So: How Many Grid Blocks Do I Need?

Edmund Stephens and Mark Bentley
Reservoir Engineering, TRACS International, Aberdeen, United Kingdom

This paper presents a practical methodology for selecting an optimal grid resolution in dynamic modelling, by the use of representative 2D sections. The workflow is illustrated in a model of a deepwater isolated channel based on an outcrop in the Tabernas Basin, SE Spain.

Empirical indicators are presented to help grid selection in advance of model building. An indicator is developed to identify bypass ‘thief’ zones, which combines geological heterogeneity with fluid type and displacement process into a single number. The result indicates if zones should be retained explicitly in the grid or merged into an effective layer.

The key outcome of this work is a quantified illistration that the geological detail which needs to be carried in a reservoir model depends as much on fluid type and the planned recovery mechanism as it does on the geological heterogenity itself.

A methodology is presented for grid selection using representative 2D areal and vertical sections. The approach is advantageous in building insight into fluid flow behaviours in the reservoir and prompts selection of a minimal model size leading to short modelling cycle times. The workflow is applied to the Tabernas model and demonstrates different gridding requirements for oil, gas and oil rim realisations.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery