrounding area.