Authors: Tom Wilson (presenter), Joseph Whiting, Corneliu Cosovanu, Ann Watkins, Anne McAfee, Core Laboratories UK
The emergence of a significant submarine fan play, in the ultra-deep waters of the Sergipe Basin, is exemplified by 6 discoveries since 2010. This paper integrates biostratigraphic and sedimentological data to better understand the evolution of the Late Cretaceous deep-water fan systems. Success in the Calumbi play, for example in the Barra, Moita Bonita and Farfan discoveries, is characterised by accumulations within stratigraphic traps basinwards of the Alagoas Hinge Line. Biostratigraphic analysis of exploration wells shows Upper Cretaceous sediment packages, which are thin or absent on the present-day shelf, thicken outboard of the Hinge Line. These packages can be related to the Drift-Transgressive and Regressive sequences and are associated with channel and fan sands. The marked increase in accommodation space occurred during the transition and drift phases, initiated by a basinward shift in the rift / spreading axis. Hyperextension of the continental crust, emplacement of magmatic crust and SDRs gave way to thermal sag and an increase in accommodation space in the outboard region.
Extensive core logging of Upper Cretaceous Calumbi sections allowed the differentiation of interbedded coarse-grained sand and gravel-rich intervals into turbidity current and hyperpycnal surge facies, driven by increased fluvial discharge (figure A.). These sediments were transported across a narrow shelf and preserved within stacked channel systems on the steep and terraced slope. Observed facies include inboard bypass deposits giving way to levee-confined slope systems consisting of amalgamated channel complex sets and associated mass transport deposits, and distal lobes characterised by discrete low-density flows. These rock-based observations are integrated with downhole logs and information on the regional geology to extrapolate the sedimentary succession and create palaeogeographic maps.
Tom Wilson, Core Laboratories
Tom is a geologist from Kingston University and holds a MSc in Palynology from Sheffield University.
With 24 years of experience in the industry, he is Senior Geological Advisor at Core Laboratories, UK, where, as part of the regional studies group his main technical role is reviewing stratigraphic data, coordinating new analyses and interpreting the results to produce consistent stratigraphic interpretations and well correlations; working with regional and reservoir geologists to place the well data in tectono-stratigraphic context, better understanding basin evolution, reservoir distribution and reservoir quality.
He spent 16 years at Robertson, initially as a palynologist working principally on West African basins. Subsequently moved to multi-client studies as a Petroleum Geologist looking at basins in the South Atlantic and then around the globe. A move to the proprietary studies department resulted in a change to working on license rounds and prospect analysis, later becoming a Technical Advisor in this department. Upon leaving Robertson he went to Xodus as a Senior Geologist looking at exploration opportunities in Africa and then spent 3 years in the Central North Sea exploration team at Eon E&P, before joining Core Lab early 2017.
Tom is a member of AAPG, PESGP and Micropalaeontological Society,