Publications

A seismic reprocessing project was initiated by ExxonMobil Cepu Limited (EMCL) to improve seismic data quality at the Banyu Urip field to aid the evaluation of potential upside hydrocarbon volumes in the primary carbonate and secondary clastic reservoirs. The existing seismic was hampered by a combination of extensive shallow gas attenuation and non-uniform seismic data coverage that was only partially mitigated by previous state-of-the-art reprocessing in 2007. The 2017 reprocessing involved applying improved pre-stack processing and Q (attenuation factor) pre-stack depth imaging to overcome these issues and obtain a substantially improved data set for interpretation. Reprocessing started from field tapes and was implemented in two phases: preprocessing/PSTM, followed by QPSDM. The preprocessing workflow included statics corrections to handle the near-surface velocity issues, and de-noise to remove ground-roll and random noise. 5D interpolation was applied to provide uniform sampling throughout the survey. A bandwidth extension approach was used to improve the resolution of the final products. The 2017 QPSDM required both accurate velocity and Q models. The Velocity Model Building (VMB) workflow used a reflection tomography based approach constrained by all available well data. The Q Model Building (QMB) workflow was an integrated approach that included using amplitude extractions and an AVO envelope attribute from the 2017 PSTM to facilitate geobody interpretation for input into Q tomography. Finally Controlled Beam Migration (CBM) was selected to optimally focus the energy beneath the top carbonate where Kirchhoff methods have difficulty handling the large, rapid velocity change (Zhou et al., 2011). A key factor to the project success was intense communication and strong collaboration between the in-country seismic processing contractor, the in-country geoscience team, global processing experts, and partners. A dedicated geologist was assigned to facilitate the long-distance collaboration and to optimally incorporate geologic context into every step of the reprocessing workflow. The 2017 PSTM data have improved reflection continuity and amplitude integrity, while the 2017 QPSDM data, besides providing significant uplift in the vicinity of shallow gas anomalies, allow more accurate interpretation and spatial positioning for resource estimation.