CHOOSING THE BEST 3D SEISMIC DATASET FOR RESERVOIR INTERPRETATION : A CASE STUDY IN TUNU SHALLOW ZONE, MAHAKAM PSC, INDONESIA

摘要

Tunu is a giant field delivering 1100 MMscf of gas and 23000 barrels of condensate per day. To support the field's development campaigns, two 3D seismic surveys were performed. In 1995, a survey was acquired over the South-West area of the Tunu field (TUNU95-3D), which underwent reprocessing in 2009 and then in 2011 with newer algorithms. The latest acquisition dedicated to the shallow zone was completed and processed in 2010 in the Central Tunu area (CT3D). The two surveys have an overlapping area. The objectives of this study were to compare the dataset quality of TUNU95-3D 2009 reprocessing, TUNU95-3D 2011 reprocessing, and CT3D original processing to choose the best dataset for reservoir interpretation and to give constructive input for future acquisition programs. The study was carried out on the Tunu Shallow Zone interval (approx. 600-2500 meters TVDSS). The first step was to analyze datasets quality using quantitative QC parameters: amplitude consistency, signal frequency, noise attenuation, sub-stacks consistency, and well-to-seismic tie. The following step was to compare the gas reservoir's amplitude response on different datasets. This study suggested that better amplitude consistency and less footprints are observed in CT3D. Signal frequency is slightly higher on TUNU95-3D 2009, but can be also associated with a higher noise level. The consistency of sub-stacks in TUNU95-3D 2011 and CT3D has been improved, as a result of the application of traces interpolation to TUNU95-3D 2011 and a denser CT3D acquisition geometry. All datasets give comparable well-to-seismic ties correlation. TUNU95-3D 2011 shows quality enhancement and better shallow reservoir images compared to TUNU95-3D 2009. Nevertheless, with minimum level of noise and footprints, CT3D provides better details on estimating the reservoir's size and shape. Trade-off between TUNU95-3D 2011 reprocessing parameters and CT3D acquisition geometry should be considered when planning future 3D seismic acquisition programs to improve reservoir imaging while ensuring cost-effectiveness.