Gonzalo D. Veiga1, Luis A. Spalletti2, Stephen Flint1
(1) University of Liverpool, Liverpool, United Kingdom
(2) Universidad Nacional de La Plata-CONICET, La Plata, Argentina
ABSTRACT: Anatomy of the Cretaceous Avilé Sandstone Lowstand Wedge in Central Neuquén Basin (Argentina)
The Avilé Member (Hauterivian) is an important oil and gas reservoir in the central Neuquén Basin. It has been subdivided in a lower shallow marine portion and an upper continental section of aeolian and fluvial origin (Avilé Sandstone). The Avilé sharply overlies offshore marine shales across a regional sequence boundary and is overlain by marine shales across an abrupt regional flooding surface.
In the Pampa de Tril region, the Avilé Sandstone is almost 40 m thick. The lower portion is characterised by aeolian dune deposits and sandy wet interdunes and passes upward into a middle section of aeolian dunes associated with damp, fine-grained interdune deposits. A high-sinuosity fluvial system characterises the upper portion, with sandy small channels and minor floodplain deposits.
In southern sectors (up dip) the Avilé is thinner and almost entirely fluvial, with only minor aeolian deposits present at its base. In down dip northern areas, the Avilé Sandstone is also thinner with basal small aeolian deposits, a fine-grained middle portion representing a more distal fluvial system, and fluvial sandstones at its top.
This facies distribution indicates a regional wetting upward trend in the Avilé, probably due to water table rise induced by a sea level rise. In the Pampa de Tril region the aeolian system is at it thickest development and interdigitates with a coarse fluvial system up dip and with a distal fine-grained fluvial/probable shallow marine system down dip. This complex facies distribution fundamentally controls reservoir quality in this lowstand unit, with aeolian deposits representing "sweet-spots".
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado