Imaging challenges at Gulf of Papua (PNG) and their solutions through high-end imaging technology

Summary

Recently, there has been increasing interest in exploration of the Gulf of Papua (GoP), part of the Papuan Basin. This Basin has undergone a complicated structural and stratigraphic evolution related to its position on the north-eastern edge of the Australian plate. The presence of shallow absorbing anomalies, as well as complex tilted fault blocks and a mud volcano makes velocity model building and seismic imaging challenging. The image underneath such shallow gas anomalies suffers from considerable wavefield distortion and amplitude loss. There are also clear fault shadows and structural ambiguity underneath complex tilted fault blocks, as observed on the vintage PSTM seismic data. All these challenges are caused by the complexity of velocity and/or absorption (Q) fields.

To overcome these challenges, we need to focus on two major aspects. Firstly, we need to derive a high-resolution velocity model. Full Waveform Inversion (FWI) is the state-of-art technology used to resolve velocity anomalies caused by shallow gas pockets. Supplemented by multilayer non-linear tomography, a high-resolution velocity model is obtained from shallow to deep. Secondly, we need to build a high-resolution absorption model. Frequency shift Q tomography and FWI guided Q tomography are applied to estimate the total absorption field, which is used in Q migration (QPSDM) to compensate for amplitude loss and phase distortion. A significant imaging uplift has been achieved by these technologies. The prominent improvement of interpretability of the new processed QPSDM seismic data will potentially enable a better understanding of hydrocarbon prospectivity in this area.

• Gulf of Papua
• FWI
• fault shadow
• shallow gas
• tomography
• QPSDM