Publications

Seismic quality in North Madura platform is strongly influenced by the lateral velocity contrast due to complex intra-reef carbonate features within Wonocolo level and severely observed in time domain seismic dataset. Its presence has long been recognized as a serious problem in data processing and interpretation. Therefore, generation of the depth structural map becomes very challenging as it is not only describing the geological model but also contribute to resources assessment. This paper is intended to compare four methods to obtain an ideal depth structure maps under a strong push-down effect. The methods are: 1) Single function, 2) 3D paleoreconstruction, 3) 3D grid velocity model, and 4) Full Waveform Inversion (FWI) combine with QPSDM. Single function method resulted depth structure maps with unsolved push-down effect artifact, as it is not respecting lateral variation of velocity. 3D paleo-reconstruction was conducted in order to get depth structure map by flattening on Maximum Flooding Surface. However, this method is only valid at the deposition of Tuban formation. 3D grid velocity model was performed by injecting low velocity in the intra-reef carbonate of Wonocolo in order to produce depth structure maps without pushdown effect. Problem arose when applying low velocity to all intra-reef carbonate without honoring the heterogeneity of it and introduces interpreter’s subjectivity. To overcome the limitation of those methods, 3D seismic reprocessing using combination of FWI and Q-PSDM method was performed. The method succeeded to generate more reliable depth structure maps which honor the heterogeneity of velocity in each geological setting with minimum interpreter intervention. Combination of FWI and Q-PSDM was able to correct the push-down effect to minimum and give higher confidence on the bulk volume of the structure which eventually resulted in better resource estimation.