Attribute-assisted interpretation of deltaic channel system using enhanced 3D seismic data, offshore Nova Scotia

Abstract

Deltaic channels are good exploration targets and form potential hydrocarbon reservoirs. Generally, distributary sand-filled deltaic channels have high porosity and high permeability sandstones hence can form good quality reservoirs. We delineate deltaic channels within Cree Sand member of the Logan Canyon formation in the Penobscot field, offshore Nova Scotia, by devising a workflow that includes seismic data enhancement and attribute studies integrating coherence attributes, amplitude curvature and spectral decomposition attributes. An exhaustive seismic data conditioning improves considerably the signal-to-noise ratio in the conditioned seismic data (-4 dB at dominant frequency) compared to the input seismic (−22 dB at dominant frequency). We perform an integrated seismic attribute study which helps in effectively mapping the deltaic channel systems at different stratigraphic levels of the Cree Sand interval. We carry out a novel attribute analysis by comparing two types of volumetric curvature attributes namely, structural and amplitude curvatures. The structural curvature although depicting the fault patterns clearly, does not delineate the channels due to the absence of any flexure across the channel. Interestingly, the amplitude curvature attribute delineates different channel systems because of the amplitude variation across the channel edges. We identify narrower and thinner channels at the deeper stratigraphic level, while wider and thicker channels appear at the shallower level. Channel width varies from 870 m to 420 m and thickness from 110 m to 52 m from shallow to deeper level. Based on the integrated seismic attributes analysis, we identify varying channel width and thickness at different stratigraphic levels, that correlates to varying sea level.