APPLICATION OF LITHO-SEISMIC CLASSIFICATION BASED ON SIMULTANEOUS INVERSION RESULTS TO DETECT OFFSHORE BARS: CASE STUDY – SISI MAIN ZONE, SISI-NUBI FIELD OFFSHORE MAHAKAM DELTA

摘要

Simultaneous seismic inversion was performed onrnthe 3D PSDM data covering the Sisi Nubi fieldrnlocated offshore in the Mahakam PSC. Thernclassification of litho-seismic facies was computedrnfrom the inverted P-impedance (IP) and Poisson’srnRatio (PR) cubes in order to predict the probabilitiesrnof various lithologies.rnThe lithology probability cubes provide usefulrninformation to update geological models and tornlocate future wells. Each lithology has distinctivernpetrophysical properties that could be defined usingrnlog data (sonic and density) and predicted fromrnprestack seismic inversion results (IP, or PR cubes).rnIn the shallower zone (less than 3000 m TVDss),rnthe cross plot of P-impedance (IP) and Poisson’srnratio (PR) shows not only a good separation amongrndifferent lithologies such as sands, shale, andrncarbonates, but also between gas- and water-bearingrnsand reservoirs. However in the deeper interval ofrnSisi Main Zone (SMZ), the differentiation betweenrngas- and water-sands is ambiguous especially due tornthe burial effects. Even though detecting the fluidrncontents is challenging in SMZ, the separationrnamong different lithologies like sands, shale, andrncarbonates is still possible and this is importantrninformation for future well planning. The mainrnobjective of this project is to detect the extension ofrnthe offshore bars in the Sisi field Main zone intervalrnby using pseudo Vclay volume calculated from thernlitho-seismic classification. A QC at blind wells wasrndone to validate the results. This study has largelyrnimproved the uncertainties of the sand probabilityrnover SMZ, and shows a good correlation betweenrnsand probability values and sand thickness found atrnthe wells. They have been directly applied torndetermine the targets for the future developmentrnwells.