Print this pageUsing Outcrop Analogs for Predicting Facies Distribution and Internal Heterogeneity of Seismic Geomorphic Elements: Oligo-Miocene Turbidite Reservoirs, Campos Basin, Brazil
Seismic geomorphic analysis of Oligo-Miocene turbidite reservoirs of Campos Basin revealed a great variety of depositional elements. The mapping of those elements, within a sequence stratigraphic framework, provided important insights into the nature of the depositional system as well as into the basic patterns of reservoir connectivity. However, to achieve a better prediction of reservoir performance it is necessary to obtain a more complete understanding of sub-seismic properties, including facies distribution, internal heterogeneity and the nature of the contact between elements. This was achieved by comparing depositional elements recognized at the subsurface with comparable elements documented in outcrops. The main depositional elements comprising Campos Basin reservoirs include: (a) channel fills; (b) channel spills; (c) crevasse splays; (d) frontal splays; and (e) ponded sands. Channels fills can be continuous or discontinuous. Spills may appear as discontinuous bodies, related to thalweg shifts, or as more continuous and elongated bodies near the channel-lobe transition. Crevasse splays can be lobe shaped, but also may present variable external shapes, due to topographic control. Frontal splays (i.e. distributary channel-lobe complexes) may be of different sizes and, ultimately, at a larger scale, are also influenced by topography. Ponded sands include small pockets preceding channel development or result from fill and spill processes at the fringes of lobes. The selection of outcrop analogs was achieved by comparing: (a) regional depositional setting, (b) depositional element interpreted origin and observed geometry, and (c) internal facies associations and inferred depositional processes. Cores and image logs were used to document subsurface facies, which were then compared to outcrops. Outcrops from different regions were used for extracting properties, with the Permian Karoo turbidites being the ones which provided most useful information. The use of outcrop data improved the estimation of properties such as NTG, vertical connectivity and horizontal anisotropy, all critical for predicting reservoir performance. In addition to the internal properties, the connectivity between elements, at different scales, was also examined using outcrop information, providing valuable insights to improve reservoir models. The approach presented herein can be applied to subsurface reservoirs at stages varying from exploratory prospects to mature fields.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil