Improved Interpretability Beneath an Accretionary Section in West Timor, Indonesia, via Marine Broadband Seismic and Beam Depth Migration.

Farouki, Mazin (PGS) | D’Alterio, Felice (Eni.) | Gentile, Erika (Eni.)



The region immediately south of West Timor, offshore Indonesia, has been largely underexplored, with only one well drilled onshore in the West Timor Block operated by eni, 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 and poses a formidable challenge to marine seismic acquisition and processing.

The seismic exploration history dates back to a legacy 2D survey in 1991. In 2009, a regional 2D survey using towed streamer dual-sensor broadband technology yielded significantly improved continuity of events beneath the accretionary section. Encouraged by these results, in 2010 eni acquired a pilot study of 2D lines and subsequently a 3D survey using the same broadband acquisition technology.

Broadband marine seismic via dual-sensor streamer resulted in improved resolution of the overburden and greater penetration at the target level. These benefits are a direct consequence of eliminating the receiver ghost. Ghost-free data is rich in both low and high frequencies, has improved signal to noise ratio, and is easier to interpret.

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

The combination of the broadband dual-sensor acquisition and the Beam migration imaging provided significant uplift in the understanding and interpretability of the seismic data promoting the development of a new exploration play in the region.