Structural reconstruction of the Southern Banda Arc / Sarut Uttraphan

Sarut , Uttraphan (2019) Structural reconstruction of the Southern Banda Arc / Sarut Uttraphan. Masters thesis, University of Malaya.

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Abstract

The Banda Arc is a zone of tectonic collision between the Australian oceanic plate and Banda plate extending from Timor Trough to Seram. The Australian plate subducts under the Banda oceanic plate to the north under a compressional regime . Shell has entered into the Southern Banda Arc with 2 blocks, one of them is Pulau X which is the target of this study. Shell aims to de-risk the subsurface prospectivity in a cost effective way with multiple business exit points. Structural and stratigraphic interpretation indicates that the Z sandstone which is the main reservoir target, could potentially extend into Pulau X from Australia region. However, due to poor seismic quality, some of the interpretations are based on conceptual model. The maps generated in this study shows that two plays exist which are the primary sub thrust play and secondary intra thrust play. The goal of this study was to understand the occurrence and maturity of source rock and to further de-risk the charge component of the Banda Arc sub thrust play. Shell has a limited 2D dataset covering the area of interest. In order to condition the data for interpretation, a 2D tie line which extends into Australia 3D dataset was selected. A well tie was done in order to recalibrate the polarity, the time shift between surveys and to determine the correct 2D version from multiple vintages. The main piece of work in this study is a structural restoration based on a thick skinned and thin skinned thrusted model. The finding of the thin skin model shows that the interpretation of the strata is valid and the sub thrust play is a geological plausible model. Forward modelling was applied to the thick skin model to help understand the potential migration in the hanging wall. The model shows that intra thrust could potentially be a viable play and the source rocks are transported close to the original deposition when it was penetrated by the decollement. Further exploration in the intra thrust should be done towards the back of the accretionary prism rather than the toe of the thrust. The forward modelling also shows that sea bed geometry is similar to the decollement which indicates that the younger strata geometry is influenced by the older strata geometry. In order to further unlock the potential of Pulau X, the acquisition of 3D seismic is highly recommended. An in-depth study using other method such a Gravity Magnetic, Seep Hunter and Mapping Source Rock presence is vital to further understand the prospect in addition to the structural reconstruction work that has been done.

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