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Description and Prediction of Thin Bedded Reservoirs in the Plio-Pleistocene of the Columbus Basin, offshore Trinidad

Maria Ramnath
University of Manchester Manchester, Lancashire, United Kingdom
[email protected]

The majority of siliciclastic reservoirs are composed of ‘Conventional Pay’; relatively easy to characterise and predict reservoir properties. As these reservoirs move into decline, focus shifts to more challenging ‘secondary pay’ reservoirs; such as ‘Thin Bedded Sands’. Thin bedded sands are defined as highly interbedded sandstones and mudstones below conventional logging tool resolution. They can range from meters at outcrop to cm-mm scale in core. It is because of these characteristics, they are deemed unpredictable; therefore knowledge of their petrophysical properties and fluid flow behaviour patterns are limited.

The project is based in the Columbus Basin, offshore Trinidad; a mature gas producing basin encompassing a number of major fields where production to date has been dependent upon ‘Conventional Pay’. A number of these fields are now in decline making thin bedded sands a practical ‘secondary pay’ target. This basin is exceptional as rocks equivalent to the subsurface reservoir are exposed along the Mayaro coastline of Trinidad forming the focus of this research programme.

A detailed analytical programme is being implemented based on high resolution outcrop and core description; intending to characterise their pore systems and mineralogical framework. This includes traditional petrographical analysis (SEM, XRD, thin sections, mercury porosimetry) and subsurface modelling (micro / nano CT scanning). It is hoped that the observations made here will significantly reduce the uncertainty in prediction and description of thin bed pay and their evaluation as well as to develop new work flows for the characterisation of thin bed pay in the subsurface.

 

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects