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Improved Understanding and Interpretability of Plover Formation beneath a Complex Accretionary Section in West Timor, Indonesia

Farouki, Mazin¹; d'Alterio, Felice²; Gentile, Erika³
¹Petroleum Geo-Services, Singapore, Singapore.
²ENI Indonesia, Jakarta, Indonesia.
³ENI, Milan, Italy.

The region immediately south of West Timor, offshore Indonesia, has been largely underexplored, with only one well (BANLI-1) drilled onshore within the West Timor Block PSC, and no wells drilled offshore. The area is located along the Outer Banda Arc, a geologically complex, non volcanic semi-circular belt where the Australian and Asian Plates obliquely collide. The main reservoir target is the clastic Plover formation. Imaging and resolution of the Top Jurassic horizon and the overlying accretionary section is the primary geophysical objective for prospect generation.

The seismic exploration history dates back to a legacy 2D survey in 1991. In 2009, a regional 2D MultiClient survey using dual-Previous HitsensorNext Hit technology showed improved continuity of events beneath the accretionary section. Encouraged by these results, in 2010 ENI acquired trial 2D lines and an exploration 3D survey using the same specialized acquisition technology.

The recent technology advances in marine acquisition and data processing have significantly improved the understanding and interpretability of the target section beneath the accretionary prism. In particular, broadband marine seismic via dual-Previous HitsensorNext Hit streamer technology has provided improved resolution of the overburden, and greater penetration at the target level. These benefits are a consequence of eliminating the receiver ghost via the dual-Previous HitsensorTop system. Ghost-free data is rich in both low and high frequencies, more closely resembles earth's reflectivity, and is more responsive to data processing. Moreover, the inherent low frequencies result in robust inversion and reservoir characterization.

A second important contribution comes from utilizing a unique implementation of Beam Depth Migration to resolve the complex overburden and underlying structure correctly. Unique aspects of this implementation include near-vertical steep dip imaging, residual multiple attenuation, and the ability to detect weak signal. These features play a critical role in imaging both the accretionary prism and the target structure below.

Data examples illustrate how advances in seismic technology in acquisition and processing positively impact the exploration effort in this geologically challenging domain.


AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012