Publications

The West Natuna Basin (WNB) is in the centre of the Sunda Shelf in the South China Sea, associated with the NW-SE Three Pagodas Fault Zone, which extends from Burma/Thailand into the Malay and Natuna Basins. The area has imparted a complex structural history of extension, compression, and wrenching related to Cenozoic regional tectonics. The structural evolution of the WNB reflects a history of Late Eocene rifting and Middle-Late Miocene inversion with signs of strike-slip movement. Complex wrench faulting is significant in reservoir mapping of the mature gas production fields. The timing of the transpression and transtension in the wrench system also has a substantial role in reservoir correlation to estimate the amount of erosion. This study aims to demonstrate how new approaches to seismic attributes combined with structural restorations will define the wrench kinematics in the WNB as a critical point for fault and reservoir relationship in the gas production field.

A new reprocessed 3D seismic integrated with production wells data was used to identify structural trends. Seismic low-frequency magnitude becomes an attribute to define faults through the Spectral Decomposition method. It provides robust attributes to identify morphology representing different structural geometry. The seismic interpretation shows the Late Eocene NE-SW pull-apart basins as part of the NW-SE sinistral strike-slip accommodated by the collision of India caused the onset of the rotation of Sundaland. Concerning the Middle Miocene oblique NNE-SSW compression, it adjusts the reactivation to the NW-SE right lateral strike-slip with wrench kinematics. It creates principal stress in the transpressional area and inverts the border fault. The post-rift deposit was uplifted simultaneously with the horsetail structure development in the transtensional area. This uplift continues until the Late Miocene and follows by erosion. As the post-rift depositions have become one of reservoir production, the connectivity becomes challenging due to high erosion and the appearance of intense normal faulting.

This research verifies that the combination of recent re-evaluations of the 3D seismic and its attributes can identify more detailed fault patterns to identify the kinematics. Therefore, palinspastic restoration has become one of the classic approaches to estimate the timing and amount of erosion, which leads to reservoir site development and production improvements.