Deepwater Lobe Complex Characterisation and Evolution Within a Salt-Controlled Mini-Basin

Abstract

A succession of four deepwater lobe complexes ponded within a salt-controlled mini-basin have been imaged in unprecedented detail using a high resolution three-dimensional seismic dataset. The ponded interval was deposited over a period of approximately 0.8 Ma and consists of four discrete packages, each of which contains at least one lobe complex. Each lobe complex is composed of multiple individual lobes which are formed of a trunk channel and a diverging network of smaller distributary channels commonly fringed by a high amplitude band. The lobes are on average 1.6 km long by 1.3 km wide and are fed by trunk channels which range from 60 – 200 m wide, and have thicknesses up to 15 m. These trunk channels branch into distributary channels with widths of less than 30 m. Lobe shape and spatial location varies in response to topographic growth along the edge of the basin as well as inherited seabed relief generated by previous lobe growth. Lobe complexes of similar scales have been described in detail at outcrop and in unconfined settings on the seafloor. However, this is the first study to describe these systems in such detail in the subsurface resolving the individual lobes and lobe elements within a ponded intra-slope basin. The high resolution plan-view images shown here link the fine-scale sedimentological studies that have been carried out on lobe complexes and sheet sands over the past twenty years with less well resolved seismically imaged systems. The sheet sands described in outcrop studies can be correlated with features seen in plan-view amplitude extraction maps. We record densely channelised lobes (channelised sheet facies) passing laterally into more branched, thinner channels and lobe elements (channelised and amalgamated sheets) then terminating in a high amplitude fringe (amalgamated and layered sheets). These features are often hard to link spatially in outcrop settings where only dispersed sections are available but this dataset allows the linkages between the facies to be explored. This new example can be used as a unique analogue to enhance the understanding of reservoir heterogeneities within deepwater lobe complexes in ponded basins throughout the world.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016