Imaging

The Sabah Basin offers a number of exploration play types within its Tertiary reservoirs across various geological terranes. The main reservoir targets are thought to be Miocene carbonate platforms and pinnacle reefs developed on the mid-Miocene unconformity. 

New broadband seismic data reveals the possibility of a deeper, clastic play in pre-rift sediments. These were very poorly imaged on legacy 2D seismic but now the petroleum potential of both horst and extensional tilted fault-blocks plays can be clearly seen.

In the structurally complicated inboard area there is a proven petroleum system in the fold and thrust belt with Miocene-Pliocene turbidites as the reservoir. The key risk in this area is the variability of the reservoir. It is crucial to be able to image the targets clearly in order to map sweet spots and to delineate complex structures.

Further outboard in the Sabah Trough and Dangerous Grounds are the Miocene carbonates and syn-rift plays. A recent discovery in the deep waters of Sabah Basin has opened up a new and exciting carbonate play.

The multisensor Sabah MC3D broadband data has enabled explorers to interpret both new prospects and deeper geology. This has been a challenge on legacy data. The multisensor imaging of the Sabah Basin creates new and exciting opportunities and allows explores to make better decisions and derisk their prospects adding more economic value to their portfolio.

Multisensor streamer acquisition provides the low frequency content and deep penetration required for advanced model building and Full Waveform Inversion (FWI) is used here to refine the velocity model.

Sabah fold and thrust belt
Regional scale seismic cross-section showing elements of the Sabah fold-belt, Sabah Trough and subducting Dangerous Grounds stratigraphy.

 

Targeted Velocity Model Building Improves Illumination Issues

Velocity building and imaging using conventional tomography tools is often regional in scope and fit for purpose for exploration. However, reprocessing and imaging using more advanced sequences provides significant uplift.

The images below demonstrate the value of using a more costly, technically advanced model building and imaging workflow to image specific targets.

Detailed velocity, Q and anisotropic models were the key to properly image and derisk a potential prospect. The information extracted from the migrated image but also from the high-resolution updated models can be later used for in-depth analyses including targeted structural interpretations, seismic inversion and quantitative studies.

The FWI velocity model reveals velocity anomalies associated with shallow gas bodies, deeper carbonate deposition and even suggests gas accumulation trapped along the Mid Miocene Unconformity.

 

Targeted FWI with KPSDM overlay. FWI methodology applied on this Sabah Basin produces a high-resolution model of the subsurface that is structurally consistent with the seismic image.